Mechanical cam valve adjustment at engine plant

[William F.]

Re: Mechanical cam valve adjustment at engine plant

Duke,
I went back and reviewed your valve setting article and it says at top "TDC #1 and #6 will not work on the Duntov cam." Correct? So, what is a method simpler than the one one for L71, LT1, etc. but that will work on the Duntov cam?
Thanks

[Duke W.]

Re: Mechanical cam valve adjustment at engine plant

The #1, #6 TDC where you can adjust the 8 valve specified works ONLY, repeat, ONLY for hydraulic lifter camshafts. Read the paper again. You can adjust Duntov cam valves at TDC of each cylinder - that cylinder's two valves, but you still need 90 degree marks to be at TDC for each cylinder.

I don't know if the "4 valves at 180" will work for a Duntov cam or not.

Duke

[William F.]

Re: Mechanical cam valve adjustment at engine plant

Duke,
Just one more question and i'll let you go and I will underatand.So, on a Duntov cam, I can adjust both the intake and exhaust valve on each cylinder while that cylinder is at TDC, rotating crank in firing order to get each cylinder in firing order to TDC and adjusting in firing order?
Thanks dfor all the information and refreshing my memory.

[William F.]

Re: Mechanical cam valve adjustment at engine plant

Think you actually answerd my question in your last reply. On my Duntov cam, I can adjust both the intake and exhaust valve clearance on a particular cylinder while each cylinder in firing order is at TDC.

[Duke W.]

Re: Mechanical cam valve adjustment at engine plant

With a Duntov cam you can start at TDC of the compression stroke for #1, and adjust both inlet and exhaust valves of #1, cold. Both rockers should be loose or verify that the rotor is pointed at #1 cap tower assuming you have the cap wiring properly configured.

Rotate 90 degrees CW as viewed from the front and you will be at TDC of the compression stroke for #8. Adjust both valves, and rotate 90 degrees to #4 and so on in the firing order of 18436572.

If you use my recommended clearances of .010/.016" you won't need to check them for 25K miles assuming normal road driving and the nuts have good torque pre-load.

Chevrolet's recommended lash check interval is 12K miles, but with the tighter lash doubling it is okay.

Duke

[John D.]

Re: Mechanical cam valve adjustment at engine plant

Here it is: This is the only adjustment of valve clearance done at Tonawanda.

Thank you for the pic. Amazing how they did this very manual operation on hundreds of engines an hour.

[Bill M.]

Re: Mechanical cam valve adjustment at engine plant

Thank you for the pic. Amazing how they did this very manual operation on hundreds of engines an hour.

I agree. I worked the summer of '69 in the Tonawanda dyno lab, so I got to walk the assembly line and watch these engines get screwed together. The speed of assembly was impressive, but the quality and attention to detail impressed me the most. I do not remember watching the valve lash process, so I can't help with how the engines were indexed.

The L-88 valve lash was adjusted at the same station as all the other engines. The L-88 (and L-89) had aluminum cylinder heads, so I assume the cold valve lash was not the same as the hot lash....? Dunno. The ZL-1s were hand-assembled in a clean room but were also lashed cold. There was no facility (or time!) to run production engines until warm.