[justadriver]

Hey guys, I have a 68 chevelle with a 327, rebuilt about 2 years ago. Bored .040, L98 Heads, Hei Distributer(older one), Air gap intake, Comp Cam 1.5 rockers(Hyd not rollers). I just recently started to get the clacking sound. I adjusted the valves to no avail. I tried to troubleshoot and took each set of intake & exhaust rockers, rods, and lifters out individually. After each set, I restarted the car and it still clacks. It sounds like a normal valve clack...maybe a little lower in pitch, but it is loud enough to hear if I am outside the car. Any suggestions?
Thanks,
Daniel

 

[furball8994]

Headers? Check for an exhaust leak. They can sound just like a valve tap.

 

[justadriver]

aftermarket headers...pretty crappy ones, but I have not had trouble with them before. They were all pretty tight last week, but I will check them again.

 

[justadriver]

just, checked them again, and it still clacks away...thanks though! Any other suggestions? I was looking at other posts, and they mentioned the fuel pump. I have a holly, how would I go about checking it-and is this even a possibility of the noise?

 

[RAGTP66]

Possibly a lobe going flat on the cam. IF you try and powerbrake it will it start to back fire or pop through the carb?

 

[swcash]

Get yourself a stethascope. The kind that you can remove the end piece and have an open hose that you can use to trace the noise. This kind also works well for finding zero lash when adjusting the valves while the engine is running.
Squido

 

[GoatDr]

Check your flywheel bolts and make sure they are tight.

 

[hellcamino496]

i had a funny tapping sound on a freshly built 454 i had installed in my old 72. there were two noises.
1. my flywheel bolts were rubbing on clutch set up. fixed that
2. i had a bad valve guide on one cylander, did not fix that one. eventually sold car.

just 2 possible options.

 

[ray1970ss]

Crappy headers = noise. I have crappy headmans. They leak even if the bolts are tight. This is what I did to fix the leaks. FORGET regular exhaust gaskets you get at autozone. What you need is a sheet of industrial graphite gasket material. I don't know where you can get it, I just found some in my fathers garage one day. Anyways, I used the old header gaskets as a template and cut out a new set of gaskets from the graphite material. Im guessing it was 1/16" to 1/8" thick material. I havent had one exhaust leak since I did that over a year ago, and I checked the bolts once since then and they are nice and tight still.

 

[bone z]

sounds to me like the spring on fuel pump broke or poped off like someone else said get a 3/8 fuel line long enought to reach the fuel pump while its running you should be able to hear it