273 Magnum pushrod clearance

[cageman]

I just got my shortblock put together and I mocked up a head on the block and I put a rocker set on one cylinder and I spun the motor over. I see that the pushrods come close to the intake side of the head, how much do I need to mill out of there, and what have you guys done to do this, will I have to put the head in a mill and do it that way, or is there another way, seems to me the mill once it is set up will be the way to go
What is the limits of the stock springs, they look weak to me, I am running a .454 lift cam so with 1.6 rockers (.484) is that too much, I have no Idea what the stock magnum lift is.
Should I get magnum style intake gaskets, or can I just punch out LA intake gaskets, seems to line up, but I dont know if punching it out is an accurate way of doing it.
Thanks.

[sanborn]

The easiest way to get adequate clearance between the pushrod and cylinder head is with a rotary file/ high speed grinder. And you will probably find the clearance varies from cylinder to cylinder due to casting irregularities. I like a minimum clearance of .030" throughout the entire lift cycle of the cam. How do I check for clearance? I wrap the pushrod with about four wraps of brown kraft paper(grocery bag kraft paper)---this makes the pushrod grow about .060" in diameter. Tape the paper at the top/bottom tightly, install pushrod and go through the lift cycle. If the paper comes in contact with the head, it will either scuff or tear. If it does, grind some more.

The .030" Minimum clearance isn't written in stone---but you want to compensate for pushrod flex, rocker side clearance, etc. that occurs during running/racing. Get more clearance if you can.

BTW, any paper will do for the checking. I just have kraft paper sitting around.

[cageman]

Hmm, I didnt think you would want to much of a gap.
I am running a hydraulic cam, and the lifter compresses and I cant get full lift out of it, can I substitute a solid lifter in there for this setup, or are they different heights, as where the pushrod rides. Thanks for the non tech way to check, as I am a welder not a machinist!

[LA360Dart]

Hi cageman;

I used a hi speed die grinder, but could easly use a round file. A friend did this on his heads and it worked fine. It is where the parting line in the casting is that comes closest to the push rod...

Denny

[cageman]

It seems to get thicker at the seam, is that all I really need to clean up?
I guess I will wrap the push rod and see.
Thanks

[Robertson_Tech]

I did less then .030 once and 4 push rods got ring machined around them now I use .030 for head to pushrod side clearance