How long does a rebuilt flathead engine smoke out the tailpipe?

[MarcDeSoto]

I have heard from someone here that a new rebuilt flathead six can take up to two hours running time for the excessive smoke to cease coming out of the tailpipe.  Does that sound right?  My engine only has about 20 - 30 minutes of run time on it, but it's still smoking out the tailpipe.  I guess it takes time for the oil control rings to seat?  Just want to know how long your rebuilt flathead ran before the smoke stopped out of your tailpipe?  

 

 

[Plymouthy Adams]

with all the trouble you had starting this who knows how much oil and other items you introduced into the intake that found its way into the muffler and as you state yourself, are your rings fully seated....

[keithb7]

I never noticed any smoke at all right from initial start up after I rebuilt my engine.   At this point in the video link below I had less than 3 mins operating time on the new engine rebuild. What you see here is condensation from a cold exhaust system. It very quickly disappeared into the air.  Smoke lingers and has a blue hue. Are you seeing smoke or moisture? 

 

https://youtu.be/7y6MCwyD4aQ?t=988

 

My oil control rings seemed to need no break-in time. They appear to have scraped the cylinder walls clean right from the get-go.

Edited March 28, 2023 by keithb7

[joecoozie]

1 hour ago, MarcDeSoto said:

I have heard from someone here that a new rebuilt flathead six can take up to two hours running time for the excessive smoke to cease coming out of the tailpipe.  Does that sound right?  My engine only has about 20 - 30 minutes of run time on it, but it's still smoking out the tailpipe.  I guess it takes time for the oil control rings to seat?  Just want to know how long your rebuilt flathead ran before the smoke stopped out of your tailpipe?  

 

 

Wasn't this engine rebuilt many years ago and not run at that time but sat until now?

If so, then you may have some stuck oil rings that will need run-time to unstick.

Just guessing.

[MarcDeSoto]

Joe, I can tell you've been paying attention.  Yes this engine was rebuilt around 40 years ago!!!  Sometimes I worry that the rings might be rusty or rusted.  I was told way before I started my engine to make sure the engine has a lot of oil so the rings would be lubricated when I started the engine.  I put Marvel Mystery oil through the spark plug holes.  The smoke I see is not water, it's either oil or fuel and is blue black.  Well, I'll just keep running the engine and hope the smoking stops or gets much better.  The engine sure starts nicely now with no hard starting.  I think I timed the engine well and put in new points, condenser, rotor, spark plugs and wires.  I also checked the point gap in my distributor and found that it was about .030!  It's supposed to be about .020, so that's where I put it.  

[Eneto-55]

Marc,

I'll be watching to see how this develops for you, as I also rebuilt my engine a long time ago, and have never started it.  (Rebuilt in 1981.)  Some have told me that I need to tear it all back down and reassemble.  The "vote" is still out on that.  Not anxious to do that, but also don't want to mess it up, either.

[Sam Buchanan]

It may just need an "Italian Tuneup"........ 

[Los_Control]

Like PA stated .... hard to say what is in the muffler by this point.

Think I would be more concerned with what is coming out of the blow by tube.

[Young Ed]

58 minutes ago, Eneto-55 said:

Marc,

I'll be watching to see how this develops for you, as I also rebuilt my engine a long time ago, and have never started it.  (Rebuilt in 1981.)  Some have told me that I need to tear it all back down and reassemble.  The "vote" is still out on that.  Not anxious to do that, but also don't want to mess it up, either.

Do you know what type of assembly lube was used? The engine in my 46 truck was in my Dad's 51 convert before and was removed at 172 miles because it wiped the bearings. At the time they said it was gunk in the galley that didn't get cleaned but part of me wonders how much of it was sitting for so many years while the rest of the car was rebuilt. For the cost of a few gaskets you could have piece of mind. Another option pressurize the oil system before trying to start.

 

[Eneto-55]

3 hours ago, Young Ed said:

Do you know what type of assembly lube was used? The engine in my 46 truck was in my Dad's 51 convert before and was removed at 172 miles because it wiped the bearings. At the time they said it was gunk in the galley that didn't get cleaned but part of me wonders how much of it was sitting for so many years while the rest of the car was rebuilt. For the cost of a few gaskets you could have piece of mind. Another option pressurize the oil system before trying to start.

 

I don't remember what we used during assembly, and my Dad is gone now.  But I would definitely run the oil pressure up.  (I used to crawl under it and turn it over a couple times every time we were back there - at my folks - visiting.  But after reading comments here about getting the oil circulating before running it, I stopped doing that, at least 5 years ago.)  My Dad helped me, and he had overhauled a number of flat-heads before that, but I just don't remember what we used.

[MarcDeSoto]

I still have smoke coming out of the joint between the ex. manifold and the exhaust pipe.  The engine today has become hard starting again, maybe because of oil getting on the spark plugs.  I'm also trying to align the shift linkage.  When I put it in gear either low range or high range, the prop shaft turns a few turns and then stops.  Also the prop shaft seems to have a bit of lop sided wobble to it.  I might have to experiment with putting the shaft on different studs so it's balanced.  

[Bryan G]

Was anything like Marvels Mystery Oil poured in the top end? That stuff really lingers in the system. After a MMO treatment, mine didn't clear up until I drove it.

 

I had a 283 rebuilt in an old Chevy. When it still smoked I was told it was just burning all the oil out of the exhaust from years of pumping oil. That one did clear up.

[Dodgeb4ya]

There shouldn't be any smoke coming out of the manifold to header pipe gasket joint.

End of the tail pipe yes..........

Hopefully it will quit smoking after a 100 miles of drive it like you stole it to break the rings ....just don't miss a shift with that Tip-Toe transmission.

