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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!
Hey guys, I'm new on here and finally just bought an Iroc- and I'm looking for some help. I used the search engine, and read through dozens of threads, but I still have some questions.
My car has the 350HO / 330HP Carb Crate Motor and Holley 650 from Jegs, and I'm wondering what I can do to it to squeeze out some more power without breaking the bank. I've read about the 355 option, but I'd like to know more about it, like what's involved, approx cost, and where I'd get started.
The previous owner told me he milled the heads, added roller rockers and a comp xe268 cam. It was dyno'd after the build at 281hp and 310 lb torque, which makes me think it was tuned for reliability. I plan on getting it dyno tuned in a couple weeks because she is running a bit rich, and I'm sure I can get some more ponies outta her just from that.
The car has a rebuilt T-5, so I'm not looking for anything crazy, because I want to keep its reliability, but I could definitely use some more power...
355 = take a wore-out 350 block and do the first maintenance to it (bore it out .030"). It's not about "power", it's just maintenance. The extra 5 CID is irrelevant. Since you have a new motor you don't need it so it's not really an option unless you're just made of money and are tired of lugging it all around or something and feel like you just GOTTA give some away in return for .... nothing.
Tuning is always good. Yerbasic outta-da-box Holley carb is NEVER right. Most often, they need smaller jets, a MUCH higher PV #, and the sec idle stop screw adjusted up so that the pri idle stop screw can be adjusted down. See the Holley Tuning sticky on the Carb board on this forum, no sense in me typing all that all over again. Of course, the improvement you get out of that, is limited by the person doing it. So since you have now read the sticky, you know ALOT more about tuning a Holley than about 95% of all dyno operators, and it's all stuff you can do yourself before you get to the dyno anyway, so go get started. May or may not make much more power but will SURELY be AHELLUVALOT more driveable and will use AHELLUVALOT less gas.
Best place to look for missing power after an engine swap usually is, the exhaust. What EXACTLY is on it now? (part #s only please, or at the very least, ACTUAL MEASURED SIZES of the pipes and stuff)
Last edited by sofakingdom; 02-06-2016 at 05:19 PM.
Thanks for the info/advice! The car has SLP Shorty Headers that Y-Pipe into a 3'' pipe and into an Edelbrock Muffler. I live in NJ so I welded on a 3'' in/out Flowmaster Catalytic Converter and I still failed emissions. I like how it sounded much better with it off, so I'm gonna take it off next week. Surprisingly, I noticed a tad loss of throttle response once I put it on and began driving it around- I also lost that hollowed out straight pipe sound, and my before and after video shows it quite well.
If those dyno #'s are at the wheel, that's not too shabby.Guessing 350 HP , at the crank.If that is at the crank, you do have problems.That combo is capable of know king on the door of 400 HP if close attention is paid to detail to tuning & exhaust.
GM crippled that motor with a .051" headgasket lowering compression to 9:1.There's some power to be had by swapping it out & getting the compression up some.Especially with that 268 cam.
Dynojet is a chassis dyno (rear wheel power).
355 is just a 350 bored .030". It only adds 5 cid and at best will only gain you 9 HP.
Like sofa said, it is done as a part of a rebuilt. As engines wear, the bores gets out of round, oval shaped some and by boring it out, you true up the cylinder bores again.
What it involves is a full tear down, removing every part from engine. Take the bare block to a machine shop and have it bored and honed. Then replace the pistons with new 4.030" pistons and rings.
$125-300 for the machine work
$200-400 for the new pistons and rings
$100 for a full gasket/seals set
Not something you do to gain power...
Setting the timing and timing curve can be worth as much as 30 HP. A recurve kit is $6 (springs and weights for the mech. advance in the dist.)
You want all your timing fully advanced by 3,000 rpm. and you want your total timing around 34*. So get you a dial back timing light, a pen and paper and go chart you timing curve at 500 rpm intervals from idle to 4000 rpm. With that info, you can then "recurve" the mech. advance to bring the timing in sooner and full in at 3,000 rpm. Then set your total timing.
Also tune your carb. Not just turn the screws, but do like sofa said. Get the jetting and PV set up right.
For basic street type engines with vortec heads, 375-400 hp is the common range and about all you will get out of it w/o a lot of effort.
