Big Block Rocker Arm Configuration

[Wayne M.]

Re: Big Block Rocker Arm Configuration

..... If I recall, the original 427's for this time period did not have the slotted ball. These M's do....

Ron -- you may find this interesting; from Chev Tech Information bulletin of 2/15/66.

"To improve rocker arm lubrication on all Mark IV engines, except the 325 h.p. 396" engine, a grooved rocker arm ball has been used in production since November 24, 1965. In service, the grooved ball, Part # 3894306 is replacing the standard rocker arm ball 3860306, and the heavy duty rocker arm ball, Part # 3879612. At a later date, a grooved tuff-trided rocker arm ball will be released for service and will replace the 3894306 rocker arm ball."

[Ronald L.]

Re: Big Block Rocker Arm Configuration

Wayne, this is very interesting when studying these parts. The rockers and ball assemblies in my car are tuf-rited, that is the better heat treatment. It has a notable color hue over the black-brown look of the standard heat treatment. The base GM vehicles all got basic case hardened rockers, checked a few batches of those back in the day.

If you recall my thread from last year the thing I was chasing on the 390 hyd. lifter engine was a tic that appeared on revs and in looking at differences I found a very slight wobble in a couple of these M rockers. That found by grabing then and rocking them, trying to find soemthing loose.

Cold weather hit before I could verify if the self prevailing nuts were ever so slightly backing off, so if this kit costs only $100 it sounded like a good was to eliminate the nut and rocker as the issue.

[Joe L.]

Re: Big Block Rocker Arm Configuration

I would appreciate the source you have to get this GM set as indicated for about $100...

Ronald-----


That's about the GM list price for the set. Any dealer that sells at list (some actually charge MORE THAN GM list) should be able to sell you a set for about $100. You can get them for even less from a source like GM Parts Direct.

[Joe L.]

Re: Big Block Rocker Arm Configuration

Bill,

Did you mean to say 65 L78?

Joe

Joe------


L-78 engines were used in 1966-70 Chevelles, 1967-70 Camaros, and some Chevy II's. They were pretty much the same basic engine as used for 1965 Corvettes but they were de-rated to 375 hp.

[Ronald L.]

Re: Big Block Rocker Arm Configuration

I tired a different part site, looks like they are all the same, $9.2 - $11 each plus shipping.

Is there valve spring recommended that goes with this rocker?

[Joe L.]

Re: Big Block Rocker Arm Configuration

I tired a different part site, looks like they are all the same, $9.2 - $11 each plus shipping.

Is there valve spring recommended that goes with this rocker?

Ronald-----


See my post #3, above.

If you buy the rocker arms INDIVIDUALLY, they cost about what you've found. However, you can buy a SET OF 16 of the rockers from GM under GM #12368085 for about 100 bucks, GM list.

[Ronald L.]

Re: Big Block Rocker Arm Configuration

Joe, that's the number I was using - the set number at gmpartsdirect, the exact numbers shown about show up as one rocker ball and nut, 9.18 tax & ship each. There must be a different number now.

Any good numbers for the springs?

[Joe L.]

Re: Big Block Rocker Arm Configuration

Joe, that's the number I was using - the set number at gmpartsdirect, the exact numbers shown about show up as one rocker ball and nut, 9.18 tax & ship each. There must be a different number now.

Any good numbers for the springs?

Ronald-----


I just ran GM #12368085 on GM Parts Direct and it shows clearly as a set and sells for about 76 bucks, their price.

A set of GM #3970627 valve springs is available under GM #12371061 for about 250 bucks, GM list. As far as I can determine, the individual valve springs are no longer available. These are the best valve springs for a street big block engine.

[Ronald L.]

Re: Big Block Rocker Arm Configuration

Joe, I have it now, the dealer in NC. thanks for the help.