Vacuum advance question
Thread Starter
Racer
Joined: Jul 2004
Posts: 351
Likes: 0
From: Pensacola Fl
Vacuum advance question
I recently got a new hei distributor throught the group purchase here on the forum. The vacuum advance does not seem to work. It does not hold vaccuum and it doesn't advance anything. I have checked this holding the engine steady at 2500 rpms. It has one of the adjustable vacuum canisters on it. I didn't know if this is something that could be adjusted or if I should just replace the canister. My thought was that it needs to be replaced if it doesn't hold the vacuum.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I recently got a new hei distributor throught the group purchase here on the forum. The vacuum advance does not seem to work. It does not hold vaccuum and it doesn't advance anything. I have checked this holding the engine steady at 2500 rpms. It has one of the adjustable vacuum canisters on it. I didn't know if this is something that could be adjusted or if I should just replace the canister. My thought was that it needs to be replaced if it doesn't hold the vacuum.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
Tech Contributor
Joined: Aug 1999
Posts: 14,374
Likes: 6,373
From: At my Bar drinking and wrenching in Lafayette Colorado
If it won't hold vacuum, it's bad. Yank it out.
Don't use an adjustable unit. For HEI on an engine pulling good vacuum, use NAPA part number VC1838. It's not worth your time yanking the dstibutor out and sending it back - the new vacuum advance unit will cost you about $12.
Don't use an adjustable unit. For HEI on an engine pulling good vacuum, use NAPA part number VC1838. It's not worth your time yanking the dstibutor out and sending it back - the new vacuum advance unit will cost you about $12.
Thread Starter
Racer
Joined: Jul 2004
Posts: 351
Likes: 0
From: Pensacola Fl
Thread Starter
Racer
Joined: Jul 2004
Posts: 351
Likes: 0
From: Pensacola Fl
That's wat I figured. I was just looking at the part numbers on your paper. Could you answer another quick question for me.
I just put a 670 street avenger on my 71 base 350 engine. I know that you have said the street avengers have been lean, but would a 670 likely be jetted too lean for a base 350?
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Tech Contributor
Joined: Aug 1999
Posts: 14,374
Likes: 6,373
From: At my Bar drinking and wrenching in Lafayette Colorado
Every one I have worked on has been lean, even for a base engine. When you get the distributor running right (very important to do before playing with the carb) and get your timing set up to 36 degrees with a good vacuum advance unit, you can play a little with carb jetting. Try bumping primary jetting up 2 sizes to start with, and then get your secondary side 8 sizes bigger than primary. I'll bet you'll feel a significant improvement. If it does improve, bump it up another 2 sizes and see where it goes.
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Tech Contributor
Joined: Aug 1999
Posts: 14,374
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From: At my Bar drinking and wrenching in Lafayette Colorado
If I sent back every bad part I bought, I'd never get a car built. It sucks, but this is the 50% hobby: Only half the parts you buy will fit or work right. You can spend all your time sending junk back and deal with the frustrations, or you can just fix it and move on. When you've been in this hobby long enough, you just fix it and get the car running. My SawZall, hammer, cutoff wheel and welder are my favorite tools.... can't make parts fit without this stuff.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
If I sent back every bad part I bought, I'd never get a car built. It sucks, but this is the 50% hobby: Only half the parts you buy will fit or work right. You can spend all your time sending junk back and deal with the frustrations, or you can just fix it and move on. When you've been in this hobby long enough, you just fix it and get the car running. My SawZall, hammer, cutoff wheel and welder are my favorite tools.... can't make parts fit without this stuff.
He has choices. He could get GM, DUI, or Mallory.
I restored my 1st car when I was 16. I have even been in the business, and have close friends still in the business.
I am now 51, and I still would jam it up.........
We are both correct. It's just philosophy.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
I recently got a new hei distributor throught the group purchase here on the forum. The vacuum advance does not seem to work. It does not hold vaccuum and it doesn't advance anything. I have checked this holding the engine steady at 2500 rpms. It has one of the adjustable vacuum canisters on it. I didn't know if this is something that could be adjusted or if I should just replace the canister. My thought was that it needs to be replaced if it doesn't hold the vacuum.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
I have nearly 23 inches of vacuum when at a steady 2500 rpms. Is this too much? Also, when I am cruising I get a very slight chug. Could this be from not advancing at cruise or is it more likely a carb tuning issue? I have recently replaced my carburetor.
Thank you.
Read these two instructions.
http://www.cranecams.com/pdf/210g.pdf
http://www.cranecams.com/pdf/210g2.pdf
You can test with a hand vacuum pump or from another car and long hose with dist cap off to see if the diaphram is blown.