Vortec heads are great but the do have limits. If you are wanting more power my opinion is... 1st get your timing curve and carb dialed in. Try to get compression up. You said the PO milled heads. Can you find out how much was milled off?
Then I would say from there it would be a head swap and cam swap if you wanted big gains
If those Dynojet numbers are SAE corrected, then your making just about EXACTLY the 330 hp advertised at the flywheel.
I wonder if the previous owner replaced the HO valvesprings when he did the XE cam. I see opportunity above 5000 rpm; looks like a valvetrain issue. could be spark scatter from worn distributor or other issues, but valve float/bounce is more likely.
And yes, as was already said, the overall tq/hp curves will benefit from fine-tuning timing and AFR.
That graph shows unmistakable valve train instability. Almost certainly, float.
It starts at 4500, just about the time it should be getting up "on the cam", and gets REALLY bad at 5000.
Your torque should be around 300 @ 5500 and 275 @ 6000, even without tuning; that is, if you had backed it off the rollers, changed the springs, and pulled it back on, no other changes, you should have seen about those #s. Which would put your HP at about 310 - 315 @ 5500 and about the same @ 6000, with the peak in between there somewhere maybe hitting 320.
But, don't get all hung up on the absolute # that the dyno gives you. We don't race dynos, and dynos are NEVER accurate. Rather, they're a tool you can use to measure the effect of changes; and most importantly, provide a torque vs RPM curve (HP is merely calculated from torque) that allows you to tune everything else, such as gearing, converter selection, shift points, etc.
Tuning tends to raise/lower the entire curve, as you dial in (or out) the timing and mixture around what the engine wants. The exception being, effects that vary with RPM, which tends to be, changes in mixture as the air flow through the carb changes with RPM. On that run, you should have paid for the addition of a wideband O2 sensor, which would have given you an idea of what your mixture was at all RPMs and therefore what direction to start in when tuning.
A typical "ideal" timing curve (while we say "every engine is different", yours isn't so different from anybody else's, it's a common and well-known combo) would be, around 15 - 18° at idle, increasing to around 33 - 34° at 2800 RPM (Vortec heads usually like a bit less timing than other chamber designs), with the centrifugal curve starting just off idle like maybe 1200 RPM and the other 16° or whatever "all in" by 2800. A stock distributor will have WAY too much centrifugal advance, usually around 24 - 28°, and so must be altered either by adding stops or by modifying the cam that the weights work against. Then for street use you should have vacuum advance on top of that, with around 15° added at high vacuum, and dropping fully out at about the same vacuum that the power valve opens (see the Holley Tuning sticky https://www.thirdgen.org/forums/carb...ey-tuning.html).
Oh and in case I forgot to mention, follow the Holey Tuning sticky, in order, skipping nothing, performing each step, in order, skipping none, starting at the beginning, skipping nothing, in order.
Wow Thank you guys so much for the advice!! Sofakingdom, that combo you listed is pretty reasonably priced and I'm thinking about going for it- what can I expect after it's installed?
Also, you guys say that dyno reads HP at the wheels? (that dyno is from the previous owner who had it done 13 years ago)
Would it be worth changing out the current exhaust set up and investing in a set of Long Tube Headers?
I've been reading about Carb Tuning all morning, and I'm torn between what to go with-
Given the new motor/carb set up has less than 30,000 miles on it, but was built almost 20 years ago, would it be wise to just get a Holley Fast Rebuild Kit? http://www.summitracing.com/parts/hly-37-1544
If it had that much valve float 13 yrs ago, then especially if it's been driven much in the interval since that dyno run, it's gotta be REAL bad now.
A 350 in street (pump gas) trim should do around 400 - 425 ft-lbs of torque at whatever RPM its peak torque occurs at. With that cam, that should be around 3600 - 3800 RPM, so that part looks about right. At the wheels, that should result in about 325 - 350 ft-lbs peak. So you're not missing that part of the equation by very much.
Your problem is the fall-off as the RPMs climb. It just CRATERS right where it oughtta be coming to life.
Couldn't say for sure about changing out the exhaust, those SLPs were some of the best headers around back in the day, but if they're the 1-5/8" size, might be a bit of a bottleneck. If they're 1¾" they're fine. Main thing there would then be, GET RID OF any part - ANY part - behind them, that's smaller than 3", as far as the muffler; and smaller than 2¼", behind that. A 3" cat, 3" I-pipe, 3" in muffler, and 2¼" or 2½" tailpipes, is enough for the rest of it.
