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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
its a 4.165 bore 3.48 stroke deal but it has his 205 cc heads and a small 231 deg solid roller which would be like a 220’s deg hyd roller. Mid 500’s lift. Peaked at 6000-6300 making 538 hp. 500 lb ft
Theres something to good size head that can flow and mild cams with good valve motion/lift. It was the emc recipe for a while in the earlier years i believe. May still hold true havent followed it much
either way i can see it being torquey
I did see his build.
One thing I did change on my build was I decided not to run the edelbrock plenum. Once it was in the van it interfered with practically everything. I ended up using a holley 17-94 adapter and mounting the 87mm TB facing up. Then used a silicone 4" 90° elbow and a 4" aluminum pipe. Allowed me to use a TBI G-van thermostat housing and upper hose.
FWIW the good heads, small cam is an OEM trend now as well. They are adding variable valve timing into the mix. Nissan is also adding variable intake cam duration and lift into it with their VVEL system. My Infiniti M56S had a 338 cubic inch engine making about 500 hp and it idled dead smooth @ 600 rpm.
Even though you kept the cam duration below 230* at .050, I don't think you will be exaclty getting the stock idle sound. The 11:0 compression will definitely kick up idle note. Comp's 110* LSA will have it loping a bit. It won't sound like a Pro Stock dragster, but it won't exactly sound like a cargo van's smogger 350.
I meant to reply back to you on this. While it is not quite the stock Vortec cargo van engine it honestly does not sound much different than the 395' marine cam I had in the 350.
Rhoads suggested 0.020" hot lash on the VMax lifters for the street. I cold lashed them at 0.014". The lifters cut about 20° duration off the cam at low rpm. My 1.7 rockers added about 3-4° to the cam compared to 1.5s. The little 215/224 cam is roughly equivalent to a 218/228 @ 0.050. At idle the cam is about like having the 196/206 @ 0.050 marine cam with 1.6 rockers. It actually idles a little smoother from the added compression, added displacement, wider 110° lsa and 1° advanced compared to the 395' cam. Pulls 20 in/hg vacuum at 650 rpm.
I run 87 octane fuel when I am not towing. Run 29° total timing @ 3,600 rpm. I had to pull a few degrees of timing at lower rpm and heavy load compared to the 9.6:1 350. When it runs on E85 it runs at 34° total timing. E85 really wakes this 383 up.
The biggest thing that separates this setup from a stock engine sound wise since I run a fairly quiet exhaust is the Rhoads lifters. Some people hate the noise but I actually like the sound of a solid lifter small block. The way I have them lashed, they sound like a nice tight lash aftermarket solid lifter cam. Its not as clacky as a 30/30 cam but it is enough that I have had a few car guys ask me if it was a solid lifter cam. Given the way the cams behave in the two engines I have run them in, my future builds will likely also be running them. I can run more lift and duration and still have a very nice idle with good idle vacuum for the PCM to stay happy. Properly set they also do not seem to cause issues with the knock sensor and false knock retard either.
One other thing I have been doing is enabling lean cruise on every 24X LS based controller I have tuned that it is an available option on. This 6.0L cruises effortlessly at 16.9:1 air/fuel ratio. The 383 runs 16.5:1 at its leanest.
That in itself (the lean cruise) is worth the price of admission. I've dialed my 350 in to a 16:1 cruise as well. Problem for me is with the timing which, as you know, is a PITA making adjustments the old fashioned way. Mechanical advance. Vacuum onset. Vacuum total. Etc. It would rattle (almost imperceptibly) while at light throttle cruise. Perhaps to point of hurting the engine (which is something I've yet to determine).
That in itself (the lean cruise) is worth the price of admission. I've dialed my 350 in to a 16:1 cruise as well. Problem for me is with the timing which, as you know, is a PITA making adjustments the old fashioned way. Mechanical advance. Vacuum onset. Vacuum total. Etc. It would rattle (almost imperceptibly) while at light throttle cruise. Perhaps to point of hurting the engine (which is something I've yet to determine).
That it is! The 71 Chevelle has a LG4 6.0L with an Elgin 228/230 cam and original rhoads lifters. Makes 18 in/hg @ 550 rpm. It has the edelbrock proflow intake and stock 2010 camaro manifolds into the dual 3" exhaust with a x-pipe and flow masters he had with the 468. Stock 4L80E, stock converter and 4.10 gears. Spins the 325 wide drag radials with relative ease on the street. Lean cruise took it from 25 mpg to 29 mpg highway running 70 mph. The screen shot above was taken on a flat section of road. The 6.0L pulls nearly 20 in/hg of vacuum at steady cruising speed at 2,500 rpm.
