Offshoreonly.com - crappy crab style distributor cap

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Quote:

Originally Posted by SB (Post 4925746)

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.035-.040” good.
.060” sucks and causes many issues

Agreed 100%. The crab cap makes it way too easy for the rotor to cross-fire to the wrong cylinder when the plug gaps are too big.

It’s also why the 496’s go thru plug wires (and sometimes coils) too quick.

OE spec .060” plug gaps. Don't do it.

Friends don’t let friends run stupid large plug gaps

as I said earlier I have been reducing the gaps just dont remember on my truck if I did that last time I put plugs in it. that was more than a year ago so my memory of that has been deleted to make room for more useless knowledge. havent pulled the plugs yet to see what I did.

changed it out and it immediately went back to normal idle (was idling several hundred high) and smoothed out so big improvement. cap did not look bad but rotor looked like it had been hot, not sure why but it runs like normal now so hopefully the brass cap will hold up better.

Quote:

Originally Posted by SB (Post 4925462)

A billion yrs ago when i started putting plugs in customers trucks/boats with .035” gaps vs crazy large OE gaps of .050”-.060” i barely ran into cap issues that plagued rest of country.

A billion years ago I did what SB said. Change the spark plug Gap to .040 & .035. they still go bad. And it doesn't matter if the cap electrodes are aluminum or brass. Talked with Jerry, a tech at MSD in Kentucky. He just said the cap is a poor design. You're only going to get 2 years MAX out of these caps. And if you've gotten more, the gods are with you. I CARRY A SPARE. And tools so I can change it out on the water.
Now it seems that a lot of people talk about decreasing the spark plug gap. But what about the air gap between the distributor electrodes and the far edge of the rotor? I don't know what the air gap is of GM and other distributor caps/rotors are. I do know what the air gap is of the vortec (crab) is. It's 0.160"! That's a huge leap for an electrical arc. That arc jump probably has more to do with the Caps demise than a spark plug gap of 0.060.
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