Pushrod clearance problems

[younggun2.0]

Guys,

i have a set of eddie performer RPM heads on my 383. the hole in the castings that the pushrods go thru is pretty small. when cycling the engine by hand the push rods (5/16 ) come very very close to the side wall of the holes. i was hoping to run a nice strong 3/8 pushrod but that is out of the question. is this just a matter of taking the heads off and enlarging the hole? im willing to pull the heads and take them to the machine shop to have this done. I am just worried about doing it and ruining the heads.

 

[stumper]

Measure the closest point of contact during a cycle. If it is less than 0.100" I would try to clearance the opening some. With a mild cam and low pressure springs you can get away with less but if you are runnning high spring pressures you should keep a good 0.100" of clearance to insure there is no contact. Those push rods deflect quite a bit during high rpms (more so with high pressure springs) and the slighest contact with the head can set up a harmonic that results in the push rods jumping out of the cups - ask me how I know.....

 

[younggun2.0]

the holes look to be about 1/2" i want to step up to a 3/8" chromoly push rod. the engine is nearly ready to fire. i spoke with a local engine builder. he told me that if i am very careful and lay down plastic or something to collect the shavings it wouldnt take much to run a next size drill bit down the hole and open it up a little bit.

 

[crackedback]

You can open them up by hand. Look for marks in the holes where they are rubbing and have at it.

Done all the time.

 

[dusterdragracer]

For sure open then up, I had this happen with my Bulldog heads (Hughes heads) and bent 2 push rods, which caused the lifters to come out. It also wiped out 2 rockers. Worst of all, I lost the race.
We jigged mine up, and longated them. My buddy did his, and burned through the intake runner. Easiely fixed with JB weld.

 

[younggun2.0]

For sure open then up, I had this happen with my Bulldog heads (Hughes heads) and bent 2 push rods, which caused the lifters to come out. It also wiped out 2 rockers. Worst of all, I lost the race.
We jigged mine up, and longated them. My buddy did his, and burned through the intake runner. Easiely fixed with JB weld.

how far did he go to get into the intake runner. that would have to be like 3/4"-1". i think i need maybe an 1/8" at most.

 

[mikedevore]

This was a problem in my small block Eddy's as well.
Jigged them up & made clearance in them.
I havn't seen anything from Eldelbrock for this concern.

 

[dusterdragracer]

Just a little hole, but we both took deep cuts.Like I said, we ovaled them.I was just telling this to you, so if you cut into runner, you won't panic. It's no big deal. We did mine first, and had no problems.