# Pushrods Pontiac 400



## Jason6512 (Dec 29, 2020)

So on a 74 Pontiac 400 with 0 deck and bring my heads from 101cc to 93cc. Does this change my pushrods height? Do I have to get adjustable?


----------



## Jason6512 (Dec 29, 2020)

Correction deck clearance is .015


----------



## BearGFR (Aug 25, 2008)

It can, and you should check. BTW "adjustable" pushrods are only used with very lightweight checking springs for the purpose of determining the correct pushrod length. You can't actually run with adjustable pushrods. They're nowhere -near- strong enough for that.
There are quite a few youtube videos out there that show the process.

Here's one:
Determining Pushrod Length

Be careful watching the one video I found from Summit. The guy showed checking the contact patch with the EXISTING pushrods and regular valve springs, and near the end talked about using a pushrod length checker (without showing how to use it) but in my opinion did not emphasize at all that you can't use one of those checkers without also using light checking valve springs.

Another caution that no one I saw mentioned: If you want to just check the contact patch using your existing lifters, springs, and pushrods then be aware that with hydraulic lifters it's also possible to get a false reading. This can happen because the pushrod cup in the lifter can get depressed some by spring pressure, due to the absence of oil pressure. This can make you think you need longer pushrods when you actually don't. You can get around this by using a solid lifter for checking (as long as it has the exact same length and pushrod cup height as your hydraulics) or by taking one of your hydraulic lifters apart and packing it with something to keep it from compressing, like aluminum foil or a short length of wooden dowel.

Bear


----------



## Jason6512 (Dec 29, 2020)

Ok I'll have to bring my buddy in to do that never had to measure for push rods this is the first not stock eng I've done.


----------



## RMTZ67 (Mar 12, 2011)

I bought a extra lifter and stuffed it with foil like Bear said, and used my oem springs. Both of them, and used a adjustable push rod to get the correct pushrod length.I took off .030 and slight mill on my heads and my length was 9.070. They only make certain size rods so I ended up going with 9.100. all is well. .015 you may still use stock....but do your check.


----------



## Jason6512 (Dec 29, 2020)

After I watched the video I'm sure that wont be a problem. I'll definitely check them thanks for the help.


----------



## RMTZ67 (Mar 12, 2011)

Jason6512 said:


> After I watched the video I'm sure that wont be a problem. I'll definitely check them thanks for the help.


If you need 9.045 Bear may have a set. unless he got rid of them already. When I got the correct length I took it to two different machine shops to make sure the ones measurement was the same or close.


----------



## Jason6512 (Dec 29, 2020)

Ok thanks


----------

