Hi.

I got a 86 Camaro w. a 305 TPI. The eng. is rebuilt and holds a pair of old corvette heads and a bigger cam (crane roller). It also holds Edelbrock TES and 3"cat, followed by 2.5" flowm. The TPI is bone stock besides the 24 lbs injectors and gutted airboxes. Despite the higher-than-stock stall converter and the 3.73 gears the engine still doesn't pull that hard. i had an 87GTA (350) with only headers and the little stuff done (AFPR, slight ported TPI etc) and that car pulled harder. Why? I am confused.

 

Which set of old Corvette heads? How big are the combustion chambers, you could easily have dropped compression really low if you weren't careful. That and heads w/ large intake runner sizes will drop air velocity.

What are the specs on the Crane Cam? Could easily be too big for the 305 w/ a stock intake, stock computer chip etc.

If somethings not wrong there I'm drawing a blank. The stock TPI intake is holding you back obviously, but it should still be decent w/ those mods. I'd look to tuning issues, custom computer chip maybe, etc. The 24lb injectors w/ the stock comp chip could cause problems, think I've heard of possible problems w/ injectors that much bigger than stock w/o a custom chip, not sure there though.

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

[This message has been edited by Ray87Z (edited October 12, 2000).]

 

Why do you say that you are slow? Because of your 1/4 mi., top speed? I tend to agree with Ray. It's probably your heads, which would lower your compression substantially if you didn't shave them. Also, the chip would probably have something to do with it as well. It's not recognizing that you have mods, and, therefore, not compensating for them. Those injectors are probably dumping way too much fuel into your heads and you're probably running way too rich.

 

Your stock computer could still be seeing your mods but you will still get more with a custom chip. What year vette are the heads from? What do you run in the 1/4?

 

Thank's for the info.
As for the specs on the cam and the heads I cannot say. The previous owner had it done and I couldn't get that info The only thing I got was that the heads came from a 75 vette (steel heads).
One thing that comes to mind when I read the thoughts about the injectors is that the car has a "raw" (not really surging) feel at WOT but runs well at part throttle and lower rpm's 2500-4000. Would it be wise to go down to standard injector size (19 lbs?) and rise fuel preassure to 47-48 psi? Also, when you set the FP, do you keep the vaccuum hooked up or not?

thanks for the info.

 

Those heads should have come w/ 76cc (305 has 58cc stock) chambers unless I'm mistaken, and if the proper pistons weren't used after the rebuild (do you know anything about the rebuild itself?) or the heads weren't milled your compression went straight to sh*t. And 75 heads were not exactly spectacular anyway, smoggers.

Without knowing what the original owner did w/ the setup who knows why the heck you're not as fast you should be. BTW, go ahead and get some track times to be sure about the performance if you haven't, the car may feel sluggish but run better than you think...

The only sure way to get a good setup is going to be to redo the cam/head setup, going w/ either a ported TPI system or aftermarket one, along w/ a custom chip. Not good. Until then everything on the car would be suspect to me...

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

 

When checking FP, DISCONNECT the vacuum line to set it.

 

Bjorn,

Did I miss something, or did you NOT port the plenum and runners? The extra fuel of the larger injectors might not do any good if there isn't enough air to mix it with. And it sounds as if the old iron heads are designed for a 350 with different deck height/ piston tops, so you are possibly suffering from low static compression as everyone else has suggested.

An easy way to measure the cam profile is with a degree wheel and dial indicator. That could be very revealing.

If you're not adverse to spending cash, a new set of heads designed for the 305 might really "wake up" your engine. The World Torquer SR 305s flow pretty well on the smaller engine, and have decent valves for the application. A danger of installing the older heads on the 305 is the potential for valve-to-cylinder wall interference. If the valves aren't binding now, they must be pretty close or way undersized for Corvette heads.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

The heads are at least a HUGE part of the problem. Going from a 58cc chamber to a 76cc will drop your cmpression, and your power, like a stone.