86 sports coupe

I dont have a T.P.I car but I will put a tpi on someday. I was walking my dog and it hit me. The tpi 305 215 hp and the L98 225 hp in 87. my question is only 5 hp difference? I see the 35 foot pounds of torque. But it seems to me the hp should have jumped more than 5 hp due to the 4 inch bore.
Also in 87 roller cams was used, the 87 brochure says" 5 hp increase due to lower friction, the 87 tpi(manuals) were still 215 hp, why not 220 hp?
Last question, in 90-92 the 305 with the manual and hotter cam made 230 hp. I know in the 90 350 lighter pistons and a speed density was used,to make 245 hp and 345 foot pounds of torque. What made the 305 make 230 hp and 295-300 foot pounds of torque? What cam did the 230 hp 305 have, lift duration stuff like that. Was it the same as the 245 hp L98?
I really love these cars, I love talking about them.
Please will somone clear this up for me or give me there opinon?
Thanks Randy

Bill Speed

The TPI sub-forum should have several threads already. My feeling, if you look at subsequent V8s after the initial tuneports of the 80s, even GM followed third parties in redesigning the plenum with much shorter runners, for example. Also get rid of restrictive exhaust manifolds, open the breathing and you can certainly improve even upon the older stock blocks.

I love the look of the long runners, but they don't add much else
Bill

86 sports coupe

I thought all TPIs had the highflow exhaust manifiolds? The L69s did.

Bill Speed

Early ones did, GM made improvements apart from induction, but you'll recall, this engine was a 'trickle down' from the Corvette, but much better then the CrossFire Injection in my mind.
I'm thinking SLP, as they offer better flowing plenums for older blocks. Recently looking at their site, the products on offer were very small, so I'm curious what's the deal there... I hope to add some Firehawk type parts down the line, myself

Bill

RB83L69

Get the picture?

The motor's inches aren't the HP limit; TPI is.

TPI is a flow restriction. Horsepower = flow. Basically, TPI makes whatever HP it makes, and that's that; because that's all it flows. Period. You could put it on a 500 inch motor, it probably still wouldn't crack 260 HP, in stock form. It might make it at 3200 RPM instead of 4400 RPM or whatever, but it will still be ..... 250 HP or so.

As far as the "look", those lllloooonnnnnnggggg runners "look" slow to me. Anybody that's ever worked with induction systems knows that. I have a REAL hard time getting past that. You know, if it quacks like a duck.... Close the hood, it IS slow. Open the hood, then whatever's under there, must BE slow.

https://www.thirdgen.org/newdesign/tech/techdb.shtml Scroll about 2/3 of the way down the page, just past the Firebird History section.

nick418

L98 wasnt really slow. It has *****. I mean running 14s in a 1/4 back in 80s was awesome. Still can smoke ton of cars out there, esp with that low end TQ

Abubaca

iTrader: (3)

There are quite a few fast TPI cars out there. You can't take one person's opinion of "fast" and make a standard. Now don't get me wrong, they're certainly not great, but they can still be fast. No one ever said the TPI was "best" but it can be "fast". (just not AS fast).

As for pointing out why the 305 and the 350 are so close, I would agree, it's the TPI.

nick418

Also the tranny held the L98 back. Nice 6 speed would be hella lot better

Mcdamit

it isn't just the tpi, its the small cam, its the crappy L98 heads.
Believe it or not you would have to look a mag did flow tests.You are better off with 882's over L98 heads.

from 1989 on the Manual TPI305 got the same camshaft as the L98. Here are the specs

1989 Best Camshaft to public cars:
Lift Dur. LSA RAR
In. Ex. In. Ex.
.415 .430 207 213 117.0 (116/-118)

1990-92 for 305 G92 cars and 350 cars only
Lift Dur. LSA RAR
In. Ex. In. Ex.
.413 .428 202 207 114.5 (116/-116)

1988 really fast 305 LM1 Police
Lift Dur. LSA RAR
In. Ex. In. Ex.
.383 .404 291 202 112.0 (108/-116)

Mcdamit

oh yeah as far as TPI on a heads and cam 383 the stock TPI ran mid 12's and was reported to create extreme amounts of torque that it was impossible to control the car, ie ground breaking torque, they switched to a stealth ram and pulled high 11's, but lost all that "show off power".

86 sports coupe

So out of the 3 hotter cams wich would be a good choice for a tpi car? What would be a good choice for a stock tpi car with minor mods like gearing stal converter, better exhaust?
Thanks Randy

Mcdamit

i would say the first one to answer your original question, or go with a zz4 which can get you a decent drive around vehicle. But if you want a fast ride, go call up comp cams. They have three cams already cut up. One is slightly better than the L98 cam the second you need mdifications to your computer and the third you makes more torque. The compcams ones are $350.

PART #08-304-8 Biggest most mods
PART #08-302-8: just computer
PART #08-300-8: for your stock engine