MSD on a 91 4.0l

I want to put a MSD on my 91 4.0 but I dont know what one to use, does anyone have any sugestions.

MSD 6A.

Save your money, though -- you will not notice any significant difference.

Spend you money on a tune-up, plugs, wires, and beer.

yeah MSD is way to pricey

I ran the MSD 6 offroad in my XJ. had a few problems with it but I think it was due to the fact that I mounted it upside down to the hood.
No difference! Yeah right. try BIG DIFFERENCE in my 94' 4.0. here is what I noticed...
Smoother idle, better fuel economy, More Power.
the idle and fuel economy I noticed right away. the power wasn't so much noticable of a gain but when I went back to stock it was a noticable loss.
Gonna try and put it back into my MJ since thats where I want the power.
And the $200 ish that it cost on summit racing... I think its worth it.
compare it to the cost of a K&N intake, the gains are better with the MSD.

I agree with Raw. I have a MSD 6AL box on my 91 XJ with a 4.6L stroker and immediatly noticed a better idle. Fuel economy increased by 2mpg on my truck. I did notice some power gains when I went to the dyno, I think it made 3hp and 5ftlbs of torque over stock with the factory coil and standard wires. Not significant gains, but the smoother idle and fuel economy was worth it for me.

AARON

Do the PN6470 Offroad Ignition Check This site even comes with performance cables... MSD IGNITION

So I've recently upgraded to the accel cap, rotor and coil and magnecor 8.5 wires and autolite plat plugs. Is the 6 gonna make a lil difference or a lot since I've upgraded these other parts?

gradon said:

So I've recently upgraded to the accel cap, rotor and coil and magnecor 8.5 wires and autolite plat plugs. Is the 6 gonna make a lil difference or a lot since I've upgraded these other parts?

Click to expand...

What you have upgraded is the path of spark to the combustion chamber. An MSD box is Multiple Spark Discharge, It kicks out multiple sparks, (about 6 at idle) to fully burn fuel in the combustion chamber. It kicks multiple sparks till about 3000 RPM where it is 1 to 1 for spark like stock.
I have put one on my XJ and really didn't notice much improvment. I have a mild worked head, header, bored tb, intake, map mod, iac mod, ect...
I have 2 of them on other vehicles we own and you can tell right away the difference they make as far as fuel milage and a bit of pep.
i still have my msd 6 I might re-hook it up to the XJ and do some testing if I can find time...

thanks for the tips i think i am going to get that msd 6 offroad and see how i like it.