1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

[Bill M.]

I have a 1966 427/425 HP L72 completely stock. The only exception is that the previous owner had a hydraulic cam installed during the rebuild instead of a solid lifter. Car ran fine, never a problem till late last year during the cold weather. I keep my car in storage but start it about every two (2) weeks during late fall, winter and very early spring. Weather permitting I take it around the block.

One day when I started it the motor started making a sound similar to having some coins in a tin can and rattling them. Would last for a minute or so and as the car ran the noise got quieter and then quiet. Only happens during the startup. Once warm it never happens. Oil pressure is excellent from the time I turn the key until I shut it off. I opened the hood and you could hear the noise under the valve covers. Coins in tin can rattling around. Nothing earth shattering loud but annoying.

Noise only came when the car sat for a while. Took the car in for a look see. They (shop) let it sit, turned it on and the problem was there for their research/fixing. They determined the problem was "valve lifters are bleeding back and collapsing after sitting". Based on this they replaced all the lifters. Drove it home and all was fine. The Vette sat for about 2 weeks and when I started it the noise was back until after it ran for a few minutes. Coins rattling in a tin can.

Has anyone ever had this problem or have a possible answer?

My thinking now is maybe a defective/sluggish oil pump...but the oil pressure is right on.
My car does not leak or blow any blue smoke at all.

Any insight/opinions/thoughts etc would be greatly appreciated as I spent some nice bucks to have it fixed and I am back to square one.

[Mike T.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Bill - This shop installed new lifters on the old cam? That's not the right way to do it. And, what did they say about the old lifters they removed?
Were they the problem and any comment about the cam?
Do you by chance still have them?

[Bill M.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

The rebuild of the motor was done weeks before I bought the car. I only drove the car sparingly between local car cruises. No highway driving. Just slow nice miles. My guess is between 1-2k miles since the rebuild.

Unknown with the old parts. The shop that did my work also had a copy of the rebuild info and what was done.

I spoke with the shop last week and they are going to call me back. Only does the noise after a long period of sitting.

[Mike T.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Since it was rebuilt before you bought it, and there's a fair amount of miles on it since then, the guess is they broke the new cam in correctly since you haven't had the noise until now? When you do oil changes what kinda oil grade have you been using?
Going off in a totally different direction, is your heat riser operating correctly?
By the way, I sent you a PM regarding your L72.

[Mark L.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

The 66 cam should have a grove machined in the rear bearing surface. This usually has to be done by the engine shop before assembly. Not sure if this would account for the problem you're having.

[Mike T.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Mark - That's true, the early 396/427's (65/66) had a different configuration for oiling and the cams had to have that groove in the rear journal.
The only thing that makes me think that might not be the problem is due to Bill mentioning he drove it for mabye a couple thousand miles before the sound issue cropped up and I would think if they stuck in a non-grooved cam that it should have reared it's ugly head sooner than it has.
I've got a 66 NOM L72 running a mild 396 right now but recently came across a 66 #942 4-bolt block and a pair of 67 L-88 aluminum heads and am in the process of putting together a true solid cam L72 engine for that 66 Roadster. When I selected the solid lifter cam from Comp Cams, I had them machine the groove on that rear journal and below there's a pic of the final product for Bill to see.DSCN5829.jpg

[Joe L.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Mark - That's true, the early 396/427's (65/66) had a different configuration for oiling and the cams had to have that groove in the rear journal.
The only thing that makes me think that might not be the problem is due to Bill mentioning he drove it for mabye a couple thousand miles before the sound issue cropped up and I would think if they stuck in a non-grooved cam that it should have reared it's ugly head sooner than it has.
I've got a 66 NOM L72 running a mild 396 right now but recently came across a 66 #942 4-bolt block and a pair of 67 L-88 aluminum heads and am in the process of putting together a true solid cam L72 engine for that 66 Roadster. When I selected the solid lifter cam from Comp Cams, I had them machine the groove on that rear journal and below there's a pic of the final product for Bill to see.[ATTACH=CONFIG]113323[/ATTACH]

Mike------


It doesn't just require a grooved rear cam journal-------it requires a special rear cam bearing, too. This design is unique to 1965-66 big blocks and, possibly, very early 1967.

However, I do agree that if lack of these was the problem, it would have been obvious long before now and the manifestation of it would involve a lot more than what has been described.

[Mike T.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Joe - true indeed, here's a pic of the Durabond CH-9A cam bearings I wound up using on that '66 vintage block and a separate pic of a set with that special rear bearing. Pardon the sideways pic of the Durabond box, I can't figure out why that happens...even when I purposely reposition the pic to begin with.
IMG_0468.jpg

[Bill M.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Thanks for the replies everyone.

The shop that did my motor before I bought it is well established.
They do race car motors also. They did the rebuild but not the Dyno.

The motor was crated up and send out to another company for the Dyno and then returned for installation.

The Dyno sheets all show everything OK. The DYNO was not taken to full RPMs but only to around 4500 rpms. Readings were all OK

The problem just showed up after over a thousand miles of driving.

To be on the safe side I had an oil change/filter..look see/check up when I bought it.
Then another oil change after another 500 miles. Wanted to look at the oil again for any bits/shavings etc. None found.

The third oil change was on the recent issue.

All oil used was top grade for these motors. About 15 bucks a quart.

Just hoping I can nail this issue down without any more guess work.

Thx
Bill

[Rich G.]

[Mike T.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Bill - Actually, the reason I asked what oil had been used in your L72 has more to do with the Grade and not so much the cost of the oil.
Quite a few years ago, the oil companies started to reformulate the oil you buy for your vehicles and they wound up reducing the amount of what is called ZDDP. They did it because of emission issues but that reduction in the amount of ZDDP found in engine oil started to show up with accelerated cam/lifter wear on older mostly flat tappet engines like we have in our older cars. The grade of oil most of us use these days on our older cars is typically CJ-4 and CK-4. Next time you're at one of your local auto parts houses or Walmart, doesn't matter which, take a look at the oil containers, especially on the backside and look for the API symbol.
Again, the cost really has nothing to do with it, you can buy oil with Grade CK-4 from high cost and low cost vendors. I buy CK-4 from Walmart and it's really the same and about a third the cost of the high priced stuff. Here's a pic of the API symbol on the back of one of my Walmart containers.
Since your engine was built not that long ago there is a better than good chance they already used the right oil on dyno and break in but even if they did, that CK-4 oil should be used from then on too.
IMG_1939.jpg

[Duke W.]

Re: 1966-472/425 ..L72. Valve lifter issue or something else causing the problem?

Thanks for the replies everyone.




All oil used was top grade for these motors. About 15 bucks a quart.


Bill

You're drinking the Kool-Aid! Do a Web search and include the quotes so it looks for the whole phase..

"engine oil for vintage corvettes"

I agree with the other posts. The rear cam journal/bearing could be the issue, but if it wasn't done properly the consequences are usually well before 1000 miles.

My bet is that the "engine builder f...ed up... tons of war stories on the Web.

Usually when I hear the "my engine builder builds great racing engine" response I just walk away... maybe offer "good luck" maybe not.

Duke