So I will give an update. I had to change up the setup to get this thing through our more thorough smog checks. Ported a stock L31 manifold and added a 48 lb/hr AUS injection spider. Went back to a 4x reluctor and put a distributor cap and rotor back on it with plug wires so it would raise less questions. Put my DUI coil and module on it along with a new set of Taylor Thundervolt wires. Did away with the 24x. To make this thing run better with the stock intake manifold, changed to a 218/228 @ .050, 0.578 lift (with 1.7 rockers), 108 LSA, 104 ICL cam degreed on a 104 ICL. Added a few degrees of duration to the previous grind and tightened the LSA. Kept the rhoads lifters and adjusted them to 0.014" cold. Cranks at 220 psi now. Even with some miles on it now the leakedown was about 5% consistently across the board and poking around down the spark plug holes with my inspection cam the cylinder walls look like new and the pistons nearly spotlessly free of carbon. Guess these pistons and 0.041" quench have a much cleaner burn than the old L31 dished smogger pistons. Then added a larger core radiator and dual 3,000 cfm flexalite fans. With the stock intake and spider arrangement this thing looks like a detailed "stock" 350 with headers. The 48 lb/hr spider also now sprays fuel directly on the back of a closed intake valve at idle and low speed. It idles dead smooth now. It was a bit rough until the manifold warmed up with the old setup spraying fuel on the floor of the intake manifold runner.
I am sure when this thing goes down the track and I have the hood open cooling it off it will have people looking for a bottle. Ran it on the stand with a carb again after bolting it all together. 19 in/hg vacuum at 600 rpm and 24 in/hg at 3,000 rpm. Insanely loud almost booming exhaust note with open headers, reminds me of a drag car when it fires.
Did the first setup run much? Any dyno figures? Did it like pump gas?
About 6K on it all together since it was built. Ran fine on pump gas. Has run about 400 with the current cam and the L31 truck intake. Just getting the timing to a happy medium. With the dual plane intake I was feeding it fuel for about 550 hp.
Finally got a chance to upload some videos of it running when I had it on the stand. Small exhaust leak where the muffler was clamped to the header collector on bank one. Was shooting a fireball out of the muffler when letting off the throttle. Q-Jet had zero adjustments after running on a 305 though too. Just slapped the carb on it and cranked it over. Could have adjusted the idle mixture with a vacuum gauge to make it smoother but it idled fine. Was also one tooth off on the distributor and hit the vacuum advance canister on the intake manifold at about 4° ATDC and could not get quite enough advance. I just twisted it against the manifold, tightened the clamp and let it roar. Was just too out of time to fix something that was only going to run on the stand for a short period. I ran it a good 30 minutes and got it warmed up really well. Hot idle oil pressure is about 30 psi at about 600 rpm. My phones microphone really picks up on the rhoads lifter/Scorpio 1.7 roller rocker noise for some reason. In the video it sounds about 3x louder than it really is. Standing next to the engine you hear the exhaust tone over the lifters. That alternator is also trying to lock up for some reason and had a bit of a rattle to it.
Well this one finally uploaded. One last one after I had retimed the distributor, hooked up a fixed orifice PCV and put a L82 vacuum advance on the HEI. Cleaned the idle circuits with B12 and compressed air. Carb has not been touched otherwise in about 10 years. That was with 14° initial timing and about 36° total advance. Has stock smog era springs and weights in it. Doubt I could get away with that much timing under full load except maybe in a light car with deep gears and a loose converter but sure makes it responsive. Couldn't ever get it not to ignite the accelerator pump shot fuel from snapping the throttle open in the muffler when the throttle was snapped shut. Nice 2' long fireballs. That is the hollow banging right when the throttle is closed at the end after snapping it open. Those plug wires, cap and rotor are atleast 10 years old as well and not in the best shape. Got zapped setting the timing so it definately could have run a little better with a tuneup and carb rebuild. However that was not the point. Basically wanted to run it, get it to temp and make darn sure there were zero oil leaks and that the valvetrain was adjusted dead nuts on. #5 had a slightly loose intake rocker, which is why it was cranking 225 psi. Re-adjusted and it dropped to 220 like the other 7. Got it down to 750 rpm where it idles in the van and it is showing nearly 20 in/hg vacuum. Idled it down to 625 and it was still making 17 in/hg. Got it up around 190°F and after an hour of running it held about 40 psi of oil pressure at 750 rpm. Mufflers and PCV dropped the idle vacuum 1-2 in/hg. Will get some videos of it running in the van someday soon when I actually get to go over to the shop. I don't daily it and haven't in years. It sits more than it is driven. Between the work I have done on it and sitting around its probably only been driven 30K miles over the past 8 years.
NICE. Here is a few pics of my test stand. A couple of differences between yours and mine:
I connect the cold water to the water pump inlet, and take the hot water out at the thermostat, but I use a garden hose shutoff valve to keep the block pressurized a little bit. The CW in is hardly flowing and I just monitor the temp of the HW out. Actually, I fabricated piping to replace the water pump. This way I don't have to run any belts --- for safety. But before the engine is actually installed, I put all the accessories on so I can check belt alignment and functionality of everything I can.
