pushrod diameter

[baxsom]

so i have been wondering. what is the correct diameter pushrod for a big block 454.

mine has 5/16 diameter but when i was looking at cams one of the recommended additional products was 3/8 pushrods. i am guessing that this would also require 3/8 guideplates which i dont have.

i talked to the tech at summit and said that all big blocks were supposed to have 3/8 and if i didnt it meant that someone was screwing around in the motor.

the heads are from a 67 L36 427 if that means anything.

is the smaller diameter ok. the summit tech said if i get the cam kit (xe268H to be exact) i would most definitely have to get the 3/8 rods.

 

[damoroso]

Actually, there were three sizes of push rods used in big blocks. 3/8, 5/16 and 7/16. I believe the 5/16 was stock for 1972. 1967 did use 3/8 rods so if the guide plates are correct for those heads, you should be okay with 3/8 rods. But hey, if you have to buy new rods anyway, maybe the 7/16 would be a good choice?

 

[baxsom]

so since i have the 5/16 guideplates it looks like the previous owner took the 427 heads and switched over the 454 guide plates and rods. i guess it makes sense now, if he bought the heads and the rods didnt fit the new guideplate he just switched it all over.

makes sense now. i guess when i finally get the new cam i will get the new plates and rods as well.

 

[damoroso]

That'd be the way I'd go. Good luck, let us know how it turns out!!

 

[TimAT]

You'll need to match the pushrods and guideplates- a 5/16 pushrod in a 3/8 guideplate will be a quick way to broken parts. A BB with 5/16 pushrods was a pretty vanilla motor- not any sort of a performance thing anyway. the spring pressure will fold a 5/16 rod like a piece of paper. At the very minimum a 3/8 pushrod with any kind of a performace cam. I'm running 7/16 pushrods on Ol' Red, but it's kinda required with the cam and springs I have. .560/.600 with 273* @.050.

 

[Hib Halverson]

5/16 pushrods were only used on some early BBCs and are not a good choice for any Corvette BB. Generally, BBs used 3/8" pushrods. Only the very high-performance engines used stock 7/16" pushrods. Today, with modern materials, the aftermarket's racing and performance 3/8" pushrods work fine in all but the most aggressive applications. The problem with 7/16" pushrods in some applications is their high mass.