Alright guys and girls. Ive decided i want to replace the 305 TPI in my 87 IROC.

Here are my guidelines:

-I dont want to simply drop in a 350 and throw on a carb. I want to keep the TPI setup.

-The car is 95% street machine, but may rarely see passes on the track.

-I'd really like to have a forged internal, 4 bolt 383 setup with mild cam.

-I'm lost on what i should do for cylinder heads.

-I'd really like to just drop in a crate. What are some available crates for TPI usage? ZZ4?

-I can get GM employee priced crate engines.

-I have a L31 (out of 97' 1500) under the workbench with approx. 180k miles. The heads are cracked due to engine being run hot. If i were to use this block, i would need to have machining for 4 bolt (splayed caps) along with bore work. Also a new rotating assembly, cylinder heads, and the proper intake. = $$$$$$$ for a possible headache with no warranty.

-I'd like to know what it takes to swap in a LS1. Are there any threads on this?


I just need some help/opinions with my options. Everyone chime in!

 

For street use, 350 or 383 with proper Vortec heads and aftermarket cam will give good performance and will still retain the stunning good looks of the TPI.

If your looking for higher power levels, LS1 is awesome, but it's a more involved swap. And an LS1 is ugly - if you don't count the cylinders carefully, it looks just like any other modern V6 you might find in your mother's minivan. There is a specific subforum just for LS1 swap.

 

i've pretty much decided against the ls1 swap, for dollar reasons lol

A 350-400 horse machine would be really nice.

 

u need about a tree fiddy!

 

Just buy the GM 383 crate with a mild cam it will make 340 to 350 hp.

 

Just which GM crates are compatible with the TPI intake tho? I was under the impression that the 383 engines have a different bolt pattern.

 

A 383 is just a 350 bored .030 over, and a 400 crank used to increase the stroke. Any head/intake combo that fits on one will fit on another. Doesn't mean they'll work well, but they'll fit.

The vortec heads DO have a different bolt pattern. A STOCK TPI manifold will not fit vortec heads. Edelbrock does make a TPI manifold to bolt up to vortec heads, but the quality, and flow capacity has received a lot of negative reviews.

....last but not least, a TPI (with the long runners) is not a good choice for a 383. That displacement just requires more air than a TPI can flow. It's been done, and it's a HUGE improvement over stock, but it could be that much better with a properly matched intake manifold.

 

I'm not really looking for a high output rpm screaming race engine, just want a good bit of extra umph than what the turtle under the hood has now. This car is a street machine, it needs to be a reliable setup. It will be a weekender mostly, taking trips out of town and such. Say, a high 12 second car would be fantastic!

As far as airflow demand. I can't justify spending the money for a new crate and spend another 2k for Stealth Ram setup at the same time. However, this may be a future upgrade at a later date.

I cant seem to make a decision as which route to take, so i seek as much input as possible from members.

 

Think again
$540
( + minor parts ,fittings , fuel lines etc )
http://www.summitracing.com/parts/WND-7540/
http://www.summitracing.com/parts/HLY-534-185/

You already have the TPI computer and wiring to run it
Custom tune and your off

 

Seems like you are set on wasting $$$
You don't NEED a forged 4 bolt setup for what you say you want to do esp if only fitting a " mild " cam

how big is your budget?
This motor and the Vortec version of a Stealth ram 400Hp

http://www.rebuiltcrateengines.com/c...ck-p-2105.html

Or crate engine long block
https://www.thirdgen.org/forums/tbi/...block-way.html

 

I don't mind spending extra dollars on a better product, ESPECIALLY when it comes to durability. I don't know where this project is headed. It could possibly change hands, or it could possible have more performance added to it. Thus i wanted to go ahead and start with solid ground on a 4 bolt/forged internals. I can get a 2 bolt L31 long-block for $1800.

 

In which case you need to decide now because you can waste money
like putting a 600Hp forged bottom end in a 400Hp engine ( not going to make it more reliable at that Hp level )
or building the engine for the 400Hp you say you want ( now ) and then further down the track deciding you want more and actually need the HD parts= extra cost later

 

Yeah, i think you catch my drift. lol. Buy a bottom end with HD parts and get what i want for right now, if i decide to make a cam/head change or anything else for that matter later down the road, ive already got the 4 bolt main block and forged crank/rods to handle it.

 

Don't forget you are going to need to get the memcal in the ECM reprogrammed for a 350.

 

Yeah, i feel thats gonna be a WHOLE nother thread figuring out what i need to do there lol.

 

im trying to figure out what my 350 Tpi setup is i know its definatly worked

 

With a informative statement like that ,you have a far better chance of knowing than we do

 

There's a difference between spending more for added durability, and just pissing money away foolishly. Sometimes it's hard to see the difference.

In the case of wanting forged internals, in my opinion, for your power level, that translates into pissing money away foolishly. Your desired power levels won't strain a cast crank & rods and hyper pistons. Think of it this way. If I need to hang a flower pot on my porch, I could use a 7/8" grade 8 bolt instead of a sheetrock screw to mount the hanger to the ceiling. Would it be more durable? I suppose so. Is it necessary? Not even close.

Going with less expensive internals and re-appropriating that money into items like cylinder heads and induction will pay huge dividends in the final product.

 

What if he races the car constantly (road racing & drag)? Would forged internals last longer?

 

Based on that comment, I think forged is a waste of money. Even if he does decide to race it a lot, I don't see the strength of the rotating assembly being the short stick in terms of reliability. That money is still better spent in other areas, namely valvetrain and oil distribution & handling.

 

Right, but say he would race, you're saying the valvetrain and oil distribution will go first in a race, but wouldn't forged last longer after racing abuse? (i know i know he does 95% street, but hypothetically saying..) Wouldn't that prevent him from downtime or having to ever dive into the engine block or atleast for longer than if he had not forged?

Also i'm not an expert in this, just asking questions I think are important to know.

 

I really don't see forged internals offering any benefit from a wear perspective. In all cases, the bearing is, by design, the softer material and is designed to be the sacrificial material in that relationship. I would expect in almost all cases that cylinder bore wear due to the piston-ring friction to be the most wear prone part of a race motor, provided something in the valvetrain doesn't break and wipe out everything else. The benefit to forged internals is in its strength, which will allow it to withstand more punishment without physically breaking, but again, at the modest horsepower levels being discussed here, I don't consider breakage to be a concern regardless of the material.

 

Very clear explanation. Thanks Jim!

 

haha my bad long night. so far what i know is 350 headman headers. ziggys or zeggys racing trans. i cant figure out what the gears are but they must be meant for the track. my rpms stay pretty high on the highway. driveshaft looks brand new. msd wires. looks like a stock intake mani and throttle body. but the heads have purple rockers i think there callled idk i wanna figure out what kind of heads they are. no ac heat windsheild wipers.