Had almost completely forgotten this post, but recently had to pull the 383 to fix a couple of issues unrelated to the integrity of the engine. The 383 pulled the threads out of the metal reinforcement bars that sit under the frame that hold the adapter plate that holds the engine mounts in. Pulled all 4 bolts out of the driverside adapter. Also had a header that still wanted to rub the frame. I put new GM hold down plates in the frame modified with grade 8 nuts tack welded in place of the GM stamp and tap retention holes. Map gas torch to the engine crossmember and a 2 lbs mini sledge made clearance for the header. Almost back road ready again. I cleaned and painted the crossmember and forward frame section and truck bed coated the inner fenders and plumbed both the p/s and trans with an lines. Cleaned and painted the accessory brackets. Also fitted a large power steering cooler to help cool the p/s system that has run in a near constant state of overheating since the hydroboost swap.
Also took the time to rewire the fans with a BP Electronics GMT800 fan harness so that they operate on low and high speed vs left and then both. Calmed down the amperage draw and 2 fans operating at low speed pulls more air than 1 on high speed. Replaced the a/c condenser, swapped to a sanden vortec replacement compressor, flushed the system completely, changed the orifice tube and added the GM a/c pressure transducer to signal the LS PCM with the actual a/c pressure. Fans and a/c now work as if they were in a factory 2006 Escalade although I trigger high fan about 20 psi less than GM did.
Been playing around with the tuning and finally decided it was safe to crank up the RPM. Engine has seen 6,500 rpm with the carb. Have the fuel kill set at 6,200 now in the tune. Absolutely rips up the rpm range. Pulling 420 gms/sec airflow and my 48 lb/hr spider is at 60-62% duty cycle on E10 to hold 12.6:1 air/fuel ratio at 5,600 rpm. I checked the fuel pressure and it is holding rock solid at 62 psi for now. Hit the fuel kill a couple times and saw a little knock retard doing that. Won't be doing that again but atleast I finally know the new AC Delco knock sensor even works. I wish audio on the recording gave justice to how beastly this thing thunders inside the shop through the 3" cutouts.
I know this is an older post but have another update. The electric fans were a bust, ended up swapping back to a stock dimension radiator and the factory fan shroud. Added an 11-bladed motorcraft fan for a 2006 5.4 3V F150. Its quiet and pulls great CFM.
Yesterday evening I strapped my 97 Express on a friend of mines dyno at his shop and ran the snot out of it for close to 5 hours. It was 104°F and felt 112°F when I was playing around. Luckily my van has ac that will freeze you out of it especially sitting inside the shade of a building.
I made about 20 WOT power pulls on it from 1,200 rpm to 6,000 rpm with the torque converter clutch locked and the 4L85E locked in 2nd gear. The engine ran the entire time without a care in the world. I have HP Tuners and a custom operating system that allows me to load and manipulate the timing and fueling with the engine running as well as save the revisions to flash into the PCM.
The fuel curve was pretty good as it was although I played with the WOT air/fuel ratio from 11.8 to 13.2:1 in 0.2 increments. I really like making several back to back pulls with equal increment changes like that. It is easy to lay the graphs over the top of each other and figure out what the engine likes and where it likes it as it can be a moving target. Around peak torque it likes 12:1 and about 12.6:1 at peak power.
Timing curve needed some tweaking. I initially started with 29° total at 3,600. Then moved up in 1° increments. Ran as much as 35° before it actually started losing power and had yet to ping or show any knock retard. Ended up finding it made peak power on 33° but it was only 2-3 hp more than it made on 31° that I was already running at on the street. Then I worked backwards on the low rpm end of the timing table that I will only really see in overdrive with the 2,800 rpm stall converter locked up. I made about 10 pulls from 1,000 rpm up to 3,500 to dial in the low-end. I was able to go another 4-6° in places before adding another 2° showed little gain. I generally run 2° less than where it makes the absolute most power for long term durability. My 31° total advance is now in at 3,200 rpm. I have 26° as early as 2,400 and 16° at 1,200 with 8° on the initial throttle hit at 750 rpm.
With a 2,800 stall converter I will never see much below 1,500 unless my foot is off the throttle because I do not lock the converter until the engine will be turning over 1,500. With fine tuning, found an additional 18 ft/lbs average torque and 8 hp average hp gain between 1,200 and 6,000. At about 1,800 rpm I gained 28 ft/lbs. At the ground through a 4L85E and 3.73 geared 10.5" full float 14-bolt (no more 5.13s) the 383 ended up making 399 ft/lbs at 3,100 and 382 hp at 5,600 (Rhoads V-Max lifters and great flowing heads FTW) uncorrected on a Mustang dyno. It repeated those numbers 3 times in a row losing maybe 1-2 on the 3rd and last back to back pull. The 11 bladed clutch fan kept it nice and cool, could not get it over 185°F although we did point the large shop fan at the radiator to give it a hand with the weather being so hot here.
