VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 vacuum advance

Is the travel of the distributor vacuum advance on a 216 the same as a 235 ? Or may not even fit a 235. Still trying to get my engine to purr like it should ! Thanks.

As an example the same vac. advance was used from 1941-1951, 235 and 216. The models up from there had some clearance problems and amount of advance differences. As an example the 1951 unit advanced the timing up to 20 degrees. The 1962 unit advanced it less than 1/2 of that amount.
How would you describe your running problems??????

It starts good, idles good. At fast idle to about 40 mph runs rough. step down on the gas and wants to really go for a moment. After 60 years who knows what parts were used. Thanks.

I changed the vacuum advance, I think the spare one I had both ended up to have the same travel ! The spark looked weak so I put on a new coil , lots of spark now . Seems to start off good ,then when up to 25 or so it breaks up. I think that the power valve is working ok. All passage ways are clean and clear. What should the main fuel jet be or where can I find that info ? Could the lower octane these days require a larger jet ? A while ago I put a 55 235 in a 51 panel with a split manifold, had a time getting that to run right. Ended up enlarging the jet and that fixed it. Thanks I know the answer if I could just think of it.

I have the stock jets in all my cars and they have been running fine for over 20 years on the ethanol gas.

First, I know nothing! However, it has been my experience (at the instruction of others) anytime I opened up the exhaust flow on an engine, I had to increast the carb's jet/s size. Ain't got nuthin to do with this crappy ethanol fuel. They just flow more air and thus need a bit more fuel (and they do perform better in most cases).

Have you increased the exhaust flow on the Chevy in question?

I have dual exhaust and run stock carburator jets...The only time I have really had to mess with reverse flow main jets, is with 2 stroke motors...You might have dry pump leather...

When was the last time you changed your plug wires...?

I have two vacuum advance parts. There are numbers on the mounting plate, 140 and 143. Do these # mean anything ? Thanks.

From what I see the 140 is for a 1952 passenger car and a 1958-1962 car.
The 143 would be for a 1940-1951 car.
The above would also be for some trucks.
The main differences is the location of the motor mounts required a different location for the actual vacuum control.

Just making sure I have the right one (140) on my engine and I do ! I tried the 143 and seam to have the same travel no difference in engine running. Would the 143 be for a 216 ? The 143 is angled out to miss the mount. Still looking for the problem ! Thanks.

They all have the same movement. The 143 would be afor a 1952 216 car as well as a 235 car.

Not certain what issue you are attempting to correct, I understand you are focused on timing advance, BUT have you checked the centrifugal weights? Is the movement free and easy? Are the springs intact and operating properly?

Had the distributor all apart checking the springs and weights only found crud . Cleaned up and put back together. Put back in engine for the 3rd time ! Would hardly run, set the timing , not any better . I must have stumbled on to something! Under the cap the rotor looked lose on the shaft so I looked thru my spare parts and found a new one, only to find that the rotor wasn't even the right part. Must have been around 1/8 to 3/16 short from the cap.Thats why it would start but not run under load! The right part is in it now and it runs GREAT. Thanks everyone for all the advice.

Always good when the final step brings success.

Glad to hear you solved your problem. You might want to check your distributor number to see if it is a 216 distributor. I had the same situation after attempting a tune up on my 51 216 only to finally discover someone had installed a 53 distributor that used the longer rotor.

I'd think one would pay more attention to the rotor length...I recall having a motor that wouldn't start simply because one of the "springs" had broke...Wouldn't think that would "kill the deal", but it did...Took awhile to figure it out...

All it takes is time !