Archaea

Alright guys. I've heard from several different forums this IS the place to be for TPI questions!!! I just wanted your opinions on a 383 strocker build I'm considering for my c4 vette.

here's the info from a shop I'm interested in using in Houston Texas called PrecisionEngine.com

www.precisionengine.com

He claims he can build me a 383 strocker for my 1990 L98 vette using my stock aluminum 113' heads(I'd ship them out to him, he'd port them and install a new valve train as described below) He'd then ship me back a complete long block using my heads and his own block with the specs below. It would bolt up to my TPI intake. It would have a 1 year unlimited mile warranty.

He said I could expect about 350HP crank with this setup using my Stock TPI intake. He said the computer would run fine with it and I wouldn't need to change my fuel system. He said this should be a drop in job, and everything should work fine without any other modifications. What do you guys think about this deal?
I looked the shop up in the Better Business Bureau in Houston, he's rated satisfactory.

Looking at the specs below are there any other changes that should be made? Any part swap out recommendations? What do you think of the deal?



SPECIFICATION SHEET


Jonathan,

Thank you for contacting PrecisionEngine.com.

Please review the following quote and specifications to your custom-built 383/350HP SS performance longblock:

 GM 5.7 block bored, honed, decked and align honed
 Durabond cam bearings
 Performance roller camshaft: - (TRW –Speed Pro Camshaft)
o 224/232 @ .050
o .501 lift
o 112 lobe center
 Matching roller lifters and springs
 New sir steel rods 5.7”
 New cast steel 3.75” stroke
 Crankshaft micro-polished less than a 12 ra finish- (Eagle or Adept)
 Speedpro pistons with Molly rings
o 9.2 to 1 compression ratio
 Balanced rotating assembly
 New Melling timing set
 New high volume oil pump
 New gasket set
 New push rods
 New head bolts
 Customer’s aluminum cylinder heads will include the 2.02/1.60 valves
 120 lbs. springs
 3 angle seats
 Bronze guides
 Positive seals
 1.6 roller tip stamped rockers
 Ported intake runners


Total price: $ 2795.00 plus shipping (he said shipping would be about 200 bucks)

So I'd be out $50 or whatever it cost to ship my heads to Houston, then I'd get back in three weeks time a 383 longblock as shown above. I gotta tell you, this price seems good, and the amount of work on my end is comfortable

DENN_SHAH

iTrader: (1)

being about a vette, this will probably be locked or deleted soon, this is after all, a thirdgen camaro/firebird site.

a stock TPI intake is not a good choice for that motor.
it will fall on its face around 4500 RPM.
if you really want to stay with a TPI type intake, look at http//firstinjections.com
other wise i would think about using one of the other intakes.
there is a guy on here who can convert a LT1 intake to work on a L98 motor, a search for "LT1 intake" should turn up some info on it.

with no changes to the fuel system, it may run ok, but it will never run right.
if it was mine, at a minimum i would go with a set of #24 injectors, a AFPR & exhaust.
also, with the stock chip it will never run as good as it should.
don't use one of the aftermarket chips, they are for the most part junk.
learn to burn your own. to learn more about it, look under the DYI PROM part of the boards here & read the stickies at the top.
you can get a much better chip by doing it yourself & probably for less than what you would spend on an aftermarket chip. plus any time you make a change to your motor, you can easily make a change to your chip.

as far as that motor goes, someone else will have to let you know if its a good deal/setup or not.

TCH

It is not about a Vette but about a L98 TPI engine. And in any case if somebody comes in and says "I got TPI engine in my Yogo, can I ask something about my engine?" and you say "no this is a 3rd gen site!" - IMO that would seem silly.

But one comment to Archaea: your car is a -90. It is a speed density system and will not run ok without new chip after stroking, porting and new cam. So, new chip made specially to your engine is a must.

Archaea

thanks for the replies guys!

