ProMag spark plug gap

Hey guys,

Curious to know what gap everyone else is running with their promag. Combination is a blown alcohol BBC, 11:1, 8:71, dart 360 heads, 22-25 lbs of boost, ProMag 20, ngk R5671A-9. We're currently running .030. The reason i ask is the car takes a while to start. It has plenty of cranking RPM and never fails to start, but just takes on average about 15-20 seconds of cranking. We've tried varying the amount of gasoline we prime it with but it doesn't seem to have an effect. Car runs perfect after it starts, i'm not looking to change it's performance, just make it easier to start. Any and all ideas and advice are appreciated!

Chris

 

.017 on the plugs,and .070 on the crank trigger. I watched a guy pickup .4 tenths changing the plup gap from .030 to .018 with a 20 MSD mag.Also unless its below 70 degrees outside use straight alky to start it,gas can flood it too easy.
-Dale

 

Dale, thanks for the input. I don't run a crank trigger, just the mag off a Summers drive. Would shrinking the gap change the heat in the plug for the run? Would i be correct in thinking the larger .030 gap might be the root of the starting issues? Thanks again! MSD tech was useless.

Chris

 

Changing the gap doesn't change the heat in the plug. I run .015.

 

we run .016 on blown hemi with a mag 20....spin the motor for 2 sec. it's running.
Darren

 

.016, everyone has a different number but most are between 15-17 as far as the slow start Its easy enough to find out, who knows maybe the priming mixture has to be at just the right point to fire the big gap. I find adding some gas to the alky works best cold engine cold day 80% gas/ hot engine cold day go to 50/50

During the summer first cold start 25% gas then after the first start I just keep on topping the primer bottle with alky during the day...worked for me

Richard Gavle

 

i would tighten the gap up 16 thousands is a good number batterys need to spin it fast are it wont fire right try killing it before you run it all the way out of fuel so the pump dont have to prime its self each time that may help also if you are using alky make sure to give it a big enough drink to get all the way down to the cylinders with gas not so much it will flood easy and you will have to crank the shit of it to start it then the batterys star to get weak and tha causes another problem not enough cranking rpm

 

That is definatly why it is hard to start.I run my gap at 18. and it fires right up.

 

Running almost same combo,mag 20 etc, should run .015-.018 on gaps also you need at least 250 rpm's to fire mag. I would check into a 24v starting system. Helps alot! Vinnie.

 

Thanks for all the replys. I'll start knocking the gaps down to .015-.018 and see how we make out. I appreciate all the advice!

Chris