Yes you should DEFINITELY rebuild the carb.
I wouldn't get either of those tuning kits. They go in the wrong direction from box-stock: you will most likely end up needing SMALLER jets and HIGHER PV, whereas those kits will give you LARGER jets and LOWER PVs. Might be perfect for a race car but BASS ACKWARDS for a street one.
Look up your carb list # here http://documents.holley.com/techlibr...al_listing.pdf and put it together EXACTLY like that says; those jets, those PVs, etc. Use the correct kit and set it up EXACTLY like it says, i.e. stock factory specs. That's your baseline.
If your carb is a 4160 (metering plate in the secondaries) change it to a 4150 (metering block w replaceable jets). Then follow the Holley Tuning sticky (I tell you what sizes of jets and PVs to equip yourself with) to tune it. You won't need squirters or any of the rest of that.
I'd suggest starting out with a NEW, GOOD QUALITY (not Accel or ebay chinesium crap) distributor, BEFORE getting serious about tuning the carb. Summit or Jegs brand might be OK, but find out who makes it and what it's built out of FIRST before laying out your $$$ on it. Get the Crane spring/weight kit & adj vac can for it, and set it up as both Night and I described above. Performance Distributors http://performancedistributors.com/p...reetstrip-dui/ would be THE BEST. If you get the DUI, call em and tell em how you want it set up, rather than buying it off the shelf, and save yourself some trouble.
With the parts I listed, you should be able to extract the full RPM range of the cam; should run to well over 6200 RPM without float. (which appears on your dyno run as the major wavy sections, which should be smooth and gently curved not all jagged, as well as the cliff plunge @ 5200 which looks like at that point everything starts just flying loosely around in space) I'd expect 400 - 425 ft-lbs @ 3800 RPM (you're not far off from that now) and 375 HP at the crank @ 5400 RPM (you're around 50 - 60 short of that now). Those numbers should result in around 325 HP and 350 ft-lbs at the wheels. It should get around 16 mpg around town and around 21 hwy after tuning. Clean, fresh, low-viscosity fluid in both the trans and rear end will uncork several HP; an electric fan instead of a clutch fan will provide SEVERAL more; and good attention to drive shaft angle, running gear (wheel bearings, alignment, brakes, etc.) will make a further improvement. Suspension work, especially LCARBs, will make a YUUUUUUUUJJJJE leap in the 60' times. The point of all those things being, just getting "lots of power" out of the motor, DOES NOT by itself, make a car fast.
Last edited by sofakingdom; 02-07-2016 at 12:35 PM.
Ok great, Thank you! I've matched up the Carb number and cropped the list for easy viewing. The carb is a 4150. I just put over $3500 into the car for maintenance and replacing OEM items. It is a G92 car, so it has the dual electric fan and an oil cooler. I plan on doing a bunch more chassis and suspension work, but I want to get the engine dialed in first, as I can feel it really has to have more potential than what it's putting down now.
Thanks for the distributor link, I will take your advice and go with that one. When you say to call and tell them how I want them to set it up, what exactly do you mean?
Also, which Carb kit(s) do you suggest going with? How about the Fast Rebuild kit?
(Sorry, I am totally new to this- my Jetting skills only go as far as working on my 2 Stroke ATV & Bike! Haha)
Just to re-cap: My First step should be ordering the Valve Springs, the Distributor Cap and a carb Fast kit?
Call DUI (maybe their web order function allows it too) and give em the curve Night & I described. Listen to what they have to say, as well; learn from those guys, Kelly (requiescat in pace) had been twisting up distributors since I knew him and had him do mine in the mid 70s, and his son and the employees have accumulated ALOT of experience in the last 40 yrs or so, as well. They might have a thing or 2 in the way of wisdom to offer.
The Holley Tuning sticky tells you how to pick what jets to order.
First steps would be, valve springs w hardware, complete distributor, full carb rebuild kit w restoration of all the metering parts to their stock values and adjustments. Next step would be, the Tuning sticky.
If those dyno #'s are at the wheel, that's not too shabby.Guessing 350 HP , at the crank.If that is at the crank, you do have problems.That combo is capable of know king on the door of 400 HP if close attention is paid to detail to tuning & exhaust.
