4 year old rebuild in Corvette - now tapping or knocking...leaking oil

Have a 61 Vette with a newer totally rebuilt 327 block, Edelbrock top end stuff. It seemed to be running high oil pressure for awhile (55-60 cold, 35-50 hot)...higher than it did right after rebuild.

Last week I noticed big oil leak under car (never leaked before). There was oil sitting up on the intake manifold as well. I retightened valve covers, filled with oil and it doesn't seem to leak up top...having a hard time see where leaking is coming from.

There is a NEW tapping sound...checked lifters and they seem tight. Any easy way to check to see if it's in a rod somewhere?

Here's video so you can hear it:https://youtu.be/35-uWjpaKYY

any ideas appreciated....hate to break it down to much as it's pretty newly built.

Remove valve covers and see if pushrods spin while engine running--if not cam is wiped out

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Originally Posted by lrsmith62

Have a 61 Vette with a newer totally rebuilt 327 block, Edelbrock top end stuff. It seemed to be running high oil pressure for awhile (55-60 cold, 35-50 hot)...higher than it did right after rebuild.

Last week I noticed big oil leak under car (never leaked before). There was oil sitting up on the intake manifold as well. I retightened valve covers, filled with oil and it doesn't seem to leak up top...having a hard time see where leaking is coming from.

There is a NEW tapping sound...checked lifters and they seem tight. Any easy way to check to see if it's in a rod somewhere?

Here's video so you can hear it:https://youtu.be/35-uWjpaKYY

any ideas appreciated....hate to break it down to much as it's pretty newly built.

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I did tighten the lifters on the tapping cylinder and was able to quieten it but didn't want to tighten to much and possibly hurt things more. Noticed that one lifter is not oiling very well...whereas the others are. Could that help inform what's going on?

chect to see if pushrods are spinning as the motor runs------a flat tappet camshaft is ground on a slight taper to cause the lifters to turn ----if its not spinning. the cam/lifter is worn-happens a lot with todays oil on new rebuilds

First, welcome to CHR. I typed a reply earlier, but it didn't post and I lost it.... My first thought was that you lost a lobe on the cam, and your statement about tightening one lifter to reduce the noise points to that even more. I'd drain the oil and check for very fine metal dust in the oil, and maybe cut the filter apart and check in the folds of the filter media, too. I assume that the rebuild of the 327 did not include a conversion to roller lifters, right?

On the leak, look at the "China Wall" gasket surface across the back. They're known to blow out, which is why using a thick bead of silicone has become the preferred method of sealing vs the rubber gasket.

Just out of curiosity, are you running a road draft tube and the oil filler in the intake manifold?

NTFDAY....as a matter of fact, yes, I'm running original draft tube and filler neck in the Edelbrock intake. Interesting question....why?

On CAM, it's a new cam replaced during the build. Engine had an aggressive racing cam and it was a pain to try and dial in, so we purchased a new cam from Edelbrock to specks with the engine. I guess I'd be shocked that the cam is worn our since I have less than 2500-3500 miles on this engine.

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Originally Posted by lrsmith62

I guess I'd be shocked that the cam is worn our since I have less than 2500-3500 miles on this engine.

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Today's motor oils no longer have zinc and phosphorus additives, which were there to deal with high pressure, point load friction, specifically cam to lifter friction. They were omitted when OEM's found that catalytic converters were getting plugged with heavy metal deposits, rendering them useless, and since OEMs had switched to roller cams they had no concern with changing the oils we can buy. If the cam is not broken in 100% perfectly, i.e. immediate start without extended crank, 2000 rpm for twenty minutes with no idling, a wear pattern can start that stops lifter rotation, and wipes a lobe quickly, often less than 2000 miles. Running a racing oil, like Brad Penn's or Joe Gibbs can work, but it's still a gamble.

I don't remember the exact specs/time, but we did do an intentional break in on the engine and I seem to remember running it for 30 min at 2000. The guy that helped me rebuild the engine was an ex-GM mechanic and a hot-rodder.

Additional info:
- I went back and adjusted all valves. Did the GM instructions, while running engine, loosening to tap/noise and then doing 3/4 turn back tight. Did for all valves including the #8 cylinder that seems to be giving the noise. Still a bit of tapping, so it's not the rockers (not rollers btw)
- checked carefully the push rods and all are rotating at a normal rate it seems
- dried all the oil off of the back (exhaust) rocker for #8 cyl. and it didn't re-oil when started. This has to mean something...no oil even though push rod is turning?
- took push rods out of #8 and they look straight and normal to me.

