Chevy Corvette 350 small block - Knocking noise, can anyone diagnose please?

sounds like lifter tick to me, has it been run a lot in the last 12 months ? my old bmw used to have lifter tick with so many short runs.

Not really, been the kind of car it is, I am also a little afraid to now take it anywhere just in case it is something serious, plus the PS leak I fixed is now back big time, seems the pump itself is now leaking big time, guess it found next weakest link, as such I have a new pump/reservoir on the way which after that will only leave the module as only unchanged item in the PS system so any luck will be on top of that.

Back to the engine got lots to look at, getting a lot of mixed messages from US side.

Some say at idle oil should be squirting everywhere from rocker arms and some argue that mine is absolutely fine, so its a case of do I have an oil flow issue or is that normal. Oil pressure is good, but good oil pressure does not equal good flow necessarily.

Many are also saying worn lifter and or camshaft and check #6 cam lobe first as it gets most wear.
Also a few have said they had same issue and it was not engine but things like crank pulley bolts backing out and catching and a new favourite is the TH350 transmission could have a cracked or broken flex plate, so I am gonna remove transmission cover and check that out with it running.

Also been told to listen to fuel pump as supposedly they can make a similar tapping noise too and are generally noisy.

Another one is to check exhaust manifold gasket on that side also, could be reason, so there is a lot to look and listen to before doing more engine work.

Its in a local garage Monday, who have a good reputation and understand classics somewhat, so gonna see what they thinnk and let them know all feedback I've had from US side. Also a guy I know in Stoke put me in touch with his mate who owns a garage and has good understanding of classic and Chevy small and big blocks, so he is my next stop.

Its really difficult as many say its fine, drive it, otherwise have no clue but don't want to look at it and then finding someone you actually trust who actually knows what they are doing is not easy.
I could do the lash, pull the lifters and it could still be present, hence gonna let some mechanics with better hopefulyl better understanding take a look before I start pulling it to bits, though I can now get the valve covers off in about 5 mins per side and intake manifold seems an easy affair to remove....

Unfortunately for me my hearing is very tuned into car noises, I hear a squeak, knock I have to fix it, most people who have seen the Corvette are just wowed by it and can't even hear the engine knock, I think there is absolutely a problem and maybe with more use it could go away, but it could also get worse and result in a major engine rebuild or replacement which would be a shame on a matching numbers car to drop a crate motor in it.
 
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It will keep niggling you. Get it booked in to a V8 specialist.

A few years ago I could have hooked you up with a best friends dad who specialised in US V8's. He built many for racing (Thundersaloons, ASCAR etc) and was a Hot Rod legend and would have been all over it and local. He moved back to Ireland and now lives west coast in happy retirement though so unless you want a road trip that won't work :D
 
No expert, but isn't US fuel different to ours? If you've used v-power or similar could that be the difference given its not got modern efi.

Some knock noises can actually be from a cracked exhaust/manifold too. Worth investigating if you haven't already.

Sounds like it needs a once over with some expert eyes. I can imagine outside of some guess work you'll end up replacing peace of mind items like the rockers, lifters pushrods etc but could still end up hearing it.
 
What oil is in it @Gibbo? Reasonably high zinc content?

It had 10-40W Millers classic with zinc in it and I changed it too the 20-50W version with zinc a month ago which had no real impact on the noise, maybe marginally quieter.

Ive added some lifter additive, so far no change but I’ve not driven car yet only let it idle.

I am gonna set valve lash over weekend just to rule that out, gonna set it with engine running so loosen rocker until it clatters, tighten until it stops and then tighten an additional 1/4 turn. I doubt this will fix it but best I do that and rule it out than pay someone.

I’ll also get the trans inspection cover off just into the trans plate is cracked or broken and I’ll have a good listen to fuel pump and inspect crank bolts just to rule those out.


No expert, but isn't US fuel different to ours? If you've used v-power or similar could that be the difference given its not got modern efi.

Some knock noises can actually be from a cracked exhaust/manifold too. Worth investigating if you haven't already.

Sounds like it needs a once over with some expert eyes. I can imagine outside of some guess work you'll end up replacing peace of mind items like the rockers, lifters pushrods etc but could still end up hearing it.