If I have to get a tune that's fine. I know how to tune using an AFC with an obd2 car, but I've not done any tuning with an obd1. What laptop scanner setup is most liked around here?

I've seen the website LT1 Intake - LT1intake.com - is that what you are referring to? I asked this vendor about that. He said yes it would be possible, but at that point in upgrading the intake I would have to do the fuel pressure, injectors, and computer upgrades and might have difficulty getting it to run straight. He thought with the TPI intake setup I should be fine.

I should tell you what I have now. The vettes got 410 gears, headman elite headers, dual exhaust using 2.25 pipe to flowmaster mufflers. Cats and resonators are eliminated. It has some sort of aftermarket computer that I don't know about - it was in the car when I bought it. I'm really looking for practicality here and a hand's off motor, (occassional things I don't mind - but I don't want it to be a constant "tuner" motor) That's one of the reasons I thought I don't want to go carbed. I might consider the intake in the future, but if the car will truly make about 350HP and 420TRQ which is the quote - that should be plenty for a good while and I can upgrade from there if I have the itch to a different intake and automatically gain 50 or 60 WHP with the various adjustments needed. I was thinking rather than adjusting to the lt1intake which makes you lose torque (which is why these cars are fun) I might just get a 75 or 100 shot if I get the urge to upgrade and get a bit more HP on demand there without effecting tuning/driveability.

TCH

You can only do datalogging with OBDI, actual tuning and prom burning is done by other means. So, different system to OBDII. Visit the DIY PROM section if wish to study how it can be done by yourself. However, I recommend you ask a pro to do it so you don't have to rebuild the engine right away.

GOY

That setup seems much more well suited for a superram than either the FirstInjections unit or the LT1 manifold. The firstinejctions unit still has runners that are too long (despite their diameter), and I don't think that's enough cam to really make the LT1 intake worth it in terms of peak horsepower vs. the lose of peak torque that would occur with swapping it.

Either way, the stock TPI is completely inadequate for that displacement/cam.

TCH

Oh, I just noticed that you said your car has some aftermarket ECM that you know nothing about? Scrap all my advice. You need learn everything about that computer and whether you car is now a MAF or MAP car, is it at all connected to the OBDI or can any of the popular software be used with it etc. Only after researching the computer in question you can know what you need to do for the chip to make it work.

Archaea

I know what you are saying on the LT1 intake swap - I've read the same thing - give up torque to gain HP and so I might be looking at a cam swap as well should I ever decide to go to a new intake. But I've done a couple of cam jobs before on another car I own and I think I could handle that if the need arises. But suppose I don't go to a new intake, and just drive the car as it is. 350HP and 420 trq are what this vendor states should be about the crank numbers I'd see......may be small for a 383, BUT that's pretty strong for a c4 and right before the level of HP/trq that starts causing additional breakdowns/problems. The transmission is rated to 450ft/lbs, but the stock clutch is rated at 350HP. I recently just replaced the stock clutch with a stage two SPEC clutch rated at 450ft/lbs. So if his 420ft/lbs of torque is accurate I'm getting into the other failure areas.
I know there are several guys on teh corvette forums that have a 383 strocker running under a TPI intake. Correct me if you disagree, but Trq is as good as HP in a car that launches well for stop light to stop light driving. And even at that 350HP is no slouch, that's what the c5's had - 350hp and 350trq stock meaning that I prolly would have a mid/low 13's in the quarter and still have a fun car to drive........

Knowing that I'm not needing to be the BEST car on the block or at the track but just want to have a powerful fun toy without a lot of headaches....

Do you think for my purposes the TPI intake is still completely inadequate? What kind of HP/trq do you expect from you knowledge in reading about these things? Do note that he would be porting the heads, and providing larger ported intake runners.

Guest

Whats he planning on getting flow wise out of the heads? Thats bottleneck #1. Bottleneck #2 is the TPI itself. Then there's that cam...