GM crippled that motor with a .051" headgasket lowering compression to 9:1.There's some power to be had by swapping it out & getting the compression up some.Especially with that 268 cam.
The GM 330 HP 350 HO I had apart had .028" compressed factory vortec head gaskets.
Does anybody live in or near New Jersey and happens to be familiar with any Tuning shops? I've been in touch with Dave from EFX Tuning in Toms River for the past month, and I was going to head down there for a Dyno tune, but now I think I'm going to do the valve springs, performance distributor and try and jet it myself before heading down there... But, do you guys think it'd be a good idea to get a Dyno run graphed to see where I stand now before doing the work? (Given that it's been 13 years)
Also, Sofakingdom, those Valve Springs will be compatible with my Valves & Heads, right?
I was told that the Intake, Cam, Heads, & Carb don't really support upper RPM Power, and that it's doing what it should...
Is there a sticky or thread that you know of for providing some guidance for doing the Valve Springs?
Your tuning shop is in your driveway. All you need is the Holley Tuning sticky, and to ask questions if you don't understand what happens at some point.
Wouldn't "hurt" to run it on the dyno, but won't really "help" much either. You already have fairly clear guidance as to what's wrong with it; save your $175 for after you fix the stuff you already know is wrong with it. Best use you could make of the dyno is for tuning, which is not the same as just collecting a new graph. If you paid by the hour instead of by the run, and your cooling system etc. is up to the task, you could keep it strapped down and make carb & distributor changes, and optimize it. Otherwise, not much to be gained by generating another graph showing valve train float.
Yes those springs are compatible with your heads.
Your cam is one of the most popular ones used with those heads, well and widely known to be a good match, and giving the HP numbers I quoted at the crank. You're not getting its full potential.
Your carb is "small", but not "tiny". It might maybe be a limiting factor in a small way but not by much if at all. With proper tuning it should be OK. A list # would help clarify that.
Can't say about your intake; don't think I know what it is yet. Too dark in your garage for me to see it ATM.
I had the car in the shop for the past week to have a bunch of work done (nothing with the engine), and I wasn't passing NJ Emissions, so right before I came to pick her up, the guy decided to change the timing a bit to "clean it up." I believe he said it was set at 4º and he changed it to 6º then 8º, or vise versa- and wow, what a friggin' difference. The engine pulls stronger, runs much smoother, and it got rid of some vibrations (that could have been a factor of other things, but most of it's gone now, thank god).
When I bought the car, the seller took it to a shop and they put in NGK plugs right before I came to pick it up; and the mechanic I just brought it to scoffed at that and advised me to put in AC Delco's, as those two plugs are apples and oranges when it comes to Chevy motors. Well, I took his word for it and put in a set of AC Delco Double Platinum plugs, so maybe that has something to do with it too; but I have to say, either way I can really feel the difference now- The car really came alive
The old plugs were only in there for a couple weeks and they were really black; so she is running pretty rich. When I have some time this week, I'll start fishing around to see what's going on in there. I'll also take some pics of the engine bay and everything and post them on here tomorrow for the hell of it. Thanks again for the help guys!
So you see how timing can wake one up.. Your timing is still way to low for your combo. Like sofa said, at idle w/o vac advance hooked up, that engine will want 15-18* and I totally agree with him. 16* is where I have found the sweet spot to be on engines like yours.
But also that curve plays a major role in performance. Most dist. are setup where timing does not start advancing soon enough, and does not fully advance until way past any range you would be in while driving, even sprinted driving. I have seen some smogger 70's HEI not be full in until 5200 rpm.
There's nothing wrong with NGK plugs. All the crap you see on the Internet (or hear in the McDonalds parking lot on Fri night... same thing) is just that, CRAP.
ALL of the OEM grade plugs are pretty much equal as far as how they make your car run. All a spark plug is, is an insulated gap that electricity is forced to jump across. That's IT. Which is not to say "all spark plugs are equal", but rather, "all OEM-GRADE spark plug BRANDS are equal". That leaves out of course, "gimmick" plugs: if you don't see a plug type in any new car, it ISN'T "OEM grade". So, NGK plugs are OEM in numerous Japanese cars & motorcycles, as are Nippondenso; Bosch are common in German cars; AC/Delco, Motorcraft, Champion, are usually used in US cars. It defies logic, science, common sense, and all other arts of intelligence and knowledge, to claim that a product that works in Mercedes won't work in Chevrolet, or that works in Frod won't work in Honduh, or anything of the kind. Any of those are completely acceptable, if chosen properly: thread size and length, heat range, tip design, gap, etc., all of which are widely and easily available in the typical configurations for small block Chevy from all of those mfrs. Improperly chosen plugs of ANY brand won't work right of course; that is, just because a plug comes out of a box that says "AC/Delco" on it is no guarantee that it will work one whit better than any other box.
