Push rod dia?

I have my DOVE heads getting bigger valves at the machine shop right now, I'm planning on running a .630-.640 solid flat tappet and my machinist said that much spring pressure would instantly ruin a 5/16 push rod but unfortunately he's a chevy guy, Any truth to this? I will be sizing up my push rods when i get the heads back and had considered going to 3/8ths before this anyway. And machine work required for the 3/8's?

Also when I ran these heads before with scorpion roller rockers the rockers were hitting the studs in the valley area, I read once that .100 thousand needed to be taken down. Is that the fix to this problem? If so .100 off the bottom of the rocker or the base of the stud?

I am running TFS 5/16 crome moly without the welded on ball with no problems so far with 6.49 lift on dove-c heads.The only reason I didn't change to 3/8 was I had already had the 5/16 set up in mine and it wasn't in my budget to change over everything at the time.If you are going to have to buy guide plate go ahead an up grade with the 3/8 it want cost any more my 5/16 push rods was a $100 plus you have more to pick from.

Thanks again for the quick reply 69F100,
I didn't even consider the guide plates, I do have a set that are for the 5/16th already. I can take those up in size at work tho if there is enough meat there, I'll have to check when I get them back home. Any issues with the rockers chafing on your build?

3/8 would be a good idea IMHO. Less defection. Not to say that the 5/16 won't work, just that the 3/8 would be better.

Satinbronc wrote:Thanks again for the quick reply 69F100,
I didn't even consider the guide plates, I do have a set that are for the 5/16th already. I can take those up in size at work tho if there is enough meat there, I'll have to check when I get them back home.


Any issues with the rockers chafing on your build?

I don't on mine but I don't have the scorpion roller rockers I am running the 1.73 Harland Sharp roller rockers.

On the 5/16 plate make sure they are thick enough as you open them up the thin ones might want to bend or flex after you cut them to open them for 3/8

schmitty wrote:3/8 would be a good idea IMHO. Less defection. Not to say that the 5/16 won't work, just that the 3/8 would be better.

X2 With what Rob said it would be a good upgrade with less defection when I go back in mine that is going to be on my upgrade list.

Satinbronc wrote:Thanks again for the quick reply 69F100,
I didn't even consider the guide plates, I do have a set that are for the 5/16th already. I can take those up in size at work tho if there is enough meat there, I'll have to check when I get them back home. Any issues with the rockers chafing on your build?

Guideplates aren't usually hardened all the way through. A good 5/16 pushrod is certainly better than a weak 3/8 pushrod so size shouldn't be the only criteria here.