Will you get 350HP at the crank out of that combo? Yes its quite possible.
Will you need to tune the computer? Oh yea, without a doubt. Running a stock chip with that cam is not a good idea. At all.
Will porting stock runners help? Seriously doubtful. There's little porting to be done and gains will be minimal.

My advice?
Forget that cam with what else you have. Its too big duration wise. It'll get you to the power level you want, but you wont be happy with it. If you were to do some other things it might be ok, but not with your plan as it sits it isnt.
Compression ratio is WAY too low. Those heads will support over 10:1 easy, with that particular cam you can run 10.5-11:1 on pump gas with no issues. Makes me wonder about the recommendations in general.
Look at spending some money on the intake. You can do what you want with a stock TPI, dont get me wrong, but talking about a stroker with a fairly decent size cam and stock TPI just doesnt mix. At the very least I'd look into getting the intake base replaced with an aftermarket base like the Edelbrock/Accel and port match it and clean up the casting a little.
Have the car tuned, its just not going to run right otherwise.

Just FYI I was running a 350 with a basically identical cam (so close you'd never know the difference) and a stock TPI and thats where my is coming from. The RPM range of that cam is way past where TPI wants to run. I ended up cutting up my base (do a search, siamese TPI) and then it allowed the engine to run more in the RPM range it needed to with the cam in there. I've since changed numerous parts and now I have a slightly bigger Comp XFI cam (280XFI) and honestly its less tempermental than the previous 224/232 cam. The added cubes of that 383 will help, but I'd find another cam. Seriously. The heads and intake arent a favorable match to that cam unless the heads are ported to flow really well and the intake replaced with something to feed it.

Another thought, forget about the massive torque idea. First, you are running 4.10's. Second, you have a relatively light car. Third, you're running a TPI. Fourth, you're going to run a 383. So... you'll have plenty of torque from the extra cubes, let alone the TPI. Aside of that, the gear doesnt fit the engine and your plan, a lower gear like a 3.2x would make more sense with a torque monster 383 TPI. That and with a vette, its not really necessary to have a bunch of low RPM torque, its just going to go up in smoke and isnt needed to get the car moving. Also it seems like every time I try to kill off some torque, I fail and end up with even worse problems so I'd put worrying about adequate torque real low on the list. It'll have plenty. I think you need to line out your plan better, or maybe go with the cookie cutter Accel/Lingenfelter 219 cam/Superram intake and make sure the heads are really flowing well and leave the rest and you'll be pleasantly surprised.

1991CamaroRslow

iTrader: (3)

I would have to say that if you're wanting to keep your current combo go with the LT1 intake, and a cam with slightly more lift and you'll be happy. If you choose to keep the TPI setup then change your rear gears down to 3.23, 3.42, or even 2.73s; or go with a fully siamesed plenum, set of runners, and possibly intake. This will allow the car to pull longer at its torque peak, and extend the RPM range. You'll literally be out of 1st gear before you get to WOT with the combo you're talking about (383 + TPI + 4.10 + vette = insane wheel spin). I love the long tube runner setups and I myself would be keeping the TPI and going with some fully siamesed intake runners (basically cutting your runner length in half and giving you some more plenum area). Do a search on here and you can find alot of guys who have actaully siamesed into there lower intake, this would be another option you may look into. Now as for your car running with the combo, it probably would run but it would be nowhere neer optimal. You'll definetly need to add some fuel and timing, beyond what you'll want to do with a fuel pressure regulator and turn of the distributor, get that guy together then tune the prom in. Good luck on your build.

GOY

ROFL - we should just take a step back for a second and read this....

NONE OF US AGREE ON ANYTHING, LOL. Poor guy. Talk about confusing.

This guy has a price quote: so let's just assume the short block is what it is, period.

Here's my view on it. We aren't talking about a high RPM, high compression motor, high displacement small block that the LT1 intake would be suited for.

