I have a set of C heads that have been pocket ported and tapped for 7/16” x 7/16” rocker studs.

What type of pushrod should I plan on running. Will 3/8” work, or an I stuck with 5/16”

I know all castings are different, but figured I’d ask.

 

I’m not sure what the rockers stud size has to do with anything but I’d use a good 3/8” pushrod. I’m guessing you’ll be using guide plates as well?

 

Yes I’m using guide plates

Would you consider running anything besides a 5/16” push rod with a 3/8” x 5/16” rocker stud

 

When I put "C" castings onto my 455, I spent hours grinding the pushrod holes just to get 5/16 pushrods to clear when using "Ford" roller rockers.

I can't imagine what it would take to find room for 3/8 pushrods.

I am under the impression that some "C" castings need more work for pushrod clearance than others--the difference being the lifter bank angle of the block they came off of. But I've been wrong before.

 

Again I’m trying to figure out why you think the pushrod diameter has anything to do with the rocker stud size.

 

Vin, what is the purpose of your engine build? Are you building a serious race engine or just a mild "have fun" engine? To use 3/8" pushrods in an Olds engine with any Olds iron head casting you will have to open up the pushrod holes. I would stay with 5/16" pushrods unless it was an all out race engine. Just my two cents. BTW, I personally have run 5/16" pushrods in a mild E block with C heads and a .600" lift solid lifter cam and Harland Sharp rockers with no problem.

 

Good point about the bank angle. I’ll have to check on that. Not sure which engine these heads came from.

Would you run a 3/8” pushrod with a COMP MAGNUM roller tip rocker kit and a 3/8” x 5/16” rocker stud on stick iron heads.

Would you run a 5/16” pushrod with Edelbrock heads.

It’s more of a have fun engine. But to run a 150 shot of nitrous at the track.

Torker intake
KB hyper 277 +.040”
Torque plate honed
Pocket ported C heads with good valve job and Manley stainless valves. Heat risers filled, exhaust dividers welded.
PRW stainless 1.65 roller rockers
Comp Cams 995 valve springs 115 seat pressure
Extra capacity oil pan with trap doors
Standard N crank
Stock rods resized with ARP bolts
Balanced
JM 25-28 cam, 236 @ .050” .523” and .544” lift 108 LSA
Holley 3310 vac secondary 750 carb
9.7:1 compression

 

Vin, I assume you have a "F" 455 block. "C" heads were used on that block the first few years of manufacture thus the pushrod holes would be correct for the 39 degree lifter bank. Those Comp valve springs probably give you no more than 325 open pressure. You should be safe using a 5/16"pushrod with that combination. I am not personally familiar with the PRW rockers but they may bring your pushrods closer to the edge of the pushrod hole thus requiring some clearancing. Of course you would need 5/16" guide plates with the 5/16"pushrods. The critical part here is getting the correct length pushrod.

 

Ok I’ll bite. You always use the biggest, stiffest pushrod you can fit in it.

 

To run 3/8 push rods on cast iron Olds heads you must open the pushrod holes to 9/16"