I had a nice conversation with AI discussing my plans for a top end rebuild, my main issue is to utilize my 113 heads worked over by Lloyd Elliot or go with a aftermarket head instead shipping is killing me to send the 113’s out (about$400 round trip) vs aftermarket at door 1200-1400 depending which brand.

I do have an another question in regards to using the aftermarket heads, the motor is from a “91 vette” it has the high performance flattop piston with a 4 valve relief along with 58cc 113 heads. The bottom end is staying it’s in great shape no issues low miles.
I can have the aftermarket 64cc heads milled to 58-60cc to match the compression of the 113’s right from PROMAXX/AFR no charge with pro max $250 charge from afr
-would i have any issues with piston to valves clearance?
-fitment of the TPIS big mouth intake slotted manifold.
any insight or advise greatly appreciated and options on my AI build.

Vehicle: 1990 Camaro IROC-Z

Engine: 1991 Corvette L98 (roller, aluminum heads)

Goal: Street/strip, mid-11 second 1/4 mile, retain TPI intake



⸻



FINAL LOCKED BUILD SHEET



SHORT BLOCK

• OEM 1991 L98 roller block

• Stock flat-top pistons

• Stock crank and rods

• Approx. 10.0:1 compression

• Stock deck height (no zero decking)



⸻



CYLINDER HEADS



Class: 185cc intake runner (locked – no larger)



Preferred Option:

• Project X SBC 185 heads

• Hand-ported

• 58cc combustion chambers

• 2.02 / 1.60 valves

• Assembled with springs matched to cam

• Stock center-bolt valve cover compatible



Acceptable Alternatives:

• ProMaxx 185 (milled to 58cc)

• L98 “113” aluminum heads with bowl work + valve job



(AF R 195 excluded due to TPI mismatch)



⸻



CAMSHAFT & VALVETRAIN

• Summit Racing 8802 hydraulic roller cam

• 224 / 234 @ .050

• ~.525 / .525 lift with 1.5 rockers

• 112 LSA

• Powerband: ~3,200–6,300 rpm

• Summit lifters (included with cam kit)

• Stock L98 spider & dogbones



Rockers:

• 1.5 ratio

• 3/8” stud

• Low-profile roller rockers (Summit / Comp / Scorpion)

• Clears stock valve covers



Pushrods:

• Stock length initially

• Verify preload (½–Ύ turn)



⸻



INTAKE & FUEL

• TPIS Big Mouth base

• Large AS&M runners

• Stock TPI plenum (ported)

• 52–58mm throttle body

• Intake system remains TPI (no swap planned)



⸻



EXHAUST

• 1 5/8” shorty headers

• 3” Hooker cat-back exhaust

• AIR / smog removed



⸻



IGNITION / TUNING

• Stock ECM requires tuning

• OR FiTech EFI acceptable

• Target timing: 32–34° total

• WOT AFR: 12.8–13.0

• Idle AFR: 13.8–14.2



⸻



DRIVETRAIN

• T56 6-speed manual

• 3.42 rear gear

• Aluminum driveshaft

• 275/55/18 tires (street setup)



⸻



EXPECTED PERFORMANCE

• 405–420 hp (crank)

• 390–410 lb-ft

• 1/4 mile:

• 11.6–11.8 sec with traction

• 118–121 mph

• ~6,200 rpm trap

• Street tires: ~11.9–12.1 sec



⸻



NOTES

• Build optimized for average power & ET, not peak dyno numbers

• 185cc heads intentionally chosen to maintain air velocity with TPI

• No AFR 195, no intake swap, no 1.6 rockers

• Balanced, reliable, repeatable street/strip combo

 

just leave the engine stock, replace the old tired valve springs and add a 200 shot of nitrous.
youll be much happier in the end, and save yourself thousands of dollars..

 

Your agent did not have adequate training data; that build will not be hitting those numbers or shifting that high. Also wrong cam for TPI. I'd recommend you check out some books by Vizard and/or Lingenfelter and then give the AI another shot.

