[chevyguy468]

i built a bbc 468 with12;5;1 compression with a soild roller cam with a lift of 714 timing at 32 degrees and total timing at 40.i had chuck nuytten build my 1050 dominator, and i am running a th350 tranny with a 4500 stall, my problem is when there is a load on the motor at around 2000-4000 rpms it breaks down like the msd box is at its rev limiter i changed msd chips , changed plugs , rotor cap and rotor button and even the coil and still no luck. can some one help me im at witts end its driving me crazy

[ap72]

Originally Posted by chevyguy468

i built a bbc 468 with12;5;1 compression with a soild roller cam with a lift of 714 timing at 32 degrees and total timing at 40.i had chuck nuytten build my 1050 dominator, and i am running a th350 tranny with a 4500 stall, my problem is when there is a load on the motor at around 2000-4000 rpms it breaks down like the msd box is at its rev limiter i changed msd chips , changed plugs , rotor cap and rotor button and even the coil and still no luck. can some one help me im at witts end its driving me crazy

check the fuel or spark curve? this can lead to misfires. Also, try a different ignition, sometimes they can go out at certian RPM's.

[bigdog7373]

Sweet jesus! 12,5:1??? What kind of fuel are you running?

[chevyguy468]

im running 115 octane, i have a msd 6al box with a msd blaster 2 coil and a mallery unilite dist. do you think the dist is junk i never had a problem with it when i had it in a small block i was told b4 they were but it never crossed my mind any suggestion on ignitions to go with. thanks

[4 Jaw Chuck]

What's the jetting? Post some pics of the plugs.

[cobalt327]

Originally Posted by chevyguy468

im running 115 octane, i have a msd 6al box with a msd blaster 2 coil and a mallery unilite dist. do you think the dist is junk i never had a problem with it when i had it in a small block i was told b4 they were but it never crossed my mind any suggestion on ignitions to go with. thanks

While you can troubleshoot what you have, I would simply try an HEI distributor and coil just to eliminate or confirm it's something with the carburetion, MSD box or the Unilite distributor. Lock the timing in at 30-34 degrees (no mechanical or vacuum advance) just for the test. No ballast resistor or resistor wire to the HEI.

[chevyguy468]

thanks guys for the info, but i think the problem is solved. the rev limiter went bad in the msd 6al box. when i take the rpm chip out it runs fine, when i put it back in the same problem, i tried a hand full of different chips and it did the same thing. so im sending it back to msd to have it fixed. thanks again