That cam, displacement and compression is perfect for the SR. For the L98 - some 33 cubic inches smaller - a 218/218 cam is recommend. He's not that far off the beating path for an engine that much larger. That compression is very pump gas friendly, and great for an engine that's not going to turn over 6k, nor should an engine with a cast crank in my opinion.

However, that cam *IS* too big for the long runners of the F.I. unit, despite their diameter. The diameter doesn't affect the pulse wave timing or "Tuning" of the intake - runner length and valve timing do.

Man, good luck guy, lol.

Abubaca

iTrader: (3)

Lot's of good advice in this thread already.

First of all, I think 350hp is very possible. Much more is there with a intake swap, but if it's what you want, I think you're OK. I personally love the TPI, and plan on doing something similar to what you're talking about.

WWWWAAAAAYYYYY to deep of a gear. I'm thinking maybe 3.23 or 3.42 with all that torque and light weight of the vette.

I agree with the mismatched cam idea too. I like the LPE 219 cam for what you're thinking. Way too much duration with what your guy is suggesting, but you could certainly add a smidgen of lift.

...and I might look into an aftermarket base, or at LEAST a ported OE base. Home porting the OE base is a freebie, and a GUARANTEED gain with what you're planning.

You'll need more fuel. Someone mentioned 24 pounders. I can't tell you exactly what you'll need, but the 22 pounders won't cut it.

...and you'll need a tune, no doubt. Learning to tune yourself is a GREAT idea, but I understand if that's a little too much for some. I don't know "tuning" yet, but I'd like to learn. Some people don't have the time. There's plenty of shops that specialize in tuning GMs. Just look around a little.

I've found that in this hobby, there's a lot of REALLY good people who just don't know everything. Sounds like your guy knows motors, but not necessarily TPIs. He knows that his combo will make good numbers, but the TPI may restrict power, which is why he's only saying 350hp out of a 383. What he doesn't know is exactly how the TPI bahaves, which is why his cam recommendation isn't quite spot on. My 2 cents is that you should take him up on his offer, with a little input from the Thirdgen.Org crew!!! Make sure the cam is better suited for the TPI. Also, decide if want to change the intake or the gear. I think one of 'em has gotta go!

Guest

The cam, heads, and compression are a complete mismatch. Large duration cams can handle and need more compression. Also he has aluminum heads. 9.2:1 would be good for adding boost, not for a NA setup. Even stock with iron heads has more compression than that. If you only had one change you could make, get the compression ratio up. A bunch.

Camarosyc427

hey i know you've got alot of people saying lots of different things but heres my approach.

My cousins got a 89 iroc w/L98 with aluminum heads(ZZ4) and a stock cam with 1.6 scorpion rockers. all that pulls threw a LT1 intake done by me/him with a BBK 52mm throttle body. it will run 13.5's all day on street tires. with the TPI the tires blew up in smoke in first gear no traction what so ever. then the motor would really die off after 4300 rpm with the stock rockers and about 4600 rpm with the full roller rockers. the car now doesn't hook in second cause the midrange power/torque is amazing. and this car also has 3.43's. that car makes 282hp@5100rpm at the wheels which is about 310 at the crank. with a cam he could hit probly 320 at the wheels with the right tune. hes also got a JET chip in it now but where taking it out this winter when we build the 383 which will have everything this motor has except for a new cam and chip. your compression probly should be around 9.5:1 minimum for that setup for pump gas

If u need someone to build u a LT1 intake i will do one for you just let me know

DENN_SHAH

iTrader: (1)

TCH, true it is about a L98, but he said its in a vette, i have seen questions like this get locked for that reason, why not let him know why before hand if it does happen? and after all, i did go on to try & answer some of his questions.


Archaea like has been said, 4.10 gears with TPI will be way too deep, first gear will be useless.
i think you would need a good set of slicks to have any hope of getting off the line with a decent 60 foot time.
4.10s with a stock TPI i believe will only slow you down, too much down low, not enough up high. i think with 4.10s, it would be a little too much fun down low.

if you don't at least port & gasket match the base, get some aftermarket runners & match the plenum to the runners, you'll be missing out some power.

pull your ECM & look for a brand name on it. if it really is one of the aftermarket ECMs, you can ask about it here, https://www.thirdgen.org/forums/dfi-ecm

Archaea, i forgot to mention, welcome to the best DYI automotive boards on the net.

