spark plug gap with HEI dizzy

[old Chevy guy]

If I have an HEI distributer should I have a bigger gap in the plugs than if I had points? I think my newer trucks with HEI plugs were pre gapped at something like 45 but if I remember right old point stuff was like 24. My trucks had an HEI for a while but as I was about to put in the plugs today it occurred to me that I had never thought about that before and just put in what I was given. If it should be a bigger gap what should that be? Can anybody tell what the difference would be? thinking it will be a hotter spark jumping a larger gap but....?

[enaberif]

0.045 is a good setting for hei

[71CHEVYSHORTBED402]

If I recall a pinch more than what it would otherwise be for your points.

Now if I could just remember what my timing should be.

[Stocker]

Yup -- .035 for points, .045 for HEI.

[EvanR]

As with everything its about the sweet spot. The benefits to bigger gap is that it ignites the fuel quicker, resulting in faster, more reliable starting and a more powerful burn. but too big and you can burn up your coil or even cause a misfire. A standered HEI is 35,000 volts and should be set at .45 spark plug gap. Whats the output on your coil?

[old Chevy guy]

Should just be stock standard. It just the factory coil in the top of the cap.

[Fitz]

Originally Posted by old Chevy guy

Should just be stock standard. It just the factory coil in the top of the cap.

The instructions from GM for my crate motor with that cap specify 0.038. for plug gap.

[LPoole]

Originally Posted by Fitz

The instructions from GM for my crate motor with that cap specify 0.038. for plug gap.

yeah .038 is what O'reileys quoted me when I put in a set of AC Delco plugs just a few weeks back.

['68OrangeSunshine]

Don't assume any plugs are ''Pre-Gapped''. A good thump on the loading dock, and a gross of plugs are all out a couple thousandths.

[GRX]

Originally Posted by '68OrangeSunshine

Don't assume any plugs are ''Pre-Gapped''. A good thump on the loading dock, and a gross of plugs are all out a couple thousandths.

^^ x2. Never had a set where they were gapped all the same out of the box.

[VWNate1]

FWIW ;

Back when HEI was a new thing in 1975 , GM told us to use .060" .

It turned out this made the engine run GREAT but chewed up rotors and caps pretty quickly so the decided .045" was a good middle ground .

My 1969 C/10's 250 CID i6 burns a quart of oil every 150 miles and fouls plugs to missing by 200 miles so I added an stock HEI and began experimenting with plug gaps ~ I now run .070" and have no smoke , little burned oil smell and don't foul the plugs any more .

So far the Junk Yard 1977 HEI has help up just fine , over 20,000 daily driven miles sans problems .

Even breaker points ignitions should be gapped to .035" , you'll feel the power .

[71K20chevy]

I'm running .045 on mine.

[old Chevy guy]

I just set them at 45 and put them in so I hope that will be fine. I going to post another thread about what wires do I need to get to be long enough as in application not brand . I cant go to the auto zone and buy wires for my 71truck with HEI cause it didn't come with that.

[GRX]

Wires for a '75 should work. First year HEI was standard equipment.

[flashed]

This is very useful info guys ,thanks as I needed to ask that very question.

[old Chevy guy]

For the record the question asked and answered in another thread I posted is 75-78 corvette wires, HEI and long enough to go around the back and under the manifold like factory original .

['68OrangeSunshine]

I usually get the Accel 8mm wire in trim-to-fit.