Hello, does anybody know how to tell apart by looking at a L98 230hp and a 245hp engine both with aluminum heads in the engine compartment. I am guessing most are going to say look up engine #, but besides that.

Thank you

 

Back in my Fbody TPI days I remember the earlier tpi had longer channels on the top of the plenum, a 9th injector (was there a mini runner associated with it, don't remember my 89 or 91 having one?) AND the 90/91 didn't have a MAF in the air intake ducting. Vette guys correct me if I'm wrong.

 

Model year would help. Look at the 10th digit of the vin #.

G: 1986
H: 1987
J: 1988
K: 1989
L: 1990
M: 1991

Other clues: A/C compressor style?, MAF?, CSI?, Coupe or Roadster, Muffler outlets (both functional)?

 

Yes, the 89 has no cold start injector

the gain in HP was because of roller lifters????

 

The ZTA, ZTB & ZTC I believe would be '91 'only' codes. '90 codes I believe would be ZSA, ZSB & ZSC.

 

wow. thank you for the detailed responses!!!!

 

WOW! that is some great information. Going to save this post.

 

So I'm guessing my 1990 coupe with oil cooler has 250 hp. I don't know the axle ratio. Wouldn't that make it the hightest hp L98

 

The Highest factory rating was 250hp in the coupes only... Speed Density, roller cams, 113 heads, increase in compression ratio, dual functioning muffler tips..etc...etc... Congratulations!

 

in an another thread on here @IHBD grinded me about needlessly (in his opinion) quoting him. I obliged by stopping.

But he has again proven me to be the fool. His posts are like those app that disappear after a countdown timer. I dont get this guy. Great guy. Nice guy, knowledgeable guy. Friendly guy. But word to the wise, I suggest you quote every thing he says before he deletes it.

Case and point: In this thread, he succinctly and accurately described the L98’s horsepower progression. An excellent post that contributed to the knowledge bank on CF. He was thanked for the post, but his requests to stop being quoted were respected. And now the post is gone, because he deleted it. Which, is totally within his rights to do, just as it is within anyones rights to quote tge cr@p out of anything he graces us with.

There is a young lad near me who has really fallen for c4’s. Hes come over alot, soaking it up, learning how to do basic mechanics. He is looking for an autocross car for him and his dad. I directed him to this thread as an opportunity to learn about the L98, which is the engine i recommend him as his first vette due to its lower hp, non opti, and lower entry price. Too bad for him, @IHBD took the time to purposely delete the post that would have taught him and spurred him onwards in his learning as a young 14 year old. Thats the case and point. I will go back to quoting him anytime i see a massive knowledge drop and disregard his request.

 

The 230 horse is perimeter bolt valve covers with cast iron heads vs aluminum center bolt covers

 

It's a bummer. I pretty well know the progression of power for the L98, but always look to pick up a tid-bit when I can....I specifically clicked on this thread, to find that tid-bit. It was likely in that post....along with other good bits that I don't know. It's gone now, I missed it, and that's disappointing.

 

In summary:

1986: L98: 235 hp. Power increase attributed to the 128 aluminum heads
1987 L98: 240 hp. Power increase attributed to roller cam (friction reduction gotta be worth something, right)
1988-1989: 240-245 hp. Power increase attributed to the 113 heads and camshaft changes with dual rating depending upon the mufflers (convertible and 2.59 gear coupe mufflers apparently offset the gains from the heads and cam).
1990-1991: 245-250 hp. Power attributed to flat-top pistons/compression ratio, camshaft changes again, SD control (and 2.5" cat-back) with dual rating depending upon mufflers.

So 5 hp for the 128 aluminum heads, 5 hp for roller cam (reduced friction), 5 hp for the 113 aluminum heads and cam, 5 hp due to compression ratio increase (90-91). Subtract 5 hp for high restriction mufflers (convertibles and 2.59 gear coupes where applicable 88-91). None of these gains are worth bragging about, but 88-89 and 90-91 engines are superior to both 1986 and 1987 despite the advertised numbers. Conveniently the changes all result in hp gains/losses in 5 hp increments.

Funny, I don't recall anybody ever drooling over the factory low restriction mufflers.

 

I remember in '91, I read a comparo of the C4 w/a manual, vs. Stealth RT/TT, 200ZX/TT, Supra Turbo...maybe something else...RX7?? Anyway, I remember seeing the 250 horse rating in that mag article, having not been aware of an increase, I was stoked! I thought; "It's only 5, but at least they're going in the right direction!"

 

Thanks Tboy!!

Will send your post to the latest kid to be pining over c4’s.