ok.

88 GTA----
230@4400 HP
330@3200 TQ

89-----
240@4400 HP
345@3200 TQ

what makes the jump? i know that some 89+ had dual cats. but does that really cause that much of a power gain? if so then wouldn't just gutting a single cat do that for u?? and headers and y-pipe bringing me above that??

 

Ya, dual cats = less restriction.
Gutting yours should do the same. Headers and full exhaust will help as well.

 

Dual cats were only available as an option and 1LE packages, I thought. I am thinking it was a better cam; check the specs.

 

ya the 89's had a better cam.

 

They upgraded from the MAF sensor to speed density type sensor. Thats what made the jump in hp + torque, plus probably better PROM programing.

 

opps, me wetarted... I thought you were asking the diff. between an 88 and a 92, my mistake. Thats what I get for not reading the post....
Yeah, I think they had a cam change.

 

The 88' and 89' 350's used the same cam. The 10hp difference was from the dual cat setup that was standard on the 89'. Your horsepower numbers are correct for a Camaro, but you must subtract 5hp for the firebirds due to the more restrictive intake. So it is really 225 for the 88', and 235 for the 89'.

 

Just to show how much an exhaust can play a part in power gains (or losses), the 1970 Chevy 350 LT-1 Engine Code 'CTL' was rated at 375 HP when installed in the Covette. That exact same engine was only rated at 360 HP when intstall in the 70 1/2 Z-28. This was due to the Camero having smaller pipes coming off the exhaust manifolds (2 1/4" compared to the Vette's 2 1/2"), having more bends in the pipes (going over the rear axle on the Camero were the Vette was under the rear suspension) and last the Camero having a dual inlet/dual out muffler (the Vette of course, having two mufflers.

The way an enigne breathes makes all the difference in how it will perform. The faster you can get the exhaust the faster you can get fresh air/fuel in!!!

Later...

Mike

 

GM also found 5 more horsepower in 1990 by changing the pistons.

 

The 5hp gain in 1990 was actually due to a few things including lighter pistons. They used hypereutectic pistons that i'm pretty sure bumed the compression up to 9.8:1, but the compression may not have changed. Someone else may know the answer to that. The other things were a revised cam profile that had a tighter lobe separation angle, and the use of a a speed density fuel management system instead of the MAF system. The only reason that helped was because of the better airflow into the throttle body since there was no MAF sensor in the way. This seems like a lot of work for 5hp, and in reality was more like 10-15, but ratings are just numbers. Ask anyone with a stock SD 350TPI and they will tell you how much better they run than any MAF car.

 

No the new pistons didnt bump up the compression, the head design was still the same, they just changed the material. (Hypereuetic, like you mentioned). I didnt think that the Speed Density TPIs actually made more horsepower than the MAFs, but then again they could be just numbers.

 

or in my case add 5 HP to the T\A #'s since my intake is gutted.

 

I was thinking the comp ratio should have increased when the revised piston design was implemented...going from dish-tops to flat-tops using the same chamber volume should account for a decent bump you'd think.

Ah well, I got no data to check against.

 

Wow, look at all the inaccuracies and misinformation in this thread!!

Hey Nitroburn, whats a Camero?? Is that like a Fireberd??

Dual cats are NOT standard on 89 cars. The single cat 89 350s are rated at 230 horsepower, with the dual cats being 240 hp. The single cat 305s are 220 horsepower and 230 with dual cats. Dual cats ARE standard on 90-92 350 cars, but still optional on 305 5-speed cars.

The 5 hp difference between 89 and 90-92 cars is the change in pistons, increasing compression from 9.3:1 to 9.7:1. This only affects 350s, the 305s remain the same, 230 hp with dual cats.

The 88 and 89 350 and 305 5-speed cars use the same cam. Its 207/213 duration, .415"/.430" lift, and 117 LSA. The 90-92 cam is 203/207, .413"/.428" lift, and 115 LSA. The speed density cars make more power with a smaller cam.

Now, gutting your stock cat may or may not improve power, but if you get caught, its a $10,000 fine and possibly jail time for tampering with your emissions equipment. Its better to spend the $100 and replace it with a good new high-flow cat, like from Car Sound. Today's catalytic converters are really good, and dont affect the power very much, 5 hp or less. You wont feel that.