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Valve clatter?

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Morris

Morris

Yoda
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My car seems to have a little bit of "Valve Clatter" when I put a load on it at low RPM. Actually, I don't know that it is valve clatter but that is what it sounds like to me. My 95 F150 makes this same noise in this same situation. Anybody have an idea what might be making/causing the noise?
 
Could it be the Connecting Rods? You should get a two or three foot long steel rod and try to isolate the sound by holding the rod to your ear and "listening" for the sound at different locations on your motor. If it is down low on the block then it is most likely the Rods knocking.
 
Are you sure it isn't spark knock?
 
Timing?
 
[ QUOTE ]
Are you sure it isn't spark knock?

[/ QUOTE ]

This would be my guess as well. Valve clatter should be there all the time. Engine loading shouldn't affect it.

BTW, if you don't have some valve clatter, you probably have your valves set to tight. /ubbthreads/images/graemlins/wink.gif
 
I think I have solved this problem, and I thought I would post my solution on the outside chance that it might be helpful/interesting.

I too thought it was spark knock, John... except that when I had a more aggresive timing curve, the clatter was not there. (my car has programmable computer controlled ignition) The problem with the more aggressive curve was that it would give me REAL knock at certain points on the map. I am utterly terrified of spark knock, so I replaced the aggressive curve with a very conservative curve. But then I got clatter and poor performance and TERRIBLE mpg!

So I split the difference and had a great drive to work this morning! No clatter and lots of umph!

So, does anybody have an idea why overly retarded ignition would cause a clatter noise at low rpm, high load?
 
[ QUOTE ]
So, does anybody have an idea why overly retarded ignition would cause a clatter noise at low rpm, high load?

[/ QUOTE ]

Please keep in mind, I'm not an expert on engine timing, but from what I know, I'd suspect that if your timing was SEVERLY retarded, your engine may have actually been igniting the air/fuel mixture so late that the combustion gases were still burning as the exhaust valve began to open.

Retarding the timing definately effects MPG. The more retarded, the worse the MPG and loss of power as the combustion gases would be "chasing" the piston down the cylinder due to the late firing.

Also, overly retarded timing raises exhaust gas temps which would raise the thermal stresses on the pistons, plugs, valves, and exhaust system.

My best guess would be that you noticed this more at low RPMs and under load due to vacuum advance and the centrifical weights in the distributor not catching up fast enough to advance the timing. At higher RPMs, the dizzy would be at full advance and would somewhat limit the effects of overly retarded timing.
 
Morris,

When can we get more info on your megasquirt project? You may or may not know that I was the first to use a V1 megasquirt on a throttle body injected Porsche 911SC several years ago.

Can you send some pictures of your setup? I wonder if a pair of SU's could be modified to give a truely stock looking appearance but have FI hidden in there.

Ben
 
John, my timing was (as far as I can tell) pretty close to stock when it was making the "clatter" noise. Also, I just rode in a late model Nissan pick-up that made the same noise under the same conditions (low rev high load). Wierd, huh?

Ben, check this out: www.sidedrafttbi.com . This guy (name of Rick) helped me with my set up and he is great! If you contact him, please tell him I sent you. I know that he has created an injector adapter for the HS6, so it should not be difficult for him to create one for the HS2.

My car is a 1500, so it won't have much in common with the 1275 set-up, but let me know if I can do anything to help you out if you decide to squirt your car. It's great to meet another squirter on the forum!
 
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