has any one ever made dual spark plug heads for SBC? i know of a few other motors with em (my Honda Hawk motorcycle for example) and i was just wondering if anyone has ever designed such a thing for the SBC..... couldnt hurt with a boosted large bore motor.... with a coil per plug DIS i dont see why it would be to hard to do either.... hehe... im mostly just curious.. anyone ever made one, even in low production? any pics? how and where did they fit the 2nd plug?

in the last 50 years there's someone that's done it, sorry but i don't know who. if i were going to look around for it i'd suspect the injected alcohol dragsters might have. smokey would be another to of tried it. not sure you could convert a set of stock heads, angle plug would be the ones to convert i think. have to look and see if you'd hit water drilling another hole for the 2nd plug.

i thought that was only done to 4 bangers and motorcycles. my ranger has a dual plug head and so did my 1985 nissan truck.

naaa... top fuel cars do it too.


i can think of a few ways to do it, but all of them envolve redesigning the whole top end... most of them envolve moving the intake ports to where the valve covers are too.... heh.

back about 85 TF was going to 3 plugs and nhra pulled the plug on them, so to speak, to keep cost down

There's an outfit developing a head gasket that incorporates the "spark mechanism" around the perimeter of the combustion chamber. They haven't done SBC to the best of my knowledge (yet), but the results on that "other brand" have been very impressive.

cool.. tell more. link?

is it some kind of way to ignite the fuel around the entire edge of the bore at once?

Aircraft engines have dual sparkplugs for a couple of reasons. One being safety and the another to prevent detonation due to the large combustion chamber. I was doing a magneto check one time and fogot to turn the 2nd magneto back on. Wasn't long until detonation set in. Allen

Blow the jug off? Pretty awsome when it does that.

Also, the second plug is more for operation at high altitudes where the air is thinner and flame propagation gets supressed because of it.

Okay, you guys started it. Anyone but me remember the old (mid-'80s) test of the BBC aluminum engines in aircraft? As I recall, they were 427s, running inverted (that's right - upside down), with dry sump, gear reduction, running two-plug low compression open chambered heads and a side-draft induction with lots of plumbing. I recall seeing that in a magazine back then.

And yes, burning off a cylinder on a radial isn't uncommon, and not a pretty sight. They have enough problems with cooling - especially on the second or third banks. I don't think it's as common on the flat sixes and eights, but it can still happen.



GTA,

Ever notice how the engine really doesn't seem to like the mags on during the checkout or at low altitudes? I initially thought that it may have been mostly due to weaker spark power, but am beginning to think plug location may have more to do with it.

Hi Morley

My first career was an Aircraft Mechanic(A&E Licience). I was doing the magneto check on the ground and caught it in time. It was on a twin Beech with R-985's.

Hi Vader

Don't recall the article but aircraft engines have been used in tanks an an example. Yea, I don't have an answer to your question but you may be right.

Yes, radial engines were used in tanks in WWII, we had some of them at my A&P school, they had a much shorter "prop" shaft than the aircraft engines.

As to engines not liking the mags on during low alt/ground run,well they have to be on to get spark. The reason the engines run so crappy on the ground is because they are made to run very rich on the ground (you keep the mixture rich) to aid in cooling, since the engines are air cooled and they have no ram air to cool them on the ground (only prop wash) they need alternate cooling. This is why you shouldn't run them too long on the ground, you'll foul the plugs.

Yes Vader thay did use (and still do use) auto engines in "experimantal" aircraft ( a lot of the home builts) they are a strange beast and still retain the liquid cooling. I doubt you'd ever be able to get a set of those heads to work in a car, and really we don't need 2 plugs/cylinder. Auto mfg's have been playing with 2 plugs/cylinder for quite some time now, my sister had a cavalier with that set up, but the second plug was set to fire after the power stroke, to burn off any unused fuel before the exhaust stroke.

My friend's Porsche 911 has two plugs per cylinder. Don't know how they're arranged because I've never looked. But next time I see him I will.

yeah so it doesn't apply to what you guys are talking about but just figured I would chime in

the rotary a lot of times has two spark plugs also
the leading one fires first then the trailing and a bit of that is due to how the combustion chamber moves around as well as having the HUGE combustion area which can zap a lot of heat causing a incomplete burn.

some of the racing style rotarys (4 rotor that won LeMans) had 3 per rotor while one motor that was benz designed I think had 4 per rotor

but they do help with emissions, gas mileage and power

on a piston motor though don't know how much really would be gained by using them

might work better for emissions though


another setup I thin done by audi on there variable compression motor would have normal spark under light loads I think it was but once the load was higher and boost went up or something like that (been a while since I read the article) the spark actually went from the plug to the piston creating a larger gap and better flame


now if you wanted to go with dome pistons though a dual spark might work better but what would prolly work best is a central spark plug, AKA DOHC style where it goes straight down from the top of the valve cov.

vader (think it was you) but if you have the link or more info on that spark design you where tlaking about I would be interested to hear what you have to say. sounds like a nice idea