Regarding 1931 - 1937 V-12 engines

[Stinson]

Should there be the same amount of suction through the carburetors on each side (with the air cleaners removed) when holding your open hand over them while the engine is running? I have less suction on one side than on the other.
Ty Stinson
CLC22330

[Steve Passmore]

That would tell you there's a lack of venturi vacuum from one bank of cylinders Ty but its not a very good scientific test. A compression test on all 12 would tell you more about the cylinder and valve condition but you could be loosing vacuum somewhere on the induction side. There is equipment to test this.
Didn't you have trouble years ago with this engine only running on one bank of 6?  If vacuum was down on one bank that could account for your bad starting problems.

[Stinson]

Thanks Steve. The engine was running on one bank at that time due to a dead coil on one side. All is okay there now having new coils. But, I wonder about the difference in intake pressure through the carburetors. Starting has always been an issue. The added electric fuel pump makes no difference.
Ty Stinson
CLC22330

[m-mman]

Intake suction only happens because of correct functioning valves, pistons and rings. If an exhaust valve hangs open, or an intake fails to open, or the rings dont seal, then the engine can not efficiently draw air into the manifold(s).

The best way to check the above is a good old fashioned compression test.

[Brad Ipsen CLC #737]

If you are talking about a low engine speeds or at idle the carburetors have to be balanced to have equal suction.  In other words the throttles have to be open identically.  There is a procedure in the late V-16's manual for doing this but much easier to use the tools that Steve's countrymen use for setting up dual SU carbs on thousands of British sports cars.

[Alex D.]

I would agree with Brad  Ipsen, With less suction on one side than the other at idle would indicate that your carburetors need to be synchronized.  Here is a couple YouTube videos showing two different procedures for synchronizing  carburetors on two completely different engines.
https://www.youtube.com/watch?v=Y_WDF6glD5k
https://www.youtube.com/watch?v=MbEBya71yiI

[Steve Passmore]

Interesting but wildly different than Tys updraught carburettors. He may be lucky and have some fitting on them for a vacuum gauge of some sort.  I have a quadruple vacuum tester for 4 carb setups but they need the little test tube fitting on the carb.

[Stinson]

I have removed the large oil-based air cleaners and find that the 68mm diameter intake hole is upright there as are the VW carbs so that may work here.
Ty Stinson
CLC22330

[harry s]

Ty, On a different subject, I sent an email earlier to maybe one of your old addresses. I'm looking for a decent tail light lens for '37 Cad. If you have one to sell let me know. hscott1937@aol.com.
Thanks, Harry

[Stinson]

Hello Scott, I have sold all my remaining parts other than a set of 12 used 1937 V-12 engine pistons; and a set of four mounted tires/rims with the two front hubs turned and ready for use.
Ty
CLC22330

[Alex D.]

Interesting but wildly different than Tys updraught carburettors. He may be lucky and have some fitting on them for a vacuum gauge of some sort.  I have a quadruple vacuum tester for 4 carb setups but they need the little test tube fitting on the carb.

Using the water bottle balancing tool is very similar to the tool Cadillac shows in the 32/33 shop manual. There should be a port on top of each intake manifold, one for brake assist and the other for vacuum.

[Stinson]

Thank you, I will look for the ports.
Ty Stinson
CLC22330

[harvey b]

Ty, first thing i would do is a compression test,because these cars have so many cylinders they will run on 9 or 10,not run well but will run,had the same problem with my 38 V16,it would run on 12 cylinders,not well but it still ran,It was really cranky to start when it warmed up,left me stranded more then once >:(if you can get it to run you can take a heat sensing gun and point it at the exhaust manifolds and the temp will be lower on the dead ones?You could have a stuck valve or 2,that happens when they are not used everyday,old gas will do that too.Its also possible you have some plugs that have fouled too.Keep trying it is something simple im sure. Harvey