Help I have an 84z with a 350 and a 700r-4. its got a 3.73 rearend in it yet i top out at around 90-100 mph.
all the electronic components have been taken off its straight engine yet i top out that low cant seem to figure out why?
Help would be appreciated.

 

Tap the catalytic converter with a rubber mallet a few times. If you hear stuff rattling around then you're cat is blocked or busted.

 

Is your tranny shifting into OD?? Probably not because the stock 700R4s had weak upshift valves and would not allow an upshift into 4th on WOT. I would go to your local GM dealer and buy one. Have a professional tranny shop put it in for you. Or as stated above you could have a clogged cat. Because of your end ratio it sounds more like your not getting into 4th. Just one question....Why are you wanting to go faster the 100 mph???

 

It Shifts into overdrive. Not a Stock 700r-4 had it built about 4 months ago. Ill check the cat. Thanks.

 

well that eliminates that!!! LOL. Try the cat like already mentioned. Sounds like a restiction problem.

 

It's not the cat. I took it off and still couldn't hit over 100. Anything else?

 

What does it feel like when it tops out. Is the motor surging? Is anything making any abnormal noise. What RPM are you at?

Try checkin your ignition timing/system and your carb settings. Those older HEI's break down sometimes and they dont like to RPM very much. Good Luck.

 

w/ 3.73s, you're gonna be well into the 5k rpm range by the time you're crossing 100 mph.

Depending on your combo and tune, you very well may be out of breath at those RPMs. Even something as simple as weak valvesprings could be your enemy. Once the valves start floating, thats it, parties over.

 

All Right Guys thanks for all the help it turned out to be a vaccum leak from hell, from the intake never even saw it there and could barely hear it. Plugged the sh*t cause i could find out where it would go to. Noticed a considerable power increase and hell gettin about 15 mpg. Thanks for your help though.