1 8 4 3 6 5 7 2.
Double check that your firing order is right.
This is the first thing that comes into my mind after reading your description of the issue.
Cylinders firing when there not supposed to will limit rpm greatly.
Pop the Dizzy cap off and look for signs of arcing or a busted rotor tip.
Next is that with the 30k on the heads they may have a intake seat or 2 that is moving around and is loosing seal.
This would also explain your backfiring.
The above if taking place is very bad because it’s likely to snap a valve head off on you.
Have you had to readjust your idle speed lately to pick it back up?
That would indicate retarded timing and maybe enough to cause backfiring.
I would put weak valve springs last on the list of things to check since you say the motor is even not smooth at idle anymore.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
Last edited by steve25; 03-24-2024 at 12:32 PM.
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