hey! the valves on my 360 just started rattling real bad under hard acceleration. it has the stock c8 heads on it now, with 72000 original miles. i'm aware they were made for leaded gas and i usually use lead substitute, but not the past few tanks. anyway i don't know if thats why they are rattling or not. i have a set of d2 heads and plan a top end rebuild but cant do that just yet. what might be causing this, and whats my options?

 

Are you sure its the valves, could it be pinging?

 

Pop the valve covers and take a look at the rocker arm shaft. I know that these will break over time on some FE's (mine did). If they break it will clatter and rattle real bad, but still start and run okay. Take them off and examine them closley, then starting from the rear of the motor, tq each bolt 1 turn at a time until they are seated, then tq to 45ftlbs. I find that a lot of the time valvetrain noise is worn/broken rocker arm shafts.

 

I'm pretty sure you answered your own question

 

thanks for the help, i was gone a few days before i could read. i seem to have them quieted down some by putting in the bottled lead again, which people always try and tell me is un-necessary. but i set my timing by ear, and have a hard time telling if its pinging or not. i get it to run smooth as i can, but don't know if i have a good ear for it, whats a good way to tell?

 

Sorry Justdan, but that ain't the valves rattling. I'll bet my reputation as a supermodel that it's pinging (detonation). The "rattling" sound you hear is uncontrolled combustion beating the tops of your pistons just like a hammer. The lead additive, if I remember right, reduces the tendency for it. Detonation will destroy your engine very quickly if you don't keep it under control. Reducing the timing, or going with the next octane level of gas will also help.

-Scouder

 

presheyate the answer i beleive your rite. i backed up the timing some, and it seemed fine then rattled bad again later. i hope something isn't coming out of adjustment on its own, awhile back it seemed i had to advance it to run good. i changed and set the points and set the carb, and backed it up a little again. hopefully it runs good until i get a chance to take the engine apart

 

Not meaning to pirate this thread, but, I'm having a similar "valve noise" problem with my 390.
I just recently got the thing running after sitting for about a year.
I installed a new EDL-1411 carb and an EDL-2105 intake manifold. The rest is stock.
During the install, I removed and cleaned each lifter. I also rolled each push rod on a glass surface.
Once bolted back together, under a little throttle it started clacking.
So, using a piece of PVC pipe, I pressed it against each rocker until I tracked the noise down to the #5 cyl. I don't recall if it's the intake or the exhaust, but, it's the second rocker (from the front) that's making the noise.
I couldn't seem to pull the lifter out from between the intake and the head, so, I had to remove the intake again and replace that lifter with a new one.
The clatter remains....(?)
In addition to the clatter, if I punch the throttle, it will back-fire, as if it's back-firing into the intake.
I can't figure if it's: 1) the cheap 87 octane I'm using,... 2) a valve problem (burnt or chipped)... or 3) something else.
I could see nothing wrong with the rocker-arm shaft...
The new carb/intake seems to be working fine and I replaced the vacuum advance, as it *was* defective.
Any ideas...?
Thanks, steve

 

A vacuum leak could cause the popping through the intake. If you replaced a manifold and carb that would be a good place to check first. Spray some carb cleaner around all the mating surfaces with the engine running and see if the engine speed picks up somewhere. If it does there's your leak. A timing chain however could caus both the problems your describing if it's stretched.

 

Thanks, tastyklair.
I've switched to 91 octane and that seemed to help with the clattering. But, not the popping. I'll try your suggestion.
steve

 

Are you running a Holley carb? could be that your power valve is shot.... maybe time for a good rebuild?

 

Have you checked your plugwire routing? If it's just the #5 it could be the plug wire is a little to close to the #8? It sounds like theres a chance its crossfiring.

 

When I used the lead substitute with every tank, I noticed that it coated the plugs as effectively as it coated the valves.

72,000 original miles? I have to wonder if you have deposits building up, also an ally to pre-ignition.

Mike