1963 340HP Valve Settings Cold w/o Knowing Cam#

[Frederick H.]

Does anyone have insight into how I can determine the cold valve lash settings for a '63 340HP without knowing what cam was installed during a previous rebuild?
In my absent-mindedness back in 1990 when the motor was re-built, I did not get a blueprint and cannot find on the receipts where a new cam was purchased (I do see new pistons, etc. as it was bored .030 over). In my current day absent-mindedness, I didn't think of this before the shop installed the motor and trans. I have the Corvette Specs book that shows hot valve lash settings of .008/Intake and .018 Exhaust but did not see a cold setting.
Other than busting the budget even further by removing the water pump and timing chain cover to view numbers on the front of the cam (hopefully), I don't know of a correct way to set them properly other than making a guesstimate using the latest revision of the Hinckley-Williams doc on settings. They stated a setting of .008/.015 and that there was not that much difference in the hot vs cold settings given the heat retention nature of the iron block and associated hardware. On the side of caution, I'm thinking of adding .002 to the original factory settings cold and then backing down to .008/0.16 hot. These only work, of course, if it's a stock cam.
Thoughts? (Please keep it simple - lots to learn about lift, degrees, indexing, etc.!).

Thanks,
Fred

[John D.]

Re: 1963 340HP Valve Settings Cold w/o Knowing Cam#

Fred, First of all you need to get a vacuum gauge hooked up and take a reading at idle. Then get back to us. Say you have a Duntov 097 cam.
At 900 RPM my 63 FI engine puts out 16".
Now if I messed up a put in a 30-30 cam then the vacuum would be much lower.
Then if I put in Dukes favorite cam I have no idea what that vacuum is but I am sure our pal will be chirping in. John

[Frederick H.]

Re: 1963 340HP Valve Settings Cold w/o Knowing Cam#

Thanks John - I will check with the shop tomorrow or next week to see what it registers.

Fred

[Duke W.]

Re: 1963 340HP Valve Settings Cold w/o Knowing Cam#

My manifold vacuum reading for the Duntov and LT-1 cams is 12" at 900 and 10" at 900 for the 30-30 cam.

The only way I can think of to figure out clearance for an unknown mechanical lifter can is to rig up a dial indicator on the pushrod socket. While the lifter is on the constant velocity clearance ramp the indicator will move very little for a given amount of crank shaft rotation, but when it transitions to the opening flank indicator movement will rapidly increase with crank rotation. With a little practice you should be able to pick out this point, which is the top of the clearance ramp.

Clearance should be this number times 1.37, which his the actual SB rocker ratio at the lash point.

Duke

[Frederick H.]

Re: 1963 340HP Valve Settings Cold w/o Knowing Cam#

Sorry Duke - I am not that mechanically inclined (to create a dial indicator) and and will have to learn the terminology about clearance ramps, etc. I used to set the valves by the old feeler gauge and bump-the-starter method but I had the settings then as well. I think the shop went with the stock .008/.018 settings for the 097 cam. Will follow up with them first of next week.

Thank You,
Fred

[John D.]

Re: 1963 340HP Valve Settings Cold w/o Knowing Cam#

My manifold vacuum reading for the Duntov and LT-1 cams is 12" at 900 and 10" at 900 for the 30-30 cam.

The only way I can think of to figure out clearance for an unknown mechanical lifter can is to rig up a dial indicator on the pushrod socket. While the lifter is on the constant velocity clearance ramp the indicator will move very little for a given amount of crank shaft rotation, but when it transitions to the opening flank indicator movement will rapidly increase with crank rotation. With a little practice you should be able to pick out this point, which is the top of the clearance ramp.

Clearance should be this number times 1.37, which his the actual SB rocker ratio at the lash point.

Duke

Excellent information Duke. Thanks very much.