Help! Clacking valve train driver side

[Bolisk]

I have a 1970 l46 sm with solid mechanical lifters. The engine is mildly hot riddled to correct lt-1 rotating and valve assembly. I've set the lash many times in the past to a cold value of .21 intake and .26 exhaust using the John hinkley procedure.

About three days ago I noticed a clicking or ticking whenever I would go through a tollbooth or get close enough to a wall to have the sound bounced back to me. Now I notice it almost all the time. This sound was not there before. It does not get louder with rpm, but does get faster. Loudest at idle, probably because the engine is quiet.

Just redid the valve lash, checked it twice, and sound is still there!

Any other ideas of what it could possibly be?

Any help appreciated.

Regards,
JR

 

[TimAT]

Setting them cold at .021 and .024 will end up with the lash well below .020 when hot. What are the cam manufacturer's recommended settings?

I see you used John's procedeure- what is it?

I always set my BB at .024 and .026 hot- Intake as the exhaust closes, Exhaust as the intake opens. And by hot, I run it (or drive) until it's fully wamed up- 180* at least on the temp gauge, shut it off, pull one cover, adjust, put the cover back on, run it to get the temp back up, and then the other side. IT takes a little bit of learning to catch when the valves are just beginning to move, but a little practice and it gets easy.

I'm running the BB now, but I've got a SB with a solid cam from a Camaro I bought new in 1973 just setting on a stand on the corner waiting for me to get something to put it in.

 

[lars]

I see you used John's procedeure- what is it?

I can send it to you - just send me an e-mail request.

Lars
V8FastCars@msn.com

 

[6880 Mike]

Oil level correct?

 

[Bolisk]

Yes, oil level is correct.

I have no idea what could be causing this. tripple checked the valve lash.

Could it be a bad spring? Everyone says is sounds like valve lash. . .and I agree. . .but it clearly isn't. I'm nearling my wits end. It is embarrasing to drive.

Oh, in case I didn't mention it. The sound fades in and out. You will hear it for about 10 seconds. . .then it will go away for about 5 seconds. ..then repeate. It's most noticeable at idle.

 

[JJS]

Bad spring

I had the same symptoms in my LT-1 several years back and the problem was a bad spring.

Good luck and I hope the problem is as simple as a spring.

-JS

 

[Bolisk]

How did you root cause down to the bad spring? Might help me narrow my effort.

Thanks,
JR

 

[Bolisk]

ok just for giggles, I went out and tighened them up a tiny bit more. . .removed a couple of thousandths. Made zero difference.

I went out to Autozone and bought a automotive stethescope (sp?)

After listening to every valve location (through the valve covers). . .intake on cylinder 7 sounds the worst. Luckly, that is right next to the oil fill hole. After removing the cap. . .the sound immedaitly got louder. Close the cap. . .and the sound got quiter.

You can actually watch the number 7 spring moving through the oil fill cap. . .and the sound appears to be synchronized to the number 7 intake spring compression. But I may be wrong.

So lets say for now that it's a bad spring.

What brands does eveypone recommed for valve springs. . .and what type of spings go on a 1970 engine. The ones on there now are new (when I got the heads rebuilt). . .and I have no idea what brand they are. . .and they have the dampner in the middle. The shop called them High Performace springs. . .

 

[JJS]

Didn't need a stethescope for mine

ok just for giggles, I went out and tighened them up a tiny bit more. . .removed a couple of thousandths. Made zero difference.

I went out to Autozone and bought a automotive stethescope (sp?)

After listening to every valve location (through the valve covers). . .intake on cylinder 7 sounds the worst. Luckly, that is right next to the oil fill hole. After removing the cap. . .the sound immedaitly got louder. Close the cap. . .and the sound got quiter.

Took off the valve covers and it was obvious which one (I don't remember which) was the NOISY one!
Sounds like you found the problem - congrats.

 

[Bolisk]

not yet. . .need to find the right replacement springs. what did you use?

 

[JJS]

not yet. . .need to find the right replacement springs. what did you use?

Used a spring out of another corvette - don't know the brand, but it was probably an original.

 

[Bolisk]

Ok. . .update time. . .

So I odered some oil defectors from sumit. . .installed them.. .then ran the engine. I was able to confirm that the loud valve was infact number 7 intake. So I tighened it down until the noise went away. Didn't take much. . .maybe a third of a turn. While running I tried to get the feeler gauge into the gap. . .and I could not get the .021 to fit. I tried all the way down to .017. . .and that didn't fit eather. . .but I could still hear a bit of clacking.

I shut he down and took the rocker off. . .to immedatly discover that the pad on the rocke that contacts the valve stem had failed. and good sized hole was beign warn into the rocker. Hole was already about .020 deep. Hence the reason why I couldn't get a feeler in the gap (the blade was wider than the hole. . .and why it was so damn noizy. I figure it was running at a valve lash about .040.

So on closer inspection. . .this rocker is NOT the same as the rest. It's a stock appearing stamped steel rocker. . .but it does not have the same markings.

The valve steam would normally have a chamfer on the endge. . .that has now been rounded off. The top center of the stem appears to be ok. . .but there is not as much surface area as their was before. . .maybe lost a total of 1mm of suraface area.

So, my current plan is to go with Com Cam's Magnum roller tip rockers. . .and I wanted peoples opinions on that.

Also, do I absolutly need to change the valve? Or do you think I will be ok?

Clearly the valve is a stonger alloy than the rocker.

Opinions. . .comments. . .

ALSO, what is that blue stuff called that engine builders put on the valve stem to test to see of the rocker is contacting the valve stem correctly.

Thanks!
-JR

 

[lars]

what is that blue stuff called that engine builders put on the valve stem to test to see of the rocker is contacting the valve stem correctly.

It's called Dykem - it's a layout dye often used by machinists and sheet metal shops. You can get it in spray cans and brush-on cans through outlets like McMaster-Carr. But you don't need it: You can just take a felt marker and color the valve stem. Then, wiggle the rocker back and forth across the valve stem as you rotate the engine through the full valve opening cycle. This will give you a nice worn-off pattern on the valve stem that you can then use for geometry verification.

Lars

 

[Bolisk]

I've head of people using a Sharpie. . .is that ok. . .or is that too hard to "wear off"

 

[Crimson Thunder]

I used a Sharpie on mine. It works fine. I would definitely replace all 16 rocker arms.

 

[Bolisk]

Just installed a new set of comp cams magnum roller tip rockers and push rods. What a pain in the arse to get just right. Lash is much more tricker with them, and I an into the problem where you cannot get a socket on the nuts without binding the rocker. Also ran into a problem where the oil drip tabs on the stock valve covers rub on the new rockers. After a lot of work. . .very happy with the new rockers and the way they sound. Not an easy fast swap though.