Tune Up Trouble

[Bob_Spidell]

Quick Update:
Looks like I have bolts (instead of studs and brass nuts) at the downpipe/exhaust manifold flange. Yellowish. Grade 8? ...

Grade 8 bolts should have five radially-spaced tick marks on the head (Grade 5 have 3).

EDIT/CORRECTION: Grade 8 should have SIX tick marks (should be 8, but that's another thread ) Thanks, Steve.

[steveg]

I'm using tube headers now, but, FWIW, have found grade 8 lock washers keep their springiness when used on the exhaust manifold studs.

[Keith_M]

I had a similar problem earlier this summer. I finally traced it to a sticking carburetor piston, which prevented the piston from dropping all the way. After fixing the piston, I realized that the carburetor was running too lean, presumably because I was tuning it with the piston stuck. Once I fixed the piston and retuned the carb, the popping and backfiring stopped.

[Joe Schlosser]

You need to hear the nice click when the piston drops down onto the bridge.
And all the pistons should slide down the chamber equally

[John Turney]

You need to hear the nice click when the piston drops down onto the bridge.
And all the pistons should slide down the chamber equally

Also, lower it slowly with your finger underneath, sometimes they will sound ok if you let them drop, but may hang up within 1/8" from the bottom.