Just got my 72 on the road . I put about 20 miles on it and the push rods have some bad rub spots on them already. They are rubbing in the hole they go through in the head. What causes this?
Pushrods not properly seated on the lifters? Loose rocker arm shafts? Are they adjustable pushrods? Lifter bores need an align hone? (badly need an align hone?) Broken lifter bores? Pushrods are bent? (stuck or sticky valves?) All the pushrods are doing this? Do your heads have the larger pushrod holes? Give us some background on the engine...what did you do to it? Do you have the stock valve train? What parts did you use, etc.
If your pushrods are 5/16's they'll rub if the heads/block are cut a total of .050(I think, could be wrong)and you're using 1.65 rockers. In that case you'll have to oblong the pushrod holes in the heads.
It has stock pushrods and stamped steel rockers. rockers are ok and rods are straight. My block is a 70 and the heads are 72. I have no clue why there rubbing. I have a set of adjustable pushrods and there is no way these would work without making the holes in the heads bigger.
Kevin, I have this problem. What was the cause for your pushrods rubbing? Not all mine, but a few leaning to the right or left. I pulled the old pushrods in the winter to find a groove worn in about 4 of them. Now, I have adjust. ones with 50 miles on them. I checked some of them tonight and a few have shiny areas where they are touching.
Yes, milling the heads and/or block throws the valve train geometry off a little and this rub is a very, very common occurance. You'd be best served to pull the heads (I know, but it really only takes a couple of hours) and oblong the holes with a die grinder. But only grind on them a little!!! You only need a few thou!
I just had a major fight with the headers on it tonight. Pulled them loose and put new gaskets on. That pass. side rear bolt caused me to loose 5 years of my life. Now the thoughts of pulling the heads takes another 5.
extra lift=too small hole in heads i had this problem first 20 years ago-if you go up almost nothing at all in camshaft lift, the pushrods rub thier respective holes in the head. all of the big name buick engine builders bore these holes out to 1/2 inch when they are porting or doing any serious work on the heads. i did my own 67 430 big port heads on my brothers mill at his machine shop 15 years ago after this problem reared its ugly head, now have a set of pae ported heads that jim bored out the push rod holes on.