[MarcDeSoto]

1 hour ago, Bryan G said:

Was anything like Marvels Mystery Oil poured in the top end? That stuff really lingers in the system. After a MMO treatment, mine didn't clear up until I drove it.

 

I had a 283 rebuilt in an old Chevy. When it still smoked I was told it was just burning all the oil out of the exhaust from years of pumping oil. That one did clear up.

Yes, a German car auto mechanic told me to put MMO in the spark plug holes to make sure the pistons and rings had lubrication for initial start up.  I checked my spark plugs since the engine had become hard starting again and they were black with burnt oil on them.  I still don't know why smoke is coming out of the ex. manifold to header.  I tightened it as hard as I could.  

[Dodgeb4ya]

Your header pipe probably does not extend up through the header flange at least a 1/2" like the original factory header pipe.The extension of the pipe goes up into the exhaust manifold to help prevent gasket blow out and exhaust leakage.

Also possibly the header flange is not flat and  bent up at each flange bolt.

[rallyace]

When I rebuilt my 218 CI engine a couple of years ago it smoked a bit for the first 300 or so miles. It now has about 5,000 miles on it with no issues.

[greg g]

Black smoke and black plugs indicate an over rich fuel to air ratio. White smoke is coolant or oil.  How thick is this smoke coming out the tail pipe?

Edited March 29, 2023 by greg g

[MarcDeSoto]

15 hours ago, Dodgeb4ya said:

Your header pipe probably does not extend up through the header flange at least a 1/2" like the original factory header pipe.The extension of the pipe goes up into the exhaust manifold to help prevent gasket blow out and exhaust leakage.

Also possibly the header flange is not flat and  bent up at each flange bolt.

Today, I removed the exhaust pipe to examine it.  It does have a 1/2" flange, but I do have a "new" exhaust pipe from Bernbaum's that I purchasesd around 1991.  I put the Bernbaum muffler and tailpipe on the DeSoto already.  My helper said he was having some trouble fitting the new exhaust pipe, so I gave him the old pipe which seemed like it was in good condition.  If you look at the photos, you will see that the Bernbaum pipe as a circlular metal "washer" on the pipe that goes on the exhaust manifold.  The old pipe doesn't have that metal circular washer.  Maybe that washer is important?  I tried fitting the Bernbaum ex. pipe on, and it seems to fit fine, so I'm going to install it and see if it makes a difference.  

[vintage6t]

50 minutes ago, MarcDeSoto said:

Today, I removed the exhaust pipe to examine it.  It does have a 1/2" flange, but I do have a "new" exhaust pipe from Bernbaum's that I purchasesd around 1991.  I put the Bernbaum muffler and tailpipe on the DeSoto already.  My helper said he was having some trouble fitting the new exhaust pipe, so I gave him the old pipe which seemed like it was in good condition.  If you look at the photos, you will see that the Bernbaum pipe as a circlular metal "washer" on the pipe that goes on the exhaust manifold.  The old pipe doesn't have that metal circular washer.  Maybe that washer is important?  I tried fitting the Bernbaum ex. pipe on, and it seems to fit fine, so I'm going to install it and see if it makes a difference.  

 

I think either pipe requires an exhaust gasket to seal the joint

[keithb7]

Rock Auto. Your local parts store will have these. Just give him the Fel-Pro number. Don't tell him year/make/model. You gotta have the

gasket in there. A little exhaust dope on both sides helps too.

 

 

Edited March 30, 2023 by keithb7

[Dodgeb4ya]

I'd use the old factory type one.

Yes a proper sized head pipe gasket must be used. I always use a semi  course file to be absolutely sure there is no heavy rust or gasket material on both the manifold flange and the header pipe flange.

The header pipe flanges cannot be warped at all and must bt up evey tight to the manifold fully.

It will not leak.

The Burnbaum pipe....naw...

A lower quality exhaust header pipe.

That ring is used to crush the header gasket. Narrow enough to possibly sit the gasket...have seen that on other pipes mike that on a Ford!?

[MarcDeSoto]

Of course I do know about the exhaust gasket.  You probably can't see it.  It's stuck on the ex. manifold.  So you think I shouldn't use the Bernbaum pipe?  I installed it today and cranked down so hard on the bolts that I squeezed a washer in half.  And I think I bought the bolts at Home Depot, so I don't think they are automotive quality.  Something happened when I cranked down.  Instead of getting tighter and tighter, the bolts got looser and looser as I cranked down!  So I'm going to go to Hank's tomorrow to get some grade 8 or higher nuts and bolts.  The Parts List doesn't show any washers, so I won't get any.  Just two 7/16-20 X 2" bolts and two nuts.  Is is OK to put two gaskets on this?

 

Edited March 30, 2023 by MarcDeSoto

[Sam Buchanan]

If the flanges are very straight and one new gasket is used the bolts don't have to be that tight....grade 5 should be fine. Sometimes stainless hardware is used to prevent corrosion and stainless is softer than carbon steel.

[Dodgeb4ya]

I saw the gasket hanging there. You shouldn't have to go crazy tight if all the parts are clean/aligned and right.

[joecoozie]

I was thinking about suggesting using 2 gaskets. It could be a possibility.

Also, be wary of tightening the bolts too much (or too tightly) because you can snap off the exhaust manifold ears on the manifold flange and then you have another issue to deal with.

Just asking.....

When you are attaching the pipe to the manifold is the pipe already connected to the muffler?

I would suggest that you, first, connect the pipe to the manifold without it being connected to the muffler. That way you can get the pipe onto the manifold nice and straight and you will have "play" to move the pipe around to get it to sit correctly (straight) before bolting it on.

Also, clean up the original pipe flange with a wire brush to get a nice flush fit