Dual plugging J heads

OK, let's try this in it's very own thread:-)
In the "Fragile J motor" thread, Ape J said if you dual plugged a J head that was milled for high compression, they might split in two like a log. Reading some history on hi po air cooled racing Kawasaki engines, they used dual 12MM plug heads for endurance racing in Europe back in '81. Were these factory J motors? 'Tried a search here but maybe my wording wasn't right, because I didn't see anything on dual plugging other than the "fragile" thread. While I have the head off my '84 GPZ this winter, I wonder why not dual plug it. I'd like to get more information on this, along with the right ignition system to go with it. I think it would run better on cheap full. It will ping if I don't use good high test. Always did, so I don't. I'm told this is the norm with a two valve head with one plug off to the side to get bigger valves. You had shrowding when that domed piston came up, causing incomplete combustion and detonation. That's why they dual plugged some Nissan and Alfa Romeo engines before going to four valve re designs. In the old days, I think a company called Orient Express did these conversions.
I don't see nothing about it on the website now. Anyone have any experience with this?
Thanks,
Stephen

go check out ward racing they still do alot of that kind of conversion,dyna also sells one of their 4000sp drag ignitions specifically for dual plugged heads if there wasn't a market for it they wouldn't sell it.as far as the heads splitting i have heard of this but only on engines that had super high cylinder pressures, turbo funny bikes, pro-mod nitrous bikes, insane high compression pro-stock motors and top fuel blown engines ,never would you ever get cylinder cylinder pressures that high in a street motor. they used to weld braces in to the ends of the heads to give them more support and keep them from splitting

timebomb33 wrote:

go check out ward racing they still do alot of that kind of conversion,dyna also sells one of their 4000sp drag ignitions specifically for dual plugged heads if there wasn't a market for it they wouldn't sell it.as far as the heads splitting i have heard of this but only on engines that had super high cylinder pressures, turbo funny bikes, pro-mod nitrous bikes, insane high compression pro-stock motors and top fuel blown engines ,never would you ever get cylinder cylinder pressures that high in a street motor. they used to weld braces in to the ends of the heads to give them more support and keep them from splitting

That is correct, it has to have over 300 psi cranking, to risk splitting.

The advantage of dual plugging is you don't have to run as much ignition advance because you are firing the mixture from two different places. This makes more power.

When they dual plug them, the second plug goes straight down and is a small 10 mm like from a GSR750.

I don't know who still does this. Serious drag racers all now use the Vortex II heads, which are dial plugged.

I have a J head in the shop now for valve work. It has been dual plugged. I will try to find our where the customer had it done.


VORTEX II

Dupe

That Vortex head looks"yummy". Just for giggles, just how much does one of them go for?
Is it from billet? Doesn't look like it from the photo. If you can't find out where the customer had his head done, then I'm wondering the possibility of doing it myself? With a jig built for the base of my drillpress to get the proper angle and location for each cylinder, I now know that you need a 12MM second plug and you say it goes straight down. With no water jackets to worry about, all I would need are some Threadserts and that Dyna 4000 ignition for dual plug heads that was mentioned. Can I get a photo of the customer's dual plugged cylinder head? I would imagine that it doesn't look like the Vortex head.

darmahsd wrote:

That Vortex head looks"yummy". Just for giggles, just how much does one of them go for?
Is it from billet? Doesn't look like it from the photo. If you can't find out where the customer had his head done, then I'm wondering the possibility of doing it myself? With a jig built for the base of my drillpress to get the proper angle and location for each cylinder, I now know that you need a 12MM second plug and you say it goes straight down. With no water jackets to worry about, all I would need are some Threadserts and that Dyna 4000 ignition for dual plug heads that was mentioned. Can I get a photo of the customer's dual plugged cylinder head? I would imagine that it doesn't look like the Vortex head.

The only price I ever found for that head was something like $2200.00 bare.

I wish I could find more specs on it myself (port flow@lift,port sizes/lengths, ect.), but it pretty far out of MY price range as of now or the immediate foreseeable future.

It seems the only head between the Vortex II and ported stock is the 83-84 GPZ1100 item, which I haven't had much luck finding used prices on just by searching the net.

The first one I saw was an '82 S1R Lawson replica and Kawasaki had discovered better burn of the fuel in the hemi head with 2 plugs.

FBG did mine( '84 GPZ) a million years ago. NA with +- 200 hp. never seen even the tiniest crack, not welded up - fins in the way milled off and a threaded spark plug hole supplied.Most of the oem split heads I've seen involved nitrous or the really old days superchargers/nitro.

Goggle doesn't come up with any related FBG sites. Any way to get in touch with them?

fastbygast.com/

The Vortex ii with Titanium Intakes and stainless exhaust, all assembled, ready to install, goes for about $3400.

This head can not be used on the street.
It is taller than a Kaw head and the frame must be modified to get it in.

It uses 48mm intake valves and 36 mm exhaust. The valve angel is changed to get them in there. The smallest top end we have been able to do was 1463cc. At that size, the intake pocket was getting uncomfortably close to the top ring groove.

In order to close those valves, it used very expensive valve springs that are good for about one weekend at the track.

The "as cast" intake ports are so big that you have to leave the line at near 10,000 rpm to keep from bogging it. It will run seven second ET without any porting.

I will try to e-mail you a photo of the customers head.

Jay

dont forget the chassis to support the motor needed to support that cylinder head!:laugh: its for sale over on dragbike.com!

when you order it save me the box ill put it in the garage with all the empty boxes plummen is going to send me from his turbo.:woohoo:
geeze thats a big price for amazing looking head,
can't affort that lol,
been wondering about this for a while
did'nt the s1 run kx coils?