Resleeving a Marvel carb

[drovak]

The Marvel heat exchanger has pinole leaks in the sleeves for both barrels on my 1931 8-86. Hard to photograph, but I was able to poke a dental pick into the pinholes. I suspect this is why my carburetor has been running lean, though perhaps I still have yet another culprit. Someone in the past did seal shut the exhaust side, but not the carburetor side.

 

Is the proper fix to resleeve the heat exchanger? Any thoughts would be appreciated. 

[Dave39MD]

Yes, that is the fix. I found tubing at McMaster Carr that was very close and had a machine shop remove and replace. I did not trust my skills to do it myself but you may be able.

 

Dave

[Hubert_25-25]

Great photos.  I don't know if I had any leaks in my tube on my 1925, but I blocked off both sides of the updraft casting, and I blocked the exhaust side.  On the exhaust, I left the shaft in, but I removed the exhaust butterfly plate so it was never closed by mistake.  Discussing only to the design of the up draft casting.  If you block both ends of the casting at the gaskets, I see no reason to replace the tube.   The path for the engine vacuum to leak into the exhaust or the atmosphere is eliminated.   Attached are photos of the blanking plates.  Made from soft metal so that they seat in like the gasket.      Hugh

 

Edited November 25, 2020 by Hubert_25-25 (see edit history)

[edinmass]

I agree 100 percent with the above post, the only difference is I would use stainless instead of copper, as I have had copper block off plates fail over the long term. Hugh......best post helping someone I have ever seen.......👍👍👍

[Steves Buick]

They come out pretty easily, once you chissle a grove being careful to not damage the heat riser casting. I pressed some new tubing that I sourced from a muffler shop. Works great.

[Robert Engle]

Just a comment on not resleeving and just sealing off the exhaust.  With the exhaust sealed and pin holes in the tubes, the exhaust chamber will become a vacuum tank.  Carburetors work best when they are very responsive to vacuum changes from open throttle to closed throttle.  the pin holes will affect the time for vacuum changes and reduce the carb performance.  Replacing the tubes ensures that there is no problem.

 

There have been a number of prewar members that have had to deal with this problem.

 

Bob Engle

 

 

[drovak]

Thanks, guys. I'll look at removing the sleeves and finding some suitable sleeves from McMaster-Carr or a muffler shop. Stainless sounds good, if I can find the right diameter.

 

Is pressing in place sufficient, or should there be any sort of sealant applied? I was thinking about a light epoxy bead applied to the ends of the sleeves to ensure a good seal. Thoughts?

[Mark Shaw]

1 hour ago, Hubert_25-25 said:

If you block both ends of the casting at the gaskets, I see no reason to replace the tube.

Sorry Hugh, but a smooth tube will work better aerodynamically than one with holes.  The heat riser is where the air/fuel mixes and needs to maintain velocity for mixing.  

 

Drovac,  I used a stainless tube for one of my Buicks.  I lubricated it with grease and used a press to install it.  However, it broke one of the internal shoulders at the bottom of the casting.  Be sure to measure both ends of the internal casting to get exactly the right sized tube.  My 1924 Buick Master tube was replaced with aluminized exhaust tubing from a local muffler shop's scrap bin.  It worked perfectly.

Good luck...

[drovak]

11 minutes ago, Mark Shaw said:

I used a stainless tube for one of my Buicks.  I lubricated it with grease and used a press to install it.  However, it broke one of the internal shoulders at the bottom of the casting.  Be sure to measure both ends of the internal casting to get exactly the right sized tube.  My 1924 Buick Master tube was replaced with aluminized exhaust tubing from a local muffler shop's scrap bin.  It worked perfectly.

Good luck...

I'll give the aluminized exhaust tubing a try, if I can find the right diameter. Seems like that will conform better than stainless. But whatever I use, I'll be sure the measure thrice! 

[drovak]

Got the sleeves out. One was much tougher to get out than the other, or perhaps I just improved my technique from the first to the second. 

 

 

Glad I got them out, though. The holes were definitely larger than I first thought. 

 

[Mark Shaw]

Good job!  That's what almost all the original tubes look like.  Your local muffler shop should be able to expand smaller tubing to fit.

Good luck,

[jps]

A few years ago I cut out the old sleeve out from my 1929 heat riser and my friend machined a new one for me down from a thick-wall oversized-OD pipe because the original pipe OD is of a non-standard size.  He sized the sleeve OD so that it would form a thermal fit with the heat riser body.  To install it, we put the new sleeve in the freezer to shrink its OD slightly, and the body in hot water to expand its ID slightly, allowing the two pieces to have just enough clearance to slide together.   After about a half our, we took the pieces out of their thermal baths and quickly took them to his hydraulic press and pressed the sleeve in.  Once the two pieces came to thermal equilibrium the sleeve was in permanently.  Worked very well.