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Originally Posted by lrsmith62

NTFDAY....as a matter of fact, yes, I'm running original draft tube and filler neck in the Edelbrock intake. Interesting question....why?

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The engine has to have a way to breathe and I've seen those who will delete the road draft tube and put a closed breather on the oil filler tube. They won't run a pcv system because they don't want to hack up the finned Corvette valve covers. That will cause a massive pressure in the crankcase pushing oil out wherever a place can be found.
I experienced that on a cherry 57 Ford in 1964 in California. After a 1000 miles or so the dipstick blew out, dented the hood, covered the right side of the windshield in oil and wiped out the bearings.

Can you see through the pushrods out of #8, or can you run a piece of safety wire through them unrestricted? I'd still drain the oil and check for metal. If you wiped a lobe that's a bunch of microscopic abrasive flowing through the engine, so you're looking at a total teardown. I wouldn't waste a nickel on building a flat tappet cam engine today. It's been said that it's not "IF" it will fail, but only "When" it will fail.

If you didn't wipe a lobe? It's a pretty healthy knock from the video, so chances are you're gonna be taking it down, at least enough to get #8 pulled out....

gotcha....I'm not running a pcv system, but do have the draft tube and the filler cap is vented around the bottom side of it.

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Originally Posted by lrsmith62

It seemed to be running high oil pressure for awhile (55-60 cold, 35-50 hot)...higher than it did right after rebuild.

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Sudden increases in oil pressure usually indicates a restriction to the oiling system and can be as detrimental as low oil pressure. Something has gone wrong, check the oil and filter (as suggested by rspears) before you continue to do further damage.

#8 exhaust tappet is the first to get oil so if it isn't and others are-------bad tappet, plugged pushrod, etc-You might be able to fish it out thru dist hole in manifold-however since you have a leaky manifold your going to need to fix that but would suggest you check out the tappet first-

for cylinder noise-you can short out spark to cylinders one by one to see if noise goes away or changes------if # 8 becomes quiet or changes siq amount? probably need to pull pan also-oh wait-oil leak

Here is video after valve adjustment....top end noise lessened but still tapping for sure. Also, engine not running as smooth as it used to....a little sluggish on idle every 30 sec. or so.

https://youtu.be/sb02Ul1NNLs

Push rod not clogged....so I guess I'll drain and look for metal, probably also pull intake and check tappet, pull pan and check #8 bearing as well to make sure it's not spinning. Need to re-seal everything anyway. Bah humbug....this is why we like old cars, right:)

Isn't there an oil additive to address the zinc and phosphorus issue?

you can get that tappet out the dist hole -to check it out before you go further

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Originally Posted by firebird77clone

Isn't there an oil additive to address the zinc and phosphorus issue?

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Yes, one can add ZDDP, but many don't realize that having too much zinc and/or phosphorus can bad too. I'd strongly recommend using a properly formulated oil, Gibbs or Penn's for example, and let the chemists handle the chemistry.

so I guess you don't want to answer my suggestion that you can get #8 out the dist hole? and or the comment about shorting out the plugs to see if noise changes????


I've seen many errors in assembly where there was a noise and the opurtunity to diagnose the source wasn't looked at fully and the noise remained after the rebuild------

Your noise and conditions shout at lifter/cam shaft but there ar other places it could be------

no8, back of block--------how about loose converter bolts???? starter nose gear??? could even be broken crank from hammering on the harmonic dampner--------just sayin----check the damn lifter-measure the cam lift on different lobes, etc

Lol! That's tell em Jerry!

wow...I was working on it:)

wouldn't come out without taking off intake. To the naked eye, the lifter looks ok, no wear marks anywhere on it. Guess it could be failing internally though and not oiling.

I'll measure lift against other lifters that are good and see if I can see something amiss with the cam lobe.

