This may have been asked before, but I'm curious and have an example to go by.

My 64 EC has a ZZ3 with Hooker Super Comp headers, Torque Tech 2.5" pipes going through Super Dynomax "hemi" mufflers and exit about 10" short of the rear bumper. It sounds great. Nice and has a low rumble at cruise and loud enough at full acceleration, but never "slappy".

On the otherhand,
my 79 Blazer w/350, stock manifolds, Hooker mandrel bent 2.25" pipes going through the same style "Hemi" Super Dynomax mufflers and tailpipes. But it had a "slappy" sound without catalytic converters installed and much better but still kind of "slappy" after I installed free flowing Cats.

Why is one slappy and the other real smooth?

My guess is the headers 1st and maybe the cam profile 2nd. The Blazer camshaft is stock.

Any ideas?

PS, for you younger guys or folks that refer to it in different terms.
Slappy=the sound you get slapping two wooden planks together real fast, or the sound a 65 289 Mustang makes with Glass-paks. http://www.chevelles.com/forum/wink.gif http://www.chevelles.com/forum/wink.gif

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Long time Chevelle fan and an owner since 1973 :)

I never heard of the term slappy, but timing can make the exhaust sound a little different. (probably a hundred other things as well)

Just a thought.

Bob

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Bob

Bob's 409 Chevy Page

http://silverstone.fortunecity.com/tvr/246/bob_s_409_chevy_page_index.html

Great website Bob.

I don't know any other way to describe slappy exhaust but you'd know it if you heard it. Some folks call it "Ratty" too.
Bill

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Long time Chevelle fan and an owner since 1973 :)

I think I know what your taking about. My car sounds "slappy" too (68 396). I am going to try to get rid of it by switching to larger tailpipes, as mine are stock, although I have Dynomax headers with 2 1/2" exhaust pipes going to Terminator mufflers in the stock locations. I also need to get an equalizer pipe put in, which I have been told may help. I think my stock tail pipes are 2", which is what I hope is causing my problem.

I think its becuase of a sloppy piston to bore clearence, therefor the piston sorta slaps the wall. ALOT of F*rds sounds like this tongue.gif

Nah this was exhaust sound. smile.gif

could emmisions equipment be a cause for this sound. just an idea