i have an 81 f150 that i swapped a 351w into. but i dont have any power above 3200 rpm. idles fine pulls hard up tp 3200 rpm but after that its sluggish.
what i have:
edelbrock rpm heads and intake
msd distributor and 6al cdi box
aftermarket pistons and connecting rods
bored 30 over
9.1 to 1 compression
upgraded c6 transmission
what ive tried:
2 different carbs 1. a remaned edelbrock 650 cfm thunder series. couldn't get it to tune. idle screws did nothing. 2 a friends 750 cfm edelbrock its kinda worn
compression test 180 +-2psi on one bank 180 +-2 psi on the other (throttle was not open)
spark plugs are clean
vacuum test erratic 12-16 steadying out to 20 at part throttle
timing advance 10 initial 34 total

any help on why my ford falls on its face at high rpms would be a great help
thanks

 

What cam?

 

mild 4x4 extreme

 

You don't have any of the stock exhaust on the truck right?.. including the stock manifolds, Y pipe and cat.

 

nope ceramic coated headers duel exhaust no cat

 

Exactly what cam was installed.. grind number?
Was it installed straight up?
Was it verified(degreed) to be what it's supposed to be?

Even with something like an XE250H or XE260H this motor should effortlessly sing to 5000rpm, so eithing something is wrong with the cam(wrong grind) or somethings up with that ignition system like a faulty box or the rev limit is set way low.. if it's adjustable that is.

 

i lost the paperwork on the cam i think it was xe260h or close to that
i had the engine built for me so i cannot be sure if cam timing is correct
rev limiter was set to 6000 and i also ran it without one no change

 

What type of fuel pump?Is it new?Maybe a restriction in the fuel delivery system.Check the fuel line from tank to carb.If it's the original tank,it might be some debris/junk is obstructing the pick-up/filter.Kink in the fuel line.Check fuel pressure at the carb.

 

new fuel lines from each tank electric fuel pump. if it was fuel wouldnt it miss or sound ruff when i surpassed the amount of fuel being supplied.

 

It might stutter or stumble with a fuel supply issue and it might not.I have a similar build with less cam (473" 493") and shortly after I got it running well I noticed that at higher RPM's it was losing power and felt like it hit a wall.I finally removed the in line fuel filter on the chassis and just have a filter after my mechanical fuel pump.Now it runs great.You very well could have an improperly installed cam/timing set especially if it's been running the same way since day one.My Comp Cams 4x4 grind is installed straight up and revs with ease.If the cam was too big it would be lazy at lower rpm's.

 

thanks vann
ive been leaning towards cam timing but haven't got to tearing the front of my engine down. my electric fuel pump is a used one one of my friends had but i didn't question it cause i thought my engine would stumble. i might just have to get another fuel pump and if that doesn't fix it at least i would have a spare.

 

Drive it again, but this time when it hits that rev limit, kill the engine immediately, then pop the hood and remove the fuel bowl sight plug and see where the fuel level is before changing the fuel pump. If this is not the problem, then I'd take a closer look at the MSD system, it wouldn't be the first time someone had problems with the settings "out of the box" with these.

 

nope not fuel pump
how could i check the msd box
or maybe an easy way to determine if it is cam timing