360, idles great stumbles uptop

[zano]

Time for a compression check. Burnt Valve or Stuck Valve, or bent push rod not opening valve far enough.

Read the spark plugs, are they all burning the same, or is there one or two odd balls?


* * * * *

You called it im pretty sure lmao they all burn the same by the looks of it

 

[zano]

So upon further disassembly, the valve train seems to be okay. Don't see anything to crazy there
But the cylinder walls aren't looking so hot, some marks on the cylinder but nothing crazy a quick home job should sort it thankfully.

 

[AbodyBB]

Remember that with rising vacuum, the advance should increase. If your vacuum advance is weak or bad, you will set timing with out vacuum advance and it won’t get proper advance with increased RPM. (Lose power right around 3000)
With a timing light on, pull the vacuum line and see if it drops to base timing. (5-10 degrees BTDC)Use a hand vacuum pump then to put vacuum on the advance to see it rise to full advance. Stock should be about 15 degrees added. That verifies if your advance works without leaks.
Also try swapping out the ignition box.
Lastly your issue could be a weak/worn fuel pump. But you would know that one right away as the engine would start missing and pre detonating as your rpm goes up.

 

[zano]

Remember that with rising vacuum, the advance should increase. If your vacuum advance is weak or bad, you will set timing with out vacuum advance and it won’t get proper advance with increased RPM. (Lose power right around 3000)
With a timing light on, pull the vacuum line and see if it drops to base timing. (5-10 degrees BTDC)Use a hand vacuum pump then to put vacuum on the advance to see it rise to full advance. Stock should be about 15 degrees added. That verifies if your advance works without leaks.
Also try swapping out the ignition box.
Lastly your issue could be a weak/worn fuel pump. But you would know that one right away as the engine would start missing and pre detonating as your rpm goes up.

Thanks for the info. When it was together I had a fuel pressure gauge hooked up had solid pressure. And I had tried several distributors ignition boxes and an hei. Base timing was always good. But it always did the same no matter what. Very well could have been vacuum advance issues, but the cylinder walls weren't doing it any favors there pretty washed out

 

[AbodyBB]

Thanks for the info. When it was together I had a fuel pressure gauge hooked up had solid pressure. And I had tried several distributors ignition boxes and an hei. Base timing was always good. But it always did the same no matter what. Very well could have been vacuum advance issues, but the cylinder walls weren't doing it any favors there pretty washed out

I’m sorry to all. I have it backwards. Advance weights advance timing on RPM and vacuum advance drops advance with throttle opening and a drop in vacuum. For anyone faced with those questions so ensure the advance weights are completely free and the springs aren’t broken. Also make sure you are on the correct vacuum port of the carb.

I did jump in late on this so I’m sorry for that but if your plugs weren’t fouled then you were having a timing issue. When you put it back together, check those timing issues.