I initally set the valves at .010 & .020 but was getting some slapping so I worked down to .08 on Intake and .016 on Exhaust.
When cold the engine runs good but gets out of kilter when hot. The carb (1bbl 1920 Holley) tunes fine when engine is warming up but will not adjust when hot. Does not run better with choke partially closed. Have to speed up idle to keep it running when hot. Screwing in or out the mixing screw has no effect when hot.
Doesn't seem to have any vacuum leaks. Has stock manifolds which were surfaced by machine shop.
Has new MP electronic distributer. Timing is best at TDC and advances fine.
Still makes a rattling/scrubbing sound. Seems to miss at tailpipe.
Except for the noise its running just as it did before the rebuild. Ran fine when cold but not when hot.


usclstaffingnet@sprintmail.com

What cam is in this rebuild, stock? The exhaust lash sounds a bit tight for a stock cam, you may want to back-off that a bit.
:
: When cold the engine runs good but gets out of
: kilter when hot. The carb (1bbl 1920 Holley)
: tunes fine when engine is warming up but
: will not adjust when hot. Does not run
: better with choke partially closed. Have to
: speed up idle to keep it running when hot.
: Screwing in or out the mixing screw has no
: effect when hot.

"Holley 1920" says it all for me, try a different carb. (hopefully a Carter)
I can not count the number of 1920s that have "gone bad" on me, most I could not fix because something went wrong inside the sealed metering block.
:
: Doesn't seem to have any vacuum leaks. Has
: stock manifolds which were surfaced by
: machine shop.
: Has new MP electronic distributer. Timing is
: best at TDC and advances fine.
: Still makes a rattling/scrubbing sound. Seems
: to miss at tailpipe.

Tight exhaust lash and a messed-up Holley carb. is my guess on the miss. The "rattling/scrubbing sound" will take some detective work, have you run it for a moment with-out the fan belt on?
:
: Except for the noise its running just as it did
: before the rebuild. Ran fine when cold but
: not when hot.

Do you have an extra carb. or do you have another Slant car around where you can "test swap" carbs to see if that's the problem.
DD

I don't have a huge amount of insight here, except to wonder about the tight clearances on the valves. The reason for the clearances is to allow for lubrication of the tip and room for expansion when the valve train heats up. This is why the exhaust requires more clearance because it runs hotter. If the clearance is insufficient the valve will be held off its seat. At the least, you lose power and economy; at the worst you prevent proper lubrication of the tips and may potentially damage the valve face and seat.
I also wonder how many 'rebuilders' actually 'dress' the rocker tips. I always pull the rockers off the shaft and regrind the radius on the valve end of the rocker. If the engine has not been properly maintained, and/or the valve adjustments ignored the rocker tips will have divots pounded in them. You can't get proper feeler guage readings with divots in the rocker tips and valve stem tips.

fglmopar@aol.com