HEI vs VR and VB921

BottleFed70 · Post by **BottleFed70** » Mon Jul 31, 2006 5:10 pm

MSII,V3PCB,2.36firmware - 1970 mustang with 5.8L(351 Windsor) V8

Fuel only has been working great so it's time to start controlling spark.

My distributor is pretty old and I want to replace it with a new one as part of the conversion.But I can't decide if I should go with a HEI (coil in cap style) distributor, or with a distributor using VR outpuy along with external coil driven by VB921. Can anyone offer some advice? I'll list the advantages of each setup and would love to hear any other advantages/disadvantages of each.

Advanages of HEI:
- Neater package
- Limp home mode is a plus
- Don't have to worry about dwell settings (I think?)

Advantages of VR output with VB921 direct coil control:
- Cheaper (already have the coil)
- Factory appearance
- Dwell control might be handy

Here's the HEI style distributor I'm interested in: http://www.procompelectronics.com/Files/1.html

Here's the VR output only style distributor I'm interested in: http://www.procompelectronics.com/Files/4.html

Anyone have any suggestions or comments?

krisr · Post by **krisr** » Tue Aug 01, 2006 12:05 am

Having your distributor up the front, clearance isn't an issue. If it was my 351, i'd go with the HEI distributor but retrofit a 7pin module. I've seen pictures of a guy that did it on a Pontiac HEI dissy and looked really clean. I think he filled the holes where the 4pin screws down with JB Weld and drilled/tapped to suit the 7pin. Just tack weld the centri-advance shut or lock it somehow and you're set.

When I bought a Pro Comp HEI for my Pontiac I found a few things wrong with it but note worthy for others so they can check theirs..

1) Button inside the cap had extremely high resistance. From memory MSD makes a low resistance button.
2) Gear was undersize which translated into 3° slop at the crank! Had to replace with an OEM gear.
3) Roll pin to hold the gear looked like a paper clip wrapped around itself and nowhere near the right duty to drive a high pressure oil pump

Edit: I found this on the Pro Comp site, which is probably exactly what you want... http://www.procompelectronics.com/Files/5.html

PSIG · Post by **PSIG** » Tue Aug 01, 2006 12:57 am

Hi! Devil's advocate here.

If you want new and clean a reman distibutor is about $35 (w/o vac cannister) and you could even pop a PerTronix in there for electronic triggering. New stock looks. Cheap. Easy. Reliable.

Or how about popping a Mallory dist plug (or mod your old dist) in to drive the oil pump and go EDIS? When's the last time you saw a distributorless Windsor? A pair of coilpacks on the firewall... And although the code is buggy right now, you'd be set for dual EDIS4 which puts it in to multiple spark discharge land. That's where I'm headed with my 427W.

I'll

now.

David

BottleFed70 · Post by **BottleFed70** » Tue Aug 01, 2006 10:57 am

krisr wrote:Having your distributor up the front, clearance isn't an issue. If it was my 351, i'd go with the HEI distributor but retrofit a 7pin module. I've seen pictures of a guy that did it on a Pontiac HEI dissy and looked really clean. I think he filled the holes where the 4pin screws down with JB Weld and drilled/tapped to suit the 7pin. Just tack weld the centri-advance shut or lock it somehow and you're set.

Thanks for the info!

What are the advantages of going with a 7-pin module? I thought they were all the same asside from how they were wired into the car.

I understand there are 4,7,and 8 pin HEI modules...this sounds like it may be more confusing than I thought.

BottleFed70 · Post by **BottleFed70** » Tue Aug 01, 2006 11:02 am

PSIG wrote:Hi! Devil's advocate here. If you want new and clean a reman distibutor is about $35 (w/o vac cannister) and you could even pop a PerTronix in there for electronic triggering. New stock looks. Cheap. Easy. Reliable.

Or how about popping a Mallory dist plug (or mod your old dist) in to drive the oil pump and go EDIS? When's the last time you saw a distributorless Windsor? A pair of coilpacks on the firewall... And although the code is buggy right now, you'd be set for dual EDIS4 which puts it in to multiple spark discharge land. That's where I'm headed with my 427W.

David

Thanks for the suggestions. I've already got the pertronix in my existing distributor.. so I suppose that's an option. I'm just not sure how much I trust the pertronix for timing accuracy. So many choices!

I think I'll stay away from EDIS for now...and go straight to COP once it's supported in the regular MSII code/router box. I'd like to keep it simple for now until I get confident with spark control and have some tuning done.

BottleFed70 · Post by **BottleFed70** » Tue Aug 01, 2006 12:23 pm

OK I did some research and there are 3 common HEI modules.

4-pin which does not allow for computer timing control.
7-pin which does allow for computer timing control.
8-pin which is essentially the same as the 7-pin but designed to be mounted outside of the distributor along with an external coil. These are for the "small cap" style distributors.

HEI uses a distributor with VR sensor, so I guess my question comes down to wether it's best to use an HEI module, or the V3PCB VR input circuit along with VB921 coil driver?