Ok given the history and the symptoms I would try one other thing before
tearing into it.
Take the exhaust pipe loose from the manifold and try starting it.
As I recall it just started doing this for no reason. I have seen
mufflers that have a baffle come loose and plug the outlet or double
wall pipe that collapses on the inside.
Could be valve timing, could be a badly worn camshaft. Try the exhaust first.
Michael Lubitz wrote:
>
> Guys,
>
> I need help. A while back I was having a problem with hard starting, etc.
> with the 216 in the '46. It was diagnosed by the group as many things:
> carburetor icing, low compression, etc. So I rebuilt the carb, and the fuel
> pump, and fixed the heat riser. No luck.
>
> Checked compression: Dry: 98, 90, 95, 45, 95, 90. Uh oh, number 4 is real
> low. So we did a wet test on number 4 and the compression did not change.
> O.K., need to do a valve job. When we took the head off, it was obvious that
> the exhaust for number 4 was burned - badly burned.
>
> Now I asked you guys again about hardened seats, valve guides, doing all of
> the valves or just doing number 4, etc. Again, good advice - go the whole
> way.
>
> I did. $400 worth of new valves, seats, guides, lapping, surfacing, etc. The
> head looked beautiful. We then put it all back together with new paint and
> cleaning everything in sight and torqueing the head bolts to 85 pounds and you
> name it, we did it. Clean and nice.
>
> We went to start the beast yesterday and Buddy (the truck's name) had the same
> problem as we had at first - hard starting and he would not stay running.
> Good fuel, good spark, adjusted the valves loose (Did the preliminary valve
> adjustment with the deaf man from across the street who used to work on old
> Chevies. He is probably 70 now. It was fun!)
>
> So we checked compression again. Dry: 50, 75, 55, 50, 50, 55. Yikes.
> Somewhat depressed, we did a wet test on number 4 and it did not change a
> bit.
>
> So, now it gets to be Sunday night. We called our truck club's resident
> expert. (He knows engines, he just knows engines.) No real answers. Checked
> my doubts: Surface rust on the cylinder walls - no problem. Cleaning the tops
> of the pistons with a wire brush and possibly scarring the cylinder walls - no
> problem (of course, the wet test would have showed that.) Valves set loose -
> no problem.
>
> The only thing that we can think of is that the valve job is bad. I asked the
> guys who did the work when they were doing the valve job about being sure that
> their work is done correctly. They said that they check each of the valves by
> pulling a vacuum on the intake port (I don't know the word here, but it's the
> about 1 1./2" round hole that connects to the manifold) and also by pulling a
> vacuum on the exhaust port. And again, I do not know the word for the
> rectangular hole that the exhaust exits to the exhaust manifold.)
>
> HELP. Any thoughts from you guys? Know that I am sad but up to the
> challenge. Just want to do things right and get my Buddy back. I miss him
> and feel when he is hurting.
>
> Thanks to all of you for the help in the past and for help now. This is the
> great group of guys (or of mostly guys).
>
> Michael Lubitz
> 1946 Chevy 3/4 ton, stock
> 1948 Chevrolet 3100, hot rod
> Austin, Texas
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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