Had this happen years ago, I had a lifter ticking I would retighten it and it would start again, it ended up that one of the pressed in rocker studs was pulling out with the higher valve spring pressure and bigger cam lobes, ended up having to put in screw in studs. Not that this is your problem but "This happened too me"! Check and see if the stud length on the rocker nuts protrude all about the same and ones not lifting. Also Welcome!

while you have intake off spin motor on starter and look for oil in the lifter hole----
by the way, you didn't put any restrictors in the galleys did you??

by hard to get out, does that mean that you had to pull it hard?????like bottom edge messed up?

Does bottom face of lifter have a radiusd face? cam lobe should just be shiny on back edge of lobe and not be real shiny on top of lobe nose

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Originally Posted by Matthyj

Had this happen years ago, I had a lifter ticking I would retighten it and it would start again, it ended up that one of the pressed in rocker studs was pulling out with the higher valve spring pressure and bigger cam lobes, ended up having to put in screw in studs. Not that this is your problem but "This happened too me"! Check and see if the stud length on the rocker nuts protrude all about the same and ones not lifting. Also Welcome!

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Matt's suggestion is great! I had forgotten, but I've seen that before, too, where a rocker stud was pulling out of the head with the dynamic loading and higher spring pressures. Adjust it, and a few days it's ticking again. Pinning the studs, or better yet, threading the head for screw in studs fixed it!

no...not "hard" to pull out. Was difficult to get to. Lifter slide out nice. Literally all the faces, edges and sides of lifter have no markings whatsoever. These are flat tappet hydraulics, so the face is shiny and flat...no grooves or indentions.

Didn't put any extra restrictors or anything in galley. There was oil in the lifter hole...though I don't know if it was enough. It slide out will the same force as the #8 intake (I took out for reference).

Rocker studs look the same length as the others....they are threaded if I remember right as these are Edelbrock Performer Series heads and I think they screwed in to set them. They look visually the same height and nut goes on rocker and looks the same amount of travel as the others.

Possible broken spring in the lifter?

That's what I'm wondering....if the internals of the lifter are damaged. That would account for the rocker not oiling.

Push Rod was turning though, so I'm hoping the lobe is ok. Still going to take oil filter apart and check to see if I can see metal. Didn't see any obvious flakes when I drained it.

I can still get these same lifters (Edelbrock) from Summit Racing, so I could get one, install it, and break it in....see if that fixes it. Getting the cam out of a Corvette is near impossible without pulling the engine. I do remember that:)

Pull the hood and radiator, raise the front of the motor and lower the tranny. Ask me how I know...

I would almost bet something got into it and plugged it up, May account for the high oil pressure you had for awhile. You'll probably find the rest of what ever past through in the oil filter. They used to make a cleaner for hydraulic lifters that you added to the oil. Might want to look into it.

Ordered a lifter...while I'm waiting for it, I'll get into the oil filter and examine for metal or other crud.

If it's still tapping after new lifter, cam may be messed up.

I'll keep you posted. Thanks to everyone for the help...

Quote:

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Originally Posted by lrsmith62

Have a 61 Vette with a newer totally rebuilt 327 block, Edelbrock top end stuff. It seemed to be running high oil pressure for awhile (55-60 cold, 35-50 hot)...higher than it did right after rebuild.

Last week I noticed big oil leak under car (never leaked before). There was oil sitting up on the intake manifold as well. I retightened valve covers, filled with oil and it doesn't seem to leak up top...having a hard time see where leaking is coming from.

There is a NEW tapping sound...checked lifters and they seem tight. Any easy way to check to see if it's in a rod somewhere?

Here's video so you can hear it:https://youtu.be/35-uWjpaKYY

any ideas appreciated....hate to break it down to much as it's pretty newly built.

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Just curious, did you ever find the cause of your problem?

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Originally Posted by lrsmith62

. I guess I'd be shocked that the cam is worn our since I have less than 2500-3500 miles on this engine.

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A local guy here in town made it less than 30 miles down the road on a new crate motor with a flat tappet cam, pulled over on the side of the road after it wouldn't run and pulled the valve cover, rockers where barely moving, didn't put any zinc or use oil with zinc and it went flat that quickly. I hope all goes well for you as we have all been down the road your going! Best of Luck Matt

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Originally Posted by jimbos56

Just curious, did you ever find the cause of your problem?

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If you look at his activity he checked in three days after his last post, September 1 at 11:43pm and hasn't been back. Yeah, it's only 8 months, but then again, it's 8 months with no posts....