You keep saying "had" this that the other done, "shop", "the guy", and so forth. YA GOTTA STOP ALL THAT, and learn to DO IT YOURSELF. You are now the proud owner of AN ANTIQUE CAR, almost 30 yrs old, complete with HEAVILY MODIFIED ENGINE; there is NO WAY you're ever going to get it RIGHT if YOU don't get it right. Go to ANY antique car show or other event: except for the Vette and Porsche owners, ABSOLUTELY NOT ONE SINGLE ONE of those people pays somebody else to create their car for them. They DO IT THEMSELVES. This is not like those guys made out of cubic $$$ on some TV show that drop off their wreck at Chip Foose or something and pick it up $150,000 later; this is the hot-rodding hobby. We're trying to help give YOU the skill set to DO IT YOURSELF.
So, stop putting some "mechanic" 's kids through braces and college and keep the money for your own; and jump in there and learn to do this stuff. It's not hard at all, and is actually quite personally rewarding, to create something with your own hands that you can then be proud of its superiority. A much better feeling than that hollow sensation of emptying your bank account at "shop".
So: for the valve springs, you need the stuff I posted up there, and you might as well get a set of valve guide seals since they're super cheeeeeeep and you're already there (Fel-Pro SS72861). You'll need valve cover gaskets (Fel-Pro VS50088R), and a length of rope to stuff in each cyl (about a foot of about 3/8" nylon rope is perfect), and a valve spring compressor which you can "rent" for free at AutoZone and similar places. Acoupla hours later, you'll have the mechanical failure fixed and will be ready to start tuning. When you've got all that and are ready to start we'll walk you through it step by step.
Hey, I totally agree with you and that's why I'm here asking questions. I had dropped the car off right after I bought it because the Starter went and I don't have a garage to work on the car myself, so I wasn't about to get into that.
I know different plug manufactures don't make a world of a difference, because as with all the machines I've owned, I've used them all and not one has ever made much of a difference over another.
Thanks for the advice and information regarding the valve springs: it's something I'm definitely going to tackle, and I'm looking forward to it. If I had all the resources, the car would be apart under my wing right now; but unfortunately as a 28 year old guy, I'm not that well equipped due to my living situation. :/
Hey, take your situation with a grain of salt. Tuning a carb is minimal in space and tools! Take your time and read the stickies and manuals! You got this!
Some of the great hot rod and engine builders started on their street, a slab of concrete or even under a tree!
Some of the great hot rod and engine builders started on their street, a slab of concrete or even under a tree!
So true: and even some not-so-great ones. (speaking strictly for myself of course) I started out in an apartment parking lot, and when I grew up, graduated to one of those driveways that's 2 narrow strips of concrete for the tires with grass in the middle.
I don't have a garage to work on the car myself, so I wasn't about to get into that.
unfortunately as a 28 year old guy, I'm not that well equipped due to my living situation. :/
Don't think just cause you do not have a 4 wall, roof, slab building, you can't work on, restore, fix, build a car man.
For 13 years I built cars in my dirt/gravel yard. Built engines in a spare room in my house, even had a 60 gal. 220 volt air compressor in my living room later on.
Built a few 10 and 11 sec cars out in the yard, twin turbo system, even built race engines for other people out of that spare bedroom.
Replaced engines, transmissions, rear ends, done suspension, roll cage, exhaust, etc all in a yard, no building at all.
You just have to do things alittle diff. working outside. Have tarps to cover things up with. Sheet metal and wood to sit ramps and jack stands on to keep them from sinking in the ground. Plywood or osb to roll engine hoist on.
Non of us started out very equipped. The 1st car I really modded on my own was an '84 camaro when I was 17. I had 1 tool box (the kind you carry with 2 handles). I put a 5" autometer tach and speedo in that car. I didn't even have anything to cut the plastic gauge cluster out with. I used my buck pocket knife to do it.
