I'd love to see a dual plane intake for a slant six.
Whaddya think about these plugs?
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jos51700
Green Bearing thread connoisseur
Hmmm.....yeah. I'm not agreeing. But if you say so. lol
chryslercruiser
Member
chryslercruiser
Member
I screwed up the cut and paste below, but SlantsixDan in post # 7 stated:
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The aftermarket manifolds are closer to equal length than the stock ones, especially the Clifford manifold, but I think it's much ado about nothing.
DON BURKHOLDER
DonsPar
Another fun option would be to leave it as is and re-install these plugs. Then install a hotter coil and perhaps an MSD6, then check the plugs again and compare with another picture!
Perhaps the idle issue would change. Agree with others about the carb issues.
Perhaps the idle issue would change. Agree with others about the carb issues.
My answer would have to be much older as in pre EGR
slantsixdan
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Here y'go.
slantsixdan
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The car's ignition system isn't selectively inadequate on cylinders 1 and 6. This is a mixture-distribution problem, through and through. You can apply whatever band-aids you want, and maybe mask the symptoms to one degree or another, but the problem will still be there.
slantsixdan
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No, that's a dual-carb intake, not a dual-plane one.
slantsixdan
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No. Offhand I can think of about seven year-split internal differences, and there are probably more not occurring to me right now.
slantsixdan
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For mixture distribution, driveability, and fuel economy, the '78-'81ish 2-piece welded aluminum intakes are the best; they underwent extensive scrutiny at the design phase to eliminate flow dead-zones and optimise the mixture distro to all cylinders, using computerised tools that weren't available prior. There were problems with these intakes at the time; some of them had porous welds that turned into big ol' vacuum leaks. The majority of those were taken out of circulation (recalled/replaced), and most of the rest of them long ago went to the crusher along with most of the rest of the Slant-6 engines. But if you find one in good condition, with no cracks in the floor and no significant warp at the cylinder head mating surfaces (minor warp can be planed flat), that's a good intake to run. The '82ish to '87ish 1-piece aluminum intakes, along with the '76 Feather Duster/Dart Lite 1-piece aluminum intake, are a pretty close second preference.
If you've disabled your EGR system, the next preference down the list is the '70-'72 cast iron intake, except the California-only '72 piece.
jos51700
Green Bearing thread connoisseur
Ahem....
The purpose of the dual plane on a V8 is to provide runners of varying length to various cylinders. Sometimes this is done to alter air/fuel to cylinders that typically over or under carburate, other times this is done to spread the torque curve of the motor out. Or both.
If one looks at what I had attached, it does behave as a dual plane. Any time the front or rear carb/intake draws from the other, the effective runner length changes, and extra air and fuel is brought from a longer air/fuel path. Dual plane doesn't specify one above or below the other. It simply implies two of them, with the intent that they are not identical.
Cut out the balance tube, and I'd agree with you guys. But it is, technically, two different planes, and it does, technically, have a different runner length depending on which cylinder is drawing air from which carb.
Want a slant intake that's split 123-456? How about this one, with dual Weber downdrafts. The engine isn't mine, it's the PO's but I have the intake, carbs, linkage, and so forth to go on my 66 when the time comes.
Where can I get me one? lol
Now, which ones? The one or two barrel intakes?
The first sentence in post #39 is incorrect.
The purpose of a dual plane intake is not to vary runner lengths. The purpose is:
- to separate successive firing cyls so that they are in a different plane
- to improve throttle response because of the smaller plenums
The purpose of a dual plane intake is not to vary runner lengths. The purpose is:
- to separate successive firing cyls so that they are in a different plane
- to improve throttle response because of the smaller plenums
slantsixdan
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That dual-plane + dual-carb intake is a South African item. So are these ones—the compound-plenum 4bbl was (??used, tested??) on some Valiants hot-rodded for police service there, and the long dual-2bbl setup was part of a performance pak I don't recall the name of. A Valiant freak down there, went by 68Barracuda online, was going to repro them, but then he seemed to fall off the planet; I haven't heard from him since 2014, so odds are against. :-(
slantsixdan
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Both of them benefitted from the plenum/runner rework.
Good, because I have a Super Six intake that fits that description! lol
Charrlie_S
Well-Known Member
At one time Offenhauser made "dual port" manifolds. They used one barrel of the carb to feed one port to a cyl, and the secondary barrel to feed a second port to the same cyl. Mostly for V-8 engines, but there were some for inline engines. I don't recall if they ever had a "dual port" for the slant six.
offenhauser dual port intake ford 300 - Bing
offenhauser dual port intake ford 300 - Bing
I'm like you, I've seen those for a lot of applications, but not for a slant 6.
Dartswinger70
Well-Known Member
I owned a slant 6 once in a 70 Duster I didnthave it long but it was a good depndable engine started every time in the dead cold of winter. The thing about the outboard plugs running rich sounds right Ive heard it before...
Has anyone tried an AussieSpeed AS0084 Plenum pig to help with fuel distribution?
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