Im soon to be doing a cam swap with a 224 from the stocker and pac bee hive single springs. My question is what size pish rods should I go with 7.400, how about if i go with 243 heads same size? Thanks

 

You should do a search here and read up a bit on selecting the proper pushrod. It's a critical item for longevity of the valvetrain.
Basically, your plans will entail dealing with two things that can change your pushrod requirement - cam base circle and head installed height.
Spring changes alone don't affect PR length, but rocker arm changes sure can.

1. The cam base circle is the diameter of the cam lobe measured at the smallest point OFF THE LOBE. Point the high point of the lobe straight up at 12:00 o'clock, and measure across from 3:00 to 9:00.
Most big aftermarket cams use a smaller base circle, and therefore need a slightly longer pushrod to compensate. You can search here and probably find the respective base circles of your stock cam and the new one, or just measure them. Then it's just a simple formula:
(stock base circle minus new base circle) divided by 2 = increased PR length required.

2. New heads are a bit more entailed. When you change heads there is no easy way to determine if the new head is the exact same height as the old one. Maybe it was milled, Maybe your new head gasket is a different thickness, maybe the val stems were resurfaced. The only way to be sure to get it right is to measure the valve train after the heads are installed. You can use an adjustable pushrod, or measure lifter collapse depth - either way it's relatively straightforward, but does require a good understanding of the mechanical aspects. Search and read herein, lots of really knowledgeable guys have published methods and details.

DG

 

Just guessing, but Id get the 7.4 and get DUAL springs if i was u. but im not

 

Thanks for the information

 

Very simple, do not buy pushrods now. Buy an adjustable pushrod and measure for the correct length. Then buy the pushrods and consider upgrading to a larger diameter to reduce deflection. Standard 5/16-0.080" pushrods are an off the shelf item and can be received in a couple of days so don't guess at length. You should also verify the rocker geometry (wipe pattern) prior to measuring for the pushrod length as any shimming will alter pushrod requirements.

 

http://forums.corvetteforum.com/c5-t...post1571895618

Listen to Vettenuts and if you want 7.4, 7.350, or 7.375 PR let me know.

Cart then horse, don't get the PR without measuring, don't measure untill you set up the rockers.

Good luck