Model A valve spring rate?

[Tim]

Many have read the "no power" post. I am pulling the valves, cleaning them, lapping the seats and valves. I need to ream the guides to clean them. The reamer will be sized two thousanths over the valve size from what I have read. But I was wondering what the spring rate at height should be. I am checking them with an old style clamp tensioner using a torque wrench if that makes a difference in the process. I will be ordering new ones but I always like to check the old ones against the new ones so I know what to expect. I need a starting point based on Henry's spec.


thank you again,

Tim

 

[pat in Santa Cruz]

length: 2 15/16ths
compression@2.5 in. 60# +- 3#

compression@ 2.75 in 36# +- 2#

do you have original mushroom valves? original split guides?

is there crud on the stems?

any burning on the faces or seats?

 

[Jim Brierley]

First measure the actual installed spring height, this will have changed if you are using 1-piece guides. The springs should have 40 psi at the installed height. Shim if needed to achieve that distance. Less pressure can cause valve float and valve & seat burning, they cool better with good pressure.

 

[Tim]

Thanks to you both. I will measure the installed height this weekend. Pat I haven't pulled it apart yet to see. I tried the Marvel trick last night. Ran a whole bunch of it through. It made a difference but didn't cure it. I drove it around the block and it still stumbles something fierce so it's got to be a burned valve. I let it run for a very long time putting MM down the carb more than enough to unstick it. I also have it in the gas. It'll rev up but it takes a bit to get through the wide flat spot and it still pops. I'm going to get into it on Saturday Morning and hope for the best. It's time to put a Cam in it anyways and what a better time than now.

Thanks again,
Tim