454: Help Diagnosing Loose Rockers

[1970BannerBlazer]

Some of you have been following this issue over in my firing order thread. Decided to move this to a new thread to get more eyes on the issue.

Engine: 454. Unknown origin or build. IV version I guess. I’m new to 454s and chevy engines. Built a 440 from scratch so I have some experience. But by no means am I an expert.

Issue: After removing all rockers and pushrods I have major rocker clatter due to loose rockers on about half my rockers.

Prior to removing the rockers I didn’t have any clattery rockers.

I removed the rockers because I found a bent pushrod on one of them when I was chasing down some rough idle issues. I removed all rockers and pushrods to confirm if any other were bent. Non were.

While the rockers were off I decided to replace the pushrod retainers as the ones in my engine where janky with the pushrod guide opening having been majorly widened for some reason.

Install process:
Placed the pushrod into the correct hole
Seated into the lifter
Placed the pushrod retainer
Used blue thread locker on the rocker bolt
Torqued to 50lbs

Initial startup:
75% of the rockers were chattery.
Let it run for about 20 min and a few rockers tightened up
Took it on a few drives, no change in the other rockers.

Oil pressure idle: 60 drops to 50 when warm
Oil pressure running: 70

My guess is that maybe my new comp cam retainers might be a tad thicker than my old ones. Thus raising the rocker bolt slightly and introducing a gap? Just a guess right now till I can measure. Also, if this is the case then it should be for all of them.

Others have suggested that my cam blew some lobes. I’m not sold on this since many of the lobes would have had to go all at the same time right on first startup.

Other option is that my lifters went bad. Again, having this many all go at once is weird.

I ran the engine without the valve covers on. I can confirm that each rocker is getting its fair share of oil.

Short of removing the intake, replacing lifters, inspecting cam, what else can I try?

Any way to force these lifters to pump up?

[RustyPile]

To begin with, your engine is probably NOT a Gen IV.. Non-adjustable rocker arms came out around 1991 and the engine was referred to as Gen V.. The most obvious difference that doesn't take much "digging" to figure out is the timing chain cover configuration. Ten bolts and tin for the Gen IV and back, and cast aluminum or plastic with 5 bolts for the later Gen Vs and up. Google "Identifying Chevrolet big blocks".. There are numerous sites that can guide you through identifying exactly what engine you have.

I agree with the theory of camshaft failure.. That many lobes probably won't fail all at the same time.. The cause of the noisy lifters is most probably due to something that happened during this recent work.

Remove the pushrod guide plates and measure the thickness using a micrometer, not a ruler.. Do the same with the old guides.. The replacement guides are probably thicker than the old ones.. Due to rocker ratio, it doesn't take much change to really move the end of the pushrod.

The other alternative is to replace all the studs, rockers, pivot balls, and nuts with conventional units.. Adjust each rocker accordingly.

[AussieinNC]

I believe this is a Mark V engine, or at least the heads are Mark V with non adjustable rockers.

I agree you should measure the thickness of the new guide plates with a micrometer.

Did you replace all the guide plates or only the ones that were chewed up?

It seems strange that more rockers are clattering now than before the work.

Did you keep each rocker / pushrod with its valve ? I have seen some engines where the builder of the engine has ground the pivot base down to effectively shorten the height of the pivot. Why? Usually a reduced base circle reground cam that sits the lifters lower and the valve clearance opens up.

Two suggestions:

Check the pivot area base of each pivot and look for machining marks or grinding marks. If you find any, the cam has most likely been reground....

If this is the case, replace the cam and all lifters and the rocker pivots.

or

Install adjustable rocker posts and rockers. If the cam has failed lobes, this will not fix the failing lobes, it will just allow you to quieten the noise.

Is the cam cover tin (mark VI) or plastic (Mark V) ?

[1970BannerBlazer]

Originally Posted by AussieinNC

I believe this is a Mark V engine, or at least the heads are Mark V with non adjustable rockers.

I agree you should measure the thickness of the new guide plates with a micrometer.

Did you replace all the guide plates or only the ones that were chewed up?

