midman

Buick Heat Riser Repair

Recommended Posts

After exhausting every other possible issue for my rough running Buick I started going through everything again, one by one and doing much closer inspections.

I had visually inspected the heat riser for holes in the tubes and not seen any, but his time I wire brushed the heck out of them and then dropped a bore scope down through, and low and behold there are a couple of holes. Small, but there all the same.

My question is, has anyone tried pressing a thin walled tube over the original tubes? Doing so would reduce the diameter from 1 3/8 to a little over 1 1/4. It would save me having to completely dissemble the riser and cutting out the old tubes, plus I have not been able to find the original tube size.

The riser is already blocked off from the exhaust.

 

Any suggestions appreciated. 

D2860BEE-17FE-418A-AF77-DE2AFB5A11C5.jpeg

  • Like 1

Share this post


Link to post
Share on other sites


Benefits of AACA Membership.

You found the culprit. The insert will need to be swedged or expanded at each end to form a complete seal to the heat riser housing. Unfortunately the throttle blade and shaft will need to be removed. It would be best to remove the old heat riser tube .I have used a piece of modern exhaust pipe trimmed to length. A muffler shop then can expand each end of the new pipe to seal to the housing. Get as close as possible to the original size. I don't think the tubing diameter will influence performance if the tubing is within 1/4" of the original. Be sure to block off the  passage to the exhaust manifold and the  passage from the valve sandwiched between the exhaust manifold outlet and the exhaust pipe inlet. This is a must in my opinion.

  • Like 1

Share this post


Link to post
Share on other sites

Hubert,

yes the exhaust butterfly is removed and the tube blocked off.

Thanks,

Chuck

Share this post


Link to post
Share on other sites

Chuck:

 So glad you found the culprit! I had suspicions since I was also down the same road. I am doing the same thing on the spare riser I have. Had a 1/2 long horizontal hole at the base of the riser above the pressed section where it was just exposed to the heat and condensation. of the inside of the chamber. I had made a driver to remove mine. I had considered doing a inner sleeve and do not know if that would do much to the volumetric efficiency. To me it would probably speed up air flow. 

 Now I have to revisit my vacuum tank as a problem. The engine had been running great. Since the summer heat I have not had to touch the choke on my updraft Marvel for 2 months. It would start within 1 or 2 turns of the crankshaft. Yesterday morning since it was below 60 degrees I actually had to use the choke! I wish my 1937 would start like that. 

  • Like 1

Share this post


Link to post
Share on other sites

Chuck, 

     Wondering why the hole is causing a problem if the blanking plates are installed.  It would be important to install the blanking plates on the correct side of the gasket.   I put the plates in with the hope that if I did have a failure in the tube, that it would not effect the performance.  The blanking plates are an easier fix than the heat riser tube.  Hugh

 

Edited by Hubert_25-25 (see edit history)

Share this post


Link to post
Share on other sites

Hugh,

The block plate I welded in is on the exhaust side of the horizontal cross tube.

I’m not sure where the riser would be pulling outside air from but I’ll probably block off the other side as well since I have it all apart.

 

Larry,

 

I saw you were having fuel problems, I’m sure you’ll figure it out.

 

Chuck

Share this post


Link to post
Share on other sites

You are better off removing the original sleeve and replacing it. A skilled operator with an acetylene torch can slice the steel sleeve where it is pressed into the iron heat jacket without damaging the casting. I have done it many times. I then machine a new sleeve to fit the jacket bore. They can vary so each one is a custom job. The sleeves used to be available but as far as I know are not anymore. You really don’t want to choke the the intake down any smaller.

Share this post


Link to post
Share on other sites

Hugh, if there is a hole in the heat jacket sleeve it is a tremendous vacuum leak no matter if the Marvel intake preheat system is working or not.

Share this post


Link to post
Share on other sites

The original rusted heat tube can be removed relatively easily by carefully cutting a slot down one side with a sharp chisel and prying it out.  I used aluminized exhaust tubing from the scrap bin at a muffler shop to replace the heat tube in my 24 Master PU.  A simple arbor press was used to install the new tube with oil to lubricate the process.    I also used a freeze plug & steel plate to isolate the riser from exhaust flow.  All this was done at a local muffler shop  during the BCA meet in Rochester.

  • Like 1

Share this post


Link to post
Share on other sites

Similar to what Mark said, I cut out the old sleeve out from my 1929 and my friend machined a new one for me down from a thick-wall oversized-OD pipe.  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, and the body in hot water for about a half hour, then quickly took it to his press and pressed the sleeve in.  Worked very well.  But I still have issues with rough running sometimes - and when I do, I always find some small exhaust leak in the crossover pipe or somewhere else that is right around the air cleaner.  Once I tighten up the leak things get better.

