Duntov Cam Valve Adjustment Clarification

[Larry B.]

After reading Duke's/John's tech paper, I am a bit confused on the duntov cam lash adjustment on my '61. Can both valves of each cylinder be adjusted when the cylinder is a TDC on the compression stroke or does the lash have to be adjusted at each 90* interval like the 30-30 cam? I wasn't sure which method was better or correct. Also, is the easiest way to index the balancer with a piece of chalk and straight edge at 90* intervals? Regards, Larry

[Clem Z.]

Re: Duntov Cam Valve Adjustment Clarification

here is another way to adjust valves

[Duke W.]

Re: Duntov Cam Valve Adjustment Clarification

What date revision of the paper do you have?

Duke

[Bruce B.]

Re: Duntov Cam Valve Adjustment Clarification

Does anyone adjust the valves on a warmed up engine while it is running?
It always worked for me on my 340 HP solid lifter 62.
Other then some stray oil it seems to me that adjusting them dynamically with the engine running gives the best results.

[Larry B.]

Re: Duntov Cam Valve Adjustment Clarification

Hi Duke,

I have the latest paper that was posted here, I believe 2008 update. I needed some clarification on the paper. Do you adjust both valves per cylinder when it is at TDC on the compression stroke or do you do the 90* index adjustment like the 30-30 cam? If you can do it either way, which is easier/more accurate?

[Stuart F.]

Re: Duntov Cam Valve Adjustment Clarification

Larry;

I interpreted it as every 90* on my Duntov equipped 63 L-76 and, through various means of communications on the subject over the years, believe that is not only right, but the intent of the procedure that Duke and John developed to cover all SHP small blocks w/ solid lifters. It worked very well for me. I did buy a timing tape which I put on in just a short time from beneath the car (cleaning, applying while barring engine over, etc.). I expect the time to be worth it as it should last a number of years.

I too used to adjust them hot and running many years ago, but got too many oil burns on my hands and fumes (which led to the worst headache in my life). After that, I pretty much stuck to the method Clem describes, but never felt it was precise enough. The 90* method showed that my intakes (from my previous adjustment) were very close, but my exhausts were about .002" too loose.

[Duke W.]

Re: Duntov Cam Valve Adjustment Clarification

The first paragraph of the second page says: "With the Duntov cam this indexing procedure may be used, or the both valves may be set with the engine at TDC of the compression stroke".

Is this not clear? If not, please suggest wording that will make it clear.

I have another request - something that you can contribute to the cause.

Adjust your valves using the procedure that is mandatory for the 30-30 and LT-1 cams. Then continue to turn the engine past TDC#2 back to the starting point, TDC #1. Check both valves on #1 then go to TDC #8 and check clearance of both valves on #8. Check the next two cylinders in the firing order sequence at TDC and let us know if they are the same.

According to my analysis of the Duntov cam, both lifters should be on the base circle at TDC of the compression stroke, but I've never gotten a confirmation from actual measurements on Duntov cam engine.

There may be some slight variation between measuring using the 30-30/LT-1 method versus checking both valves at TDC of the compression stroke of each cylinder because the base circle runnout tolerance is +/- .001" from the nominal base circle diameter.

Duke

[Larry B.]

Re: Duntov Cam Valve Adjustment Clarification

Thanks guys! I will do the 90* method and verify at TDC. The 90" method appears easier to accomplish.