You build up your tools over time.. For now and just starting out, buy only what you need, when you need it. For most basic stuff harbor freight is fine, it's cheap. For stuff like welders, air compressors, cordless tools I buy higher end because its a big ***** even for the HF brand and I know the ingersoll rand compressor will last for 30+ years and the Hobart welder will as well.
A lot of my tools have came from yard sales, flea markets, pawn shops, etc.
Like for example I have a Dewalt 18 volt cordless set up.
I have 6 batteries, 3 chargers, 3/8 angle drill, 1/2 drill, 2) 1/2 hammer drills, 4.5" angle grinder, jig saw, recep saw, 1/4 impact, flashlight, skill saw, 2 bags, some drill bits and screwdriver/socket bits... All bought at a pawn shop for $400
I took off the intake manifold today because my Emission readings were reading a vacuum leak, and not to my surprise, the gaskets were totally shot. I'm running an Edelbrock '7116' Intake Manifold and I noticed that it's blocking off the two water ports at the rear of the Heads.
This has to be why the engine keeps over heating and the temperature runs through the roof if I don't turn the electric fan on when sitting (I replaced the Thermostat today as well). I spoke to somebody at Jegs, and they said this is normal for that engine. But I find that hard to believe, because there's no way this thing could run that hot in the winter, and why not utilize the cooling bungs in the rear? So then I called Edelbrock and they suggested running their '75163' Intake Manifold as an alternative, but that would just be like replacing it with what I have now because it doesn't have any water ports for the rear either.
Keep in mind, I'm running Vortec Heads and the previous owner confirmed with me today that he did have them Milled .030
Can somebody please explain to me what's up with this?
it's blocking off the two water ports at the rear of the Heads
Virtually ALL intakes for SBC are built like that. Whether your motor is actually "overheating" or not, that's not the cause of it. Changing it won't have any effect on engine temp.
Most common causes of overheating are: running pure water in the cooling system instead of 60/40 (or thereabouts) mix; bad radiator cap (doesn't cause "overheating" but DOES cause SPEWING); and poor tuning, especially but not limited to, not enough ignition advance.
Your fan, assuming it's the stock cooling system, should come on at around 235°, cool the motor down to around 215°, and shut off; sitting there idling, it should be able to cycle like that until it runs out of gas.
"Vortec" and "milled" has nothing to do with any of it.
What is the ACTUAL engine temp, as measured by an ACTUAL measuring instrument? (NOT the trim package in the dash) What makes you think it's "overheating"? i.e. what is it ACTUALLY doing?
Well, the reason why I added that they were Vortec Heads is because hunting down the correct Gaskets to match that Intake for those Heads today wasn't easy, but I did find a set (Auto Trader & Pep Boys for instance stopped selling them, because they're "discontinued"). I also threw that in there for relation to our previous conversation because it was "new" information that I just found out about from the seller.
I haven't measured it with an instrument, but going by the dash, normal operating temp when running is 160, and when it's sitting at idle, it climbs steadily up to 260+ within a matter of minutes. My electric fan switch is manual, and the evening I bought the car, I forgot to switch it on as the car was warming up, and the pressure popped the coolant overflow reservoir cap right off with steam smoking out like a gun and coolant spewing out.
Since then, I flushed the coolant and it still acts up the same way, but it doesn't climb as quickly. Once I start driving, or switch on the fans, the temp drops back down pretty quickly now.
Would there be any performance benefits from upgrading to the new style Edelbrock Intake Manifold (75163)?
Not really; the one you have is the Performer RPM, and the other is the Air Gap. About the only difference is, the carb and runners are somewhat isolated from the "base". A tiny improvement perhaps, if you NEVER drive the car in cold weather (which of course in NJ you don't have any of, so maybe that's an option) but FAR LESS than you will get from getting the valve train to stabilize, or from tuning.
