The Stovebolt Site Forums The Shop Area Engine Shop 261 Sparkplug gap ....

.... Is what?

AC-Delco R45S


(Ole Charlie receve les bougies nouveaux au jour'hui! )

John, as I recall the gap for standard type ignition is .35 and if you have HEI, I'd say .45 or so.

Probably closer to .035 than .35

Yep, an HEI might be able to jump a 3/8" gap, but it would be a challenge! Thirty-five THOUSANDTHS (.035") is right- - - - -not .35! That pesky decimal point, again!

The higher the secondary voltage the wider the gap, but it tends to eat the wires.

My factory manual lists gap as: .035" - .038" That's for a AC 44-5.

Thanks Geoff!

Jon ... If I had HEI??? Wiseguy, eh?? But while I'm at it, I'm finally going to install that fancy condenser gadget you sent me...

Seems like the guys who specify the gap are using some sort of voodoo. My Buick V6 (HEI, normally aspirated) calls for 0.060! Plugs came out of the box set to 0.045 and that's what I use.

0.035 for points and 0.045 for electronic sounds good. YMMV (really!)

Buick (also Olds and Cadillac) was running those emission control engines so lean that they needed the wide gap in hopes that something combustible was between the electrodes when the plug fired! Cadillac actually specified an .080" plug gap on some engines!
Jerry

Back in the day, I bought a new 1974 GMC K15 when in my senior year of high school. It had the Chevy 350, HEI, must have been one of the earliest light duty GM trucks with HEI. Plug gap on that was .060", non-catalyst, leaded gas, Q-Jet, SM465.

I just typed those numbers like that to see if anyone was paying attention.

.035 for Ac and Champion J12y, And the J12y variants.

I've been running A/C Rapid Fire platinum #7 in my 261 w/ HEI.

HEI....

Charlie would need a "heart transplant" to 12 volts to use any of the HEI systems except the infamous pertronix setup- - - - -and all of us know that thing's about as popular as a good case of hives!

I have never had a problem with using a 6v battery and a 6v Pertronix unit in my 1954 Suburban (with a 1960 261).

Is it possible to convert a 6v system to HEI or is a 6v Pertronix the only option?

FWIW .... Ol Charlie seems to be doing fine on his original 6-volt set up. With the 261 and the 4,10 rear and the 17inch wheels, he's handling highway traffic just fine in the greater Scottsboro area. He cruises the left lane on AL 79 and US 72 just fine. And he climbs up Cumberland mountain with no issues in 4th gear. So I see no need for any conversion to Pertronix or HEI or 12 volts or any of it. 12 volts is just like a V-8 -- work of the Devil.

6 in a row makes it go ... on 6 volts.

And bias plys and Huck brakes. Harrumph!

I'm all in there, John.

Non-detergent oil?

Bear grease for the wheel bearings? How about a hand crank, and an acetylene generator for the headlights?
Jerry

We all draw certain lines in the sand when it comes to our trucks. And I think it’s best if we can all just admit that the lines we draw, probably make sense only to ourselves. Perhaps not even to ourselves.

Case in point….my own internal conflict and inconsistency with my truck’s charging system….

My truck isn’t a factory correct museum piece. It’s mostly period correct for the time that it spent in actual service….through the 70s with its previous owner.

Took me several years to get it back on the road and I’ve not made any huge modifications. But now that it’s on the road, I’m more interested in driving it more often and for longer distances, and like the idea of being able to acquire anything I’d need at any old parts store.

There is pretty much ZERO logical for me to be holding out on converting from 12v generator to 12v GM alternator. More reliable. As common as dirt. I don’t even hate the way they look in the engine bay. Easy fix if I find myself in a bind and far from home when compared to GEN/REG.

But I’m still resistant to the idea of an alternator. For no good reason at all.

There's a sneaky work-around- - - -Keep the "generator" in place as an idler with dummy wiring and a non-functional "regulator" on the firewall, and drive a small alternator off the slip yoke at the back of the transmission to keep the battery charged. As long as the driveshaft is turning, there will be a charge going into the battery.
Jerry

It is a thoughtless and lazy man who doesn't have one of each.
A resto-mod with a V8, auto trammission, A/C, power steering to travel in luxurious comfort.
A basically stock looking one with inline Stovebolt engine with some upgrades to be able to drive 70 MPH and still pull stumps, maybe while driving 70 MPH. (haven't done the stump pulling and then drag it behind at 70 yet. Bucket list.)
And one built bone stock as original.
I'm currently in the process of building the latter.

Sounds like a hassle….managing all those different plug gaps, Carl.

At least Carl is only managing a V-8 and a Stovebolt, not, say, a Convair B-36 with 336 spark plugs ...

I first read that and assumed you misspelled “Corvair” and that 336 was the part number for some oddball spark plug.

Then my dummy brain realized what you were referring to, which sent me on a reading mission.

Lordy, what a nightmare design. My wrist would be awfully sore after I pretended to properly torque 336 spark plugs.

168 cylinders- - - - -2 plugs each! Then there's the 4 jets, with a couple of igniters for each one!
Jerry

I've forgotten a lot but still remember seeing a B-36 flying overhead as a kid. That was something different, for sure

Dennis

Just a friendly reminder...You guys realize you've veered far from the original question. Just doing what they pay me so handsomely to do here.

Maybe I can help put it back on track, lol, .035 for the plug gap with stock type points distributor.

Thanks Jon. New plugs have been in for awhile now. A couple of trips out, even. .035 seems to be working. Imagine that...