Hello,

Just after some comments as to what is the best gap to run on the plugs in a 1986 5L (305) TPI Ponitac Trans Am.

I have the orginal Service manual, and would you belive it is not in there! An aftermarket book I have claims 25 thou (0.64mm). I find that so hard to belive that such a small gap on a high output electronic Ignition system is right! I have set them up to 44 thou (1m), but I wanted to hear from what everyone else is running or even if there is a size that give problems.

Thanks.

 

When I bought plugs from Napa the gap was on the receipt. My 3.1 is gapped at .030, .025 doesn't sound unreasonable.

 

Really! See I would think thats way to small for a big electronic ignition spark.

I would say 40 - 45 thou is about normal, but I have also heard of some Ignition systems running 60-65 thou so I dont know.

 

it's either .035 0r .040 depending on which year and manual you look at.

 

Well I would think that 40 is a good size gap for Electronic Ignition.

The reason I asked (I'm sure some have said "why is this guy so worried about the gap size") but see there was a model Holden here a few years ago that had a slightly smaller gap then the older and newer models inthe same run. If you used the more conmen pug that had the larger gap in these models you had intermittent idling problems. It had, and still does have people changing Coil packs, leads and even fuel pumps and regulators to fix it. It was and still is a commen mistake that the plug that fitted all the other models before and after this one year get installed, and most times you will have un-explainable problems.

I wanted to make sure I had my TPI set up spot on and wanted to make sure something like this does not play up on them. See the TPI's were never used out here, so no one knows any of the finer detail, so that's why I have had to annoy you all with my silly questions chasing perfection.

Thanks to all that offered help. I really appreciate it.

 

Well for me, the spark gap was on a decal on the underside of the hood, you know also near the decal that shows the vacuum routing. Mine is supposed to be .035 but with high output coil, I changed it to .040 and it ran perfect. So Im sure that .040 is perfectly fine, as long as you have good tune; coil, cap, rotor, plug wires etc.

 

.035 to .040 should be fine.

 

xpndbl3 what size rear wheel are this? what's the back spacing?
I'm buying the same wheels but I don't want then to come out of the wheel well.

They look very nice!!!