Not sure about "discontinued"... you just need gaskets for a 96 - 2000 Chevy truck. Should be pretty common in the world at large. http://www.autozone.com/gaskets/inta...ers-r-5-7l-sfi for example. All you need is the "lower"; the "upper", or "plenum", is for a part the stock truck has but your setup doesn't have. Alternatively you could order them, for example http://www.summitracing.com/parts/fel-1255
Sounds like it would be wise to IMMEDIATELY put the electric fan system back like it belongs. For example http://www.autozone.com/cooling-heat...estid=13801306 The mind boggles trying to figure out how people EVER think it's A Good Idea to make their fan "manual"; all it takes is forgetting ONE time to turn it on, and you get INSTANT DISASTER. You can easily improve on whatever hack job you inherited.
when replacing intake gaskets on the vortec heads, ensure to get a set with the metal inserts around the intake bolts. I got a set of VR from AZ for around $29.
Follow the proper torque requirements for the intake bolts. Those heads require less torque than a standard SBC head.
The above is required to prevent gasket crush at the front water ports which can allow coolant to seep into the forward cylinders. Pretty common issue on the truck boards.
Haha yea man, I kept thinking why anybody would install a manual switch as opposed to an automatic one! What else will I need to convert the electric fan to an automatic? Thanks for all the links, you've been a great help bud...
Do any of you guys have any experience in the Holley Quick Change Kit?
Yes.
Does it really make changing the main jets much easier?
Maybe a little.
Would it be worth doing?
Compared to spraying silicone lube on the blue gaskets and smearing wheel bearing grease on the transfer tube O-rings? Not really.
With luck, your fan relay is still in place, and the wiring isn't too hacked up. If any of the above is beyond resuscitation, you can get a Hayden or the like aftermarket relay, and it'll do the same thing. The switch SHOULD just operate the relay, and then the relay should do the grunt work of handling the big current that the fan motor draws.
For vortec heads, I always use fel pro MS98000T intake gaskets. Only ones I had any good luck with.
You mill the heads to reduce the chamber volume, therefor increase compression. Vortecs are advertised as 64cc heads stock but ever set I have CC'ed has came up as 62 to 63 cc. Try to find out from the PO how much was milled off the heads. 0.008" = 1 cc
Sorry guys, I've been away... To answer your previous questions, I was told the Heads were Milled .030"
So, I fixed the intake leak and for whatever reason, the engine feels like it lost a lot of power, and the throttle isn't nearly as snappy anymore. Could this be because the intake was taking in so much air, that the engine was running much leaner, and now with the new gaskets, it's not?
I started taking the carb apart last night, and all of the gaskets are totally shot out. So far, it seems that the jetting has never been changed, and they're the same main jets that came from Holley- 67 Primary and 73 Secondary.
I printed out the Tuning guide from Holley's website, so I've been reading through that, as well as other Tuning articles for 4150 Holley Carbs, and of course the sticky here.
How many sizes down should I try starting out with? What other jets / areas of the carb am I paying close attention to?
Probably has nothing at all to do with leaks. More likely, its because the ignition timing is severely retarded from wherever it was.
Advance it some. See what happens.
How many sizes down should I try starting out with?
Answer:
buy some that are 2 sizes, 4 sizes, 5 sizes, and 6 sizes smaller; and 2 sizes larger.
What other ... areas of the carb am I paying close attention to?
Answer:
a MUCH higher number power valve.... probably a 105 or a 125
Then, you'll be paying a great deal of attention to the transition slot, which you will be targeting at an exposed height of .030" - .050". You will probably be accomplishing this by opening the secondary throttles with the throttle stop screw, as detailed in intimate detail in the sticky.
I'd suggest not paying too much attention to the instructions Holley gives. They haven't helped anybody else much, probably won't do much for you either.
Wondering I have an 88 IROC. Curious how much power they can handle with just an engine swap. Without changing drivetrain for a good ride with a bit of get up.
So liva, did it turn out that anything else had been done to the carb? (power valve blowout protection for example... although being new-ish, might have come with it) What list # is it?
I should have mentioned above, the secondary jets RARELY need much work in a street setup. They're generally "close enough". However, there is often some improvement available in the choice of secondary diaphragm spring, which is what controls when and how fast they open in response to flow through the primaries. Most often it's too weeeeek, shich makes them open too soon and too fast, which makes the car stumble if you mat it from a stop. Working right, the carb should control itself smoothly and automatically and above all CONSISTENTLY, like a properly setup automatic transmission should. But, you'll get to that later; they don't have a chance if the primaries aren't right. Get the valve springs done and the distributor curve right and the primaries dialed in, then after all that and only after, it'll be time to tweeeek on the secondaries.
02-06-2016, 04:23 PM
