TheSamba.com :: View topic - Intermittent exhaust smell with stale air heat. 36hp.

Sun Mar 21, 2010 11:52 am

I’m trying to figure out what could possibly cause an exhaust smell from the stale-air heat in my 60 sedan. It has a bone stock, rebuilt 36hp engine. All the tin is in place. All engine compartment seals are new. The j-tubes are in good condition, however, I did have to use those repair tubes from WW. The engine has NO oil leaks. (Yeah…I know! But it IS possible to have a no-leaker. You just have to be anal about it like me.)

The heat works very well. It will actually make the car too hot if I drive it with the heat wide open for very long.

When the car is idling, the air coming in is just fine. It just has that “hot engine” smell, which is fine (and I kinda like it).

It’s not bad enough to make driving with the heat on unbearable (smell wise), but I do not want ANY exhaust fumes coming in for obvious reasons.

What could be the possible culprit? Keep in mind that the exhaust smell only comes in right after I rev the engine, then it goes away as the engine idles down.

Sun Mar 21, 2010 12:21 pm

Didn't stale air cylnders come with copper sealing rings at the head end? Are those known to be in good condition?

Sun Mar 21, 2010 1:30 pm

KTPhil wrote: Didn't stale air cylnders come with copper sealing rings at the head end? Are those known to be in good condition?

Yes they did. When I assembled the engine I installed new ones.
I know that "new' doesn't necessarily mean good though.

If a copper sealing ring was bad wouldn't that cause an oil leak?

Sun Mar 21, 2010 2:40 pm

Last year I did a valve job on a 36hp for a temporary driver while I started working on a full rebuild of another motor. It had clean heads, new jtubes and new muffler. When I pulled it apart, I saw that over half of the exhaust connections had small leaks of one sort or another, carbon blow-by past the gaskets. With the rubuilt jtubes and aftermarket muffler, fittment standards are not exactly up to factory tolerances, and those connections are not all square with each other. You may not hear the leaks, but they might still be there.

On this motor I just finished building, it took me about five hours of test fitting, flattening flanges with a grinder, and minor tube bending to get all the connections as close as i could before bolting it all together.

Another thing I have seen is motors with excessive crankcase pressure push oil out through the crank pulley and the mist gets sucked up into the fan, blows on the heads.

Then there's always the possible leaking valve cover gasket onto the jtube.

Mon Mar 22, 2010 5:28 am

duginabug wrote: The j-tubes are in good condition, however, I did have to use those repair tubes from WW
Did you clamp these on or weld them? I like to weld them all the way around for a sure seal. Also how are the donuts at the muffler and tubes? Sometimes they like a little dab of silicone to help seal them tight.

Mon Mar 22, 2010 12:21 pm

duginabug wrote: KTPhil wrote: Didn't stale air cylnders come with copper sealing rings at the head end? Are those known to be in good condition?

Yes they did. When I assembled the engine I installed new ones.
I know that "new' doesn't necessarily mean good though.

If a copper sealing ring was bad wouldn't that cause an oil leak?

I thought the copper rings were specifically to provide a secondary seal against leaking exhaust gasses, not oil leaks.

More likely to be the leaky connections mentioned above, though.

Mon Mar 22, 2010 12:53 pm

KTPhil wrote:
I thought the copper rings were specifically to provide a secondary seal against leaking exhaust gasses, not oil leaks.

More likely to be the leaky connections mentioned above, though.

Yip.

Mon Mar 22, 2010 1:22 pm

Bart Dunn wrote: KTPhil wrote:
I thought the copper rings were specifically to provide a secondary seal against leaking exhaust gasses, not oil leaks.

More likely to be the leaky connections mentioned above, though.

Yip.

I did not know that!

Now that it has almost 300 miles on it I'm gonna pull the engine and check nuts and bolts. I'll pull the exhaust system and seal everything real good.

Thanks for all the input.

Mon Mar 22, 2010 2:41 pm

duginabug wrote: Bart Dunn wrote: KTPhil wrote:
I thought the copper rings were specifically to provide a secondary seal against leaking exhaust gasses, not oil leaks.

More likely to be the leaky connections mentioned above, though.

Yip.

I did not know that!

Now that it has almost 300 miles on it I'm gonna pull the engine and check nuts and bolts. I'll pull the exhaust system and seal everything real good.

Thanks for all the input.

If you pull the heads, have some new copper gaskets. They're "crush" gaskets and if you re-use them you won't get a good seal.

Mon Mar 22, 2010 5:10 pm

They do call it stale air for a reason. Check all the exhaust connections.

Sun Mar 28, 2010 11:00 am

60ragtop wrote: duginabug wrote: The j-tubes are in good condition, however, I did have to use those repair tubes from WW
Did you clamp these on or weld them? I like to weld them all the way around for a sure seal.

BINGO!

I pulled the engine and checked the j-tubes (I had them clamped) and they were both leaking. I didn't have a welder when I did the engine but now I do. I welded them up so this should no longer be an issue.

Thanks

Sun Mar 28, 2010 11:03 am

gt1953 wrote: They do call it stale air for a reason. Check all the exhaust connections.

Yes!...indeed you are correct. They do call it "stale air heat" for a reason.

And they DON'T call it "toxic air heat" for a reason. :wink: