Plug Gap - Suggested or Altered with HEI?

[Dejure]

My new truck, a 78 C15 step side, has a swapped out 350 with HEI (Accel). I'm running the shorty plug equivalent.

Anyway, since the engine has HEI, should I open up the gap a bit more than the oft recommended .35 gap?

 

[squaredeal91]

Pretty sure its .45 for HEI

 

[legopnuematic]

A 78 would have had HEI regardless (1974 was the last year for points as std, 1975 HEI was standard, with option to delete for points).

Anyways, .040-.045 should be just fine.

 

[Ricko1966]

.035--.045 .035 is easier on the coil but really anywhere in that range is acceptable.

 

[fast 99]

There's generally 30-50 KV in those coils. Most point systems were in the 20kv range.

You will be fine with any gap in the .035-.045 range.

 

[Rustisbest]

.040
Dont forget the first zero lol

 

[Dejure]

.040
Dont forget the first zero lol

What's heading toward a half inch among friends. . . .?

 

[xm20k]

Even with an MSD setup it's still .035-.045 on a SBC.

 

[75gmck25]

GM confused things back the day by initially recommending a gap as wide as .060, which was apparently intended to get a better mixture/burn for emissions. However, they quickly realized their mistake, and since then it’s been .035-.045 for most HEI engines.

 

[1STLS1]

GM confused things back the day by initially recommending a gap as wide as .060, which was apparently intended to get a better mixture/burn for emissions. However, they quickly realized their mistake, and since then it’s been .035-.045 for most HEI engines.

I thought it was .080. First couple years HEI used to burn the rotor up as a result.