Chattering noise from head after a track day

[JGood]

Yeah, I'm going to just skip the whole rebuild idea then, I am not looking to spend north of $1k to put an m20 together. I've found a few m20's with ~100k miles for about $300, so I'll just go that route. I'll be sure to put a baffle or crank scraper in though. I'll need to do some research as I never really paid much attention to those discussions.

[Dave]

rod end will be moving back and forth on the crank. The bearing material is worn away/gone and so there is now a gap between the rod and the crank.

I suppose you might get lucky and just put new bearings in, but I'd get the rod and crank checked out first.

[JGood]

Damn it. My spare is the original motor, which has 270k miles. I swapped this 140k mile engine in last year as "preventive maintenance".

Guess I'll put that motor in and either do the bearings/rings/gaskets in this motor, or just get another used m20.

Questions: If it is a rod bearing, what exactly is making the noise? Did the bearing wear to the point where the rod is actually moving around inside of it? Will the rod likely be bad as well then?

[Dave]

My rod bearing that spun started with a noise at a certain rpm and then got worse.

Good thing you have a spare. Put a crank scraper on it and overfill the oil a bit.

[jlevie]

The piece of shit HF tester uses proprietary gauge threads or something. So no go there.

But I zip tied the throttle open above 2k and went underneath with the stethoscope. Bingo. The noise is coming from the bottom end. Mainly the lower block and oil pan area. I might even venture to say it's specifically coming from the sump area. Ideas? Remember, it starts instantly at exactly 2k, not gradually.

That is what I suspected. That noise is almost certainly rod bearings. There's a slim chance that it could be the oil pump, but the odds are against that. If it is the pump the noise should be loudest where the blank off for a distributor would be.

[Jean]

Can't really add much to this thread, but good read.

[JGood]

The piece of shit HF tester uses proprietary gauge threads or something. So no go there.

But I zip tied the throttle open above 2k and went underneath with the stethoscope. Bingo. The noise is coming from the bottom end. Mainly the lower block and oil pan area. I might even venture to say it's specifically coming from the sump area. Ideas? Remember, it starts instantly at exactly 2k, not gradually.

[JGood]

I think I'm going to run to the hardware store and get two 100psi gauges and put them on the HF leakdown tester, and re-test the engine. I will also pick up an oil pressure test kit.

What size is the m20's sender, and what is the pressure supposed to be? Does it change based on RPM/load?

[JGood]

stupid question, but how's oil pressure?

Hmmm... didn't check it.

[Jaxx_]

stupid question, but how's oil pressure?

[JGood]

What a piece of shit. The harbor freight leak down tester is a dual gauge setup. The second gauge is not identical to the 1st gauge. The 1st gauge reads 0-100 PSI. The second gauge reads 100-0% (for % leakdown). The process is to hook up the air supply, use the built in regulator to zero the second gauge, connect the cylinder hose, and wherever the needle on the second gauge goes, is your percent leakdown. The interesting thing is, the first gauge serves no purpose other then to tell you what the inlet pressure to the second gauge is. And that's a whopping 15psi. Which is not enough to accurately test an m20 IMO. I did some research, this is a known issue with these HF units, and it has been verified by HF tech support that it's a 15psi tester.

I did run it on all 6 cylinders and got about 15%.

I also used my stethoscope to try to track down the noise. I can't hear it through the head, block, valve cover, timing cover, injectors, anything. It happens at exactly 2k RPM's now, it's exact every time, and starts and stops instantly, not a gradual onset.

I'm out of ideas. I'm pulling the motor and putting in my spare m20.

[JGood]

Will do. I actually just bought one from Harbor Freight yesterday, when I got the leak down tester. Whether it's from the head or block though, it will still need torn down, which I won't do.

[jlevie]

Use a stethoscope to find out if the noise is from the head, or the block. The noise you've just described could be from a rod.

[JGood]

Pulled all the belts off and started the car - still tapping at 2k RPM's. It's like an on/off switch for the tapping, as I rev it up it starts, and as I rev it down it stops at the same RPM. It doesn't gradually start... it goes from not tapping, to tapping, at the same exact RPM. It also only does it when warmed up.

I pulled the timing covers off, and checked for tension on the belt and to make sure nothing looked unusual. The cam sprocket nut is tight, the belt is rubbing anywhere, nothing unusual at all. The water pump was smooth and didn't make any noise when I spun it.

I pulled the valve cover, again. All rockers were fine, no loose eccentric nuts, the spring clips were all in good shape, valve adjustments were perfect.

Finally got a leak down tester at Harbor Freight (for $30!) after coming up with nothing at Autozone, Pep Boys, Advance Auto, CarQuest, etc. So, I'll do that test this week. If it tests OK, I'm just going to ignore the noise. There's no point in tearing down an m20 to rebuild it, it would be much cheaper to just get another used m20. And I'll need to do that anyway if anything happens to this engine.

[JGood]

try taking the belt of the waterpump, start the car and see if it goes away. Another guy just had a 2500 mile Graf water pump fail on him, made some awful noises. Just because it's new doesn't mean it's good!

Never thought of that. Will do that before I fork over the cash for the leakdown tester and/or a new water pump. Thanks!