[boss351]

Okay, my engine seems to make a knock type sound. It happens on start up, and keeps making the noise until I rev the engine once. Once I rev the engine it go's away at idle, but the noise is there upon acceleration. The car does not make the noise under around 1300 RPMS. I can have the car in third gear on the highway cruising at about 50 with the rpms around 1000 - 1500, and the noise is not there. As soon as I hit the gas and bring it past 1500, the noise starts. The guy at the body shop said it sounded like a cam/lifter problem. It makes a very loud tap or knock, and sometimes it seems to disapear with the longer i run the engine. Also, when I run it for a while, and go to stop at a light, the engine will drop to around 500 RPM's and sputter like it wants to die. I know it has fuel, because All I have to do is tap the gas and it revs. Could I have a bad cam and or lifters, causing the valves not to open and making the engine sputter? Also, it doesn't like to rev very high. I don't really have the money to re-build the whole engine, but I would like to fix what is wrong with it. Please tell me what you think.

 

[SacBill]

David: It probably wouldn't hurt to pull the cam out (along with the lifters) and at least see what's going on in there. Who knows, you may find the problem on the way to it! /forums/images/icons/smile.gif

All you'd have to pay for is some new gaskets and sealant and your time. Good luck and keep us posted!

BTW, the knock in mine appears to have come from a missing thrust washer! EEESHH!!! /forums/images/icons/tongue.gif

 

[motorhead]

If you take off the valve covers and start the engine you will know immediatly if it is a lifter and which one it is. A mechanics stethescope can also be used without removing the valve cover. Just listen to each valve cover when it is knocking. It should be pretty obvious if its a lifter under one of those covers clacking the rocker arm.

You can take off the fan belts and start the car to eliminate water pump, alternator, power steering.

Whenever an engine is feeling sick a compression test is a usefull test. Changing the oil and looking for metal is also a good test.

If its just a lazy lifter i wouldn't rebuild the engine.

 

[camachinist]

Run a cranking compression test... do it both cold and hot

Is valve lash/pre-load changing on one or more valves?

Does the sound appear to cycle at half crank speed?

How is the engine's performance at moderate and WOT?

Note any service or maintenance work which has been done recently...

Get back to us...

 

[Axnjxn]

When this happened to my brother's '67, it turned out that the cam had ground off a lobe. My guess, he forgot to put assembly lube on one of the lobes, but he swears he did.

In any case, he replaced the cam under warranty, and had it fixed in about 3 days.

 

[Woodchuck]

Don't forget to take a good hard look at the fuel pump.