 

thanks for the response.
please enlighten me on a can selection,

 

That's where the books come in, but for starters you'll want max duration closer to 220 @ .050 because TPI is done at 4800rpm and you will simply throw away torque under the curve for a powerband you can't access.

Keep in mind TPI is a grunty torque truck intake that GM happened to put in sports cars. If you want the fastest possible 1/4 mile time before they kick you out for not having a cage, you need 450hp to the tire on a full body / interior car and it's simply not happening on an intake designed to efficiently make 200hp out of a 305.

I'm not saying you can't add HP to TPI, but you're going to do all that and run 13's like everybody else.

 

Totally

What you CAN get is a car that is super fun to drive on the street....but no way you'll be trapping 121 with that combo. I also agree that there is no way it's going to rev to 6300 (making meaningful power). TPI won't allow it, and I don't believe that a 185 head will allow that either. I think the engine that you spec'd would be more likely to make 420-440 or so, tq, and 360 ish net, crank hp.

Which would be a hoot to drive, and might get into the 12's, if that part matters.

 

what I have an issue with is understanding why some people can achieve 325-350 hp with a simple cam and bolts on’s such as exhaust, etc. I’m modifying the whole intake system with aftermarket, replacing the heads, matching a cam as best as possible. fuel system gears pulleys exhaust etc.. Why is it so unheard of to see 375-400 hp from a 350 a simple search on this forum and people run 12s all day long and get 375+ hp from their 350s with the TPI set up.
richard holdner has

 

Then go ask Richard how he did it. Most other people in this forum greatly exaggerate/overestimate their HP numbers, so good luck getting an accurate picture of what anyone has done to achieve it. Unless they have dyno numbers to prove it....

Also, asking ChatGPT how to build an engine is similar to asking the village idiot who the dumbest person in the village is (he isn't going to know, he is an idiot).

 

i’m blown away by how many of you are so offended by AI. i never said it was the all to end all all i stated it was interesting having the conversation. i also asked some real questions that no one has responded or recognized the only responses are to AI
says a lot!


quick to judge but slow to help discuss

 

B/c Richard Holdner did it on an engine dyno with no accessories, no exhaust, no intake/filter/ducting, optimized tune, and engine temps likely in the low 100's degrees F. That is called GROSS horsepower, and it is kind of cheating (IMO) since it's not representative of what it will be in the car.

To wit: Richard Holdner also dyno tested a box-stock '90's LT1 on his dyno and got 350hp. HUH? We know that the '90's LT1's were 300 hp, as installed in the car. So your...
....is alot more like ~320 crank hp as installed (what you'd experience), in the car.

 

Saaaaay WHUT!? I didn't say one word about AI...and if I did, please point it out so that I can edit that, right away! Who else "was offended" by AI in this thread? I didn't see one post that indicated "offense"....except for yours.

 

I would lower my expectations with TPI. HIgh 12's is more realistic than 11's. I would also look at the AFR 180 heads as an option.

 

So do this instead: Build your engine exactly like you listed in your OP, drop it in the car, take it to the drag strip, and then post the time slip ITT. You will then immediately know whether posters here were blowing smoke up your chimney---or else know what they're talking about. I go with the latter of the two.

However you decide to proceed, good luck.

 

like i said up there, nitrous is the answer here.

 

Getting to 400hp or a little above it is relatively simple if you start in the right spot. Heck, there's plenty of crate motors that start you there or close. This forum has been around for a VERY long time and a lot of what you'll find in the "historic" posts is well intentioned BS. Lots of "man, I got me some corvette heads and that added 100hp!"
Look for the posts with receipts (time slips, dyno charts, etc.) and that will tell you the most. I think your limiting factor is the stock TPI. Switching to a different intake system might open up more possibilities.

Also, chatGPT has a bad habit of telling you what you want to hear so keep that in mind when making plans. That's not a knock on AI, each platform has it's issues, just good to know what they are going in so you can prepare.