noise when hot

[Al]

Hi

Since I swapped stock heads for Eddy Performer rpms (and added a new cam with new lifters) the engine makes a clacking noise but only when hot. The engine is a 383 and I kept the stock valvetrain. The noise seems to come from the heads but only after the car has been driven for about a quarter of an hour.

So far:
- I have changed the oil from 20w 50 to 10w 40: no improvement.
- I have changed the pushrods for a set of stock lenghth new ones: no improvement:

Any ideas of what could cause this?

Al

[John_Kunkel]

Aluminum heads expand more than iron when hot so the rockers move away from the lifters as the heads warm up. Even "new" pushrods can be too short...did you check to see how far down the lifter disc is with the valve closed?

[Al]

Aluminum heads expand more than iron when hot so the rockers move away from the lifters as the heads warm up. Even "new" pushrods can be too short...did you check to see how far down the lifter disc is with the valve closed?

The "lifter disc" is it the upper part of the hydraulic lifter that is in contact with the pushrod? If so how could I check it ?

[XH29N0G]

When I swapped a cam, lifters, pushrods, and heads I had noise that was cured by replacing some of the stamped steel rocker arms.  I think maybe () the old rockers were a little worn.  I wonder if that might be an issue.  People here can guide you on how to check if it is a possibility.

[ottawamerc]

Mine does the same, I believe that the aluminum heads transfer noise more efficiently than the cast iron heads do so some noises that are normal in a cast iron stock engine sound abnormal with the aluminum Thats what my engine builder told me anyhow but it could have just been a story to get me off his back too

Scott

[Al]

When I swapped a cam, lifters, pushrods, and heads I had noise that was cured by replacing some of the stamped steel rocker arms.  I think maybe () the old rockers were a little worn.  I wonder if that might be an issue.  People here can guide you on how to check if it is a possibility.

Good idea, I'm going to check it out over the weekend thx.
Al

[XH29N0G]

Hope someone else pipes in,  What I did was to isolate the location of the loudest sounds by listening through the head (and I think valve cover) using a long Al rod (a large screwdriver or mechanics stethoscope would also work).  (Putting one end on the block, and pressing the other end against the part of my skull just in front of my good ear.  I always find it amazing how well my skull transmits clicking sounds.)  I may even have run it a little bit with the valve covers off.  I am sure there must be a way to check with the engine off. 

Hopefully with this, someone else will pipe in to tell you if what I say is OK or should be done differently.  It did cure my issue.  The other thing is that the non stock cams can be a little noisier (or a lot -depending).  Good luck and let us know if this works.

[Al]

Hope someone else pipes in,  What I did was to isolate the location of the loudest sounds by listening through the head (and I think valve cover) using a long Al rod (a large screwdriver or mechanics stethoscope would also work).  (Putting one end on the block, and pressing the other end against the part of my skull just in front of my good ear.  I always find it amazing how well my skull transmits clicking sounds.)  I may even have run it a little bit with the valve covers off.  I am sure there must be a way to check with the engine off.  

Hopefully with this, someone else will pipe in to tell you if what I say is OK or should be done differently.  It did cure my issue.  The other thing is that the non stock cams can be a little noisier (or a lot -depending).  Good luck and let us know if this works.

I'll try that 

[Al]

Back to report.

So before going deeper into things I replaced the 20w-50 oil with SAE 30 as per Service Manual. Lo and behold, the clicking noise when the engine is hot seems to have nearly disappeared. To my great astonishment.

Maybe the 20w-50 is too thick for my engine. However the SAE 30 oil I used has API SA specification and that is not too good (of course I added a bottle of ZDDP).

I've searched the net but a good SAE 30 oil with a more appropriate API classification like SF or even SL is hard to find. Any suggestions would be welcome.

greets
Al

[myk]

I can't imagine where 20W50 would be a good oil to run in an engine.  I'm surprised the 10W40 didnt cure the problem, though...

[Al]

I can't imagine where 20W50 would be a good oil to run in an engine.  I'm surprised the 10W40 didnt cure the problem, though...

... probably also too thick when at normal operating temperature ?

[BSB67]

I can't imagine where 20W50 would be a good oil to run in an engine.  I'm surprised the 10W40 didnt cure the problem, though...

If the lifters are bleeding down, the heavier oil will help the lifter valveing and cup plunger from leaking as much oil.  It will also help restore some of the lost RPM with the fast rate cams.