Frank_Blotto

I put my rocker arms back on after changing the valve seals, and when I start it up, it's really loud. It sounds like someone running a lawn mower and a bandsaw at the same time. Really loud low end sound, and a softer higher pitched sounds. It's making it very difficult to hear the valve clatter. What could be causing this sound? Did I over-tighten one of the rocker arms? The smog compressor belt isn't attached, and the air hoses are removed on one side. It's running smoothly, but it's insanely loud, like I described before. I'm kinda at a loss, anyone have any input? Thanks.

AJ_92RS

Ding Ding Ding!!! We have a winner!!!

The exhaust is making noise coming out of those holes/pipes. Cap them off or crimp the lines shut.

Frank_Blotto

Ok, I by air hoses, I meant the AIR Injection piping, just to make sure we're talking about the same thing. So assuming we are I just need to plug up the four holes on the exhaust manifold? Then it will be quieter and I can set my valves down correctly? THanks for the speedy response.

AJ_92RS

Yup. That's what I meant to.

Frank_Blotto

Alright. Too bad it's too late to go anywhere that would have caps right now. I guess I'll finish that up tomorrow. Thanks for your advice !

Frank_Blotto

Well, I plugged up those AIR holes, but It's still making a loud noise, kinda of a fast thumping like I said before. It's also idling really high, like 2000+. I'm kind of at a loss. Maybe the rocker nuts are too tight?

AJ_92RS

It was probably both. Regardless, at least you got rid of one noise so you can hear the other.

And yes, valves hanging open (tightening them too much) will cause that also.

Perhaps you should have mentioned the 2,000 RPM idle earlier instead of this??

Frank_Blotto

Heh, I hadn't noticed it was idling so high earlier, as I had only run it for a minute or two, otherwise I'd have been more alarmed by that. I'm gonna back everything off and start over.

*EDIT* it was running smoothly, just really fast.

Frank_Blotto

So I got my valves set, everything is smooth, idling at 1200 or so according to the stock tach, but it's still making this weird noise. Kind of a low pitched, thump thump thump thump. It's not too loud, but it's there. I have no idea what's causing it. Everything else seems ok. I'm gonna play with the timing a little. Anyone have any ideas about the thumping sound?

RB83L69

Why? Do you just like creating extra work for yourself? Leave it alone unless you've already dinked with it.

This thumping; does it seem to be at crank speed, or cam speed, or not correlated to engine speed at all? Where is it coming from: intake, exhaust, top of motor, bottom, front, rear, etc.? Have you tried the heater hose in your ear trick to locate it?

Frank_Blotto

Ok, as per your advice, I won't play with the timing. The sound is definatley coming from the bottom end. I can't tell what speed the sound is at (crank, cam etc...) It's a pretty steady sound, maybe two thumps per second at 1200 RPM. I have not tried listening to the heater hose, what exactly is the trick you are refering to? Thanks for the help.

RB83L69

Take a piece of heater hose, and stick it in your ear. (I just love telling people to do that!!!) Then probe around with the other end of it and see if you can pinpoint the source.

So you've adjusted the valves; you know the rate at which a valve ticks when you back it off. That's cam speed.... one tick per cam revolution. Is this other sound occurring at that exact rate? Crank speed is exactly twice that rate (since the crank turns twice for every cam revolution). Is it at that rate? Or is it at neither rate? Faster, or slower? The same speed as something else that you can see (belt, pulley, accessory, etc.) is turning or moving at?

Frank_Blotto

Having listened to the engine further, and consulted a freind of mine, we determined that the sound is at the crankspeed, not the camspeed as I earlier thought. It's also definately coming from the bottom end. I'm going to aquire a compression tester and see what that says, as I haven't even run one on the car anyway. Anyone have any other ideas to help me out?