distributer swap from mechanical to vacume advance

[Steves Buick]

Hi guys, I'd like to swap out my mechanical dual point distributer for a single point with an petronics modual that has a vacume advance. I have a new distributer from a 1935 buick, 8 to use.. my dual point is on my 1932 series 90. My question is ...can I run the vacume line off the manifold as my Marvel does not have a ported vacume port .. Looking for thoughts and ideas at this point.. 

Thanks,

Steve 

[Ben Bruce aka First Born]

Results are different if manifold versus ported. At least where the port is on mine.

 

  Ben

[DonMicheletti]

For what it is worth, on the '38 the vacuum advance is connected to the carb via a closely calibrated port in the carb. The port is above the throttle plates, so the advance does not see full vacuum at idle.

Be sure you know what yopu are doing - Buick wasnt stupid.  (not suggesting that you are)

[southpaw]

Steve,

I was told by John at Brillman Co. 888-274-5562 not to use the Petronix electronic ignition on a 6 volt system. He has points, condenser, and HOT coils. My '32 Series 50 Model 57S runs great with his ignition products, dual points and all. Give him a call he is very knowledgeable. 

Jim

[Steves Buick]

Thanks  for the input, I'll try John thanks Jim.. I've just been pulling my hair out tryting to smooth out the engine at Idle, nothing has changed since it was running like a singer, Still looking for the sweet spot on the Marvel!! I used sea foam yesterday and sis not seem to help.. thought a single point dist with an electronic ignition might be a nice upgrade .. time to breat out the heathkit fish finder!

Steve

[midman]

Steve,

I was struggling with getting my 31 to idle and run smoothly. It ended up that I had a couple of holes in a heat riser tube. I couldn’t see them until I ran a scope through the tubes. I replaced them and it solved the problem. It might be worth checking if you haven’t yet.

Chuck

[Steves Buick]

Thanks Chuck, 

 

I was thinking the same thing based on previous posts. just was saving that for last.. did you block off your heat riser tube? 

 

Steve

[hchris]

 

 

On 1/5/2020 at 12:50 PM, Steves Buick said:

Hi guys, I'd like to swap out my mechanical dual point distributer for a single point with an petronics modual that has a vacume advance. I have a new distributer from a 1935 buick, 8 to use.. my dual point is on my 1932 series 90. My question is ...can I run the vacume line off the manifold as my Marvel does not have a ported vacume port .. Looking for thoughts and ideas at this point.. 

Thanks,

 

 

If you have an accessible vac port hookup a vac guage  and see how it's behaving,  great diagnostic tool.

 

 

[hchris]

18 hours ago, Ben Bruce aka First Born said:

Results are different if manifold versus ported. At least where the port is on mine.

 

  Ben

 

Correct, distributor vac is drawn above the throttle.

[midman]

9 hours ago, Steves Buick said:

Thanks Chuck, 

 

I was thinking the same thing based on previous posts. just was saving that for last.. did you block off your heat riser tube? 

 

Steve

Yes Steve I did that first. I did not see a change until I replaced the tubes in the heat riser itself though.

Chuck

[Mark Shaw]

15 hours ago, midman said:

I had a couple of holes in a heat riser tube

This is the single most common issue with updraft Buicks.

[Hubert_25-25]

Steve, 

    I agree that your issue likely lies with the pre heat tube.  I blocked off the pre heat tube on both ends.  I am not sure how different this is than yours in design, as mine is a 1925 Buick Standard.  I actually installed blocks in 3 places.  

- For the distributor advance, you want to use ported vacuum.  This will supply 0 vacuum at idle.  That is when you want no advance.  

- Manifold vacuum is used for windsheild wipers and vacuum tanks.

 modifying an advance unit will do nothing for a rough idle.  The spark can be set at the same place at idle using both manual or automatic advance.  At idle, the timing light should be firing around  0 to 7 degrees before TDC.  Simple as that.  If it is not smooth, it is not the advance method.  

Hugh

 

Edited January 6, 2020 by Hubert_25-25 (see edit history)

[Steves Buick]

Thanks everyone,  I did put a vacume guage on the manifold and it pulled about 17.5 inches,seemed pretty steady. Hugh thank you for the excellent photos and details much appreciated. I will open up my heat reiser and block it off before I do anything with the dual point distributer, I follow Mark Shaw's post and believe he is correct on the heat riser leak being the culpruit. 

As for the ported vs manifold vacume use,  in 1935 did Buick have a port on the Carb?  I get the concept of why to port on the bottom side of the butterfly ( updraft carb ) or above the throttle for a down draft.. and the use of manifold vac for wipers etc. This 1935 Delco has a vacume chamber, Ii just didnt think they started porting vacume off the carb until years later..I question the idea of drilling a vacume port in my Marvel!! Thanks all for responding.. 

Cheers.

Steve 

[Hubert_25-25]

Steve,   

      I recently had poor running from my Marvel carburetor.  The spring in the air valve had some surface rust on it.  This fine rust got between the plunger and the interior wall of the air valve adjusting barrel.  This was causing the air valve to not close all the way.  This gives a poor idle.  In addition, the pot metal venturi in these old marvels will grow over time.  This will also cause the air valve to not close all the way as the gap at tail of the air valve is impacted by the growth. 

Consider inspecting inside your carburetor to ensure that the air valve will lay across the back of the carburetor and that there is still a tail gap.  

I cleaned this tiny bit of rust out of mine.  I soaked the spring in evaporust and then I replated it.  All is working well now.   Attached is a procedure for going thru your carburetor.     Hugh