Never even turned the ac off for the pulls either as the compressor relay kicks the clutch off the moment the go pedal hits the carpet anyway. Definately about the most confortable tuning work I have done as most of the older LS swapped stuff I tune lack a/c and half the time have half an interior and the loudest mufflers made and working with an old school engine has you under the hood setting the timing on a hot engine.
For those that want STD corrected power, the air temp was 102°F, humidity was 38% and the barometric pressure was 29.70 giving a 1.079 correction factor.
Wow! That's a lot of data. Wish I could be doing the same.
So, after all of that, where does that leave you at highway cruising speeds in terms of MPH, RPM, ignition advance and manifold vacuum?
LT275/70R16s that are 31.5" tall, 3.73 gear and 85E. Puts me at 1,200 rpm @ 40, 1,500 @ 50, 1,800 @ 60, 2,100 @ 70 and 2,400 @ 80. In 3rd at 70 I am at 2,800 which should still tow my TT well, lots of grunt there. Get even more grunt if I unlock that 2,800 rpm converter in 3rd gear as it puts the engine at 3,100-3,200 rpm and adds torque multiplication, on a long hard pull I would rather downshift to 2nd though and let the converter lock up. At 65 mph 2nd lockup is only 3,800 rpm. In lean cruise at 60-80 mph on flat road its at 44° of timing which is the maximum for the Vortec distributor and about 16.5:1 afr. CNP 24x on the old 350 it liked 48-52° so likely a little under timed at cruising speeds now. On the engine stand with a HEI it ran smoothly at 46-49° of timing at 3,600 rpm depending on if it was at 15 or 18 initial timing. Its building about 12-15 in/hg vacuum, less at lower rpm and more at higher rpm. To drive faster than 75 mph the vacuum starts to drop off. Idle is rock solid at 750 rpm and 19 in/hg. A/C drops the idle about 1 in and so does having the 4L85E in gear. So idle in gear with the a/c on is about 17 in/hg. Idle is at about 25° of timing.
I have 5w20 synthetic oil in it right now and have yet to put the oil cooler and associated lines to the radiator back on it. Its holding 25 psi oil pressure at hot idle and increases to 60 psi by about 1,500 rpm. WOT it was carrying 70 psi.
I would post the timing table but without understanding or datalogging the newer LS GM/CYL load scaling for this engine it would be difficult to comprehend and its specific to this engine as gm/cyl is basically a measure of VE.
...about 16.5:1 afr. the old 350 it liked 48-52° .
That would match my most aggressive attempt at lean cruise. It did manage to take my overcammed 355 to better than 21+ US MPG but that was always on the verge of light detonation.
26" tire, 3.73 gear, lockup converter with O/D puts me at 2300 RPM at 70 MPH. Very cool engine temps but no cold air intake. Getting my cowl hood to be functional would be a step in that direction. The worn out shortblock probably didn't help things either.
Thanks for the info as always.
That would match my most aggressive attempt at lean cruise. It did manage to take my overcammed 355 to better than 21+ US MPG but that was always on the verge of light detonation.
26" tire, 3.73 gear, lockup converter with O/D puts me at 2300 RPM at 70 MPH. Very cool engine temps but no cold air intake. Getting my cowl hood to be functional would be a step in that direction. The worn out shortblock probably didn't help things either.
Thanks for the info as always.
Getting the most out of an engine always puts it on the verge of detonation, which is why the newer engines have a knock sensor. That point is why I also prefer to give up a couple hp by using MBT advance rather than highest output. With MBT advance you are getting say 99° of the power available but it is backed down a little to help prevent detonation.
If you run on a dyno without corrected numbers and without smoothing as you cross over MBT you will often actually start seeing the combustion pressure spikes. Instead of a nice smooth graph it starts looking wavy like this. \/\_/\/\_/. At that point some cylinders are starting to build substantial cylinder pressure before 15° ATDC stressing the rotating assembly and its usually on the verge of detonation.
I pulled this thing out today and put a full hour behind the driver seat for the first time in a several weeks. When I drive this big heavy van, makes me want to build a similar engine for my 1980 Z/28. Then that budget thing comes up. The Camaro will still be a rocket with the freshened up 350 that came out of this van. If I built another engine, it would be a Dart SHP block 415 and it would go in the Van and this 383 would get the big Bootlegger bumpstick and go into the Camaro. I currently have a 3.73 G80 rear in it. I really like how tight the custom built stock diameter 4L85E converter is at part-throttle. It will flash about 2,650 rpm from idle but it drives nearly stock. Put it in drive, idling at 750 rpm and it eases forward even up a slight hill with no pressure on the accelerator. Pulling away from a traffic light or stop sign it is very smooth and the converter really tames the twitchy off-idle transition of the BBK 80mm throttle body. Get into an open area, hammer down a little and it gets up and goes without having to even put the pedal close to the floor. Lay into it harder from a stop and this ~6,200 lbs van behaves like a 1970 Chevelle 396 SS. The 383 comes alive instantly off idle, flashes the converter, the tires dig in and within reason it feels about like its getting catapaulted off a carrier flight deck compared to the old 350 before it had 5.13s. The 383 with 3.73s actually has a somewhat less impressive launch feeling than the 5.13s but it launches clean with minimal tire spin with the 3.73s and just keeps pulling. 0-60 in 1st gear and it could do 100 mph in 2nd. With the front suspension, steering and brakes completely redone, the added 1-3/8" rear sway bar and all the polyurethane bushings this has it corners level and tight, steers as well as new and stops better than new with the big 1-ton brakes and hydroboost. This 383 has made the get up go side of the equation very nice. Its decent on gas, has good driving manners, has great power, will sit and idle in traffic with the ac blasting and stay perfectly cool or blast down the highway with a trailer in tow and run even cooler than it does idling. Just felt like throwing some feedback on what this 383 is like now that I have some decent seat time.
