Hi all, new to the forums and getting back into hotrodding. I have an 81 camaro 355 sbc with a 671 supercharger. I did not build this engine but bought it recently. It has started to make a knock/slapp sound. It will not do it while idling or in nuetral and revving the engine. It will only do it while accelerating while driving.

Some things that I will be trying or have been told to check. The engine runs about 180-190 but under the hood its about as hot as the sun. I know that blowers make lots of heat in its exhaust. I was told that pre-detonation would cause this or even the fuel pump. I know there is an exhaust leak from the rear passenger side header. I can see the blow back on the seal.

I had this problem with my 68 camaro years ago and I tightened the cylinder head springs as one worked itself loose. I havent checked this out yet.

I know that there are more serious things it could be but I want to get the easy checks out of the way before I go throwing money into an engine.

As far as the heat thing goes I bought header wrap and plan on wrapping the headers in the very near future. If you think it will help I can take a video and link it. Thanks in advance for any help.

 

Do you know what compression the motor is? Are you sure it can run on pump gas? You really want to be carful tighening the "cylinder head spring" Assuming you are talking your valve adjustment. There is a very good chance you do not have hydralic lifters in this car. Do you know how you adjust your boost?

Yes a video will help.

 

Thanks for the reply. The compression is 8.5:1 I do use a high octane gas with a booster additive for fuel. Ill get a video of it up tomorrow.

 

Ok Ive tried to take video but its not coming out well enough to hear the noise Im talking about. I did discover two really bad exhaust leaks. One on the right side aft end where the header hooks up and the really bad one is where the headers bolt on the pipe right underneath the passenger side car. Enough to where it will blow a pile of leaves away. So I guess I will get this fixed first. Ill still try to get some video up if I can figure out how to get video without all the background noise.

 

Ok removed the valve covers on the right side and this is what I found.


Upon closer inspection I found a grove worn in the stud girdle between the 2nd and 3rd bolt.


It looks like it making contact with the valve cover by the port. Thos two little pieces there stick up about a 1/4 inch.

Now what would suddenly cause that girdle to come into contact with the valve cover like that? I havent turned the car over to see if anything is flopping around yet, but everything is at least hand tight and cannot be moved. Any ideas and help is appreciated.

 

Could be it just barely cleared when the valve covers were first put on. Then the valve cover gasket compressed some, the cover bolts got retightened, which made the cover hit the girdle.
If all is tight with the valve train, just grind down those baffle mounting bosses inside the covers to clearance them.