What could cause a low-mileage 302 to suddenly not want to rev past 4000 RPM, when previously it easily pulled to 6000? The engine in question makes no strange sounds (popping, misfiring, surging, etc.), yet seems to hit a "wall" once the tach reaches 4000 RPM. It idles and runs fine under normal driving conditions, but when the throttle is floored, it will not rev any higher and feels like something is pushing against the car in the opposite direction. Checked to see if the throttle was opening all the way, and it is. Has anyone experienced this before? Need some opinions. Is it more likely to be a fuel problem, or ignition?
If it happens out of gear then it's valve springs(though I've never seen springs go that soft) or maybe ignition, ign should give some erratic symptoms... If it revs freely to 6K neutral but won't pull past 4K in gear, it's probably a fuel delivery issue... That could be anything from the carb back to the tank, though is usually clogged filter, weak pump, restriction in the tank or maybe a collapsed fuel line... In rare instances a pin hole in the steel lines has caused such problem... Would prob be a good idea to check fuel pressure if filter or pump doesn't fix it...
Check your timing. Pull the vacuum advance hose off the carb, pull the distributor cap off and while sucking on the hose, watch for movement in the breaker plate inside the distributor. Also check the secondaries on the carb to see if they're opening.
Yes, this is while driving. I have not tried to rev it in Neutral. Not really comfortable "free-reving" to 6000. I will look into all the suggestions. I know it's either fuel or timing (but which?).
If the timing was so far off it wouldn't turn past 4K RPM, it'd be so sluggish you'd know something was amiss without really pushing it... If it runs somewhat normal then lays down fairly quickly, it's most likely a fuel issue... Do you have a MSD or similar that has a rev limiter??? If so something could be triggering that, but otherwise I'm voting fuel...
Make sure you're running the correct coil on it. Mine had the wrong coil and that caused it to run strange, can't recall exactly what it did though (been a few years now since)
fuel tank Check to See If Tank Pickup Screen Is Clean...I ran My Tank Dry Pulled The Six Cylinder A year Later V8 Installed, Fresh Fuel and 30 Miles on The New Motor and Its Running Like *%#. Put New Fuel Pump, Lines & Filters with New Engine..........IDK What the Chemical Makeup of the Crap On There Was But I Removed It.
sounds like a plugged fuel filter and the back two barrels not opening AND lets not forget to check your transmission to make sure youre kick down is working and youre shifting down when you step on it
Well, 'took the carb apart and cleaned everything real good. There was a lot of crap in the secondary fuel bowl and metering block orifices (the car sat for a while). Changed fuel filter, power valve, gaskets, (also replaced the accel pump squirter and umbrella check valve while I was in there) and put it all back together. The motor now pulls to 6-grand again. I Put some fresh gas in the tank and some Sta-bil.