89Nighthawk

All other things aside it looks like a good combo for what you want. However, you need more compression. For an aluminum head without thermal barrier coating you want to bump up compression by a full point to compensate for their heat transfer properties compared to iron. So put another way, would you put the engine together with iron heads at 8.2:1 compression? Because basically that is what you are doing using aluminum heads at 9.2:1. Get what you want be happy with it. It's easy to upgrade the runners if you want to later, but you definitely need to bump up the compression, it makes the engine more efficient as well as making more power.

And I agree part of the TPI attraction is the torque and that is FUN!!!!!! And belive me I have LOTS of fun every time I drive mine.

Archaea

Guy's thanks a LOT for all the advice! I'm soaking up as much of this info as I can!

Archaea

Alright Guys...I actually directed the vendor here and to the other thread I created on the board and asked him to read through this stuff. He got back to me a couple days later and said he didn't agree with everything he read, but that he understood that perhaps he should make the compression higher, and the duration on the cam a bit shorter.

He said he wouldn't want to go to a 10.5.1 compression because he felt that was too high for a troublefree engine and someone (like me) who lacks knowledge required to keep an engine like that running optimally. Which I don't take as an insult. I think the guy is genuinely concerened about my exp. with his product, and wants to make sure I have an engine that is as reliable as it is fun.

The changes he said he was going to make after taking these recommendations into account were:

Change the compression to 10:1.
Use a CS1080R roller cam with a 210/215@50 110 lobe center and 470 lift. He said this cam should better compliment the intake and makes good power from 1500-5000RPM.

He said I could pay 200 extra and get 1.6 roller rockers instead of stamped tip.

He was already going to port the heads for me, but said if I wanted to send him the lower intake he would match port that for me as well for free and if I sent him the upper intake he would be able to maybe minimally help me out there because he said there isn't much to port on the upper intake.

The total price shipped with the roller tip rockers and other changes discussed above was going to be about $3200 shipped.


Do you guys feel these are appropriate changes?

Guest

Sounds a lot better to me.

RednGold86Z

iTrader: (1)

Go to a 214/22x cam or 218/22x in a 383.

Gunner823

iTrader: (2)

well, now I'm worried. I was going to go with a crate 383/vortec heads that comes with an even larger duration camshaft, 234/244 @.050 and .487/508 exhaust, 112 lobe non-roller. 9.5:1, iron heads. I have a polished HSR I won off ebay, but was considering selling it and sticking with TPI due to hood clearance. Would both HSR and TPI be wrong for that cam too?

Camarosyc427

the HSR would be much better than the TPI. well think of it this way the static compression ratio is 9.5:1 but thats static the chamber is not sealed the whole time the piston is moving up and down the bore cause of valve overlap. the larger the cam the more overlap wich means less actual compression. with a cam that size it would be best probly around 10.5:1 which would get u an actualy ratio around 9.7-10:1. thats regardless of wether it's aluminum or iron

Camarosyc427

don't do the 1.6 RR's go with the 1.5 RR's, the cam u spec'd would be about the same as the cam before it with 1.6's. here think of it this way

Valve lift with 1.5's: .470 in
Valve lift with 1.6's: .501 in

the duration will also change

Abubaca

iTrader: (3)

I'm not a huge fan of that new cam he picked. First off, the 110 centerline for a daily driver? Not saying it can't work, but there are TONS of 112 cams being used for big inch hi perf small blocks.

Second, the duration seems good. We could nit pick it to death, but keeping a TPI from going toooo far over 220 is a good starting point.

