adr3naline

Hey everyone. My mustang runs great at lower RPM's, but when I give it a little throttle and the RPM's climb, it's like the horsepower just is gone... and all I have is a weak loud car.

I'm going to be adjusting my timing soon, and I'm hoping/guessing it will help, but does anybody have any other suggestions for me?

andrewmp6

You need to dyno the car to see your power band and yes theres a point higher up in the rpm you loose power thats why most v8s have redlines kinda low.

Gun Jam

How "high" of an rpm? 3-4k or 5-6k?

if its around 5-6 thats probably normal for you engine.
Does it sound like it might be losing spark or fuel? or just not in the power-band any more?

-Gun

mjr46

is your motor stock?? if so don't expect much power over 4800 to 5000...if it's not stock what cam and build do you have???

cmanf

+1
if its built like mine the faster it goes the more gas it will useand A hotter spark that can stay that way in high rpms.
My last engine(289) was fine I thought untill I added a msd and a holly blue fuel pump then it pulled up to 6500 hard.
5 grand seems to be were a lot of cars Ive had v8's anyway seemed to max out pulling power unless they were modified.

Starfury

The factory 289 cam falls off hard after 5000 (not that I'd trust 40yr old valve springs that far). It's designed for low-end torque and driveability, not high rpm power.

But yes, start with the timing. Check the function of the mechanical advance while you're at it. A bad mechanical advance curve will cause severe performance issues.

adr3naline

My 70 doesn't have a tach inside, and I wish it did... but I'm always on the higher RPM side. The engine is totally stock, except it has a 4 barrel, rather than the 2.

My transmission usually takes a bit to shift when I give it some gas like that, so it drives me nuts because I don't have any power for a little while.

Anyway, thanks for the info everyone!

67mustang302

You have a weak cam with scrawny springs, so it ain't gonna rev all that high. But you REALLY need a tach if you're gonna rev the engine, otherwise you're just asking for trouble. Get a rev limiter too.

KBunny

Or just keep it simple and don't push your car that hard unless you are ready to pay the expense of when it breaks and the possible harm it could do to you in the proses... the more you womp on the engine (or the whole car for that matter) the faster it is going to break down.

Daze

My father had the exact same problem on a 351 in his F100 turned out the vacuum advance was sticking and not advancing the timing at high RPMs. ran great at lower RPMs but got weaker the faster you went.