66 427/425 backfiring

[Tom C.]

My 66 427/425 runs very smooth and strong up to about 4800rpm at which point it
"bogs" and backfires refusing to rev any higher. I am running a single point tach drive distributor rather than the TI system. Anyone have a suggested troubleshooting list? I do believe it is getting enough fuel. I am also using the Lectric Limited braided stainless wires.

[steve wallach]

Re: 66 427/425 backfiring

I had this problem on my 67 / 427-390 I replaced the power valve and checked the timing and plugs.
I was very frustrated and replaced the power valve again, still no luck.
A friend of mine convinced me to replace the power valve again with a Holley
PV and that fixed the problem!

I don't know if this is your problem or not, but it may help?

Regards,

Steve

[Duke W.]

Re: 66 427/425 backfiring

Could be distributor issues. The old single point dist. would barely run over 5000 when new, and given all the wear and tear...

Hook up a dwell meter and free rev the engine to 6000. If the dwell drops more than two degrees the distributor needs work.

I never got the single point to work right and rev consistently to 6500 on my L-76 until I shimmed up the end play and installed the high breaker arm tension points. Chances are your old breaker plate is wobbly, too.

Duke

[Dick W.]

Re: 66 427/425 backfiring

You might want to check the plug wires also. The repro wires leave something to be desired.