Valve lapping

M

Mort

Senior Member
I am in the process of changing heads on my 31 coupe. While the old head is off I am going to lap the valves. Got the keepers off and checked and cleaned the seats etc. I would also like to check the clearance. My question is about the springs. Nothing I can find talks about removing them (Andrew's book, service bulletins, this forum etc.). Is it necessary or can I just compress them to check clearance?
Thanks
Mor
 
Mor,

Remember you only want to "Lap" them lightly to a clean seal all around. If they need more than that, have them ground.

You can just work the springs out over the bosses or leave then in. Do you have the mushroom stems or straight stem "modern" valves?

I would just lap the valves lightly. Clean all the compound off. Put the retainers back on and adjust the valves.

Remember the valve has to be on the heal of the cam lobe when you lap it.

Richard
Anaheim CA
 
Just finished lapping mine. Reinstalled the springs and old style keepers. The lifters are lock nut type with the lifter bosses uncut. To adjust the valves I would put the lobe toe on the lifter then pry up on the spring until I could get a spacer under the valve head. After all of that I could get the lifter up high enough to adjust. Once it was set I would turn the heel of the lobe to the lifter and check the clearance. .015 exhaust and .013 intake.
 
Just curious, why do want to lap the valves?? What was the compression before head removal?? The valve lash/clearance is normally checked with everything assembled.. Do you have original or adjustable lifters??
 
Patrick L. said:
Just curious, why do want to lap the valves?? What was the compression before head removal?? The valve lash/clearance is normally checked with everything assembled.. Do you have original or adjustable lifters??
Click to expand...

Compression on #4 was low and there appears to be just slight pitting on the exhaust valve. I thought I would just lap them all.
Have original mushroom type valves.
 
Richard in Anaheim CA said:
Mor,

Remember you only want to "Lap" them lightly to a clean seal all around. If they need more than that, have them ground.

You can just work the springs out over the bosses or leave then in. Do you have the mushroom stems or straight stem "modern" valves?

I would just lap the valves lightly. Clean all the compound off. Put the retainers back on and adjust the valves.

Remember the valve has to be on the heal of the cam lobe when you lap it.

Richard
Anaheim CA
Click to expand...

I thought you could lap them with piston about halfway up on the compression stroke?
 
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