[64speed]

Rotor button is totally burnt up. Can’t tell it from the pic really but the terminals are green.

[Gach]

That’ll do it !

[Joe's Garage]

My recollection is a bit fuzzy as this was forty-plus years ago......

My younger brother had a 1977 Nova with a built-up 350 in it. 11:1, big hydraulic cam, Torker, Holley 750, Hooker headers. Fairly quick for a small block.

He was running the factory HEI distributor with ACDelco cap and rotor, using an MSD 6A box to have more spark energy.

It ran great for a few months and then it intermittently started running bad/rough and finally stopped completely.

When we pulled the cap off, the terminals were covered with green corrosion, the center post was completely cooked/melted and there was a big hole burnt through the rotor.

I recall that we replaced the rotor and cap with the better Accel parts and used a special center post (button) from MSD that had different resistance. We also drilled four 1/2" holes in the side of the cap to let the ionized air out.

I recall that the amount of ionization from having so many sparks going off inside the well-sealed cap was a known potential problem.

That cured the ignition issue for at least a few years.

Good luck figuring out yours!

[68WarDog]

MSD caps and possibly some imported ones are known for corrosive buildup. I usually drill a couple of 1/8" holes in the cap for ventilation after spraying a little WD40 inside.

[grivera]

Any pics of the rotor?

[steve25]

When you have drilled your cap to vent it you need to be extra extra careful when doing carb work or having fuel leaks with the air cleaner off and the motor running.

I once saw a guys car go up in flames from fumes due to a fuel bowl vent overflowing when he was adjusting the rear float on his Holley with a vented cap and the fumes lighted off in 3 seconds.

[Gach]

Originally Posted by 68WarDog

MSD caps and possibly some imported ones are known for corrosive buildup. I usually drill a couple of 1/8" holes in the cap for ventilation after spraying a little WD40 inside.

I also drill mine, just remember to put electrical tape over the holes when doing any work in that area. Have a good size one for dialing timing in with the crank tiger.

[68WarDog]

Although it still may be possible, but I went Holley EFI several years ago. Hopefully David got his issue resolved. There's always a learning curve with aftermarket components.

[64speed]

Cap should come in tomorrow. Replacing plugs as I haven’t done that since initial fire and I’ve added MSD. What’s the appropriate range for gap with a RTR billet distributor, 6AL digital box, and a blaster 3 coil? Plugs are the recommended RC12YC Champions from Edelbrock.

[Gach]

Originally Posted by 64speed

Cap should come in tomorrow. Replacing plugs as I haven’t done that since initial fire and I’ve added MSD. What’s the appropriate range for gap with a RTR billet distributor, 6AL digital box, and a blaster 3 coil? Plugs are the recommended RC12YC Champions from Edelbrock.

.040 is what I would go with

[Gach]

You should really think about going with NGK race plug much better plug.

[Gach]

I’m not really sure on heat range but my guess would be NGK 8. Up to you.

[64speed]

I had NGK in it and then I watched the engine masters episode where plug brand and price range made absolutely no difference. A 1.88 Champion seems a lot better than a 6.99 NGK under that circumstance..

[Gach]

Yeah what really matter the most is getting correct heat range, sounds like you pretty happy with the Champions.

[HWYSTR455]

Some of the issues which were caused by moisture have been addressed by many of the manufacturers, by putting a 'rattle' vent on the cap. You can look at other distributor caps and figure out which ones fit, sure the Summit distributors follow a popular design and the caps will fit.

It might take buying a couple caps to find out, but it's worth a try. The rattle vents are a better option than drilling holes.

I don't think your problem is from moisture though, believe it's possible the rotor strap was either bent up and providing too much psi contact, or it was too far away. It's possible the cap is just a cheap one, and they do that, but considering the number of hours on that engine, I don't think that's the case. Thinking it was due to the strap being bent.

Take a pic of the body of the distributor from the top looking down and post, and maybe we can figure out which aftermarket caps fit.

The rotor button cooking was a known issue with HEI distributors and was because of added resistance from the contact on the coil to button resistance. That was addressed by MSD by making a low restriction button contact, but the issue can occur in regular distributors when resistance is high.

Things that can cause high resistance are wide plug gaps, cheap caps, or the plug wire from coil to cap.

Personally, I run .035 gaps regardless, specifically to make parts last longer and easier to tune. With an MSD, since it's multiple sparks, the gap kind of doesn't matter too much when it comes to performance, unless you're running N2O or a boosted application.

I might get flamed on that last comment, if need be, there can be another thread to discuss that topic.


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[HWYSTR455]

The main advantage of some spark plugs over others is that they last longer, basically.

In some applications, they are used specifically for longer intervals for service, which is one reason the OEs use specific plugs. Many OEs have service intervals in the 50-100,00 mile range. (as an example).

Lean mixtures and certain types of fuel also tend to work better with different plug types and gaps. Lean mixtures and high voltage systems are used in new cars for obvious reasons, but another extreme example is nitro.


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[HWYSTR455]

Technically, the only spark that matters is the first spark. Adding multiple sparks after the first does help burn any remaining fuel, but there's very little performance gain if any.

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[64speed]

On the road again

[Gach]

Originally Posted by 64speed

On the road again

Great! No more Breaking up. Put that baby through its paces. Come on I want to hear those 1-2 shift’s. In that little 500 hp Tempest

[64speed]

Dead in the water again. The cap wasn’t helping I don’t guess but it’s the MSD box. Cut off, wouldn’t restart, couple of smacks to the box with a screwdriver handle and lights came back on and it fired back up. Drove it home and parked it, took the box off and sent it back to MSD cause it’s still under warranty. In the meantime I got plenty to do to get ready for my big show debut in mid March.