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1927 Standard 6 27-25 Heat Riser Bore Diameter


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Just taken the heat riser off and the exhaust side has been blanked with a plate inserted against the flange so therefore not getting any exhaust contamination into the intake side, which some people suggested as to why the car is slow.

It looks like it has a new thick walled tube up the riser. The OD is roughly 1.42" and the ID 1.17" This seems to restrict the air flow area by nearly 20% which will certainly make a difference. The bore at the throttle butterfly measures 1.43" so I guess somebody just found some tube to fit and pressed it in?

Any thoughts or suggestions of what people have done?

 

Many thanks.

 

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Your heat riser tube may not be your only problem.  There are a lot of areas to address if you want to put your carburation in good order and to bypass all of the heat addition components that are no longer needed and are negatives when running modern fuels.    Hugh   

 

https://forums.aaca.org/topic/372573-1920s-buick-marvel-carburetor-rebuilding/#comment-2311177

 

 

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Kevin:

 I bought from BOB's 2 riser linings. NOS Hygrade H-4 for 1925 Standard and a H-6. The only problem was that both are the wrong size for what I have for both cars The tubes are marked with a label to identify the riser # they are to fit. Well neither fit! The H-6 for Master is too small. (to big for the 1925 Standard). The H-4 for the Standard riser was stated on the label on the tube to fit 1925-1928 Standard.  NOT! It is larger than what my 1925 takes. I believe I sold that to someone with a 1927 last year at Hershey.

For Frank. If he can remove the throttle shaft and take to a machine shop that could chuck it up securely anc=d center accurately on a lathe he could just have it bored out larger. Also on a vertical mill which would be more secure. 

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Frank :

 As to what Hugh has posted the venturi blocks on both my Master and Standard carbs I had filed to fit for the proper tail clearence. (When I first got into my carb the block was installed upside down.) After a year they had grown again. Keeping the dashpot valve open. Also the idle jet is suposed to be centered to the venturi hole. Mine was almost 3/32 off center and oval in shape. The newly manufactured blocks solved those problems.

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Thanks for your comments and I have knocked the tube out of the riser. Will measure it and taper the ends to aid flow and re-fit while I source some thin walled tube.

I found Hugh's superb carburetor rebuild notes and am steadily working my the way through them solving the issues at each stage of which there are many! Mine has an original venturi block which I have filed as the air valve was not shutting, but will look to obtain a new one in time. 

The new float material from Bob's has just arrived in the post so hopefully I can get the rebuild of the carburetor completed and see what difference that makes.

Thanks again for all the input.

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Frank:

 I found some photos of the carbs I redid with before and after.

DSC00475.JPG.28ec0ed6e4dd7109e8a17fb6ad0e3f9e.JPG Quite a bit of distortion here. Tail clearance of the block to the vane on my carb was supposed to be .009-.017

DSC00476.JPG.a1f2172c914ee2705ffc037983d69253.JPG

New aluminum block top right with warped, crumbling originals below.

DSC00468.JPG.ce4d68ce5b3bb39b46239512201b6033.JPGAnother carb in the condition I bought it. Dash pot valve over 1/4" away from fitting the bore. The idle jet 1/8" off center.

DSC00474.JPG.b403eb7feeb8293e037c83210a07150f.JPG

New block fitted and the dashpot with a good fit to the bore.

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This is how I did the final fit of the dashpot vane to the bore by putting light finger pressure against the vane while pulling 240 grit abrasive paper repeatedly to see no light around it. This is after the block has been closely filed to fit the tail of the vane. The Marvel service book indicates to file the block not the vane tail edge. On both my carbs there was evidence the tails had been filed before.

DSC00479.JPG.20a9c8a5d57e098aaf9d5fc30d210d90.JPG

 

 

Edited by dibarlaw
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Larry:

Thanks for the photos most helpful. My venturi block seemed in good shape and I only filed the block to get some clearance not the vane. I hadn't thought about checking the idle jet was central in the hole, will do tomorrow. Should the jet top be flush with the top of the block?

 

I still need to get the vane to be a better fit against the body as can still see gaps so thanks for the tip re emery paper. 

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Frank:

 Here is a sectional view of my 1925 carb showing the relationship of the idle jet to the venturi.

Marvel10-11001.jpg.68e7baa4c90a7bc4adb52747aaf3fc0c.jpgIt looks as though on my carb the idle jet top is in the the center of the block. So I mentioned when I first got into my carb the block was upside down and the top of the jet was about flush with the block.

Here is a copy of the Marvel calibration chart.

