[Mertz]

I put on one of my Comp Cams roller rockers (1412) to check the valve geometry. Before I pulled the original rocker I checked to see how much pressure there was on the pushrod. There was no up and down play but it turned with only slight resistance. I have never had any lifter noise. If I turn the nut down less than an eight of a turn more it would be too tight to turn. I checked some of the other valves and they were the same. If I do as the manual says and turn down the valves with a full turn after zero lash I think they will be too tight. I ran the truck for only a short while before the test but I think it was long enough to match sure the lifters were pumped up. It takes a long time to get it up to operating temp while idling. I had not run the truck for a week before then. This is a stock 72 350 block and heads.

BTW the geometry check showed the touch points started at the center of the valve and extending out to the exhaust side about 1/16”. How much shorter of a pushrod would I need to get it in the middle?

 

[61Burb]

valve geometry

Mertz,
An easy way to check the contact point is remove 1 intake and 1 exhaust rocker.Clean the top of the stem to remove the oil.Take a black marker and coat the top of the stem, reinstall and adjust as you did before.Turn the engine 360 degrees and remove the rockers.You will see your exact contact point on the stem.The most critical is the open contact but the marker will tell you the truth.If the contact is more towards the center of the engine you need a shorter pushrod, the other way a longer pushrod .AS for length change .060 will move more than you think.Do you have an adjustable pushrod ? Worth the money and then you can be exact .

 

[Mertz]

Thanks for the info. That is the method I used and found I was just off center. I tried laying out the valve on autocad and I got a difference of 0.3 to get it to center. I think that is probably to much. I couldn't find and adustable pushrod locally. I think I will try a few stock rod and different lengths and see where that gets me.

 

[xntrik]

try .060 longer

 

[engineczar]

try .060 longer

Longer would put him even further towards the exhaust side of the valve.

Most off the shelf pushrods come in .05 increments. Without an adjustable pushrod or a handful of different lengths to try our guess is as good as yours. However from what you describe it doesn't seem like the right size would be too much shorter than stock. Maybe .05 shorter or at the most .100 shorter.

 

[xntrik]

Longer would put him even further towards the exhaust side of the valve.

.

You are correct, Sir. :thumbup:

( I need a nap..... )

 

[Mertz]

I have had a hard time finding any pushrods that are shorter without going to the high end ones. The local Rocker Arms Supply had some Elgins (PR432S) that were 7.694. I tested them this weekend and they were right on. The touch point is now in the center of the valve. They only had eight so I tried to find some more around town with no luck. I kind of wanted Comps High Energy. This is not a race motor so these should be fine.

BTW I set them to zero lash plus a half turn.