Wait... You have a 3rd gen?!
Why is this the first time I've ever heard of that?
I have had 3 different 3rd gens, currently my only F-car is a 2nd gen. If I could find a nice affordible stock speed density dual cat G92 305 5spd I would have another 3rd gen.
I also forgot to mention above in the update. On E85 with 34° total timing at 2,400 rpm the 383 made 430 hp @ 5,200 and 460 tq @ 2,700 at the rear wheels. On E10 91 the corrected numbers previously were 412 hp @ 5,600 and 430 tq @ 3,100. It really loved the added timing on E85. I have as much as 8° more timing in places (low rpm @ WOT, 22° @ 1,200 rpm now for example) on E85 where it was previously knock limited on 91. Its interesting to me how adding timing brings the peak hp and tq on earlier. E85 did the same thing on the old 350. More power and torque, sooner in the rpm band. On the highway at 70-75 mph it has been getting 18 mpg on E10 91 octane and a recent trip on E85 netted 15 mpg. E85 is $2.90 a gallon and 91 octane is about $4.00 a gallon. It is cheaper to run on E85. Only downside is less range but the tank is 31 gallons and I can still comfortably go 420 miles per tank with some added reserve distance not towing. Down where this thing cruises at ~1,500-2,200 there is as much as 35-40 ft/lbs more torque. Climbing a long 6-8% grade on some of the 2 lane roads I frequent with the ac on, it will hold overdrive at 60-70 mph at 1,800-2,100 rpm without even unlocking the torque converter.
Those are truly impressive numbers through a truck drivetrain!
While it sucks more power than a car, I don't think the loses are too bad with it. On gasoline, I am feeding it about ~520 hp worth of fuel if the BSFC is 0.450 and ~550 hp if the BSFC is 0.425. I think the BSFC is a bit better than the often quoted 0.500 that is thrown around for injector sizing. The Something New Something Old TPI 355 build had a ~0.400 BSFC. On E85 the fuel consumption is a good bit higher as expected.
I also forgot to mention above in the update. On E85 with 34° total timing at 2,400 rpm the 383 made 430 hp @ 5,200 and 460 tq @ 2,700 at the rear wheels. On E10 91 the corrected numbers previously were 412 hp @ 5,600 and 430 tq @ 3,100. It really loved the added timing on E85. I have as much as 8° more timing in places (low rpm @ WOT, 22° @ 1,200 rpm now for example) on E85 where it was previously knock limited on 91. Its interesting to me how adding timing brings the peak hp and tq on earlier. E85 did the same thing on the old 350. More power and torque, sooner in the rpm band. On the highway at 70-75 mph it has been getting 18 mpg on E10 91 octane and a recent trip on E85 netted 15 mpg. E85 is $2.90 a gallon and 91 octane is about $4.00 a gallon. It is cheaper to run on E85. Only downside is less range but the tank is 31 gallons and I can still comfortably go 420 miles per tank with some added reserve distance not towing. Down where this thing cruises at ~1,500-2,200 there is as much as 35-40 ft/lbs more torque. Climbing a long 6-8% grade on some of the 2 lane roads I frequent with the ac on, it will hold overdrive at 60-70 mph at 1,800-2,100 rpm without even unlocking the torque converter.
And this builds my argument from earlier on in that timing trumps compression.
If a marginal condition exists, such as being knock limited on 91 octane, I'm in the camp that says less compression but a full timing curve will make for an all round better performer. This isn't just about power but drivability and fuel economy as well. These are points highlighted in the commentary above.
If a full curve can be implemented and there's room to spare, then obviously the compression ratio could be bumped.
But I'll say it's not a effective, the other way around.
Then of course there's E85. Or the difference in the higher compression ratio requiring the use of premium to keep that timing where it belongs. It's often said that the improved efficiency of compression plus timing would offset the additional cost of premium fuel.
As always, YMMV.
And this builds my argument from earlier on in that timing trumps compression.
If a marginal condition exists, such as being knock limited on 91 octane, I'm in the camp that says less compression but a full timing curve will make for an all round better performer. This isn't just about power but drivability and fuel economy as well. These are points highlighted in the commentary above.
