When and why would it be necessary to gap your spark plugs this high? I'm currently running AC Delco R45TS plugs and was told by the mechanic who built my engine to run the gap at 55. The car runs good but wanted to get some other opinions on this matter.

No need to open them that much.....45 is fine.....

I tried mine with more than .045 and it didn't run as well as with the recommended .045 gap.

Newer vehicles are going to .060, but they have an individual coil very near each plug.

Wider gaps are supposed to be advantageous, but only if you have enough power to jump the gap effectively.

cjlandry, you actually answered a question I was going to ask about plug gap with the vortecs

Thanks

Jerry

the greater the compression, the less gap you can run. I am running between .025 and .030" 11.6:1 BBC with MSD and 50,000 volt coil

on my 396 a few race seasons ago i was playing with my plug gap........11.7 to 1 compression...........for nitrous i ran a .035 gap and it was left there for years weather i ran nitrous or not.......but during a testing session at the track i open them up to .060 for the hell of it and on my next pass i gained 1.3 mph and dropped my e.t. .15 thru the traps i made another run to make sure and it was solid gain..........and i dropped the gap down to .035 and it slowed back down........so i put them back to .060 and ran it the rest of the day.....but i had a msd 6AL box with a hei unit sporting an accel coil...........

i had read before opening the gap can give you a gain and also sniping off the spark plug "strap" was good for more gain.....for last ditch effort for bettering your e.t. and mph........but it also said that it was hard on the ignition system.........i never tried going that far......but there seems to be some gain for certain set ups.........testing is the only way to find out........i guess.......

I had the same results as ddeennis. Now all of my street cars run atleast .060 gap. They all have good plug wires and HEIs or clones of them.

I've always seen the best e.t. out of my cars when the plug gaps are as wide as I can run without it missing. I open them to .045 and then add .005 at a time till it misses and then back off about .010. It always runs best with a big gap and indexed plugs.
However, the ignition system MUST be in first class condition. The best wires with sleeves, careful routing, dielectric silicon on the plug terminals and dist terminals, indexed rotor, etc.

In Stock Elim. cars, they clip off the ground electrode for a one shot qualifying pass if they need a couple hundredths to make a field. But it is EXTREMELY hard on the ignition system with the grounds clipped away.
Food for thought!

Randy

I haven't tried the .060 gap since switching to the MSD Superconductor plug wires. Might be worth a shot.

In the early releases of the HEI, there were some GM applications that stock specifications were .080! It is my understadning that there were some reliability issues (coils) so the gpa was later reduced by service bulletins and such.

I am not a racer, but on the street I have had no issues with .060. (stock HEI with Accel coil), but I have alower compression.

If I understand correctly, the voltage output of the coil increases with the gap size. (If you have a rated coil for 50,000 volts, but the small gap only needs to 35,000V to jump the gap, that is all the coil will output). However, the larger gaps, and therefore higher voltages, are harder on the coil. My 2¢ perhaps others can clarify better....

Exactly what Ron said, the bigger gaps work the coil much harder. Once again, a pref v. reliability thing. FOr a street car that you're not trying to shave tenths off ET with, why bother.