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Help with explanation of down nozzles and such

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Help with explanation of down nozzles and such

Postby Ken0069 » Fri Nov 18, 2005 7:09 pm

I've been looking for some good used Brodix SBC 12 or 15 degree heads. I see a lot of used sprint car heads but all of them have the "down nozzle" holes machined in them and I was wondering what the advantage was of this setup?

The application I want these heads for is a 434 CID SBC in a rear engine dragster. I'm presently running a pair of Rupert 750cfm alky carbs and a BoLaws belt driven fuel pump. Since there aren't many dual carb manifolds available for these heads I was wondering if there would be an advantage to switching to injection and running a Kinsler DSR setup instead of a carburetor, which I would have to buy also as I don't think a single 750 carb would be enough. A good used alky Dominator is going to cost around $900 and I think I can find the Kinsler setup cheaper than that.

Anyone have an opinion on this?

Thanks,

Ken
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Postby John Wallace » Fri Nov 18, 2005 11:29 pm

Try a Ron's 'Toilet Bowl'?

Works great.
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Postby mbmotorspt » Mon Nov 21, 2005 9:34 am

Sprint cars run constant flow mechanical fuel injection. The idea behind the down nozzle is to put the fuel as close to the intake valve as possible. Because they run on Methanol, a large percentage of the fuel is used for its cooling properties.

I used to have two very similar 410 sprint car engines. One had 8 down nozzles and the other had 8 up nozzles (below butterflies) and 8 down nozzles (16 total). Although the down nozzle engine made more power on the dyno, the up/down 16 nozzle accelerated faster and always out-qualified the engine that was better on the dyno. Go figure.

Good thing for you is that there are probably a lot of good used 15 degree heads out there on the market. I think Brodix actually makes manifolds for many of them so you might check their website. www.brodix.com

Good Luck!
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Postby mbmotorspt » Mon Nov 21, 2005 9:36 am

Oh yeah, by the way, you should be able to plug those down nozzle ports if you don't want to use them.
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Postby Ken0069 » Tue Nov 22, 2005 12:34 pm

mbmotorspt wrote:Oh yeah, by the way, you should be able to plug those down nozzle ports if you don't want to use them.


Yeah, Brodix makes an intake for a single four barrel carb but not a dual. That's the reason I was looking at possibly using a FI setup like the Kinsler unit. Not too fond of the Toilet as I've known a few ppl with them that didn't like them.

As for the used 15 degree heads, the one thing that keeps me from buying these is the fact that they probably have been run to death before the owners decided to sell them. Sunken seats, valves with no margin left and worn out guides doen't appeal to me, if you know what I mean. I've seen a bunch of these for sale on Ebay and often wondered what kind of condition they were in.

Interesting facts on the down nozzle/upnozzle thingie? I would think there would be better fuel atomization with the up nozzles because of the distance that the air had to travel to get to the cylinder. Hummm, interesting results for sure.

Thanks for your input.

Ken
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Postby SupStk » Tue Nov 22, 2005 12:54 pm

John Wallace wrote:Try a Ron's 'Toilet Bowl'?

Works great.


Thats the thing about the "Flying Toilets", it seems my customers either love or hate 'em. Gotta admit from what I've seen they are deadly consistant on methanol if set up properly.
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