[grparen]

I just developed an intermittent metal rattling or knock that seems to be coming from the top of my engine. It is not consistent but gets louder when I accelerate. I sometimes hear it at idle. The engine is recently rebuilt and has an aggressive hydraulic cam. I pulled the valve covers and checked the rocker arms and all are secure. I did not pull any push rods but all seems to be as it should. The oil is clean on the dipstick with no signs of metal sparkles. Oil pressure is between 50-60. I checked the timing and the marker shows it set at 6 BTDC. Any ideas what may be going on or next steps?

[66bonne]

Need a little more info: Is cam a flat tappet or roller ? Do you have an adjustable valve train ? Stock style rocker arms or roller rockers ?

Depending on your valve train make-up you could have a rocker arm hitting the valve cover. This can happen with roller rockers. Look for marks inside the valve cover and on the rocker arms.

Even tho' the rocker arms are secure, I would re-lash the valve train.

Let us know what kind of valve train make-up you have.

Jim

[Stuart]

Make sure it isn't something as simple as an exhaust manifold gasket leak. That can make a knocking sound.

[grparen]

Flat tappet hydraulic cam with roller tip rockers, hydraulic lifters.

[grparen]

If I find a rocker arm is hitting the valve cover, can this be solved with thicker gaskets or do I need taller valve covers?

[66bonne]

If it is a rocker arm a thicker gasket may do it. Or you can shave/sand a bit off the offending rocker.

Jim
PS: Take Stuart's suggestion and look for a possible leak.

[66bonne]

I still think it would be a good idea to re-lash the valves. This is something that should be done on any newly rebuilt motor after it has gone thru a few heat cycles. Just because the rockers seemed secure doesn't mean that the lash is correct. Improper valve lash can make a knock sound with the push rod.
Good luck and keep us posted.


Jim

[Engine-Ear]

I didn't catch whether you mentioned it: Is your valve train pushrod-oiled or rocker stud oiled?

[grparen]

I'm no expert here. There are no oil holes in the push rods so would assume rocker stud oiled. That make sense?

[Stuart]

Originally Posted by grparen

I'm no expert here. There are no oil holes in the push rods so would assume rocker stud oiled. That make sense?

What make/model/year car is it, and what engine?

[grparen]

1963 Tempest with 1965 Gran Prix 421 engine

[ho421]

If your roller rockers are making contact with the stock valve covers, Butler sells a very nice 5/16" blended cork gasket set for around 16.00. You will have to go to a 3/4" long hex style bolt to get enough threading into the heads. Available at ur farm n home store.

[LASJayhawk]

65 oils through the pushrods...

[61-63]

What heads Gary, and what compression ratio did the engine builder say you would have?

[tom s]

Just check if there is oil in the top of the rockers,cant believe the pushrods have no holes.Tom

[grparen]

#62 heads and compression about 10.1 to 1.

[61-63]

#62 heads have no provision for stud oiling and as someone mentioned above neither does the block, so the pushrods have to have holes in them or you aren't getting lubrication to the upper valve train.

Look at your plugs. Are they white? About 10.1 is right on the edge for iron heads. Are you running premium unleaded?

I bet you are hearing detonation. Back your timing off a couple of degrees and see if you still get the rattle.

[grparen]

I took a 40 mile drive in the car previous to getting the knock and had no issues with detonation. It was my longest drive since the engine rebuild about 1 month ago. Wouldn't detonation have shown up then? I run 93 octane. Also, if the rockers were hitting the valve covers, wouldn't it have shown up then? Or could there have been some heat expansion over that 1 month period?

[Deadhead]

Would check to see if correct pushrods were used then… Floor it when you are out. If you hear the noise, progressively back off the timing and repeat to see if any difference. Detonation can show up randomly with varying conditions & fill-ups. You are now in a period when the gas formulation has changed, so it could be from that.

[61-63]

Yes you would think both detonation and a rocker hitting the valve cover would have shown up from the start. Also a too lean calibration on the carbs would have shown up from the start.

Take a 3' piece of hoe handle or wooden stick and grab it on one end with your thumb over the end. Then with the engine idling place the other end on one runner after the other and along the length of the valve covers, and other locations on the engine, with your ear against your thumb. You will really be able to hear what is going on inside the engine that way. This may allow you to isolate where the rattle is coming from.

I don't know what to tell you other than the above, and taking the valve covers off and look for tiny worn spots on stuff where it may be in contact with other things. Check lash again as someone said.