Share this post


Link to post
Share on other sites

McMaster Carr had stainless tubing very close to the size needed for my 31. I think it may have been.003 or so over but the machinist that took the old ones out said it would be no problem to install.

 

Dave

Share this post


Link to post
Share on other sites

Thanks for the replies everyone. I got the old ones out. It looks like I’ll have to machine down 1  1/2” OD pipe for this. The pipe is actually flared out on one end. It is 1.43 OD on one end and 1.475 OD on the other. Go figure.

 

Share this post


Link to post
Share on other sites

Please understand that I am not making light of your problems here, but, man am I glad that my 1916, 1920, and 1922 do not have these heat risers to contend with.  These Marvel Carburetors are a handful by themselves.  We'll hope that everything works out for midman and his Buick.

 

Terry Wiegand

South Hutchinson, Kansas

Share this post


Link to post
Share on other sites

Terry,

 

You are lucky your cars don’t have these, that’s for sure.

If I didn’t want to keep the car looking original I’d toss out the whole mess and put a downdraft setup in it.

 

Chuck

  • Like 1

Share this post


Link to post
Share on other sites
59 minutes ago, midman said:

Terry,

 

You are lucky your cars don’t have these, that’s for sure.

If I didn’t want to keep the car looking original I’d toss out the whole mess and put a downdraft setup in it.

 

Chuck

 

Think of it this way, if it helps.  By blocking both sides of the exhaust exposed to the riser, and replacing the riser tube, it will last forever and never have to be addressed again! 

Share this post


Link to post
Share on other sites

So I am struggling with where a vacuum leak would occur if the top and bottom ends of the heat riser section are blocked.  You do not need the heat riser with today's fuels.   Blocking both sides should be the easy fix and sufficient.   Hugh

Edited by Hubert_25-25 (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites
47 minutes ago, Hubert_25-25 said:

So I am struggling with where a vacuum leak would occur if the top and bottom ends of the heat riser section are blocked.  You do not need the heat riser with today's fuels.   Blocking both sides should be teh easy fix and sufficient.   Hugh

 

The updraft tube in the heat riser is a restriction, of a specific size.  Even with both sides of the heat riser blocked off from exhaust flow, there is still the chamber around the updraft tube. 

 

If the updraft tube has a hole, the updraft stream to the cylinders is now exposed not only to the tube restriction but also to the chamber in the heat riser around the tube.  Now the updraft tube restriction is increased, perhaps doubled, due to the hole in the updraft tube.  The area of the updraft tube, and the area of the heat riser chamber around the tube, are joined by the hole in the tube, at least as far as how the carb and engine react. 

 

Wouldn't that have an affect on how the carb works, and how the engine runs? 

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, Hubert_25-25 said:

So I am struggling with where a vacuum leak would occur if the top and bottom ends of the heat riser section are blocked.  You do not need the heat riser with today's fuels.   Blocking both sides should be teh easy fix and sufficient.   Hugh

Hugh,

After removing the old tubes I can see that the heat riser is basically a cast shell, hollow on the inside, and with holes in the tubes it can pull air from the linkage holes drilled on either side of the casting. Also, in my case I had not plugged the carb side of the heat tube, only the exhaust side so I'm sure it was pulling from there too. 

Chuck

  • Thanks 1

Share this post


Link to post
Share on other sites

I pressed in the tubes and flared the one end and loctite sealed them for good measure. It runs a lot better but I’ll have to spend some time resetting the carb since I had messed with it so much. Much smoother running. Hopefully I can start moving on to other things soon.

 

i appreciate all the help.

 

Chuck

  • Like 4

Share this post


Link to post
Share on other sites

My heat riser is missing. The previous owner took it off, he told me it was because gasoline was almost kerosene in those days and this was needed to heat the fuel. He said it's not needed with modern fuel. My car runs great without it, don't know what will happen during cold weather.

Share this post


Link to post
Share on other sites
19 hours ago, Otto Cycle said:

My heat riser is missing. The previous owner took it off, he told me it was because gasoline was almost kerosene in those days and this was needed to heat the fuel. He said it's not needed with modern fuel. My car runs great without it, don't know what will happen during cold weather.

 

Heat risers on cars that are driven today have the heat riser tubes removed or blocked.   True on modern vs old fuels.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now