If you have the original heads on there (which would actually be 1.94" double hump) I would regap the plugs to .045". Not ideal on a plug that's meant to be at .035" originally but with an HEI the wider gap is better. Going by memory I don't know of a .045" gap plug that is a direct fit for your head.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
In case anyone is wondering, the reason it's not ideal to set a plug gap wider than recommended on a plug is because then the gap is not even across the electrode, it's angled. Likely makes zero difference on a stock engine but I'm sure racers wouldn't do it.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Are you having an issue with the factory plugs? I ran then on a similar engine, with a few different combinations of cam and intakes for many years without issues.
I do remember having to gap the plugs out of the box, and I ran the same with both points and hei... ran up past 7000rpm no problem and burnt nice.
ak
-- Edited by ak 67sd on Wednesday 2nd of August 2017 08:55:41 PM
Yes sir they have the washer. I didn't notice it run any better,but I found they just last longer. I used to run them in my 340 duster and was impressed how they stood up to the leaded gas in the "ole" days.
Interesting, I had never looked in the Delco book for platinums for our old cars. Sure enough, they are there. They still say to gap them at .035" which makes sense. I certainly would make them .045" with an HEI though.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
On the majority of HEI equipped engines the gap was .045". Some were .060" and there was one year I think they did the gap on some engines at .080". .045" seems to work great.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Hi Carl, I ran .035 and swapped back and forth from hei to dual points... the hei was a junk yard peice, the dual point was an accel. The points revved way faster past 7000, but I had to adjust it often to have it perform like that. Stock HEI, stock plugs were ok for many years, and that engine liked 4000-7000... maybe running it hard kept the plugs clean. I over-carbed the engine more often than not. 2-4s, six pack, 650 double pumper, etc.