US fuel is same as ours but can tend to be a lower octane but I just put basic unleaded in this, I did try Vpower but again no difference.
 
I've had lifter tick in my bmw occasionally when left sitting for a few weeks. The noise does not sound like yours. N52 things.

Your noise is more of a knock/banging than a tick to my ear.

Listening on my phone I thought it was a tick, now I’ve listened on my PC with a lot more bass, I thought the same.

No expert mind you!
 
Lifters or cam BUT.... for some reason on yank muscle lifters always go they have the same problem on the newer 2011+ MDS 6.4 hemi SRT's mate, and everyone goes literally every engine now.

HOWEVER... TBH though, that sound if it is a lifter is a little deep sounding to me, lifters in my experience are a higher tappet sound literally like tappets rather than a low down knock. Tough one, can't add anything but would be interesting to see how this one goes, good luck fell! I wonder if this is like the HEMI tick, which people here but there is simply nothing anyone can do... wonder if it's that kidna thing and no one knows why it occurs!!!
 
Lifters or cam BUT.... for some reason on yank muscle lifters always go they have the same problem on the newer 2011+ MDS 6.4 hemi SRT's mate, and everyone goes literally every engine now.

HOWEVER... TBH though, that sound if it is a lifter is a little deep sounding to me, lifters in my experience are a higher tappet sound literally like tappets rather than a low down knock. Tough one, can't add anything but would be interesting to see how this one goes, good luck fell! I wonder if this is like the HEMI tick, which people here but there is simply nothing anyone can do... wonder if it's that kidna thing and no one knows why it occurs!!!

Really no idea listened to lots of 350’s online which have similar sounds and they don’t seem to be complaining or worrying about it.

I feel there is absolutely an issue the question is discovering how serious or not.

Part of me hopes it is a lifter or worn cam as that will be an excuse to put a new cam in that gives some extra power, some roller rockers and a tune up should make it good for 300 horses with those basic mods.

not had a chance to work on it today, miserable weather and for obvious reason I don’t like running it in the garage.
 
Hi there

I’ve set the valve lash today. Did the engine running procedure and doing this also does seem to have increased amount of oil flowing to the top as it made quite a mess lol.

I slackened off each rocker nut until the rocker arm started clattering and then tightened until it stopped so at zero lash, I then gave an additional quarter turn very slowly.

I did notice as undoing a few oil flow to the rocker arms improved, even got a few squirting and car was at idle.

Buttoned it all back up and car is quieter and the tapping I could feel on the valve cover has reduced and is near none existent.

Id say they were all set to between 1/2-3/4 turn before I started and I’ve set them all to just 1/4 turn for a touch more power and hopefully better flow.

Took car out and it also felt smoother and a touch peppier.

Car is in garage tomorrow so will see what they have to say, they are experts with classics and land rovers, so see what their opinion is and let them check the fuel pump, crank pulley and transmission for excess noise.
 
Having compression and not hanging valves open will tend to do that! :D

Yep I think a lot of people think they should turn them more as I’ve seen some recommend one full turn once at zero lash but there is equally many who say as you said, 1/4 turn and let engine give its best and if they back off and clatter again then just readjust as it’s an easy job, just messy.

But I guess how worn the cam also plays a part also, will report back on what garage says in week.
 
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Dropped car of this morning, spotted @paradigm also, hope your well mate.
Mechanic says the engine noise is tappets and he says in his oppinion they are pretty quiet (car is much quieter now since I did lash), he said I did the correct thing only making 1/4 turn on the rocker arms.
He is gonna give the car a thorough checking over and fit the new steering pump, sort the alignment and centre the steering box/wheel.

He said if engine gets noisier then he will do a proper cold lash adjustment and check all the parts for wear and replace if necessary.
 
Dropped car of this morning, spotted @paradigm also, hope your well mate.
Mechanic says the engine noise is tappets and he says in his oppinion they are pretty quiet (car is much quieter now since I did lash), he said I did the correct thing only making 1/4 turn on the rocker arms.
He is gonna give the car a thorough checking over and fit the new steering pump, sort the alignment and centre the steering box/wheel.

He said if engine gets noisier then he will do a proper cold lash adjustment and check all the parts for wear and replace if necessary.

over paranoid gibbo lol enjoy the motor.
 
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