cold valve adjustment

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river_side
Posts: 14
Joined: Sat Aug 31, 2019 6:30 pm

cold valve adjustment

Post by river_side »

I followed the book and turned an additional 3/4 turn after the "play" was removed.
My problem is I am getting a backfire now.
Did I turn in too much? not enough?
Thanks.

joelsplace
Posts: 1163
Joined: Wed Oct 13, 2010 12:51 pm
Location: Northlake, TX

Re: cold valve adjustment

Post by joelsplace »

Probably too tight. Common mistake.
Even if done right some lifters don't like that much preload.
113 Corvairs, 5 Ultravans and counting
Northlake, TX

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bbodie52
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Re: cold valve adjustment

Post by bbodie52 »

Is the "backfire" firing through the carburetor intakes or through the tailpipes? if an intake valve is adjusted too tight, the intake valve may not be closing completely for the compression stroke. When the spark plug ignites the fuel/air mixture in the combustion chamber, some of the ignition pressure may be leaking back into the intake manifold. If an exhaust valve is adjusted too tight, the ignition that drives the piston down on the power stroke may also be leaking into the exhaust manifold via a leaking valve that cannot fully close.

You may want to readjust them all — using only ½ turn for pre-load to center the piston in each hydraulic lifter. Or you may opt to adjust the valves of a running engine, tightening each rocker just until the tapping sound stops — then slowly adding another ½ turn.

At 18:00 minutes he gets to the initial cold adjustment of the valves...
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

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