[JUDGE3]

455/E heads/hyd roller/holley carb...car has been running perfectly, restoring and start it routinely. did drive it last summer running perfect.

started it today after last start it didn't seem to be running right. so today it definitely pops at idle, seems to be the drivers side. at quick hit of the throttle it will backfire. seems to be smooth at 3,000 rpm holding steady. engine temp cool and no changes, oil pressure good/same as always. adding that it pops thru the exhaust, backfires thru the carb.

no water in the oil. no "popping" thru the carb at idle. put fresh premium gas in due to car sits, to rule out bad gas.

new dui distributer, I had a new spare replacement module, changed it just to check, no difference.

removed valve covers, nothing broken or loose there. removed float bowls only because I once had a jet fall out on a new demon carb once and it was similar symptoms. all ok under there.

checked for vacuum leaks, found none. timing is steady at 14 degrees initial/no changes have been made always ran great.

appreciate any help and where best to start from here. do blown power valves act this way? does it sound like a blown head gasket? collapsed roller lifter?

Eric

[25stevem]

If it pops back out of the carb when you wing the carb open, yet it’s clean and smooth at a steady rpm then to me like there’s two possiblitys for that and there both related to a carb issue.

1( the accelerator pump discharge either side of the carb( assuming a two plane intake) is not working.

2) the passage way for the jet on that metering block on that same side of the carb is not passing fuel.

My moneys on old dead jelled up crappy fuel stopping the working of the accelerator pump.

[JUDGE3]

Originally Posted by 25stevem

If it pops back out of the carb when you wing the carb open, yet it’s clean and smooth at a steady rpm then to me like there’s two possiblitys for that and there both related to a carb issue.

1( the accelerator pump discharge either side of the carb( assuming a two plane intake) is not working.

2) the passage way for the jet on that metering block on that same side of the carb is not passing fuel.

My moneys on old dead jelled up crappy fuel stopping the working of the accelerator pump.

I will check, would this cause the popping thru the exhaust just sitting at idle?
(I hope its a carb issue and not worse for sure) do blown power valves do this? thank you for the input

[25stevem]

A bad power valve would effect both banks of the motor.

[JUDGE3]

I thought i had been starting it often enough to keep things "fluid". it did in fact just need a good carb cleaning, running perfect again.

now back to weld/gap fitment and bodywork. yeha

[25stevem]

Good to hear!
You likely had a clogged air bleed on the top of the throttle bore on the primary side.
Nice easy fix, they should be this way, lol!