31 PA vac spec needed.

[Brooklyn Beer]

I have finally got my 31 PA running, idling, and driving on the correct DRT-08 carb but with the wrong jet idle tube that I was able to get set to factory specs by reaming out the holes in the tube. It will have to do for now as it seems the correct tube is unobtanium. Think I started with a chevy tube but no numbers on it. What I am looking for is what number in vacuum should I be looking for as I work dialing it in. Also psi for compression. Working from the factory carb sheet has gotten me this far. I never knew just how small a size #62 drill rod actually is till I needed one !

[hchris]

Steady 18" Vac at idle is good, below 15" means wear and tear making an impact. Compression around the 80 - 100psi is desirable but anything above 60 means there's life left in it, so long as all readings are within 10 - 15% of each other. 

[Brooklyn Beer]

I think it all just went to nil as moving cars around this morning it developed what I can only determine is a rod knock or wrist pin knock after a quick 1 mile ride down the hill and back. Pulled the belt and sure enough, there it is in the front lower part of the motor. And it is pretty loud. Not that familiar with these early plymouth 4 cylinders so time to start some research.  Just when it got to running good too after all the carb work. I was going to look at rebuilding a flat 6 as a project but think one just might have found me.

Edited June 27, 2020 by Brooklyn Beer (see edit history)

[Brooklyn Beer]

As I am now tracing down an odd tap tap that started saturday morning I did a compression and vac test to see if the valve train was working correctly.  From front to back on a cool motor they were between 80-76.  Vac was 18-19 but at increased RPM it actually dropped. Little flutter at idle 17-19. The tap tap has gotten quite a bit less just doing the vac test. It is in the lifter gallery as far as I can tell.  It is odd that it just came out of the blue.  No warning.  Still has same 35-40 oil pressure at idle hot.

[auburnseeker]

I would have guessed a broken valve spring but the fact Compression is not affected I would think that may not be it. 

[Brooklyn Beer]

Real shame after all the work and headaches I went through getting the carb issues worked out. Fun car to drive. But the difference in going from driving the 31 Franklin to a 31 Plymouth is like a caddy and a yugo.  Plymouth has to be over 1/4 smaller to start.

[auburnseeker]

Can't wait to drive the Auburn one of these days,  but I still have to get to the mechanics.  Dad's 47 Ford truck ate a new Mallory distributor and timing gear, (later Flathead)  so I had to replace all that first to get him up and running before getting back to the 51 Dodge,  then finally on to the Auburn.  Just finished that up today.  Start it tomorrow and set the timing,  then hopefully it's back to him.  I've got my finger's crossed.  

[Brooklyn Beer]

Wish I had done a little more research into the DRT-08 209s "correct" carb before I bought it trying to bring the car back to stock. Evidently that one year carb was so problematic that it was replaced instantly sometimes with the BB1 within the first few months.  Wish I had gone that route and avoided the headache of having to make a jet idle tube from a chevy work 95% in the DRT-08. But it starts instantly and runs and drives very well with it. Just idles a little bit higher then it should. Brass bowl carters are an experience for someone who never worked on one before.  Maybe one day I will forget the expense and headache and get the other carb. Evidently the original air cleaner I have is worth more then the carb as they all got pitched when the DRT-08 carbs were changed out.

[carbking]

 

 

12 hours ago, Brooklyn Beer said:

Wish I had done a little more research into the DRT-08 209s "correct" carb before I bought it trying to bring the car back to stock. Evidently that one year carb was so problematic that it was replaced instantly sometimes with the BB1 within the first few months.  Wish I had gone that route and avoided the headache of having to make a jet idle tube from a chevy work 95% in the DRT-08. But it starts instantly and runs and drives very well with it. Just idles a little bit higher then it should. Brass bowl carters are an experience for someone who never worked on one before.  Maybe one day I will forget the expense and headache and get the other carb. Evidently the original air cleaner I have is worth more then the carb as they all got pitched when the DRT-08 carbs were changed out.

 

The brass bowl carbs were NOT problematic in 1932; but the design was quite outdated compared to the brand new type BB-1 carbs. And today, the brass bowl carbs are approaching 100 years of age!

 

The fall of 1931 was a GREAT year for carburetors. Carter introduced the type BB-1, Stromberg introduced the types SF and SFM, and Zenith introduced the types 63 and 263, all for use on 1932 models.

 

And, believe me, there were a LOT more replacement Strombergs and Zeniths sold than Carters. And while I personally feel the Strombergs and Zeniths are a better design than the Carter BB-1's, perhaps the reason Stromberg and Zenith sold so many more was the forethought and marketing.

 

Just considering the Stromberg type SF alone: Stromberg produced 38 different sizes of the SF (Carter produced 3). Stromberg listed specific calibrations for several thousand vehicles. Carter listed 188. 

 

But many of the early designs were NOT problematic; they simply were an earlier design. Of course, some of the earlier carbs were problematic. From the 1920's: "You have a Marvel carburetor??? It will be a MARVEL if it works"! (Very old mechanics pun).

 

As far as the original air cleaners: I have sold several on Ebay after I tried to sell them here. Best I ever got was $75. each, and I paid the shipping!

 

Jon.

[Brooklyn Beer]

Just what changes in the broad line up of BB-1 carbs between plymouth models VS other makes?  How would I know I am buying a BB-1 for a cylinder plymouth VS for a 6 cylinder Dodge?