1badroc_87

Hey so i’m looking to rebuild my L98 tpi. I’m tryna get something high performance but cant seem to find anything that suits me. I want to boost hp so something with a good cam and pistons and crank. I’m trying to squeeze as much horsepower out of the tpi as i can for personal reasons, i might swap it for a stealth somewhere later down the road but cant afford that beast lol. Anyone know a kit that might do me some good?

TransamGTA350

iTrader: (2)

Depends on how much horsepower you are looking for and your budget. If you’re keeping stock TPI parts, then you aren’t talking about big horsepower and high rpm, so a stock-ish rotating assembly would be fine. There are a number of rebuild kits out there, then machine work, measure everything and assembly. Mild cam (ZZ4 isn’t a bad choice) and some head and and intake porting work and headers would get you around 275-300hp. Sounds simple, but it’s takes experience to do a rebuild without making mistakes. Those who have built a lot of motors will say it’s easy, and it is when you have lots of experience. The first few times it’s easy to overlook something simple that will cause problems later.

For the cost and time to rebuild the stock 350, I would just buy a new L31 Vortec 350 long block and get an SDPC Vortec TPI baseplate. That motor with headers would be around 280hp, swap the L98 cam would be 300hp and with a ZZ4 Cam about 320hp. Porting the vortec intake and some large tube runners would add another 15hp or so. Just to give you an idea. You could go a bit bigger on the cam, like an LT4 hot cam and that would get you to around 350hp. At that point, the TPI is becoming pretty restrictive and I would use a different intake for higher horsepower levels.

Swapping a cam on a new crate motor would kill the warranty, so another option would be one of the GM Performance crate motors.

GeneralDisorder

iTrader: (1)

So you can't afford a Stealth Ram, but you think you can afford a "high performance" rebuild?!?

Full stop!

What's the budget?

GD

Kevin91Z

iTrader: (1)

Don't bother with Vortec heads on a TPI engine. The Vortec TPI base flows the same as stock and has little room for improvement by porting.

AFR 195 or Trick Flow 195 are the best heads.

TransamGTA350

iTrader: (2)

This is true and would agree if rebuilding the stock motor. If using a new L31 long block, Vortec lower base is necessary.

1badroc_87

Well i’m looking at being able to afford to drop $1500 on the engine, and the rest of the budget is going into overhauling the front suspension and rear gearing which is around $2500. I just can’t afford a stealth ram on top of a HP rebuild when the car really needs the rebuild and suspension.

TransamGTA350

iTrader: (2)

$1,500 isn't going to get you very far at all. That won't even cover the parts and machine work for a rebuild, and that's not including any performance upgrades and then all of the other things you end up replacing while the motor is out (belts, hoses, plugs, wires, gaskets, sensors, injectors, and on and on). It adds up quickly. Budget is way too low for what you want to do.

So, why are you wanting to do a rebuild? Does it need one? How does it run now?

1badroc_87

It runs pretty good, it just has a bad leak at the rear main seal and is burning oil so i figured a rebuild would be the way to go so i get it all done. It will be my first rebuild, i wanted to go with a mild cam & crank/adjust valves, and i was gonna over haul cooling system while in there. Ive seen a couple of kits that include mild cams for around $800 but figured i’d see what rhe general opinion here would be, before doing anything

TransamGTA350

iTrader: (2)

Is it burning oil only on startup, or all the time? Visible blue smoke from the tailpipe, or just noticing loss of oil on the dipstick? How many miles on it?

1badroc_87

138k miles, it blows a fat blue cloud *sometimes* on startup, sometimes it is always blowing blue smoke, sometimes not at all. Indecisive old blue bitch, lol. Ive been noticing the loss of oil through the brown lake i leave behind when i pull it out of the shop, i’m usually putting a quart in every two weeks when driving regularly. Runs strong, pulls strong. Also has this weird rattle noise on startup until it gets warm, then purrs like a kitten. Rattle noise only lasts 20-30 seconds. My best guess is a bearing *maybe* or the AC compressor, when i first got the car the alternator went out and i busted a valve off the AC by accident trying to put the new one on.

1badroc_87

Also, i WOULD swap the motor for LS1/T56 combo but its original IROC and the motor still runs strong, i’d like to keep original block/maybe tranny is why i’m gonna go through the pain of rebuilding

TransamGTA350

iTrader: (2)

138K miles isn't all that much. Could be valve seals, could be stuck rings, or could have cylinder wall damage from who knows what. With a bigger budget, I would be pulling the motor and replacing it with a crate long block, new belts, hoses, gaskets and tune up parts and be on my way. I wouldn't be messing with rebuilding the old motor. It's just not worth the hassle and won't really be cheaper.

Now, with the budget you have, tearing into the motor and doing a rebuild isn't on the table. You will easily spend twice that, and it takes experience to do it right. A small mistake and you trash all of the work and money you just invested. So, with a limited budget, I would be working through and correcting the multiple issues the car has one by one and getting it to run reliably and safely and get everything works as it should. That's first priority before things like camshafts and other performance upgrades.

The oil burning may warrant a new motor, or it may not. Hard to tell right now, but if it were me, I would do a few things to the existing motor first, to see if I could make the oil burning less. I would replace the valve seals (very common on small block chevy's and relatively cheap and easy to do) and replace the valve cover gaskets while you are in there. If the car had been sitting a long time, the rings may be a little stuck and sometimes they free up over time by just driving it. On well worn motors, I have also used thicker oil to help with oil burning and that sometimes helps.

Bottom line is, try to work with what you have and fix the issues, make it reliable and safe and then keep saving to bring your budget up to something more appropriate for a future motor swap.

GeneralDisorder

iTrader: (1)

Machine work to "freshen" my L31 block, crank, and rods - change the cam bearings, set it up for new main bearings (line hone), etc was like $1600. That's ZERO parts other than bearings and ARP main and rod bolts - just the short block machine work.

GD

1badroc_87

Alright, thank you for the advice! I appreciate everyone’s input and i’ll take it all into consideration once i get everything squared away and i’m ready to purchase. And yea the car was a barn find before i bought it in ‘17, had been sitting for almost 10 years before he decided to clean it up and sell it (as far as i know, it could be 230k, damn 5 digit odo’s lol). Im still unsure of my total budget as idk what i’m gonna have left from my tax return after bills but i’m looking at a good 4-5k for the car. I’d put it all in the motor but she needs new front sus more than anything, was just looking for ideas and i appreciate your help!