It seems strange that more rockers are clattering now than before the work.

Did you keep each rocker / pushrod with its valve ? I have seen some engines where the builder of the engine has ground the pivot base down to effectively shorten the height of the pivot. Why? Usually a reduced base circle reground cam that sits the lifters lower and the valve clearance opens up.

Two suggestions:

Check the pivot area base of each pivot and look for machining marks or grinding marks. If you find any, the cam has most likely been reground....

If this is the case, replace the cam and all lifters and the rocker pivots.

or

Install adjustable rocker posts and rockers. If the cam has failed lobes, this will not fix the failing lobes, it will just allow you to quieten the noise.

Is the cam cover tin (mark VI) or plastic (Mark V) ?

All the pushrods went right back into their original locations. But they were also all the same length.

I’m going to get back in there and measure the guides. Probably will end up switching back to the old set since I don’t have a tool to grind down the new set to the old thickness, if they are different.

I’ll check on the mark V cover. Not sure it matters right now but would be good to know.

[1970BannerBlazer]

It’s the guides. My gap on the rockers was .035.
New guide was .125
Old was .086
Diff: .039

[AussieinNC]

The new guides....

Where did you buy them? Aftermarket?

This has been a PITA for you but this has become a very good learning post for everyone.

Check old parts against new...at all points in the repair scenario....

The GM part number for the Mark V engines is 12562369

Here is some perhaps interesting information....


Big Block Chevy, Standard Length Big Block Intake 3/8" / .080" 8.275"
295-7941-8 Big Block Chevy, Standard Length Big Block Exhaust 3/8" / .080" 9.250"

295-7969-8 Big Block Chevy, Standard Big Block +.100" Long Intake 3/8" / .080" 8.375"
295-7979-8 Big Block Chevy, Standard Big Block +.100" Long Exhaust 3/8" / .080" 9.350"

295-7951-8 Big Block Chevy, Standard Length Big Block Tall Deck Intake 3/8" / .080" 8.675"
295-7961-8 Big Block Chevy, Standard Length Big Block Tall Deck Exhaust 3/8" / .080" 9.650"

295-7800 V8 396-454 Retro Fit Pushrod Set, Intake & Exhaust, 1965-Present


3/8" / .080" 7.725 Int. 8.675 Exh

[RustyPile]

Originally Posted by 1970BannerBlazer

All the pushrods went right back into their original locations. But they were also all the same length.

I’m going to get back in there and measure the guides. Probably will end up switching back to the old set since I don’t have a tool to grind down the new set to the old thickness, if they are different.

I’ll check on the mark V cover. Not sure it matters right now but would be good to know.

This is one of the pitfalls when ordering on line. You can't compare the new parts to the old.. I suggest you take those old guides to a local parts supply.. check the thickness of the old against the new..

I highlighted a statement in your post. If what you said about the pushrod length is true, that is probably part of your problem. BBC pushrods, because of the valvetrain design, are not all the same length. Over the production life of the BBC engine, the lengths vary somewhat. Exhaust pushrods are longer than the intake pushrods. They will not interchange.

[1970BannerBlazer]

Originally Posted by RustyPile

This is one of the pitfalls when ordering on line. You can't compare the new parts to the old.. I suggest you take those old guides to a local parts supply.. check the thickness of the old against the new..

I highlighted a statement in your post. If what you said about the pushrod length is true, that is probably part of your problem. BBC pushrods, because of the valvetrain design, are not all the same length. Over the production life of the BBC engine, the lengths vary somewhat. Exhaust pushrods are longer than the intake pushrods. They will not interchange.

Thanks. I miss worded that. All the intake are the same length. All the exhaust are the same. Someone had asked about different lengths.

The guides are Comp Cam I purchased from Summit. Definitely a learning moment for me with this 454.

[AussieinNC]

Just order one plate for the cylinder that was chewed up

The GM part number for the Mark V engines is 12562369

Replace the others with the originals....

Enjoy the now silent 454....

[mattfranklin]

There is a conversion kit in case you want to make things adjustable: https://www.summitracing.com/parts/cca-4514-kit/reviews