Im tryin to figure out what the stock rear wheel horse an torque is on a 1989 trans am gta i know to the crank the hps 240 and the tq is 345, does anyone have a rought idea or know??

 

It should roughly be around 200rwhp on a stock L98 with the 700r4 auto trans.

For manual transmission cars I usually use a rough estimate of 15% power loss due to the drivetrain.

For automatic transmission cars I usually use a rough estimate of 20% power loss due to the drivetrain.

For the L98/700r4 combination:

(240 fly wheel hp) * (.2) = 48hp = power loss through the drivetrain

(240 hp) - (48 hp) = 192 rear wheel horsepower

There is a magazine article that talks about the rear wheel horsepower output of the L98 when it first came out in 1987 in the IROC. I'll see if I can find it. From what I remember that magazine said the 1987 IROC L98 was thought to have around 200rwhp.

I found the article click on this link to read it:

http://www.iroc-zpostforum.com/NewsTitleBout3.htm

It claims that the LB9 showed about 170rwhp on the dyno and the L98 had about 200rwhp on the dyno.

That sounds about right to me. For 1987 you could get the LB9/T-5 combination for the first time. If you got the G92 package for that powertrain combination you also got the borg warner 9bolt rear with 3.45 gears and positraction. With this set up the LB9 had 215 hp and 290 footpounds of torque.

This is the same hp rating as the 1985 LB9 but with 15 pounds of added torque. The 1985 LB9 had 215hp and 275 foot pounds of torque. This was the highest powered 305 that was paired with the 700r4.

For the 215hp LB9/700r4 combination:

(215 fly wheel hp) * (.2) = 43hp = power loss through the drivetrain

(215 hp) - (43 hp) = 172 rear wheel horsepower



For the 215hp LB9/T-5 combination:

(215 fly wheel hp) * (.15) = 32.25hp = power loss through the drivetrain

(215 hp) - ( 32.25hp) = 182.75 rear wheel horsepower

 

I agree with the above info.....

 

thanks a bunch guys for the info and help!!

 

You can also dyno your car.

 

The 1986 Corvette with iron heads was rated at 230hp. Later that year the Corvette had aluminum 128 heads and was rated at 235hp. From 1987 thru 1991 the Corvette had 113 heads and was rated at 240hp, except the Z51 option which had a less restrictive exhaust and upped the HP to 245.

http://www.transamworld.com/fbird-history-php3.php
http://www.f-body.org/tech/tech.htm#ThirdGen

 

To answer your question, 190-200bhp.



After '86, All CORVETTE L98 350s had aluminium heads. To the best of my knowlage, no L98 ever installed in a thirdgen had this option (factory)

 

http://store03.prostores.com/servlet...L98-TPI/Detail

The aluminum heads didnt show up til late 86 I think, by 87 they were using the 113 heads they used until 91.

Those heads are garbage by the way, the iron ones are I think the same ones on that awful "Goodwrench 350" phone company van engine.

 

85 and 86 Corvette L98's had iron heads. In 87 the Corvette L98 had aluminum heads with a 128 casting, and then later that year they were equipped with casting 113 till the end of the L98 in 91.

I've torn apart at least one of each, installed the FIRST system on an 87 Corvette and work on my 88 Corvette every day just about.

You are correct about the RPO option for the 3rd Gens, all came with iron heads and are not true L98's, although everyone would like to think so.

 

Oops. Sorry, I meant after 86 they all came with Alum heads.

Why were they garbage (the aluminium heads)? I thought those were the ones to go for.

 

My mistake, I was referring to the 624 heads. The iron ones. The 113 heads are okay. They dont have much real flow advantage over IROC L98's 083 heads, but they are lighter. 083 heads are still decent, though.


GM labeled them L98s... I mean I guess I can sort of see what you're trying to say there, but if GM is selling cars with the L98 RPO code then I think the engine is an L98.

 

Wow, that thread sure got heisted.

I dyno'd my '88 GTA bone stock and it put down 186RWHP, and ran 13.9 1/4 miles on old tires. The HP rating did go up for 1989, so "your results may vary".

TA

 

Yep. Plus, cars loose hp over time because of wear. Mine probably has 10-15hp less it did when it was new.

 

89' GTA, 350TPI, dual cat, 700R4. I put down 198hp with the only mods being a K&N conical air filter, TB airfoil and Magnaflow cat-back. Stock probably would have been close to 190hp.