When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
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!
Hey guys! So I am finally getting the rest of my 383 build together. I have crunched the numbers but I want to make sure the numbers I have come up with are as accurate as possible.
It will be a 350 Vortec block with the stock bore, 3.75" scat crank, 6" rods, and Keith Black claimer hyper pistons with 5cc of valve relief. Block will be decked to achieve a zero deck height and will run 0.038" compressed head gasket.
4.00 bore
3.75 stroke
6.00 rod
0.00 deck height
4.100 x 0.038" compressed head gasket
64cc Etec 170 Vortec chamber
+5cc valve reliefs
I am coming up with 11.003:1 compression.
With the Lunati 276/300 advertised, 224/236 @ .050 bootlegger cam cut on a 108* LSA, 104* ICL I am calculating a Intake Closing of 66*. I could not find the cam timing anywhere on this.
276/2 = 138-108 = 30
276-180 = 96 -30 = 66
I am getting 8.7:1 DCR. I plan to run this on E85.
I get an IVC of 62° using my calculator.
Of note is the cam itself. Is that a blower or nitrous grind? That's a lot of exhaust duration compared to the intake. 24° where the typical split on a dual pattern cam is 6-8°. Just wondering.
That said, with the IVC as mentioned, your DCR is closer to 9:1.
I think to verify, you need to get the cam card.
I get 62 deg close since its in at 104 icl. 8.96 dcr
I see my error, I used LSA instead of ICL in my calculation. I am a bit rusty when it comes to calculating this stuff. Thanks for the replies and correction.
The cam is designed similar to the Comp Thumper cams. The intake side of the Etecs breathe better than the exhaust side will, especially through a full exhaust system so IMO should be a decent match.
Off topic but do you think the 170cc intake port will support 383 CID? I've seen box stock 170cc Vortecs delivering about 450 HP on 350 dyno engines at 6200 RPM (sealed circle track stuff). But the added 30 cubes? Unless your building an engine with plenty of low RPM torque and forgo higher RPM HP. Again, just wondering.
Off topic but do you think the 170cc intake port will support 383 CID? I've seen box stock 170cc Vortecs delivering about 450 HP on 350 dyno engines at 6200 RPM (sealed circle track stuff). But the added 30 cubes? Unless your building an engine with plenty of low RPM torque and forgo higher RPM HP. Again, just wondering.
A given head tends to produce roughly the same hp regardless of displacement; it will just happen ~500 rpm lower in this case. And that may be exactly his plan.....with hyper pistons and (assuming) a cast crank, not wanting to spin it very high. I for one would not trust any cast aftermarket crank over 6000 rpm. Better to build for torque in that case. The high rpm harmonics is what kills the aftermarket cast cranks.
A given head tends to produce roughly the same hp regardless of displacement; it will just happen ~500 rpm lower in this case. And that may be exactly his plan.....with hyper pistons and (assuming) a cast crank, not wanting to spin it very high. I for one would not trust any cast aftermarket crank over 6000 rpm. Better to build for torque in that case. The high rpm harmonics is what kills the aftermarket cast cranks.
Exactly! This is intended to be a grunt engine. Will be topped off with an edelbrock vortec TPI base, siamessed SLP runners, ported TPI plenum and have tri-y headers. Backed to a 4L80E with a ~2,600 rpm converter and 4.56 gears in a 1997 Express van.
A given head tends to produce roughly the same hp regardless of displacement; it will just happen ~500 rpm lower in this case.
Hence my comment about forgoing high RPM HP.
We've found that 276 intake duration and a 350 Vortec makes peak HP around 5700 RPM. Take 500 off of that and you can see where I was going.
Hence my comment about forgoing high RPM HP.
We've found that 276 intake duration and a 350 Vortec makes peak HP around 5700 RPM. Take 500 off of that and you can see where I was going.
I THOUGHT so!
Yep, I do not even care if the thing turns 5,500+ RPM, so long as it makes a TPI like torque curve in the 2,500-4,500 rpm range. With 4.56 gears it turns right at 3,000 rpm @ 80 mph in OD.
Something noteworthy perhaps and that's the amount of overlap this cam has. With the 107° LSA (and assuming symmetrical lobes), overlap comes in at 72°. As a comparison, the XR276HR has 59° and the XR288HR, 71° both on a 110° LSA. I can manage about 10" of idle vacuum with 30° a spark advance and a 875 RPM idle speed (with the 288).
Won't this complicate things in the tuning department seeing as it will be built using a TPI arrangement?
As far as the symmetrical lobes go, I think the Thumpr series of cams has an asymmetrical lobe profile but I haven't worked out the math via the cam card.