If a full curve can be implemented and there's room to spare, then obviously the compression ratio could be bumped.
But I'll say it's not a effective, the other way around.
Then of course there's E85. Or the difference in the higher compression ratio requiring the use of premium to keep that timing where it belongs. It's often said that the improved efficiency of compression plus timing would offset the additional cost of premium fuel.
As always, YMMV.
I am still of the argumemt that higher compression is more efficient even if the timing is backed off and it comprimises a little power at WOT. A normal street going vehicle spends little time at full throttle/full load. At part throttle at steady crusing speeds the cylinder pressure is greatly reduced. At higher compression, even with less timing I feel I am still making as much if not more power especially torque than a low compression engine. What naturally aspirated sub 10:1 383 do you know of that makes over 500 ft/lbs of torque even if it were running 34°+ total timing? Cylinder pressure is cylinder pressure and by running less timing the cylinder pressure starts to build later, further along in the compression cycle making for less negative work on the crank. Also E85 has more benifits other than just higher octane. Comparing the timing for peak power on E85 from octane alone is a fairly poor comparison. There is alot more E85 than gasoline going into the intake and combustion chamber and that latent heat of vaporozation helps cool and pack in the air/fuel mixture. The E85 also burns more quickly.
I have been playing around with more part-throttle stuff, trying to optimize part throttle shift points and squeek as much fuel economy as possible out of it without sacrificing performance. Here are some screen shots of a part-throttle pull up a 1 mile long ~6% grade from a standing stop.
On this datalog run, I unintentionally caused some detonation and knock retard pulling a hill at 60 mph and 1,800 rpm. Part-throttle timing loops I have been doing by watching the TPS and MAP at specific speeds on flat roads and frequently traveled hills and adjusting for the least throttle to maintain speed. I was up 12° over the stock vortec 350 at the RPM/Load I ran into detonation so putting a decent amount of timing into this high compression 383 to get it running efficiently has not a problem. I was at about 8 in/hg manifold vacuum, 1,800 rpm and 38° of timing. I have since backed it down to 34° in that area and have not had it spark knock since.
I have also played with the EOIT so that the PCM starts spraying fuel in after the exhaust valve has mostly closed. It drove my fuel trims 5-10% richer than they were. Should help mileage by not allowing the cam to pull air/fuel mix into the exhaust during the overlap period but I have not checked the mileage yet or even pulled the extra fuel out of the VE/MAF tables yet.
Overall it runs extremely well and I am happy with this 383. It cruises on flat land at 75 mph and 2,200 rpm with 15% throttle and 13 in/hg of vacuum with 41° of timing. With the ac on it pulls a 6% grade at 75 mph in overdrive with the converter locked and power to spare. Was holding 75 mph uphill without using PE and at 33% throttle and 86 KPA on a 100 KPA baro reading. Engine had a fair bit of power in reserve especially if I had pushed it into PE.
Good lord man! This is data overload!
I'll have to get into it when I'm able to concentrate more fully on all of that posted.
But I will say, I like the focus on fuel economy without a sacrifice in performance. Two metrics that I strive for.
Good lord man! This is data overload!
I'll have to get into it when I'm able to concentrate more fully on all of that posted.
But I will say, I like the focus on fuel economy without a sacrifice in performance. Two metrics that I strive for.
I meant to throw this one in there too. One of the few times I have seen knock retard on this.
I have some more data as I get this engine dialed in even closer. I took care of the spark knock at ~1,800 rpm by removing a couple of degrees of timing. Then I adjusted the lockup to where it could drag the engine down to 1,100 rpm. That was a MISTAKE because the engine does not like it at all. It bucks, misfires and even detonated a little as the load increased. Then again, I was loaded up to ~7,400lbs and lightly accelerating up a 5-6% grade in overdrive/lockup from ~35-mph to the 60-mph speed limit when I noticed this. I was attempting to save a little fuel by locking the converter at a lower speed. I have since changed it to not drop below 1,500 rpm and revised the timing table to pull a little out of heavy load, low rpm when the TCC locks up. I made a 108-mile local trip a couple of days ago. Speed Limit/Traffic dependent, I had the cruise control set at 70-80 mph a lot of the way. There is a 2 mile long, 6-8% grade in a 75mph zone on this trip. I hit the grade with the cruise set at 80 MPH and cruised up it at 77 mph in overdrive with the converter locked. Somehow, I have managed to lose 10% on the throttle opening angle the cruise control can achieve. Factory setup pulled 75% throttle opening; it can now only reach 65-66%. I could adjust the cable, but I do not see the reason to. Opening the throttle further would force a downshift or at the minimum unlock the converter, but in doing so I would trade 600-800+ rpm for 2-3 mph more speed. In fuel consumption. 600-800 rpm higher for 2-3 mph more speed on a 6-8% grade does not seem worth it, so I am just going to leave that alone. 18.8 MPG hand calculated this trip and I have yet to mess with lean cruise.
