1964 -389 cam
 

Hello,
I have a 1964 Pontiac Grand Prix with a 389. The car was sold to me 24 years ago as a 421. Pulled the engine to seal it up and this when we discovered it was a 389 and not a 421. We put all new bearings, cam, lifters in the motor.

Parts were ordered thinking it was a 421. We were told no problem as the parts were interchangeable for what we had ordered. My mechanic noticed the stock cam had two holes drilled in journals 2 and 4. The new cam did not have these holes. Apparently this was a 1964 thing that Pontiac did.

When we started the engine not much oil was coming up into the rockers. This is when we found out that the new cam was not for a 64 but for a 65/66. The difference is that in the 65/66 they had hollow rods with an oil holes in the rockers. The stock 64 rockers have no holes.

The question I have is could we upgrade the rods and rockers to the 65/66 rocker and leave the new cam in our should I go back to the original cam with drilled journals? Ironically the engine does have hollow rods already.

Asking because obviously trying to save some time and money as changing the rockers and rods is a pretty quick fix vs new cam.

And thoughts would be greatly appreciated. Thanks,

Put ‘65-‘66 rockers on it that have the spurt hole in the pushrod socket and you’re good.

This way you’ll be bypassing the stud oiling (that you’re not getting anyway because of the cam) and using the superior pushrod oiling of the rockers like on high-performance 1964 engines and subsequently all 1965 and later engines.

Early Super Duty engines also had pushrod oiled rockers.

Thanks so much. This was the thought my mechanic had just wanted to verify with some knowledgeable Pontiac people. Really appreciate the quick response. Thanks again!

Push rods
 

Hi B-man
One more question. So I will be basically be upgrading my 1964 - 389 to be like a 1965 - 389 correct. The push rods existing measure at 8.6875

What I am finding for 65/66 - 389’s the push rods measure 8.686 a difference of 0.0015.
Does this sound right to you and would they be .0015 shorter due to the oil spurt rockers possible being slightly thicker. This is a stock motor.

Also wondering if you have any recommendations on what rockers I should purchase and from where. 7/16 bottle style with 3/8 threads

The first order of business is to inspect all 16 of your rocker studs.

Remove all the rockers and balls and look for gouges and ware spots where the balls ride.

Sometimes it's difficult to get the rockers off because the balls are hung up in a ware groove.

Seeing as your motor is a 64 they may be worn and if worn enough you will never have a quite valvetrain even with new parts.

One and a half thousandths is immaterial. Even 15 or 20 thou means nothing here. Depending on where you find that pushrod length listed the number seems to vary a little depending on the source.

Here in this post a little further down you’ll see how we determined the correct pushrod length for my 1964 421, 8.670” which is essentially stock length:
https://forums.maxperformanceinc.com...2&postcount=75
Finding those later 326 / 389 /421 rockers new may be difficult to impossible. They’re slightly different than the later rockers geometry-wise.

Perhaps look at sourcing a good used set where someone has properly kept the individual rocker pivot balls paired with the individual rockers they were originally used with.

+1 for open-top rockers.

I ended up with upper head oil starvation in my '63 with a solid cam (no oil holes) and my original (closed) rockers. #1 Intake valve (last one in line to be oiled, all the way up front on the driver's side) ended up wobbling so badly that it took a bite out of the exhaust valve next to it. Not pretty. All stock pushrods with open rockers seems to be doing the trick (just got the car back out on the road today).