0590trab

Hi, guys I am needing to know can i run a JM-20-22 with stock valvetrain

1969 olds 455 bored over .040 / C heads / L2323F pistons

jm-20-22
Lift .496 intake
.512 exhaust
dur: 226/230 @ 50
LC 110
the mondello parts book list it in the manual as usable w/ stock rocker
just wanted to know what you guys think...

thanks in advance for any help you give.........trab

My442

I have run that cam in 2 different engines.

You will need to rejet the Q-jet and recurve the distributor.

I get 16" of vacuum at idle, so it works with power brakes.

Used the Comp Cams roller tip rockers.

Bobsw32

I have found that stock rockers are very inconsistant with their ratio.
If you are going to use them I would check them to make certain they all give the same valve lift......Also I hope you are going to install new springs.....Old springs get very tired.......then you will need to check the lifter pre-load as it may very well have changed........and the stock system is non-adjustable so the only way to adjust the rockers is by milling the pedestals or shimming the pedestals depending and which way you should go...

0590trab

Thanks Guys, I had a comp cam 292H in this engine, it did not work well ,it mushroomed the bottom of the lifters, rounded off the lobes on the camshaft, bent a few pushrods, so Iwas thinking this JM-20-22 was a little bit smaller, i had heads redone the vavle springs came new w/ comp cam kit,so they are in great shape, so the engine builder said. anyway thanks again for all the help............trab