Dad's '66

I was hoping that someone could give us some advise on valve springs for a L72 motor.

My Dad has had our '66 427/425 since it was new. It actually was my Mom's "grocery getter" when we were kids. Over the years, I can remember my Dad changing a broken valve spring here and there. My Brother said he remembered my Dad changing one on the side of the road on day. I guess he was pretty good at it, and he kept all the stuff to do it in the car.

Since my Dad passed away this summer, my Brother and I have inherited the car, and we are trying to learn as much about it as we can.

My brother drove the car a few weeks ago and he mentioned that the driver's side exhaust sounded different, and he wondered if something in the exhaust, a baffle or something, came loose. We have been too busy to do anything with the car, and yesterday we pulled off the valve cover to check the springs. We found that the #3 exhaust spring was broken.

I have quite a bit of experience with motors, valves, springs, etc., but it is all with full race blown hemi motors. So, I am mechanically inclined but I do not know much about big block Chevrolet motors. What I would like to know, is what springs should be on the motor, and should they be checked periodicaly? How often should they be changed? The motor was re-built about 25 years ago, new stock cam, pistons, etc. I did notice that most of the springs had a purple paint stripe on them, but a few did not. My guess is that the purple stripe springs were put on with the re-build, and they have been replaced with stock(?) springs when they have broken. There are two new GM springs, in their boxes in the car. The broken spring on the car does not have a purple stripe.

Any tips on how to change a spring would also be appreciated. We have the spring removal tool, etc.

Thank you for your help.

JohnZ

The correct/original L-72 valve springs (P/N 3970627) are still available from GM - about $12.00 each; I'd replace all of them, and keep a couple of spares. You probably have the "lever" tool for replacing the springs - the procedure is outlined (with photos) in the Chassis Service Manual.

Dad's '66

John,

Thanks for the information.

$12 each sounds better than the $100 each we were spending for the ones we used on our TAD. And those only lasted for 4 miles!!!!

rgs

Ber aware of the seat pressures and spring bind when replacing springs. If there is any chance that the cam has been replaced, you should take a few measurements before just dropping in new stock springs. Also, even stock springs should be pressure checked and shimmed for proper seat pressure, and installed height.
I just replaced the valve train in my 396, if you want more info on how to do any of this, send me a PM.