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> Twin-plug /4 motors...(pictures)
Mueller
post Jul 30 2003, 10:48 AM
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This is a Type I head, but it'll give you an idea for the 914 /4 motors.

Paul Guard, of Guard Transmission (maker of bitch'n parts for Porsche transmissions)
loaned me this head to get an idea on how to twin-plug my motor.

The secondary plug is a 10mm motocycle plug.

A modified distributor cap from a Nissan 4 cyl truck engine is adapted to fit on the stock /4 distributor...the rotor is from Nissan as well. I have the drawings for this modification somewhere in my garage (IMG:style_emoticons/default/smile.gif)

Using an aftermarket distributorless ignition would be ideal, but for cost savings, the above will work.

There is a company that'll machine these heads for about 300 dollars or so (they do this for aircraft...not for performance, but for redundancy (saftey))

The sockets in the head are to give you an idea of the angles.


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Mueller
post Jul 30 2003, 10:49 AM
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another one:


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Mueller
post Jul 30 2003, 10:50 AM
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Mueller
post Jul 30 2003, 10:50 AM
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post Jul 30 2003, 10:56 AM
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Curious, what are the advantages of a twin plug engine?
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Brad Roberts
post Jul 30 2003, 10:57 AM
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He just woke up.


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J P Stein
post Jul 30 2003, 11:03 AM
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QUOTE(L8Apex @ Jul 30 2003, 08:56 AM)
Curious, what are the advantages of a twin plug engine?

One can run higher compression without detonation....and spend more money.
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redshift
post Jul 30 2003, 11:17 AM
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Also the redundancy, you don't want to be unredundant, or totally redunduntless.



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J P Stein
post Jul 30 2003, 11:33 AM
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Not to be redundant, but....Mueller is talking airplanes which have 2 seperate ignition systems....magnetos, me thinks.
The down side of twin plugs & high compression is if one plug fails and the other keeps on firing, detonation will occur, you may not notice and keep on truckin'. At some point, you will notice the hole in your piston, tho.
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914werke
post Jul 30 2003, 11:45 AM
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Given the propensity for the heads to crack at the spark plug hole in stock form why not weld up and re-tap for the 10mm plugs anyway?
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Brad Roberts
post Jul 30 2003, 12:12 PM
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Oh.. that is a good one Rich. (IMG:style_emoticons/default/clap56.gif)

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URY914
post Jul 30 2003, 12:17 PM
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Two things:

1. Is there really enough HP gain to justify the cost and PITA factor?

2. You're adding more weight (plugs, wire, cap, etc)

OK, maybe item 2 isn't that big of a deal to most of you.

Paul
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redshift
post Jul 30 2003, 12:25 PM
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QUOTE(URY914 @ Jul 30 2003, 10:17 AM)

2. You're adding more weight (plugs, wire, cap, etc)

OK, maybe item 2 isn't that big of a deal to most of you.

Paul

LMAO

It just hit me, you drive a kite.



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Brad Roberts
post Jul 30 2003, 12:31 PM
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Words that I thought I would never see "together"

Drive a kite.

Sooner later Paul will make the car remote controlled so he can remove his weight.


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Aaron Cox
post Jul 30 2003, 12:56 PM
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Mueller
post Jul 30 2003, 01:05 PM
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From what I understand, the addition of the second plug was needed due to the increased cylinder pressure when RPM(?) installed the supercharger(s)* on the 914's.

*not sure how many had been installed, I have a copy of a magazine article with the /4 supercharged powered 914, it does not say if it was a one-off or if more had been built and sold.

On a bone stock motor I'm sure you'd see some gain from the second plug, but it is cost effective??? I doubt it.

Even in a run of mill aircraft powerplant, there is noticeble change in the running of the motor when one set of plugs is turned off while doing a magneto check.
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Targa
post Jul 30 2003, 01:09 PM
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It looks as though you would have to remove your rocker assemblies, push rods & tubes to have enough room to change those 10mm plugs. Is this true? (IMG:style_emoticons/default/unsure.gif)
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Mueller
post Jul 30 2003, 01:17 PM
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It looks as though you would have to remove your rocker assemblies, push rods & tubes to have enough room to change those 10mm plugs. Is this true?  


Nope, that is one of the reasons for the 10mm plug instead of the 14mm(?) size of the factory plug.

The location of the new plugs have to be dead-nuts on however to ensure that dis. will not be needed.
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SirAndy
post Jul 30 2003, 01:19 PM
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QUOTE(acox914 @ Jul 30 2003, 11:56 AM)
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kiefer sotherland- flatliners right?...anyway, im back from a week long lurking experience........

Worf in Enterprise TNG ...
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PatW
post Jul 30 2003, 01:24 PM
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QUOTE(Mueller @ Jul 30 2003, 08:48 AM)

A modified distributor cap from a Nissan 4 cyl truck engine is adapted to fit on the stock /4 distributor...the rotor is from Nissan as well. I have the drawings for this modification somewhere in my garage (IMG:style_emoticons/default/smile.gif)


I'd like to see the set-up for that Ignition. The WOW factor for this is good. Thoughts also about timing, cams, run with D-Jet?, etc. Would make a powerfull motor. My.02 (IMG:style_emoticons/default/wink.gif)

Pat
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