HEI in a 71

[racefan]

I have a 1971 Elk. I am thinking about putting an HEI dist. in it. I have heard that sometimes the dist. will hit the firewall does anybody know if this is true?Also are there any other problems known of? thanks, Mike

[dennis68]

Not in a bodies, some nova's and camaros have firewall interfierence but A bodies have lots of room

[Tommy]

You should not have any clearence problems. Just remember to use a new wire for power. Your stock wire will not handle the power requirements of an Hei. A Hei is a good choice for power & reliablity.

[Mrapii]

Yes Tommy is right about the wiring. Do not use the old ignition wire because the voltage goes thru a ballast resistor which reduces the voltage. The engine will start and run but the spark output will be low and the engine will run poorly. Trace the wire and remove the ballast resistor or you can bridge across it.

[Mama Mayhem]

I have a GM HEI in my 71, there is not a lot of room left but it fits fine. I also put in an MSD HEI kit (cap, coil, rotor, module) that I bought from Summit for about $139, works great. But you definitely need 12 volts to the dist, and don't try running too far on low voltage (bad alternator) with the MSD, it requires lots of juice.

[ElkyPete]

Originally Posted by Mama Mayhem

I have a GM HEI in my 71, there is not a lot of room left but it fits fine. I also put in an MSD HEI kit (cap, coil, rotor, module) that I bought from Summit for about $139, works great. But you definitely need 12 volts to the dist, and don't try running too far on low voltage (bad alternator) with the MSD, it requires lots of juice.

I have the MSD 6A they call it the HEI Super conversion kit. According to the manual the MSD ignitions will run on as little as 5v DC. Maybe that is not true for the normal HEI kit or maybe the manual is just misleading the user?

[Mrapii]

Maybe the MSD box will still work at 5v but I doubt very much the ignition coil would function at that low voltage and provide enough secondary voltage to the sparkplugs to fire them. If your electrical system only puts out 5v then you better fix it.

[ElkyPete]

Originally Posted by Mrapii

Maybe the MSD box will still work at 5v but I doubt very much the ignition coil would function at that low voltage and provide enough secondary voltage to the sparkplugs to fire them. If your electrical system only puts out 5v then you better fix it.

If the ignition will run on from the trickle voltage through the Dash Alternator light, when the key is in the off position, then I would say the statement made by MSD about needing as little as 5 volts is true and they are not talking about power just to the MSD Electronic Module Box.

Racers use only a Battery no Alternator. I am sure that in some cases by the end of the night it is possible to have a very small charge left over and it could be as little as 5V.

However I would feel comfortable knowing that in the event my Alternator goes out on a rainy night that I'll have a little extra from the ignition to help me get to someplace I can fix it. I don't think their point was that you "should run it at 5V". just that if it happens then it will still function.

[Mrapii]

MSD makes good stuff, if they say the ignition will still work at 5v then I'll believe them. But I know my electric fuel pump won't so I'll have to fix the charging system anyway.

[Mama Mayhem]

Ever notice that almost all the Nascar stock cars run MSD ignitions and when one loses the alternator they end up losing the race, voltage in translates directly to voltage out. It might well run on as little as 5 volts, but it won't run good or far. I a problem with pulley trouble for a while and kept losing belts and I could nurse it home from a futher distance with the stock HEI than I could after I converted to the MSD. That's why I said about having a good alternator and battery.

[Mrapii]

The fact that an MSD ignition will operate on as little as 5v is interesting but not really helpful. Many mechanics think that the car's electrical system runs off of the battery which is incorrect. The battery is there to store electricity to start the car only; when the engine is running the electricity is provided by the alternator. Drag racing cars sometimes use only a battery but it is kept fully charged. Go thru the pits and you will find that many racers now use very small racing alternators or 16v batteries because they need to keep system voltage at 12v. We street rodders need to keep voltage above 12v because ignition systems, electric fuel pumps and cooling fans don't work well much below 12v.

[MI2600]

When I bought my '72, it had an HEI in it. The problem was it was so close to the firewall I couldn't turn it to set the timing. I went back to a points type.

[John_Muha]

Originally Posted by MI2600

When I bought my '72, it had an HEI in it. The problem was it was so close to the firewall I couldn't turn it to set the timing. I went back to a points type.

I have a GM HEI in the 72 350/350 Elky. Came out of a 78 truck. There is about 1 inch between the rear of the unit and the firewall. Biggest problem I have is trying to get a wrench under it to adjust it.