does it matter what diameter my pushrods need to be? my engine builder said to get 7.400" pushrods but i need to know what diameter i need and cant get ahold of him before i need to put my order into summit.

trickflow 23 degree heads and comp promag 1.6's if it helps

 

Stock SBC pushrods are 5/16". Larger 3/8" pushrods can easily be installed with no modifications. You will need guideplates big enough for the 3/8" ones. The larger diameter should be used when you have high spring pressures.

As for the length, if your engine builder says 7.400" and he's wrong, will he pay for the pushrods? The only way to know for sure what length you require is by using a pushrod length checker.

 

I don't know what you're building; but if your open spring pressure is less than about 600 lbs, 5/16" push rods are plenty. Select the correct length from the Comp 7700/7900 series of numbers.

Don't order push rods until after the rest of the motor is completely built (heads on & torqued, cam installed, rockers installed). Use an adjustable push rod to determine the correct length.

You will probably find that the 1.6 rockers aren't any better than 1.5s, with the TF heads; and may be more trouble than they're worth.

 

my builder used an adjustable pushrod length checker to get the 7.400"

im running comp 987 springs and would rather get the 3/8" but ill have to measure my guide plates to see if they will fit.
i went to comps site and the spring charts arent up so i cant find the exact specs of the springs.

 

From Comp Cams website:

<img src="http://www.compcams.com/Technical/CurrentCatalog/HTML/JPG/338.jpg">

 

3/8" push rods won't do anything for you beyond what 5/16" ones will do, except add dead weight to your valve train. I'd recommend leaving the guide plates alone and using the Comp ones as described. The part # for 7.400" would be 7955-16.

 

thanks for all the help everyone. ive decided on trickflow pushrods part no. TFS-21407400 over the comps because they are $50 cheaper and are still 5/16" hardened chromemoly.

now the motor will be ready as soon as these come in!

 

I have trick Flow 23* heads and comp 1.6 pro mags as well and I went with a 7.300 trick flow rods. thats what trick flow recommended with the use of a comp cam and comp rockers. My machine shop also agreed.

 

hmmm.......makes me wonder. i guess i will have to double check with him.