Just had my car dyno tested today, it is an 87 Corvette.
I have TPIS ZZ9 cam, Big mouth intake, AS&M semi-siamised runners, ported plenum, comp pro magnum roller rockers 1.52,
underdrive pulleys, air foil, ported 113 Corvette aluminum heads, flow matched Ford 24 # injectors, completely stock exhaust including pre cats and main cat and factory pipes, manifolds, & mufflers and stock computer chip.
car dynoed at 234.5 hp and 315.4 torque.
I was expecting more, I know the exhaust and chip are holding it back but how much more can I expect with headers, exhaust, and cust tune on the chip?

 

That is a little low. My 1990 Corvette has the following:

-350 block bored .040 over
-K&N filter
-air foil (no laughing, it was free)
-flowmaster 50 series with the rest of it stock (all 3 cats, stock manifolds, stock 2.25" piping)
-ZF6 tranny

It would rev to 4100RPMS, then break up. Still haven't figured out the problem, I think it's the cap and rotor I need to replace. But it made 224.7RWHP at 4100RPMS and 336.8 ft/lbs torque at 3200RPMS.

With a cam, the rockers, the base and runners, along with the ported D-port heads, I would expect to see about 255-260RWHP, with another 30-35RWHP with some headers, a tune, and new exhuast

 

Not bad there notch.

What are the specs on the ZZ4 cam? About the only difference between our setups are my ported iron heads, 211/219 LPE cam, and headers/full exhaust. I'm pretty sure I'm putting more than 240rwhp down.

Still need a tune, but that won't do me any good cause an Lt1 intake is going on.

 

The exhaust is probably killing you. I it would be on a 3rd Gen. I'm running a setup very close to yours. Same cam with 1.6RR but Trickflow heads. All else except exhaust is about the same except I have a custom chip that still needs work.

I have the SLP 1 5/8 Tri-Y headers with 2 1/2 inch to the dual cats and 3" to the SLP muffler. Mandrel bent by the way.

I'm putting down 283RWHP at 5000RPM and 311TQ at 4200RPM as that is where my dyno graph starts because I'm running a 700R4 transmission. I really don't know what my peak TQ is as I'm sure it is lower in the RPM range and the graph did not go that low. This works out to 354HP at the engine considering 20% loss for the A4.

Just got back from the track and ran a 13.30 and 103.59 in the quarter. This is with a race weight of about 3800 pounds including my 250 pound butt.

Get a first class exhaust system on there and you will be very happy. Allen

 

I think you have quite a bit to get yet...a full exhausti.e headers/catback...could yeild 30+ crank hp...a good tune on your setup coulds get a bit more as well..how extensive is the porting on the heads?...get your exhaust and a good tune and depending how much work you have done to those heads you should pick up some good power...not to mention have a 12 sec capable car...ZZ-9 specs: .480/520 lift/212/226 duration...I know I 've read several build ups with this combo running 12's...

 

If the Corvette exhaust system is anything like the Camaro it is killing you big time. I have a combo that is very similiar to yours. Same cam with 1.6RR but with Trickflow heads. All else about the same except I have a custom eprom that still needs some fine tuning.

I'm running SLP Tri-Y 1 5/8 headers, 2 1/2 inch exhaust from the headers to the dual cats. 3 inch exhaust from the dual cats to the SLP muffler. All mandrel bent. I'm putting down 283RWHP at 5000rpm and 311RWTQ at 4200 rpm. My dyno graph starts at 4200 so I really don't know what my peak torque is.

This is through a 700R4 transmission. So figuring a 20% loss that is 354HP at the flywheel. I just got back from the track today and I ran a 13.30 and a 103.59MPH. Lot's of Gen 4's running high 13's and 14's as the atmospheric conditions weren't the best.

So put a first class exhaust system on your car and you will be a
happy camper. Allen

PS: you need a custom eprom.

 

Glad to see the boards back up.

Thanks for the replys.
I have talked to an exhaust shop here local that is owned by a car enthuist that is a friend of a friend.
I am supposed to take the car to him and we are going to drop the complete original exhaust from the bottom of the factory headers back and replace it with a true dual 2 1/2" exhaust system with FlowMaster mufflers eliminating the 2 pre-cats and the main cat atleast for the time being and getting a custom chip done.
After this I will get the car back on the dyno and see where I am at.
I have been told the factory headers are restrictive also because of the small openings and tubes but with the cost of headers they will have to wait, I figure this will atleast show me if I am going in the right direction.

 

Replacing the stock manifolds is what will uncork your exhaust system more so than replacing everything from the behind the manifolds. But I guess you'll find out soon enough.