I was wondering if a governor would cause the 4k rpm wall my Z28 keeps hitting. I have it revving really nice and smooth with plenty of power. Maybe I need to replace the prom? What about the fuel pump? Don't know what the fuel pressure is at 4k though. Maybe it is time for a came, still have the stock LB9 one. Haven't bothered to play with the timing either. Guess I need to establish some baselines.
I was having a blast driving it around today, but felt like I was short shifting the car due to this "wall" the car hits at 4k.
For those who don't know the car, it is a 91Z28 with a 305 TPI, 5 spd, TPIS intake, TPIS TB, 3" catback, gutted cat, Hedman Headers, Accell coil, good wires, plugs, fuel filter, etc. (Did I forget something Bill?)
Bill owned the car before I acquired it and had the same problem.
Well, I am stumped, so any additional ideas would be greatly appreciated.
Bill, drop me an email bro.....


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-Jason
"Get this, no man with a good car needs to be justified."

91 Z28 305 TPI/5 Spd
92 Formula 305 TPI/5 Spd

 

it sounds like the wall your hitting is typicaal of aa sd car the intaake and throttle body were changed now there is a larger quantity of air entering the engine but the ecm is still adding the same amount of fuel for a stock engine i would suggest working on a prom for it

 

Well quite a few people on SEThirdgen suggested that it is possibly the fuel pump quiting at higher rpms. I need to drive it around a bit with a fuel pressure guage attached to it.
Bill, didn't you have one hooked up in her before I bought it?
I also have a air/fuel mixture guage.... maybe that would tell me something. I will watch it tonight on my way home from work.

 

Well, I drove it home, and pegged the rpm's in 3rd gear. It actually climbs to around 4750 on the tach before it stops. The air/fuel guage shows it being rich. Anymore ideas?

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-Jason
"Get this, no man with a good car needs to be justified."

91 Z28 305 TPI/5 Spd
92 Formula 305 TPI/5 Spd

 

due to its long runner design, tuned port injection doesnt make power past ~4900rpm. unless you modify it of course.

 

I would check your ignition system. The stock 305 LB9 engine should easily rev past 4750 in third gear. I would also check your exhaust system for blockages like kinked pipes or plugged cats. My 1987 GTA 350 had a plugged cat and it would launch hard but then fall on its face as the RPM went up.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

I will check the ignition, but I think it is in good shape. My exhaust is has no kinks in it, and the cat has been gutted. It will fly until it hits that wall at 4750 or so. No hint of losing power until that exact movement. The best way to describe it is using a rev limiter. It is getting frustrating to say the least. Oh well, time to fix the brakes anyways.....

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-Jason
"Get this, no man with a good car needs to be justified."

91 Z28 305 TPI/5 Spd
92 Formula 305 TPI/5 Spd

 

Is the ignition aftermarket, (MSD 6AL) rev limiter is in that might be if it is??? My other guess would be a cat but that is a fancy looking hollow tube now


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89 GTA 350 - stock all the way. But came with goodies, 3.27, dual cats, alum shaft. Mods and Website coming soon!!!

 

Yeah, that cat is not an issue in its current stat. The only mod to the ignition is a Accell coil. Not much else. I will pull the cap and see how it looks tomorrow. Thanxs


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-Jason
"Get this, no man with a good car needs to be justified."

91 Z28 305 TPI/5 Spd
92 Formula 305 TPI/5 Spd