MarvelChart001(1280x748).jpg.76ae3c5d7024048e52d1ccf2fe293a08.jpg

 

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Peter:

Thank you for this reference. As I said before I have an HT-6 that is labeled ON THE TUBE as fitting the 1925 Master. It does not. The HT-4 that I had specified that it fit 1925-1926 Standard which it was too large for my 1925 Standard riser. 

 Frank:

 I was able to scan the Marvel diagram and parts list for your carb. This is from my original 1931 Master Book of Parts that has extra sections for accessories and such. Marvel, Delco Remy, Wolvereen Bumpers, Buffallo wheels etc.

img03262024_041.jpg.2ec3d0fc74d6e4efa929445dfcd3c1e9.jpg

I noted that they mention that the riser and lining are avaiable as a unit as well as an assembly. But no lining available untill the later aftermarket source provided them.

Edited by dibarlaw
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Peter:

Many thanks for the information, great to see the after market specification sheet and an original replacement still in a box!

 

Larry:

Thanks for providing the spare parts list, very useful. I'm missing the choke return spring 24-63.

 

I fitted the new float material and carried out the rebuilding of the carb today and the car runs very much better. Sounds as if it is running rich but will look at the plus after a good run out. It has the jet sizes in from the manual. I plan on finding some thin walled tube and fitting this in the future but at least I have the car running much better and can use it so I can get used to it.

 

Thanks again for all the input, this is such a great resource for helping new custodians of Buick's.

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Frank, 

Glad that you are making good progress and that the Buick is running better.      

Bob's Automobilia has replacement choke springs.  I bought two in case I messed one up, but I have been able to replace this spring without taking the lever off the choke shaft.    Hugh

I am also surprised to see the heat riser tube OD the same for Master or Standard in 1925.  

 

Hugh

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Hugh:

 What is in the spare 1925 Master riser as close as I can measure is 1.587 O.D. 1.512 I.D. length is 5 7/8".  Much larger than our standard riser liner.

 I set up a vacuum gage for my Master and found it to be at 17" vacuum the best I can dial in at the carb. To me it still needs some timing revision and dwel adjustment. But no matter how I adjust the system it idles much too fast. The only way I can slow it down to a reasonable RPM is to retard the spark. The stop screw on the throttle is all the way out. So I will have to check if the former owner bent the butterfly plate. Or if the smaller diameter riser lining has the same effect.

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I made a driver to remove the liner from my Master riser. A few good raps and it moved down past the top bore. But it started to collapse at the bottom where it was rusted. So my only option was to try to crush what was inside with a variety of things in my shop. I was able to carefully cut the bottom ring that was left of the liner. It took about an hour to carefully the crush liner so as to not damage the bores. Also the bolts that connect the back of the riser to the exhaust manifold snapped off. 

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I was able to center accurately and drill out in steps and with some fine drifts I had made I was able to remove the bolts and save the threads.

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  • 3 weeks later...

So I am going to throw this out there for general discussion regarding these heat tubes.

In the case of the 1927 car, I would replace the tube because someone installed a smaller ID tube than stock. 

Replacing a tube looks like a lot of work.  I have put copper blanking plates on both ends of the vertical intake heat tube on my 1925 Buick. 

I put the blanking plates in - in case I ever have or could develop a pin hole leak in the tubing.  The blanking plates should stop any airflow from entering or leaving the casting.  So I don't see a compelling reason to change out a heat tube.            Hugh

 

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exhaust blanking plate 2.JPG

exhaust blanking plate 3.JPG

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Hi Hugh,

Thanks for your comments, I actually put blanking plates in and also removed the oversize riser tube just leaving the shell of the riser. I ran the car and although it started and ticked over under load when driving it had no performance at all. I put it down to not having the riser tube in place to give a smooth airflow up through the riser and into the intake manifold. I reinstated the riser tube with the same blanking plates in and car ran OK again. Its on my jobs list to find some thin walled tube to replace the thick walled tube in the riser. Main priority at the moment is getting new half shafts and a pinion without chipped teeth for half shaft so I can get it back on the road!

Andrew 

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One of the points on removing the sleeve liner tube. It should be pressed out from the bottom if possible. On both my Master and Standard risers the bores were about .020 smaller at bottom. I may have been more successful by pressing out that way but it already had rusted out around the bottom.

Presently I am trying to remove a liner from a 1924 big 6 riser. It was very rusted with a solid block of carbon /rust in the surrounding chamber. Access is a problem as the manifolds are still connected by thoroughly rusted bolts. Soaking and waiting.

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