I just bought an msd ignition system for my 89 5.8....as for spark plugs I was going to get the accel U groove copper plugs, they have a heat range of 4. I know nothing about heat ranges...anybody on here that does? I have no idea what the stock plugs heat range is. I bought the whole setup, msd billet dist, ford racing 9mm low resistance plug wires, I already have the msd 6a box, and a Pertronix flame thrower 60k coil. I dont wanna be putting to hot of a plug in there and frying something.

 

Best to email msd and ask what heat range and give what setup you use, I use ac rapidfire plugs in my big block with 7AL or a crane fireball. I look in the book and whatever is recommended for my motor I use, never had a problem, also autolite plugs are the best for heat ranges, and no accel, no jap plugs in my Fords.

 

I would NOT use Accel plugs....go with the Autolite Double Platinum....much better plug and will last 10 times longer....

I know...I used to be a hardcore Accel plug fan...got tired of changing dead plugs...they are cheap and foul very easy and dont come back once fouled...

if you havent raised the compression much over stock stay with the factory heat range....I drop 1 range for 1 point of compression...IE: 8:1-9:1....