Thread: Musty smelling exhaust

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This is a 427 ci small block. The exhaust smell is terrible. It smelled the same with my old 350 block. 3 different carburetors, new short block (Dart) used same heads (Trickflow) and intake (Edlebrock Air gap) and it smells the same.

Have had the car dyno'd and exhaust analyzed which came out right on at idle and high speed. The car idles perfect with no surging. It does not smell rich as in burning your eyes but smells musty and strong enough to take out a large area. I'm embarrassed to take it anywhere. I suspect something with the heads or intake. Any ideas?

56 Chevy Nomad
427 small block
Trickflow heads 62cc chambers (195 runners)
E. B. Air gap maniflold
KB pistons...forged, dished 10.2 - 1 compression.
Comp Thumper cam: @.050 .227 and 241 dur. @ 106 lob sep.
Holley 9380 (850 cfm) carb. prior carbs...650 and 750 cfm all 4150s. (all smelled)
MSD ignition. 34 deg. total, 12 deg initial timing.
With ported vacuum advance.

What kind of gas are you using? I know that may sound funny, but switch to a different brand and see if that helps. I know that here in Oregon when the State mandated 10% ethanol, my cars all started getting 10-15% worse gas mileage and I can not run Arco with their blend. My cars all seem to like Chevron, 76 or Shell.

You may also want to try a good dose of Techron.

Good Luck,
Glenn

could you have a dead critter in your exhaust ?

I'd bet it has something to do with the additives in the gasoline you're running in it. I've had my cars smell that way a few times over the years, even the newer daily drivers, and a change of brand cleared things up. In today's environment, with the normal cars having catalytics on them, fuels are blended differently to go along with the systems, and sometimes, burning certain ones in an un-catalyzed system may make funny stinks. That's the take on it from an old, opinionated "non-chemical/mechanical engineer".

.......maybe sumbudie' put blue cheese on the intake........

Once had a bad smell in the fan, rat crawled up there and died!

Well put a whole new short block (the 427) in with same heads, manifold, cam and complete new exhaust system. No change in odor.

I have Mobil and Chevron Credit cards so that is the only gas it has seen. I have a full tank now but I'll try a different brand next fill up. I'll let Ya all know and thanks for the tips.

Speaking of exhaust, I put on 40" Thrush glass packs and I love the deep "Old school" sound without it being too loud. It has a nice low rumble while cruising along instead of the hollow tinny sound typical of the now popular Flow Master or Turbo type.

OK, tried a tank of Shell and although not totally gone, it seemed to help quite a bit. It's not as strong.

Thanks for the tips guys.

I just put some Sea Foam in my daily driver to try to clean the injectors out a little, and the exhaust smell is not good either. I think the can said something about that.

Two thoughts come to mind with your problem. One is the gas you are running and the other is some condensation coming down the exhaust system. The other morning a car in front of me pulled away from the light and tons of water poured out of his exhaust pipes..........I mean a LOT of water. At the next light it did the same thing, and it wasn't some old clunker either. I've seen cars drip some moisture from the tailpipes, but never one that dumped as much as he did. Maybe your engine isn't coming up to temp or something and isn't getting complete combustion?

Don

I have been struggling with this same thing since the rebuild on my Buick 455. I've gone from the fuel tank through to the exhaust. Nothing I've done has changed it one bit.
Everything tests out perfectly, tried every trick. It seems to get better sometimes, then comes raging back.
Can the cam may be advanced too much? When does advancing it cause an overly rich condition?

I know the alcohol race cars have an additive that comes in many flavors, coconut, strawberry and febreeze,. Maybe you can get smell good for your gas.
I think it's the motor, I have a 307 2 barrel that I will swap you straight up that doesn't smell musty.
If I had a 427 small block I wouldnt' care how it smelled, I would know its BA, and cruise it as is. It smells musty because it's old, or maybe it's the mothballs used for octane boost causing the smell.

Well - here's the answer:
http://www.scooterwest.com/item_deta...vy-Grape/2456/

Fiberglass in the new mufflers? I used to have this complaint a lot when a customer would go get his glass packs put on and it took some time to get rid of the "musty" smell.
Just a thought.

Maybe not enough initial timing.?
I'm hoping that's my problem.
I've also noticed that every time I change carbs, so does the exhaust bouquet.