Mechanical Advance Distributors
Melting Slicks
Joined: Jan 2000
Posts: 3,326
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From: home
In another post, OP is having an engine built. He is planning to eliminating the ecm, ecm controlled distributor and carb. Engine builder is insisting on using a mechanical advance only distributor.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If the builder “insists” on it, have him give a solid reason why.....
Jebby
Race Director
Joined: Jul 2015
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From: SW Florida.
No vacuum advanced works just fine. In a boat, and at the drag strip. Any setup where you actually want to continue going after you've lifted you foot off the gas, you have to have vacuum advance or some kind of computer controlled part throttle advance.
Last edited by derekderek; Sep 12, 2019 at 10:26 AM.
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Thread Starter
Instructor
Joined: Jun 2019
Posts: 232
Likes: 14
What's happening, is that the guy building my engine, says he is going use the existing ECM distributor in the '81 Vette and convert it to mechanical advance to run the ECM deleted engine. He is putting an AVS2 Edelbrock on a 2701 intake and instead of a regular HEI dist, he is going to use the stock distributor with a kit to convert it.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
What's happening, is that the guy building my engine, says he is going use the existing ECM distributor in the '81 Vette and convert it to mechanical advance to run the ECM deleted engine. He is putting an AVS2 Edelbrock on a 2701 intake and instead of a regular HEI dist, he is going to use the stock distributor with a kit to convert it.
Converting the distributor to mechanical and leaving out the vacuum advance is not a good plan.
https://www.rockauto.com/en/catalog/...stributor,7108
Purchase the new distributor....install and time it correctly and hook the vacuum advance to full manifold vacuum....you will thank yourself later.
The vacuum advance is there at idle and under light load conditions to help boost mileage and responsiveness and it is a big deal on a street car.
Jebby
Safety Car
Joined: Oct 2004
Posts: 3,926
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From: Youngstown Ohio
A distributor like mine is not for low RPM or fuel mileage, neither of which matter to me. Strictly high performance street/strip application here.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
OP
Don't let him bastardize-rig your '81 HEI ... get another one like was OE on '75 thru '80.
Most street motors with carb and No computer need Both Mechanical & Vacuum advances ... as '75-'80
Don't let him bastardize-rig your '81 HEI ... get another one like was OE on '75 thru '80.
Most street motors with carb and No computer need Both Mechanical & Vacuum advances ... as '75-'80
Racer
Joined: Jan 2008
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From: Arvada Colorado
Race Director
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Race Director
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From: Napa Valley California
The engine builder helping me set up my 496 discouraged me from going with just mechanical advance on my MSD.
He said he can set it up to work, but told me that since I’ll be using my car on the street, I and the engine will be much happier with the vacuum advance set up.
You are getting excellent advice here from those who are professionals in their field and really know these cars.
I never used vacuum advance on my drag boats, but racing is a whole different animal than street driving, even if you plan on driving it hard on the streets.
He said he can set it up to work, but told me that since I’ll be using my car on the street, I and the engine will be much happier with the vacuum advance set up.
You are getting excellent advice here from those who are professionals in their field and really know these cars.
I never used vacuum advance on my drag boats, but racing is a whole different animal than street driving, even if you plan on driving it hard on the streets.
Thread Starter
Instructor
Joined: Jun 2019
Posts: 232
Likes: 14
All is Well
I went over to the builder and he wasn't there. Spoke with the mechanic actually doing the build. He agreed with me that the dist should be vacuum advance. The owner has a high performance, racing mentality and I got it across to the mechanic, and he agreed, that I want a good efficient driver that has a little extra initial acceleration and decent milage.
Probably going to have around 12 initial with 32 total.
Probably going to have around 12 initial with 32 total.
Race Director
Joined: May 2006
Posts: 18,728
Likes: 2,579
32 total?
I went over to the builder and he wasn't there. Spoke with the mechanic actually doing the build. He agreed with me that the dist should be vacuum advance. The owner has a high performance, racing mentality and I got it across to the mechanic, and he agreed, that I want a good efficient driver that has a little extra initial acceleration and decent milage.
Probably going to have around 12 initial with 32 total.
Probably going to have around 12 initial with 32 total.
are you using aluminum heads?
what compression ratio will the engine have?