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If running dual plugs required every combustion chamber to be a different shape, I can't see why you'd want to run them on the street.

You'd need to tune each individual carb throat with an EGT on each exhaust port...it would be a total PITA.

If they check out well for street use, run single plugs and standardize those chamber shapes.

Stripped66 wrote:If they check out well for street use, run single plugs and standardize those chamber shapes.

Thats what I would do.

They could sure take a lot more abuse, potentially. Very interesting to say the least.

I don't know how those particular heads will turn out, but I ran dual-plug aircooled heads successfully for years. Back then, the crankfire system wasn't available, so I used my own dual-ignition distributor with separate coils, etc. Each system could be turned off and on, for the sake of demo.

There was a bit to be gained with the second bank of plugs -- perhaps 2-3 horsepower on my 100 hp engine. If I had been more of a tuner, I would have gone a lot further than I did with developing the system.

I'm certainly not knocking the merits of a dual-plug set-up, but when it requires you to run 4 different combustion chambers in the same engine, ditch it. On an airplane where this redundancy is necessary, and the engine isn't seeing dynamic changes in RPM, no problem...on a car, have fun tuning it

And 500lb'er, the .gif in your sig is hilarious! Absolutely love it!

It's really only two different chambers, but... still a valid point.

Pablo- how did your second set of plugs enter your heads?? Were they different chamber shapes as well?

And full agreement of the sig animation. I saved a copy just in case. For some odd reason, I can relate to it....... darn computer programming!!

- David

I finally settled on 10mm motorcycle plugs. The way I have them set up (pointing toward the exhaust) they're tucked away pretty nicely, and leave the combustion chambers identical.
http://www.thesamba.com/vw/forum/album_ ... _id=232008
This photo shows the lower plugs a bit better, along with my billet distributor fit with Bosch cap. http://www.thesamba.com/vw/forum/album_ ... _id=232010

That's pretty slick, Pablo.

And David, you're right...it would only be 2 different chambers

Nice looking setup Pablo. Did you do the machine work yourself?

Sure. Anything I "show & tell" is my own work.

Do you have a picture of the dual plug heads installed in your car?

No. All you would see from the engine compartment is a lot of ignition wires, half of which feed through rubber grommets in the rear shroud. I used right angle plug connectors on the lower plugs to get the correct wire angles/routing.

The two reasons for using the 10mm lower plug were:

1) ability to remove both lower plugs without removing anything else, while also having both lower plugs directed TOWARD the exhaust. It's a tight squeeze. Only one possible angle on one side.

2) least amount of "stuff" in the chamber to adversely disrupt air flow.

The only other dual plug heads that I had seen previously were the EPCO aircraft heads, which used standard sized plugs, one of which pointed toward the intake. Also, the angle EPCO used made entry beneath the rocker shaft, which necessitated removal of those parts, and the use of four 1.25" (I think?) freeze plugs to seal the entry holes.

Nice pictures! Thanks for posting them!

- David

Any news?

- David

Where you asking something of me, David?

I failed to mention the other main reason for 10mm plugs --- to allow deep flycutting.

- Pablo