High Octane and PE Timing Tables. AFR table gets referenced by RPM and then the PE is added to the High Octane table values. The Cyl/AIr typically runs between 0.72 and 0.96 at WOT depending upon RPM. The higher timing numbers in the lower left of the main timing table operate like launch mode spark in RBob's EBL. To help flash the converter from idle with added throttle response. The lower value at 1,400 and 1,600 rpm allow for interpolation of the data when the converter is locked and the engine pulls down to 1,500 rpm.
This is the IAT and Coolant Timing compensation values I am running. At 70 MPH the IATs are usually within 5*F of ambient temperature. Around town at slow speeds, heat soaked I see as much as 170*F. I also see coolant temps as elevated as 208*F at idle in traffic with the a/c on. Once moving the coolant drops down to about 185*F.
The single instance I encountered detonation, climbing up an elevated overpass of an entrance ramp with a ~6% grade. I was already rolling at the speed limit of 35 mph when I entered the ramp and fairly lightly accelerated in overdrive and lockup which put a heavy load on the engine. Cyl/Air vs MAP vs RPM shown on the datalog.
This 383 likes cruising at 80 mph better than it does 55-60 mph. Its smooths out, knocks a hole in the wind and runs. Getting a lot closer on the fueling now in both Speed Density and MAF blended mode. Compared to a stock 350 tune, I had to add 225% to the Wall Impact factor and 120% to the Fuel Boiling Time table. Those are very similar to squirter, pump cam and pump cc changes on a carb or AE duration and multipliers in a GM OBD1. Prior to adjusting the Transition Fuel the short terms and wideband were indicating a substantial lean spot, on acceleration. Now the wideband is showing a very slight dip (0.5:1) in AFR and the short terms are pulling a slight amount of fuel. I cannot believe how hungry this setup is for AE fuel, but then again GM probably setup the factory 350s pretty lean on throttle opening and throttle stomp to clean up the emissions. Maybe I should have expected that as the heads on the 383 have larger ports than the 350 vortecs, are much higher flowing and the 383 makes 2x the horsepower.
Finally, we have the 2-mile grade climb gauntlet. No problem climbing at a reasonable speed in closed loop, in overdrive with the converter locked. The cruise lays into the throttle as much as it can, the engine lugs down a little and it just grunts its way up the grade. Smooth and quiet with no hunting or shifting between gears. So much for the internet wisdom theory that a 210cc port will not work well on a 383.
The single instance I encountered detonation, climbing up an elevated overpass of an entrance ramp with a ~6% grade. I was already rolling at the speed limit of 35 mph when I entered the ramp and fairly lightly accelerated in overdrive and lockup which put a heavy load on the engine. Cyl/Air vs MAP vs RPM shown on the datalog
OK. I think I'm seeing 1572 RPM, about 25" of manifold vacuum (is that right?) and only 12 1/2° of total timing? With 4° pulled out for spark knock?
At cruise speeds of 75-80 MPH locked up in OD at about 2500 RPM (not apples to apples with your post obviously), I'm well into the high 40's with timing. 16° base timing, about another 14-16° from the vacuum advance and whatever mechanical there might be at 2500. Maybe 10-15° . It's at that point, with moderate throttle as in ascending a slight grade (locked up in OD), that I hear the engine rattle. Very subtly but with the car up against the left hand side concrete barrier, the sound reflection is pretty good.
You may have posted it earlier but what does your data log look like for the parameters I described with my cruise combination?
OK. I think I'm seeing 1572 RPM, about 25" of manifold vacuum (is that right?) and only 12 1/2° of total timing? With 4° pulled out for spark knock?
At cruise speeds of 75-80 MPH locked up in OD at about 2500 RPM (not apples to apples with your post obviously), I'm well into the high 40's with timing. 16° base timing, about another 14-16° from the vacuum advance and whatever mechanical there might be at 2500. Maybe 10-15° . It's at that point, with moderate throttle as in ascending a slight grade (locked up in OD), that I hear the engine rattle. Very subtly but with the car up against the left hand side concrete barrier, the sound reflection is pretty good.
You may have posted it earlier but what does your data log look like for the parameters I described with my cruise combination?
MAP is 25 IN/HG, Baro is ~30 IN/HG for about 5 IN/HG vacuum in that screen shot. ~6% grade in overdrive at 1,500 rpm.
OK. I think I'm seeing 1572 RPM, about 25" of manifold vacuum (is that right?) and only 12 1/2° of total timing? With 4° pulled out for spark knock?
At cruise speeds of 75-80 MPH locked up in OD at about 2500 RPM (not apples to apples with your post obviously), I'm well into the high 40's with timing. 16° base timing, about another 14-16° from the vacuum advance and whatever mechanical there might be at 2500. Maybe 10-15° . It's at that point, with moderate throttle as in ascending a slight grade (locked up in OD), that I hear the engine rattle. Very subtly but with the car up against the left hand side concrete barrier, the sound reflection is pretty good.
