any guess what this sound is? The video is dark (taken at night) but the sound it what is important. According to the gauge I have good oil pressure and there is enough oil. I plan to do a compression check on the cylinders. oil change didn't reveal any metal in the oil, I plan to open the oil filter and check. Back ground: - basic stock rebuild 331 hemi - aluminum adapter so I could mount a 700R4 to it - usual break in with no issues - did have bad back fire through the carb around the 1500 rpm mark under load (lean issue fixed) but it did back fire bad enough once that it stalled the engine.
Sounds like heavy valve clatter to me. Take a long screwdriver and hold it to cover your ear, and go down both sides of engine, at valve covers, and also head or intake castings. .
It sounds like it is in time with the cam / valves i would pull the valve covers and have a look see.
Tell us about the rebuild. What cam-lifter-rocker parts? How long (miles/hours) has the 'noise' been apparent? .
I'll check the paperwork from the rebuild tonight when I get home from work. I think I have a mechanics stethoscope to take a listen, I'll do that tonight as well. As for how long the noise has been there, it's been progressively worse, before(few weeks ago) it would be on start up and go away. I'm trying to remember if the noise has started after the back fire incident (about four months ago), which my gut say it has. Also the engine, not counting break in, has about 10 miles on it.
Another friend mentioned I showed the video to mention exhaust leak or something up with the flex plate. I'm going to inspect the flex plate tonight as well. Keep the ideas coming. This is why this site is my goto for help, this level of knowledge and experience is hard to find.
My 331 also has a little valve clatter. Sounds similar but not near as prominent. I just ***umed early hemis had alot of valve train noise. Mine has less than 3k miles.
My 331 has hydraulic lifters and rattles bit when first started 'til the lifters pump up. Only lasts a few seconds. yours sure sounds like an exhaust leak especially at the very end of the clip where you appear to drag the camera lower on the block and the noise gets louder.
Check valve adjustment and look for an exhaust leak. If you put a quiet muffler on it, it will help in your diagnosis.
Solid or hydraulic lifters? Sounds like valve noise but an exhaust leak can easily mimic valve noise. Stock valve train in good condition should be silent. Even with normal wear you should not hear anything with the hood closed.
Instructed to preoil from from the distributor and then run at 2000 rpm for 20 mins. the problem at the time is over heating so had to stop cool it down and run again. Finally removed the thermostat all together which took care of the over heating.
trying to find the paperwork on the rebuild but should be hydraulic lifters, I have to check on whether adjustable.
Going to check exhaust as well today when I get home from work. Along with listening more closely, compression check and checking flex plate. more to come later today.
Your Hemi was like my early Olds with mild Hyd cam. Mine boiled during break in also, So I bumped the timing higher which made it cool and then did the break in. another similarity is that mine also developed the same noises that this "audio" sounds like. (I get the fact that it may sound way different in person). My noises were definitely valves clattering. Mine are adjustable, so when I found just two loose ones, I adjusted those and it's ok now. Today, if you narrow it down to valves or noise under the valve covers; take them off, pull the coil wire out, then keep bumping the motor over while feeling for freeplay (rocker) lash on each valve that is up, while it's other valve is down. I found my two loose ones very quickly, doing that with a remote starter ****on. your noise does not sound like flex plate to me. Those can be a sharper rap, and not really in time with the rpm. If it were exhaust, it should bark more as soon as you hit the gas in the video, and it seemed like it did not?
If your cam and rockers are stock configuration, there will be no adjustment. Adjutable pushrods would have to be used for that. If it's a reground cam with a reduced base circle, you would need longer pushrods to tack up the lash. Only the engines that came from the factory with solids have adjustable rocker arms. Such as 392's in 300 letter cars.
Ok so it appears to be an exhaust leak issue, a few (about 5) of the exhaust nuts were loose (about 6 quarter turns) I started it up and is much better no noise detected when listening. I did take the stethoscope to the engine and the noise can be heard when listening to the valley tray. This is a huge relief. And again this community helped me tackle this and think of a problem from different perspectives. I was going down the worst case road. I still have to go through the rebuild paperwork to see what was done to the engine, it's been two years since that happened. Now back to my older thread about fixing the brake issue.
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