I do think there's a LOT more lift to be had. 470 just seems too low. The Lingenfelter 219 is a PROVEN winner in 383/superram set-ups. I'm curious how it'd do in a TPI combo. I've been here on TGO for YEARS making little mental notes about what cam characteristics worked well for the TPI. Unfortunately most aren't on big inch small blocks. Like the 305 faithfull, we TPI guys start off knowing darn well there's more power with other intakes, yet some how we keep moving forward!

Keep in mind that TPI will drop off sooner in a 383 than a standard 350. More need for air means the TPI shortcomings happen sooner. Getting the most air in there as possible is key.

DENN_SHAH

iTrader: (1)

the TPI intake was designed for a 305, so its lacking on a 350, even more so on a 383. that said, gasket matching the base to the heads will help some, but the base still needs some more work for it to flow as good as possible. if your going with this guy, then get him to open up the rest of the base while he has it.

some info on the plenum if your not going with siamesed runners,
3rd° Tech Tips~Porting the Plenum

a good set of aftermarket runners wouldn't be a bad ideal IMO.

1991CamaroRslow

iTrader: (3)

The TPI was actually designed for the 350 engines installed in the corvettes; never the less there's ALOT of material that should be removed in the base.

Abubaca

iTrader: (3)

It was in fact designed for the Vette, but GM planned on it being a 305, not a 350.

Guest

The 219 cam does quite well with a TPI as well.
I could pick a different cam for that combo too but this is at least closer. The long duration and low CR of the last combo would have made a dog.

I think they're trying to point you in the direction of something more like this:

http://store.summitracing.com/partde...2D08%2D502%2D8

I can see the guy building the engine is trying to be pretty conservative and honestly thats pretty typical out there. Seems he has a source he's using on a specific product line so I'm not sure what they have thats comparable but I'm sure there is something.

Archaea

Thanks guys - I appreciate the advice...It's all boiling down now.

The vendor called today and left me a voicemail.....he asked me to confirm with him what I wanted my cam specs to be...He has assembled the block and pistons and recieved my heads and has begun porting them...He said he has not put the cam in yet and asked if I had decided change the specs............He said he can still change it to whatever I want it to be should I decide otherwise.

Could anyone describe the difference between the 110 vs. 112 lobe seperation spec?

I called Comp Cams and asked for advice on a cam selection...they pointed me to 08-501-8 which is very close to the one madmax suggested.....The numbers on it are 212,218 with 488 lift on intake and 495 lift on exhaust. Comp Cams said it would normally make power between 1,200 and 5,200 RPM, but on a 383 would make power between about 1,000 and 5,000RPM. He said I should chose 112 lobe seperation because 110 doesn't idle right on a computer controlled car. He said I should put a 58mm throttle body on it and I'd be golden.


There's a side note here....after reading the thread linked below I'm starting to feel like the more torque I can generate out of the engine is probably the route I want to go....The car will be primarily a daily driver.......The TPI intake is probably here to stay...I'm having the vendor port the lower intake out and I'm cleaning up the upper plenium a bit.


http://forums.corvetteforum.com/show....php?t=1534167

ZZ28ZZ

I built my 383 with a Lingenfelter 74211 cam. It was designed especially for tpi.
The torque from idle thru abt 4200 is awesome. Not the best cam for drag racing, but for the street, it works very well.
The heads will need a little work to accommodate the high lift, but if he's working the heads anyway...

I'd also recommend full roller rockers (like the Comp pro magnums) instead of roller tipped rockers. They have much less resistance and run a lot cooler.

Definately need a steeper rear gear. Even with my 3.27 gears and posi-trac, it's still difficult to control wheelspin.

Definately will need an aftermarket intake, runners and plenum porting or that 383 won't be able to breath.

3rdgenZ

iTrader: (1)

thunder racing has some comp cam custom grindes that are made just for TPI

link:Thunder Racing - Camshafts for your 1982-1992 F-Body

for your motor id look at the 502 grinde
if you wanted to get crazy look at the 466 cam