Engine noise - can't identify

[agnes the dog]

I've been working on this issue for a while and feel like I need to reach out for some help. My engine is making a ticking noise in cylinder 6 or 8 (most likely 8), like a noisy rocker arm, but only on a hot start. I can start the engine cold, no noise. If I drive it for a while and shut it off for 15 minutes or so, restart, and it gets the awful clacking for a while. It'll eventually go away again. Here's a history:

The engine is a 350 sbc. Came out of a 1974 caprice. Two bolt main. I sent it out to be machined and then I assembled it. It runs really good. No issues with performance.

Trying to identify the noise, I did the following:

New rocker arms - checked and retightened too many times to count
New Comp camshaft
New Comp lifters
Melling High volume oil pump
New pushrods
Swapped to World heads
Running thicker oil (20w50 now)
Even changed the valve cover gaskets to see if that was an issue
Header gaskets twice

So, I've changed all that stuff and I still have the noise. The only thing close to the noise that I have not changed is the headers. They are Hedmans and I can't find any evidence of a leak.

Has anyone ever had a cracked header that only showed up when the engine is hot and the headers have cooled a bit? I'm wondering if the difference in the metal thickness could play a part in allowing a small leak until the headers warm back up. Any help or suggestions are appreciated.

[Dead Parrot]

Do the heads have a provision for exhaust crossover? I tracked an exhaust leak tick for a while before changing the intake gaskets to fix a vacuum leak. Also fixed the exhaust leak tick. Sounds like you changed things enough to have fixed an intake gasket leak but something to consider.

Might try getting the engine hot then removing all the belts and starting. Eliminate any chance it is one of the accessories making the noise.

Compression good on 6 and 8 when hot?

[geezer#99]

Might be excessive lifter preload.
Back off the rockers to zero lash and test.
Just try those two cylinders first.

[GASoline71]

Had a worn distributor shaft bushing in a 79 K25 once. The shaft was "ticking" as it spun in the housing. Drove me nuts until I finally did a tune up and when i grabbed the rotor noticed the slop in the shaft. Had the distributor rebuilt (back when we actually had things rebuilt) and it solved the ticking noise.

Also loose torque converter bolts can cause ticking and knocking. Or even a cracked flex plate.

Gary

[paul mora]

I suspect the headers When it’s warm metal expands and the ticking nose is more dominant. Be sure all the header bolts or tight and if you blew out a gasket look for black burn marks about the header. I had a leak on mine that everyone heard except me. Have a friend with you when you listen to the noise

[mattfranklin]

Originally Posted by GASoline71

Also loose torque converter bolts can cause ticking and knocking. Or even a cracked flex plate.

Gary

A while back someone on here was working through a cracked flex plate issue. I think it was on his suburban.

And that comment about headers... Exhaust leaks can sound like a tapping. As metal heats up it expands. I got some really good header gaskets for my build: Remflex #2006 gaskets. My machinist recommended them.

[Ironangel]

+1 on the cracked flexplate or loose bolts. Also, I have a tick coming from where the four header tubes come together at the collector. Welded it once and it worked for awhile but it's back. I've got a cracked flexplate hanging on the wall that drove me nuts thinking the bottom end was knocking because it was a periodic knocking that usually only happened when it was hot...

[agnes the dog]

Thanks for all the replies. I got a mechanic's stethescope tonight. I ran the truck from a cold start and listened to the rockers through the valve covers. All sounded good and pretty much the same. I got the truck good and warm, then let it sit for about 5 minutes. Sounded the same. I let it sit for another 20 and it started tapping pretty loudly from the problem area. The rockers all sounded the same, so I think I can rule them out. After a couple minutes, the tapping went away. I heard a change in the sound of the #8 header tube that was in rhythm with the tapping.

I think I'm down to the headers. I did replace the header gaskets last year with some really nice ones. I'm wondering if there's a small crack near a joint that's allowing a small gap under certain conditions, but not big enough to allow carbon to visibly build up. I guess I'll have to pull the header when they cool down. Maybe tomorrow. :-)

The truck has a 5 speed manual transmission, so it has a flywheel, no flex plate. I doubt that the flywheel is cracked. It was brand new a couple years ago.

