i have just installed a 450hp 385ci stroker motor in my 91 firebird that was originally a 305 TBI car. Going into this projected i decided i did not want the dash to light up like a x-mas tree, nor did i want to hack all the wiring out of it and put in a carb(seemed like the hillybilly way of doin things to me). So i sent my TBI unit to ExtremEFI in texas. they bored the throttle bores to 50mm each side, made new throttle butterflys, raised the injector tower 3/8",
removed the air horns, and machined the top of the tbi unit smooth. they then supplied me with a set of injectors for a 454ss truck, a custom made pressure reg(adj. from 12-50psi) and a late model corvette fuel pump.

Problem is..... it starts and idles about as well as one can expect with a monster cam, but if i rev it above 1500rpm IT KEEPS REVIN ON ITS OWN!!!!
all the way up to like 4 or 5,000rpm. i first assumed vaccume leak, however all the lines checked ok, i have good vaccume on the gauge(14psi) and even resealed the TBI base gaket and adapter gasket to be sure. THIS MADE NO CHANGES TO THE WAY IT RUNS!!! I even put an extra return spring on to make sure the throtlle is not sticking.

HELP ME PLEASE!!!!!!!!!!!!!!!!!!!!

 

ok maybe i will throw out the obvious question first.HAVE YOU TUNED IT YET?
there is NO WAY that motor will run on a stock tune.That could be your problem.

 

I am in no way an expert on this subject, but with the last guy. I once ran a performer rpm cam, intake, 1 3/4 headers and an adapter plate for a stock 454 one ton on a 400 small block with a home made pressure regulator giving us 20 psi. We ran a stock TPI fuel pump. It ran terrible on the stock TBI chip in the 90 firebird 5 speed car.

This was back in '94, and we put in a cheap ADS super chip (I think it was about 80 bucks) and it ran a lot better. We had to buck up and go to super shops back then and got a custom PROM that cost us about 300 bucks!

It ran great after that, though! High twelves until we shattered the T5!!

 

i have a chip burnt by TBICHIPS to my motor and driveline specs. any other ideas????

 

Although I recommend Brian for a chip to get you running, it is in no way spot on. However, with a crazy setup like yours, I would venture to say that G0d himself would have a problem tuning it through the mail. Hell, even in person I would say that it's going to be difficult.

This is the exact reason why I've been thinking about going to a carb for a while now. With a dyno and a wide band, it only takes a screw driver to dial it in . . . seems awfully tempting to me.

With all of that said though, I hear that the EBL seems to resolve those tuning issues . . . still have to jump on the DIY PROM learning train though, super-duper computer or not.

I too am scared of the wiring nightmare going over to a carb though.

 

Guys I went from TBI to TPI and now running carb. No big problem with the wiring. Im and very glad I did the swap.

Also if any of you guys are interested, I have a carb in my sig for sale.

Pics of the carb can be seen at 1989 Chevrolet Camaro - WAYNE's Chevrolet "Bluegrassz"
I can work with you on shipping and price.

 

PROBLEM SOLVED!!! DAMON U WERE RIGHT!! i checked my throttle operation a dozen times with the motor off. but when i checked it with it running, sure enough, the airflow was to great for them to shut all the way. I now have the sotck spring on the tbi and a dual throttle return spring for a carb on there, and that barely closes it!!! gonna get heavier springs tomorrow. and believe it or not, it runs and idles pretty damn good with a tbi setup, needs some minor tuning(fuel pressure, idle speed, etc), but i am impressed. THANK YOU FOR ALL THE HELP!!!!

 

You're giving up anywhere from 30-130 hp by not properly tuning it. There is just no possible way on this earth some one can tune a chip for you via the internet and have it spot on for a motor like yours.....it just won't happen. I've talked to several guys that are on there 8th and 9th chip from Brian on much milder motors and they still run like crap.