I have 11.5:1 compression and a MSD pro billet distributor with 6al box. What should i gap my plugs at. Also I have an automatic trans and Ive heard that a vacuum Sec. carb is better then a DP for auto. What do you think? I have a Holley 650 DP with a proform center section and a Holley 750 with vacuum sec. just curious on which would be better for my application

 

That's a lot of compression. I'd start around .035" (always a good starting point) and then maybe try to go up a little from there. .045 max, I would think to keep from chewing up ignition parts on a regular basis.

 

I have a similar setup and I gap my plugs at .040...so somewhere around .035-.040 is a good starting point. I would definately not recommend a vac. secondary carb for your combination, go with a mech. secondary dp carb you won't be disappointed.

 

I was going to gap them at 45 and use the DP, but i called summit tech line to see what they suggested. They told me to gap the plugs at 55 and use a Vac. Sec. carb. I wasnt sure if that would be right so i posted up on here.

 

just curious, are you SURE about that compression ratio? like what heads are on it? I'd think you'd need dome pistons and teeny heads for that.

I think .055" gap and vacuum secondary is a very bad idea for you.

Might want to use iridium plugs after you've got the car dialed in

 

Normally double pumpers for automatics are not recommended, due to throttle issues at low rpms. Since you have an aftermarket stall (Jegs 3200-3600 stall). I do not see any problem with it. I plan on running a 750 DP on my new 383.