dual spark plug heads

[gears]

I'm happy to share (via photos) info that I once considered proprietary .. but I left my machine shop behind when I moved from Maui 20 years ago. I'm pretty much retired now (except for wholesale parts sales).

In a few days, I'll post the DIY distributor mods for budget dual plug conversions. I'm actually surprised I haven't seen any of my dual plug kits (from '92-'93) mentioned on Samba. My Kiwi friend Ray Whiting made the 1-piece distributor housings for me ..

Previous discussion on the subject:
https://www.thesamba.com/vw/forum/viewtopic.php?t=374534
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aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[bugguy1967]

I was going this route with some new 914 heads from my machinist, but they'd need too much work to be on-par with the Remmeles.

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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[Howard 111]

To me, dual plugs is just a gimmick. I use an MSD ignition. That's a Multiple Spark Discharge ignition. That means each plug fires multiple times in rapid order. That's all you need.
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1973 Karmann Ghia
Turbocharged, Fuel Injected
http://www.thesamba.com/vw/forum/viewtopic.php?t=531270

[gears]

Well .. obviously Raby and Porsche can learn from you ..
Does your MSD allow 11:1 CR ?
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[ALB]

[rodeking]

"To me, dual plugs is just a gimmick. I use an MSD ignition. That's a Multiple Spark Discharge ignition. That means each plug fires multiple times in rapid order. That's all you need."

Actually it's multi-spark at relatively low rpms's only, it's single spark above the low 3000 rpm range or so. It does nothing different at high rpm that a good CDI box won't do.

[raygreenwood]

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Here is a set of dual plug 050's we just did. We do all the machining in house as we designed and built a fixture when we were building airplane heads. I have never done any testing as to how much better, worse or the same that they run compared to single plug heads.
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Cylinder Head Reference Sheet

[bugguy1967]

You're always going to get these kinds of responses from people that have never tried it or don't even understand it...
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

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[bugguy1967]

Well that last comment wasn't geared toward you, but maybe you'd like to explain why you STILL claim your heads the ONLY 200+HP heads on the market and STILL call your heads the best cooling even though you've done no side-by-side tests. You also must lock yourself in a box if you don't know that there are plenty of 200+HP shelf heads out there - some with smaller valves. If you mislead the public, I'll call you out on it.

And btw, my comments weren't concerning your dual plug mods. It was only your misleading statements. Instead of setting the record straight, you could only delete the comment
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[lelef]

I've modified some motorbikes engines for dual spark, not a big gain of power but better from idle to max rpm ,drivability seems better
it was necessary to sacrifice a head to understand how to do it !
have someone more info how to add another spark plug in vw head ?(angle and position with the milling machine)
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13b Buggy

Supercharged 1302

[Alstrup]

Plug location is almost certainly an issue if best possible result is chased. I know this is on sgl plug, but just look at the difference between a type 4 1,7/1,8/2,0 heads versus a 914/2,0 head. Ports are almost similar, the 2,0 has 42/36 valves versus the VW´s 41/34 (for the comparable 1,8 head) The 914 has sligtly different chamber shape and different plug location/angle. On the same engine and all things equall the 914 heads easily pull 5 hp & 5 Nm more power over the 1,8 heads. Theoretical it should´nt do that (torquewise) with the larger exhaust valve.
WRT type 1 heads the most normal solution to twin spark is the aviation angles like Mofoco and a few others make. We know it makes a positive difference. Question is whether a "turn" on the plug that faces away from the exh. valve can/will give any improvcement. I guess there is only one way to find out.

Gears, thanks for the pictures. I have been searching a long time for a better angle for the type 4 heads. Your pictures got me thinking. I will ask the guy that helps me with CAD to a test drawing, then we can try on a scrap head and see how it looks.

CDI/MSD on brand or the other is definitely a step in the right direction, especially at idle and in the lower rpms. above approx 3300 rpm the difference becomes less, and is VERY influenced on resistance in the delivery system. It is SO EASY to kill half the improvement with the wrong parts.

Plasma igntion which I have been working with for a while now, as some of you will know already, does wonders for the emissions, but is not "steady" in the performance increase departement. I have yet to figure out why there is such a large difference on almost similar enines.

We KNOW that twin spark works well, also performance wise, especially when bore increases. But it has been noted that even on smaller bores (stock 85,5)) with semi hemi headsthere has been seen increases up to a whopping 7 hp with twin spark. Now the Semi Hemi head shape is maybe also an easy target, but still.

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