Something noteworthy perhaps and that's the amount of overlap this cam has. With the 107° LSA (and assuming symmetrical lobes), overlap comes in at 72°. As a comparison, the XR276HR has 59° and the XR288HR, 71° both on a 110° LSA. I can manage about 10" of idle vacuum with 30° a spark advance and a 875 RPM idle speed (with the 288).
Won't this complicate things in the tuning department seeing as it will be built using a TPI arrangement?
As far as the symmetrical lobes go, I think the Thumpr series of cams has an asymmetrical lobe profile but I haven't worked out the math via the cam card.
I run a Blue/Green connector 1meg PCM for a 2006 DBC Express van and the EFI connection 24x coil per cylinder ignition with the D585 LS truck coils.
I am hoping the overlap can really help the TPI intake and Tri-Y headers work well to scavenge the engine and boost the VE in its operating RPM range. Idle vacuum is not super important to me since the only thing vacuum operated is the HVAC controls and it has a large vacuum canister for that. The Express van has hydroboost. It can idle 850-900 rpm for all I care with the looser than stock converter it practically stands still when you let off the brake at 750 rpm now.
Why the short rear gear? Do you intend to tow a house with this thing?
Its ironic you say that because I do tow a house on wheels behind this. 23' Jayco that is 28' from hitch to rear bumper, 11' tall, 8' wide with a single slide that weighs 6,000 lbs. So it is moving roughly 12,000 lbs. The tires are 31" tall and the 4L85E only has a 2.48 1st and 1.48 2nd. I tow down the highway in OD with the converter locked up on the flats and drop to 3rd on long inclines.
You will probably have the coolest 2006 DBC Express van on the planet.
Its actually a 1997 it just got updated to the 2006 electronics about a year ago from the 0411 PCM I upgraded to back in like 2012. I moved to the newer electronics so that the flex fuel stuff would be easier to run along with the improvements in coding GM had done on that PCM.
My other possible choice was to use the LQ9 6.0L shortblock and a set of LS3 heads along with a 6.2 Escalade intake and a cam made for that combination.
I think I am sticking with the traditional smallblock though because I already have doug thorley tri-y headers and numerous other performance parts for that setup like underdrive pulleys, roller rockers, etc. The torque curve of the 1st generation smallblock better matches my needs than the LS would. The LS also fits so tightly that you could not do maintainence things like pull a valve cover or oil pan without pulling the engine.
When it was built it was a pretty cool van for being built in 1996. It had LCD screens in the back of the front seats, a TV, VCP, rear radio and the rear of the van is wired for a game system and audio headphones along with the rear speakers wired to the TV through a switch. Rear lighting that is like a limo and alot of finished wood inside. Its great for camping especially after adding the diesel battery tray on the frame and adding a 12v deep cycle battery and battery isolator relay along with a 200a AD244 alternator. I also added a heavy gauge forklift battery connector on the back bumper to charge the dual 6v golf cart batteries I have on the nose of the travel trailer. In the cooler months I can stay off-grid for days at a time.
Its great for camping especially after adding the diesel battery tray on the frame and adding a 12v deep cycle battery and battery isolator relay along with a 200a AD244 alternator. I also added a heavy gauge forklift battery connector on the back bumper to charge the dual 6v golf cart batteries I have on the nose of the travel trailer. In the cooler months I can stay off-grid for days at a time.
Sounds the perfect application for a power inverter. I have a 4500 watt unit (relatively small) that I use in place of a generator when doing off-line electrical work (or the occasional power outage as the case may be). It allows the use of my 120 volt equipment (and recharging my phone and laptop easily). I prefer it as it's completely silent and there's no fuel or maintenance otherwise.
And it IS a cool van. I like the hot rod part of it especially.
Sounds the perfect application for a power inverter. I have a 4500 watt unit (relatively small) that I use in place of a generator when doing off-line electrical work (or the occasional power outage as the case may be). It allows the use of my 120 volt equipment (and recharging my phone and laptop easily). I prefer it as it's completely silent and there's no fuel or maintenance otherwise.
And it IS a cool van. I like the hot rod part of it especially.
The van has a 3000 watt hardwired inverter under the rear sofa bed and is wired with 3 outlets inside.
The trailer has a 400 watt solar system and 5000 watt hardwired inverter on an automatic transfer switch. I can watch TV, run the 900w microwave and a few other things and the battery stays pretty charged on sunny days. The furnace has a 12v fan and runs on propane. The refrigerator runs on propane and I have a stove, oven, and water heater that are all fired on propane. With 60 lbs of propane it has lasted me 2-3 weeks in the dead of winter staying in it continuously when I was remodeling the house I was in.
10-02-2017, 11:30 AM
