I am building a 383 for my car from scratch and have a question about the pushrods. I am not using stock parts, (comp cams xfi cam, afr heads), but will I still be able to use the factory size pushrods for a roller cam motor?

 

Even if they would fit, and they're probably now too short, they flex too much for use with an XFI cam. At this point, all they're good for is checking your valvetrain geometry once you get the new combo together.

 

Length should always be checked especially with a head swap to achieve the proper valve train geometry.

I'd recommend upgrading to 3/8" pushrods from the stock 5/16" ones. They won't deflect so much trying to compress heavier than stock valve springs.

 

Do I need to change anything to upgrade to 3/8 inch or will they simply just go right in without modifications? The heads have guide plates also, so will clearance be an issue with the bigger pushrods?

 

you'll need to change the guideplates

 

http://www.circletrack.com/techartic...gth/index.html

 

I will just go with a pushrod length checker then. What adjustment range should I buy the checker in? Will there be that much of a difference by going up to a 3/8 inch? I didn't think I would have any deflection problems by going with a chromemoly and using the guideplates.

 

Stock SBC pushrods are 7.800" long.

You really don't need to upgrade to 3/8" pushrods but it won't hurt. I doubt you have enough spring pressure where 3/8" pushrods are required. My valve springs have over 200# on the seat and over 800# open and 3/8" pushrods are still surviving. For me a 7/16" or tapered pushrod would be better. The best thing to do to get a stronger pushrod is to buy them with thicker walls. 0.080" is a standard heavy wall pushrod. Factory pushrod walls are very thin. Something like 0.065". Extreme thickness is around 0.120"

When using a pushrod length checker, you will need some lightweight checking springs. If you try to compress the regular valve springs with the checking rod, it will bend or break.

It's unlikely you'll have shorter than stock length pushrods but you have a few options for a checking tool

Comp Cams 7901-1 measures from 7.500" to 8.700"
Comp Cams 7703-1 measures from 7.800" to 8.800"
Comp Cams 7711-1 measures from 7.800" to 8.800"

Pick up whichever one is available plus some checking springs. Proform, Comp Cams, Moroso etc all sell them.

For a SBC, you only need one adjustable pushrod checker and one pair of springs.

 

I have stock pushrods in my 350 TPI. I also have stock roller rockers. I read that stock pushrods are 7.800" in length. Im about to install some AFR 1040 heads. So which of the 3 Comp Cams testing rods should I buy?

 

You have a roller cam... "stock" length in that system, is 7.400".

Doesn't too much matter though. More often than not, aftermarket stuff - bigger cams in particular - tend to require a longer size. But as Alky said, you MUST measure if you want the optimum fit.

 

Well that's why I'm asking about the sizes. I don't wanna buy an adjustable pushrod that is too small or too long for the AFR heads which is gonna have Summit Racing 1.6 aluminum roller rockers.

 

Heads and rockers have nothing to do with it directly
SBC Flat tappet pushrods are 7.800" long
SBC Roller cam pushrods are 7.200" long ( because roller lifter is taller than flat tappet lifter by .600" so pushrod is shorter)

Your final pushrod length requirement to suit your individual combo of heads / rockers will be within +/- .200" of the stock length so buy the pushrod checker that covers the length of what pushrod you " should " be using
I say " should" because you may be converting from flat to roller cam or vise versa
in which case you need pushrod length to suit what you are going to ;
not what you "had" before

 

Just the answer I was looking for. Thank you vetteoz.