heavy duty pushrod holes

[andyv8van]

Hi All,

i have got my 3.9 running with only one problem.i think i have a heavy duty pushrod touching the bigger holes in the cylinder head.
does anyone know what size hole they should be and is there a measurement to a datum point i can use to get them in the correct position.i looks like they need to be off set to the original holes,which i have opened up to 14mm.
i have this problem on one pushrod on the left side,so i seem to be lucky on the others.

Andy

[adamnreeves]

What pushrods you using 5/16? I used 5/16" crane HD adjustable pushrods and for these I needed to bore out to 13mm. I to had the problem with the pushrod not seeming to be centrally placed in the bores, especially the outer pushrods, which I think might have been caused by extra material in the head on the port causing the drill walk. I used a pillar drill in the end and clamped the head down well. I had to offset the bore. I had no datum point but took assembled the heads and pushrods and took measurements. All came well in the end but I am left wondering whether the bore of the holes were not spot on in the first place or me drilling with a hand drill for the first attempt. I also only drilled out 1mm at a time to ensure accuracy.

Hi All,

i have got my 3.9 running with only one problem.i think i have a heavy duty pushrod touching the bigger holes in the cylinder head.
does anyone know what size hole they should be and is there a measurement to a datum point i can use to get them in the correct position.i looks like they need to be off set to the original holes,which i have opened up to 14mm.
i have this problem on one pushrod on the left side,so i seem to be lucky on the others.

Andy