drilling out pushrod holes

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Mar 9, 2019 | 10:41 AM

patSS/00

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From: AZ

drilling out pushrod holes

Found a few threads about this, but no updates on whether there were any problems from doing it. For my 241 heads I'm considering whether to drill them to 1/2" before sending them out for some work. Just from looking at where the pushrods sit within the holes, many of them are close to one side not centered. Also there are faint rub marks on many of the pushrods. These are regular 5/16 pushrods. My question is whether the holes are supposed to support the pushrods, like guide plates, in which case I don't want to drill them.

Last edited by patSS/00; Mar 9, 2019 at 10:52 AM.

Mar 9, 2019 | 11:00 AM

Che70velle

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From: Dawsonville Ga.

Holes are not supposed to support pushrods. If contact occurs it’s not a good thing. You can open them up if needed, but I’ve never done it on an ls Head. My MMS 265’s have been clearances by Tony for the 3/8 pushrods I run, but I never saw a before and after, so I can’t help you on how far you can go.

Mar 9, 2019 | 04:14 PM

Dragls

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From: Orlando, FL

I had to drill 1/2" hole on my 243 heads to accommodate the 3/8" trend pushrod I put in.

I also had to grind. It's not just a drill and go mod.

Mar 9, 2019 | 09:28 PM

patSS/00

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From: AZ

You mean grind to smooth the edges, or where?

Oct 29, 2019 | 09:57 AM

LilJayV10

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From: Evansville,IN

When I had my heads sent back to TEA for a VJ, I asked them to enlarge the holes to accept a 3/8 push rod. Greg said they couldn't do it because they would have drilled through head. I'm guessing he meant where the valve cover seals.

Nick@BTR said he would like me to run a bigger push rod than the 5/16.

Will a 11/32 rod work without having to mod the head?

Thanks.