You may have posted it earlier but what does your data log look like for the parameters I described with my cruise combination?
MAP is 25 IN/HG, Baro is ~30 IN/HG for about 5 in/vacuum
I will have to look through the logs and find conditions as you describe. But generally that would be low 40s, high 30s for timing. In that log with the IATs over 100°F for practically the whole trip it was pulling between 2 and 5° of timing from the high IATs.
... pulling between 2 and 5° of timing from the high IATs.
This is definitely something I'll have to address when I'm operational again.
Despite having a cowl hood, I've never incorporated the cold air aspect and I really need to. I've the plans and the material. Now I need the execution...
Well one more change on this engine. Most likely swapping the intake manifold and throttle body. Its a clone of an Edelbrock 7137 that actually looks like it may be a cleaner casting. With the manifold and fuel rails at $368 shipped to my door was worth a gamble. A little port match to the intake manifold face and it should outperform the vortec truck manifold.
I made a 200 mile all highway trip running 70-75 mph and netted 19.7 MPG hand calculated. It lean cruises flawlessly on level road at 70 mph, 2,200 rpm and 16.5:1 afr and 44° of timing. Just starting to pull a little bit of an uphill grade in this screen shot. Air/Fuel was starting to slightly richen up and the timing dropping off.
Did you ever try the plenum spacer they sell for the truck intake? Or know anyone who has?
I know of a few people that tested the manifold spacer. They made one for the marine intake as well. I had one, no way to fit it without a ~2" body lift. The one tested on a 383 with a ported truck intake did gain power nearly everywhere. Guy went by Vortec Stroker. Had something like 380 wheel hp.
There is not enough room to get a cut down 3.5" Cobra head intake duct on top of the throttle body much less an intake spacer. Getting more air into the throttle body would do more for me than an intake plenum spacer.
In speed density, I put this guy on top of the throttle body and gained probably 40-50 hp compared to the stock GM air inlet elbow. Not something that could be used long term though as it lacks almost all dust filtration but for a short term test it protected the engine from large debris.. With the stock air hat in place I was pulling down to 88 KPA on a 99 KPA baro reading. With the L31 350 Mag MPI marine flame arrestor it only drops to 97 KPA. 88 KPA is the equivalent of being at 4,000 ft elevation. I am at about 800 ft where I tested it. Average engine loses 3% power for every 1,000 ft elevation increase. 9% of 500 is 45.
When I had the dual plane marine intake, the 1,000 cfm 4bbl throttle body and the much freer flowing spectre 4" plenum on top along with the slightly hotter Bootlegger cam this engine was using 550 hp worth of fuel. When I swapped the cam and intake I was feeding 490-500 hp worth to it. It appears most of the power lost is because of the air inlet elbow off the throttle body. The air cannot make that sharp 90* turn into the throttle body. I am reasonably certain that adapter alone is why the 305 and 350 are both rated 10 hp less in a van than a truck.
I even tried to get a stud width 4" dryer elbow in between the throttle body and the body and it is too thick to fit into place. The internal cross section of that low profile 4" dryer duct is 3x what the stock elbow is. It's amazing the stock inlet elbow moves enough air for 300 hp much less 500. This scenario makes me laugh every time someone claims a larger streamlined CAI will not make power on any engine setup. It also reminds me of the stock throttle body is good for all the HP guys. The Ramjet 502 came with the TPI 46mm throttle body. A 58mm throttle body adds 50 hp on that engine. The MAP sensor does not lie! When the MAP starts dropping at WOT the engine is losing power.
Got the knock off 3717 today. Casting quality is very good. I will do a little port matching and sanding roll cleanup and call it good for my sub 6,500 rpm 383.
Good? That's amazing!
Edelbrock wishes they could make castings that clean.
China wins again.
If the machining is accurate, you're golden.
With any luck.
One thing they should have done is realized that the 4-bolt pattern on that intake is propriatery to Edelbrock and only matches their $700 throttle body. I had my fingers crossed it had the standard 4-bolt LS pattern. I will be having to lightly dremel the bolt holes in my 92mm FiTech throttle body. The manifold looks like I can open up the inlet to match the 92mm FiTech no problem. Edelbrock makes a plate to mount a 78mm LS throttle body but I do not want to choke a 4" air intake system down to a 78mm throttle body. I will be having to grind the bottom of the throttle body where FiTech bumoed it out and stamped Fi-Tech as well as some off the lower side of the throttle body flange. The flange is far larger then the throttle body sealing surface and I want to get a TBI Caprice water neck under it to be able to keep my stock upper hose design and routing. It needs 1/8" off it to clear.
The L31 Marine T-Map is a perfect fit and has the same signal as a standard GM 1-bar MAP as well as the standard CTS/IAT resistance curve.
Then I have the issue of possibly having to build a plate steel bracket to shift my ac comoressor outboard. Just looking at it, the throttle body, especially the TPS and the compressor look like they might try to occupy the same space. No AC is not an option here.
11-22-2019, 04:48 PM
