Mysterious engine noise

A little history,

1969 Chevelle SS396
396 engine, hydraulic cam (not sure which cam), Crane roller rockers, 750 double pump Holley, M-20 trans.
I use this car as my daily driver, approximately 30 miles a day since last January. The engine has developed a strange noise that sounds like a loose lifter. It only happens between acceleration and deceleration. It’s during that period of time when there’s no load on the engine. It doesn’t seem to do it at idle or by revving the engine. I adjusted the valves (one full turn from zero lash) but the noise is still there.

Any ideas???????

Thanks,
Bubba


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ACES member #04788
Maryland Chevelle Club member #075
Maryland Automotive Modelers Association
Have you ever noticed that those instruments designed to detect intelligent life in the universe are all pointed AWAY from Earth???
http://www.chevelles.com/showroom/Bubbas396.jpg

Could be a small exhaust leak. An exhaust leak will often make the same ticking sound as a lifter.

What did you do to that chevelle now http://www.chevelles.com/forum/wink.gif
Btw did you ever get the new tires you were talking about.
Brandon

Hey Brandon,

I didn’t hurt the old Chevelle too bad. When you drive them everyday things tend to wear out a little I guess.

Yes I did get the tires just a few days after I saw you last. I bought four TA Radials, 245/60 14’s for $280.00 mounted and balanced. I put them on just before we went to Ocean City for the Rain Cruise.

Is the 72 in hibernation yet?

Bubba


------------------
ACES member #04788
Maryland Chevelle Club member #075
Maryland Automotive Modelers Association
Have you ever noticed that those instruments designed to detect intelligent life in the universe are all pointed AWAY from Earth???
http://www.chevelles.com/showroom/Bubbas396.jpg

Sounds like you need one of them listening probes, that might pick-up the tick while it's idling or the old standby, along screwdriver to pinpoint the tick. You could always take the hood off and strap the wife down have her listen why you cruise down the street accelerating and de-cellerating. It is "dear" season.
What about a blocked rod that's not getting oil thru it? Just throwing ideas out.

Andy

Well I did what you said Andy. I put a screwdriver on the tip of the rocker arm and then tried to listen. That wasn’t such a great idea. Now I have bruises all over the side of my head http://www.chevelles.com/forum/biggrin.gif

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ACES member #04788
Maryland Chevelle Club member #075
Maryland Automotive Modelers Association
Have you ever noticed that those instruments designed to detect intelligent life in the universe are all pointed AWAY from Earth???
http://www.chevelles.com/showroom/Bubbas396.jpg

I agree, could be an exhaust leak also- minor ones sound just like lifter noise.

Comment: 1 full turn after zero lash is a lot!! You're adding friction by doing so - I'd back it down to 1/4 turn personally.

I've made cheap stethescopes by hooking up vacuum tubing to a short piece of brake line, and a vacuum "T". They really work great for this kind of stuff.

I'm glad to see you put the right end to your ear http://www.chevelles.com/forum/smile.gif
Did you pick up any unusual noises in between the thumping?

How do you track down a small exhaust leak? Sure don't want to feel for it.

I’ll check for an exhaust leak and hope that is the problem.

Thanks for the info,
Bubba


------------------
ACES member #04788
Maryland Chevelle Club member #075
Maryland Automotive Modelers Association
Have you ever noticed that those instruments designed to detect intelligent life in the universe are all pointed AWAY from Earth???
http://www.chevelles.com/showroom/Bubbas396.jpg

Bubba,
I never really have the 72 in hibernation as long as the weather is decent and there is no salt on the roads I drive it year-round, and now that I got rid of those 2.73 gears I'm driving it alot more. http://www.chevelles.com/forum/biggrin.gif

And the 2.73's were replaced with ????

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ACES member #04788
Maryland Chevelle Club member #075
Maryland Automotive Modelers Association
Have you ever noticed that those instruments designed to detect intelligent life in the universe are all pointed AWAY from Earth???
http://www.chevelles.com/showroom/Bubbas396.jpg

I went with 3.42's I was considering the 3.73's but was told that it would make my highway rpm's a bit high, and I added an eaton posi. I also had the entire suspension rebuilt new springs, new shocks, new bushings and balljoints, every bushing front to rear top to bottom was replaced with the polygraphite bushings. I also got new wheels and tires I went with the weld draglites and bfg radial t/a's 215/70 front and 275/60 rear, it looks and drives like a different car. I'm still waiting for April to come.