Thanks for all the suggestions guys!! Really appreciated!!

[YoungPup1977]

what was the part number of the gaskets you bought ?

[cadillac_al]

I have had good luck with copper header gaskets. There are other gaskets that are even better. I can't remember the name right now (Remflex?)

[agnes the dog]

Originally Posted by agnes the dog

Thanks for all the replies. I got a mechanic's stethescope tonight. I ran the truck from a cold start and listened to the rockers through the valve covers. All sounded good and pretty much the same. I got the truck good and warm, then let it sit for about 5 minutes. Sounded the same. I let it sit for another 20 and it started tapping pretty loudly from the problem area. The rockers all sounded the same, so I think I can rule them out. After a couple minutes, the tapping went away. I heard a change in the sound of the #8 header tube that was in rhythm with the tapping.

I think I'm down to the headers. I did replace the header gaskets last year with some really nice ones. I'm wondering if there's a small crack near a joint that's allowing a small gap under certain conditions, but not big enough to allow carbon to visibly build up. I guess I'll have to pull the header when they cool down. Maybe tomorrow. :-)

The truck has a 5 speed manual transmission, so it has a flywheel, no flex plate. I doubt that the flywheel is cracked. It was brand new a couple years ago.

Thanks for all the suggestions guys!! Really appreciated!!

Ok, so I pulled the headers and found that the metal gaskets had split at the top of the gasket between the 4/6 and 3/5 cylinders. So I thought I found the issue. Nope. Painted and reinstalled the headers with new gaskets. Still doing it. New plug wires. Nope. So I started looking into oils and came across a strange topic. The oil filter anti-drain back valve. As I researched, I found that I have been using a filter that didn’t have that feature. $9 for a new filter with the valve and my problem was fixed. Lesson learned. Always do your own research before buying parts. The parts guy who recommended the filter gave me the wrong style. I’m sure he just didn’t know the difference. Thanks for all the replies.
Posted via Mobile Device

[mongocanfly]

New one on me....

[MySons68C20]

So why would the lack of a ball bearing, spring and seat cause that noise?
I'm not doubting your findings just trying to make sense of it.

[garyd1961]

Why does a sbc need an anti-drainback valve when the filter is facing up and the oil can't drain out?

[67 Burb]

Originally Posted by garyd1961

Why does a sbc need an anti-drainback valve when the filter is facing up and the oil can't drain out?

I was thinking the same thing. I think the only instance when an anti-drainback valve is required on a SBC is when using an engine oil cooler in the rad. Then there is engine oil higher than the filter and it would drain back to the oil pan when sitting.

[YoungPup1977]

Originally Posted by agnes the dog

Ok, so I pulled the headers and found that the metal gaskets had split at the top of the gasket between the 4/6 and 3/5 cylinders. So I thought I found the issue. Nope. Painted and reinstalled the headers with new gaskets. Still doing it. New plug wires. Nope. So I started looking into oils and came across a strange topic. The oil filter anti-drain back valve. As I researched, I found that I have been using a filter that didn’t have that feature. $9 for a new filter with the valve and my problem was fixed. Lesson learned. Always do your own research before buying parts. The parts guy who recommended the filter gave me the wrong style. I’m sure he just didn’t know the difference. Thanks for all the replies.
Posted via Mobile Device

What is the filter part number you used to fix this issue ? Thanks

[mattfranklin]

That's wild.

[richards72chevy]

What oil filter fixed the problem?

[YoungPup1977]

Please provide the old oil filter type/part number and the new oil filter part number. Thanks again !
Posted via Mobile Device

[YoungPup1977]

AC delco has a ADBV filter which is PF1218. On a 1974 chevy caprice sbc engine ? Got to love when you ask a simple question on this forum and no one cant or wont answer it, which means this thread is worthless to me.