duntov valve lash

[William F.]

Duke,
Know this has been covered and am embarassed to ask, but new to adjusting solid lifter valves. I have read article by you and John. Specifically, With Duntov cam, NOT other mechanicals, are you saying put #1 to TDC and adjust both intake and exhaust ON #1, then rotate 90*, do both on #8, on through firing order till finished?
Thanks-considering '62 340 hp
'67 L79
'67 L36

[Duke W.]

Re: duntov valve lash

Yes, as stated in the paper that method is optional for the Duntov cam only. Or you can use the method outlined for the other mechanical lifter cams.

Duke

[William F.]

Re: duntov valve lash

Duke,
On solid lifter BB's, do you have to use method you describe for 30-30 cam or can you use method as for Duntov-adjusting both intake and exhaust for same cylinder,starting at #1, then going to next in firing order, etc.?
Thanks again

[Clem Z.]

Re: duntov valve lash

the most accurate way to adjust solid lifter cams. this will work with any cam

[Duke W.]

Re: duntov valve lash

Duke,
On solid lifter BB's, do you have to use method you describe for 30-30 cam or can you use method as for Duntov-adjusting both intake and exhaust for same cylinder,starting at #1, then going to next in firing order, etc.?
Thanks again

Use the 30-30 method. The optional method for the Duntov cam is only applicable to that particular mechical lifter cam - no others.

Each method requires rotating the engine 90 degrees seven times beginning at TDC #1. The only difference is what valves you set at each position. It's easy to keep track of because you don't have to keep rotating the engine and watch the valves go up and down to figure out which one you can adjust. I always prepare a sheet on a clipboard with what valve to adjust and each crank position and record the clearances I initially measure. If you follow the procedure, it's easy to keep track of where you are and fool proof.

Due to the very long duration of the 30-30 and L-72 lobes (which is also the LT-1 inlet lobe), including the clearance ramps, the lifter is not quite on or barely on the base circle at TDC of the compression stroke. The method required for all mechanical lifter cams other than the Duntov ensures that the lifter is on the base circle with plenty of margin.

The total duration of the Duntov from the beginning of the opening clearance ramp to the end of the closing clearance ramp is about 450 degrees, and 540 for the 30-30, so with a 30-30 cam the lifter is only on the base circle for 180 crank degrees, which is 90 cam degrees.

Duke

[Larry B.]

Re: duntov valve lash

Always adjust the intake valve when the exhaust startsto open and adjust exhaust when the intake starts to close .This will always be the valve being adjusted on the base circle on any cam and is easy to just follow right down the the row.