MSD 6A and distributor.
Thread Starter
Instructor
Joined: Jun 2005
Posts: 156
Likes: 0
From: Liverpool NY
MSD 6A and distributor.
I'm using an MSD HEI distributor on my 350. The engine has been modified...heads, intake, cam and carb. I am getting some conflicting opinions in regards to using an MSD 6A box with this distributor.
I'm told that the distributor has a built in rev limiter (?) and this makes the box innefective.
I dont really know what HEI or a rev limiter is and why they wont work together. It seems to me that the box would be beneficial.
Does anyone have any thoughts on this situation?
I'm told that the distributor has a built in rev limiter (?) and this makes the box innefective.
I dont really know what HEI or a rev limiter is and why they wont work together. It seems to me that the box would be beneficial.
Does anyone have any thoughts on this situation?
Instructor
Joined: Sep 2003
Posts: 119
Likes: 1
From: Part breakage is just weakness leaving my Stingray
I don't know all the details of your distributor, but HEI stands for High Energy Ignition. These distributors usually have the coil built into the top of the distributor rather as a stand alone unit. I'm not sure if there is a build in rev limiter.
Rev Limiters are used to prevent over reving the engine by controling the spark and therefore the ignition of fuel. The MSD units have a fuse like unit that is plugged into the box. There are different "fuses" for pretty much any max rev range that you choose. I think that they are available in 200 RPM increments. I have mine set at 6000.
Rev Limiters are used to prevent over reving the engine by controling the spark and therefore the ignition of fuel. The MSD units have a fuse like unit that is plugged into the box. There are different "fuses" for pretty much any max rev range that you choose. I think that they are available in 200 RPM increments. I have mine set at 6000.
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
I had the same distributor in my 540 when it was in my boat, it ran great and no need for the 6al box that msd has a rev limiter built in.
Check on MSD website for a download on the instruction manual for that model and you will see that if you remove the cap there are dials under it and you can set it to where you would like your motor to redline at or cutout for a overrev type protection.
I know it works cause I bumped a few times in boat when it came out of the water
Check on MSD website for a download on the instruction manual for that model and you will see that if you remove the cap there are dials under it and you can set it to where you would like your motor to redline at or cutout for a overrev type protection.
I know it works cause I bumped a few times in boat when it came out of the water
Advanced
Joined: Sep 2006
Posts: 84
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From: Hickam AFB Hawaii
Keep the box. MSD means Multiple Spark Discharge. The box will give you multiple sparks to burn fuel more completely. The 6A box does not come with rev limiter. The 6AL box does have rev limiter. Since your distributor has rev limint you are good to go with the 6A box. I would hook it up, if I were you. You should see small improvements in both power and fuel economy.
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Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
You might get a concensus if you would specify exactly which msd DIST you have ... what is part number of msd dist?
Some msd dist require 6 box (or similar CD box) while other msd dist don't require a CD box at all.
Some msd hei have a rev limiter built into the module (aka ignition amplifier), others don't. None of the older msd hei did. When was yours first purchased NEW?
If dist is truly an hei w/ coil-in-cap, and you wish to connect a 6 box (or similar CD box) ... you must first remove or bypass the module ... that would nix any rev limiter you MIGHT have in module. There are 6 boxes that have a built in rev limiter ... ie 6AL. There are also separate discrete rev limiter boxes that do only that.
Unless your motor REQUIRES a CD box, I don't recommend a CD box for vast majority of street cars. CD Box adds very little performance to a properly tuned street motor but does introduce another gateway for failure/stranding.
What is p/n of your msd dist? And when was it first purchased NEW?
call msd but first have your ducks in a row.
Some msd dist require 6 box (or similar CD box) while other msd dist don't require a CD box at all.
Some msd hei have a rev limiter built into the module (aka ignition amplifier), others don't. None of the older msd hei did. When was yours first purchased NEW?
If dist is truly an hei w/ coil-in-cap, and you wish to connect a 6 box (or similar CD box) ... you must first remove or bypass the module ... that would nix any rev limiter you MIGHT have in module. There are 6 boxes that have a built in rev limiter ... ie 6AL. There are also separate discrete rev limiter boxes that do only that.
Unless your motor REQUIRES a CD box, I don't recommend a CD box for vast majority of street cars. CD Box adds very little performance to a properly tuned street motor but does introduce another gateway for failure/stranding.
What is p/n of your msd dist? And when was it first purchased NEW?
call msd but first have your ducks in a row.
Last edited by jackson; Apr 16, 2008 at 11:19 AM.
Thread Starter
Instructor
Joined: Jun 2005
Posts: 156
Likes: 0
From: Liverpool NY
OK, the distributor is an MSD 8365 (with limiter) and the box is an MSD 6A (without limiter).
I have the instructions but am still not sure how to hook this damn thing up.
how do I post a photo in this?
I have the instructions but am still not sure how to hook this damn thing up.
how do I post a photo in this?
Burning Brakes
Joined: Jul 2006
Posts: 1,047
Likes: 12
From: SoCal
Have you tried the MSD website?
This is from the MSD website: "If you did not find a schematic to match your application, or if you need assistance, please contact MSD Tech at (915) 855-7123 or e-mail us at: msdtech@msdignition.com" - they can probably answer your questions, especially since you're asking about hooking the 6A box up to an MSD HEI distributor.
This is from the MSD website: "If you did not find a schematic to match your application, or if you need assistance, please contact MSD Tech at (915) 855-7123 or e-mail us at: msdtech@msdignition.com" - they can probably answer your questions, especially since you're asking about hooking the 6A box up to an MSD HEI distributor.
Last edited by VCuomo; Apr 16, 2008 at 09:00 PM.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
That 8365 is a true HEI ... as I said before you must remove or bypass the module in order to connect 6A box and as I said you will lose the on board rev limiter. I suggest not using 6A box ... the 8365 dist is plenty hot enough for about any street car. Look in the 6 series instructions for a GM "4 pin" HEI ... that shows a general schematic for connecting 6 box to HEI ... again I would not use the 6 box ... again 8365 is plenty for most.
