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Discussion Starter · #1 ·
i'm throwing this out there to see what you ppl think. I got talking to the guy who bought a 450 project from me. He want to put a dual plug on the DOHC engine. Anyone do ever do conversion? Is there a benefit to it? He's also looking for a shop to do the conversion. Looking foreward to your comments, danWI
 

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Dan, I guess ANYTHING can be done, but it would be a nightmare to install the secondary spark plugs in the 450 head once the hole is drilled and tapped (due to the shape of the casting).... Your friend might be better off running a specialized piston whose crown is shaped to center the existing plug in the "squish" area..... Either way, (and I'm NOT the final authority on this) I believe it would be a wasted effort..... However, I'll defer to Terry Noughtin's opinion on this matter.....Did you ask over at MSN 450?.... Steve
 

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Discussion Starter · #3 ·
Steve, good info to have, I had not considered a specialized piston. I didnot mention this topic on DOHC450. I gave Terry's info to the buyer so he can contact and discuss directly. Personally, i wonder if there will be a benefit, but like you said, ANYTHING is possible! I'll keep the group updated on the buyer's progress.

Happy holidays alls! keep warm, safe, full of good food and spirits, danWI
 

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I have seen it suggested for racing but can't see the bnefit for the street though.
 

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would you time them together or delay the secondary ignition?

from the applications I've been around dual ignitions, it was strictly for emissions standards...

is the advantage just for hotter ignition and thus more 'power'?
 

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Well, they did (and maybe still do) use dual spark plug heads on the Hemis for Drag Racing. I have seen something on the 450s, but can't remember where it was, right off. :roll:
 

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I could see the use of a dual plug head on these bikes as a benefit, seeing has how they like to have a LOT of timing to really run well up top. the trouble is, at least with mine anyway, all that timing advance seems to necessitate some higher octane at the pump...


fun fact: the new production chrysler hemi's run dual plug heads stock
 

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A dual plug head would not require as much timing advance. If flame front propagation originates from two points instead of one, the time from ignition initiation to full combustion chambre pressure is cut in half, and that's ignoring the pressure/temperature destabilization of the fuel. When that threshold is crossed, remaining fuel vapour in the cylinder detonates. That's what causes pinking if this takes place before TDC, and the higher the fuel octane, the higher the pressure/temperature threshold at which this occurs. dual ignitions are usually triggered separately, and whether they are simultaneous or not would depend upon the application. With the Honda, it would be mechanically simpler (and the ignition is triggered mechanically) to use dual secondary coils - Honda uses these for 450 type two motors with 360º cranks.
 

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Discussion Starter · #10 ·
thaks for the link! i did just talked to the guy interested in dual plugs the other day. the build is going really well and looks awesome. I'll pass on the link. danWI
 

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I won't pretend to be very knowledgeable on the subject. But I know the Harley guys ran daul plug heads a lot on shovelheads. I was told it was so they wouldn't ping on the lower octane fuels.

I kwow as late as 1980 Harley recomended a minimum of 94 octane fuel. The only other solution was to put in lower comprssion pistons and then performance suffered.
 

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