i've been chasing this odd ball problem on my car, it looses power after 4500 rpm, i can't seem to grasp on whats going on. i've so far swapped my 670 to a 750 double pumper, which made everything better except the problem i was trying to fix, checked my timing i'm running 34 degrees of total timing, the heads are roush 200 cc heads. i'm out of ideas. the car runs fantastic upto that point, then falls flat on its face. any suggestions what i should check next?
they should be ok, my cam is about as biggest i can go on them, springs are rated for up to 560 lift so i should be ok.
reason i ask is some have the 1.250 valve spring (sounds like what you have) and it probly isnt helping your situation either there really weak springs and the voodoo cams have a pretty agressive ramp i ran the same cam in a 351w
my guess is that your fuel pump is not geting enough fuel to the carb. does the motor just shut off till you release the gas pedal or does it stumble and surge at 4500rpm? what type of ignition system are you running.
i would check the fuel supply i had the same problem i couldnt figure out what the problem was then i realised i was running a 2bbl fuel pump i went with a edelbrock hi perf pump i gained hp and the car quit loosing power on the top end
i've already tried swapping fuel filters, i'm running holley blue at 7.5psi before the carb, you are correct on the springs, but i still think it should go past 5k with no problem, i'm planning to install better ones this winter. my ignition is msd 6al, billet electronic distributor, blaster ss coil, i'm running accel shorty plugs. I've already tried swapping msd pills, and running without any, still does it. Only thing i haven't tried is running with no air cleaner, tomorow i may try that, then check and see what kind of jets are in the carb.
check inside the distrubor cap. ive seen the advance components come apart and ground out somehow at high rpms. can you free rev it up to 5500 rpm?
One other time I lost power I found the problem by swapping out the MSD box. That was after I chased my tail for a while also.
Did you have the vacuum advance disconnected when you set your timing? If not then under load you won't get enough advance.
Well then, I guess that isn't the problem. Do you have anything connected to the ignition circuit - like a fan or choke? Is your air gap set correctly? What is the gap on your plugs? What are you running for wires? Your problem seems to be active only under a load... Ignition, fuel and air demands are higher under load. You mentioned that you are using a pump before the carb - is it mounted up front or back closer to the tank? If it is mounted up front then move it back near the tank as low as you can. The pump may not be able to pull fuel from the tank under load with it mounted up front.
Do you have anything connected to the ignition circuit - like a fan or choke? I know for a fact that my coil positive and negative run on separate circuit, i think the msd box gets power from my fuse block, will try running separate power wire for it tomorow. Is your air gap set correctly? Not sure what you mean by air gap? What is the gap on your plugs? Will double check tomorow, i'm running accel 276s for plugs if it matters, what gap i should gap them? What are you running for wires? Accel 9002c Ceramic boot spark plug wires. the only wires i can run without melting boots every week. Your problem seems to be active only under a load... Yestoday i adjusted secondaries fuel bowl level, and double checked the timing, set for 13degrees at idle and to 33 of total advance, went for a spin and the car was able to rev to 5500 under load, but towards top end seemed to loose a bit of power and then hit like a rev limiter. it seems, it does the same thing at idle free reving.
