Converting Distributor to Vacuum Advance?
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Converting Distributor to Vacuum Advance?
Hey guys, I wanted to upgrade my ignition system to go with my Miniram and AFR set up.
I plan on purchasing the MSD 6AL2 ignition box along with a D.U.I. Vacuum Advance HEI distributor. The distributor part number is 12720.
What would I need to make this change? Would I have to make any modifications to the wires to get the tach to work or anything?
Is it possible to remove the EST in the tune?
The car is a 1985 with an 870 ECU.
Thanks!
I plan on purchasing the MSD 6AL2 ignition box along with a D.U.I. Vacuum Advance HEI distributor. The distributor part number is 12720.
What would I need to make this change? Would I have to make any modifications to the wires to get the tach to work or anything?
Is it possible to remove the EST in the tune?
The car is a 1985 with an 870 ECU.
Thanks!
Burning Brakes
Joined: Jun 2000
Posts: 865
Likes: 6
From: Auburn Michigan
Hey guys, I wanted to upgrade my ignition system to go with my Miniram and AFR set up.
I plan on purchasing the MSD 6AL2 ignition box along with a D.U.I. Vacuum Advance HEI distributor. The distributor part number is 12720.
What would I need to make this change? Would I have to make any modifications to the wires to get the tach to work or anything?
Is it possible to remove the EST in the tune?
The car is a 1985 with an 870 ECU.
Thanks!
I plan on purchasing the MSD 6AL2 ignition box along with a D.U.I. Vacuum Advance HEI distributor. The distributor part number is 12720.
What would I need to make this change? Would I have to make any modifications to the wires to get the tach to work or anything?
Is it possible to remove the EST in the tune?
The car is a 1985 with an 870 ECU.
Thanks!
I don't think you'd have any problem w/ the 6AL2, but by going with a different dizzy, you'd lose the computer's ability to advance or retard the timing. It would then advance due to the weights & vac. in the D.U.I. instead. (I THINK....BUT I COULD BE WRONG).
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
That's what I want
Burning Brakes
Joined: Jun 2000
Posts: 865
Likes: 6
From: Auburn Michigan
Well, f.w.i.w., last summer, I converted my '85 from T.P.I. over to a carb. I put on a standard vac advance M.S.D. hei distributor. Everything seems to be fine. No, I don't have any computer control on the engine, i.e. knock sensor retarding the spark, etc.
Intermediate
Joined: Oct 2013
Posts: 38
Likes: 1
From: ontario ny.
You will have to make sure the stock computer still receives a tachometer signal to keep your air and cruse working. You will also have to tie the 6al tach wire to the tach filter to keep you stock tach working. I just installed the 6al programmable in my 90 and found out the hard way you need a full 12+ switched volts or it will not turn it self on. I had 12.4 at the source and only 11.5 at the box. Bad wire.
Racer
Joined: Nov 2013
Posts: 338
Likes: 8
From: South NewJersey
Not trying to hijack, BUT cohocarl can you elaborate on your carb conversion? How does IT run? is it just as dependable did you do the torque conveter lock up switch "thing"?
Sorry I'm just trying to get as much info as I can, Thanks
Sorry I'm just trying to get as much info as I can, Thanks
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
It receives it's RPM info from the dist reference pulse on the Ppl / Wht wire of the 4 wire connector at the dist base
( which the OP loses with a non CC vac advance dist )
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Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Burning Brakes
Joined: Jun 2000
Posts: 865
Likes: 6
From: Auburn Michigan
Intermediate
Joined: Oct 2013
Posts: 38
Likes: 1
From: ontario ny.
Vetteoz you helped me get mine wired correctly I tied the msd tach wire directly to the ecm (the purple white I believe) and every thing works fine now. Thanks Again.......................Jim S.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
No. But I realized that I need a Distributor Reference Pulse in order for the computer the fire the injectors. So if I want to use this distributor, I'll have to buy a crank trigger, and most of them are around $250.
Does anybody know of a cheap one? Maybe around $100?
Thanks
Does anybody know of a cheap one? Maybe around $100?
Thanks
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
You may find that the non-computer HEI distributor will not fit when you install it. The vacuum advance canister may very well interfere with other components attached to the intake manifold.
I have read that the early HEI distributor housings are larger in diameter than the 85-later OEM Corvette C4 distributors. Could be that that alone will cause a problem.
Check with D.U.I. before you order.
I have read that the early HEI distributor housings are larger in diameter than the 85-later OEM Corvette C4 distributors. Could be that that alone will cause a problem.
Check with D.U.I. before you order.
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
The benefit is that I won't have to tune the timing tables. They take too long and are a hit or miss. I have to guess what load variable is at which RPM, and I have no knock count data, it relies all on ear. This just makes it a lot easier.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 113
From: Michigan
You may find that the non-computer HEI distributor will not fit when you install it. The vacuum advance canister may very well interfere with other components attached to the intake manifold.
I have read that the early HEI distributor housings are larger in diameter than the 85-later OEM Corvette C4 distributors. Could be that that alone will cause a problem.
Check with D.U.I. before you order.
I have read that the early HEI distributor housings are larger in diameter than the 85-later OEM Corvette C4 distributors. Could be that that alone will cause a problem.
Check with D.U.I. before you order.
Racer
Joined: Jan 2014
Posts: 324
Likes: 7
From: Littleton Colorado
It makes more sense to me to convert to an EFI system that is easier to tune and gives better feedback. But, that's just me, I guess.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
It would be easier and cheaper to upgrade the ECM so you don't have to guess.
