Jerry's right. He usually is. I just checked mine and it is connected to "ported vacuum" on my carb.
I started the engine and then pushed the vacuum advance linkage to "full vacuum" with my finger. The engine stalled as expected.
My timing is set to 7 degrees before top dead center at idle, which is 2 degrees more than the book calls for, but the engine seems to like it better. I set it "on the BB" which is 5 degrees before TDC with a timing light. Then I adjust the "octane selector" to where it seems to run best. That way it is easy to take it back to the factory (or anywhere else) setting without needing a timing light.
This was done on my GMC with a Carter YF carb and a '56 Chevy distributor. Chevys and GMCs used the same part number distributor in the late 50s, I don't know about early 50s. Your Chevy/Rochester mileage may.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Don't forget to PLUG the vacuum line when you disconnect it to set the timing or you'll just be trying to set the timing with a vacuum leak.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
If the idle speed is set correctly, there will be little or no ported vacuum on the line, at the RPM he needs to prevent the centrifugal advance from kicking in- - - -usually 500-600 max. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The '51 GMC Maintenance Manual says to crank the idle speed down to 350 RPM so no mechanical advance was taking place while checking ignition timing. The book says that 2 degrees is in by 400 RPM. I don't know if the '51 GMC and Chevy trucks used the same distributor, but I do know that the 55-59 years did.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
I’m still thinking that my Rochester B carburetor is giving me trouble. Some have suggested changing it out to a Carter. I have found this one for sale. Would it be the right replacement for me? I want to stick with manual choke and keep as close as I can to original period.
52 Chevy 3100
Jesus said to him, "I am the way, the truth, and the life. No one comes to the Father except through Me." -John 14:6
I found the numbers on this one and it is a 938 which does not appear to be one that will work with my 235 engine. I now have found a Carter YF 2100. That appears to be one that will work. Any thoughts???
52 Chevy 3100
Jesus said to him, "I am the way, the truth, and the life. No one comes to the Father except through Me." -John 14:6
Best to contact Jon H Carbking about that specific carburetor.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
I found the numbers on this one and it is a 938 which does not appear to be one that will work with my 235 engine. I now have found a Carter YF 2100. That appears to be one that will work. Any thoughts???
The 2100 will be a good fit for your engine. Many here running one, including me.
PastorMatt - the 938 was used on the 134 CID 4 cylinder Jeep; it should not be used on your 235.
The 2100 should work out fine for you.
Jon
Good carburetion is fuelish hot air The most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes! The Carburetor Shop
