Dual vs. single plane slant intake and other build questions

[Trevor B]

Now it's time to rebuild the 225 slant 2bbl that was in the 1968 Barracuda. I've been collecting parts and have some decisions to make:

1) Go with the header that came with the car (didn't leak, also doesn't have any of the friendly linkage for throttle, kickdown, etc.)? Or go with the stock manifold I got with the mostly complete super six setup minus the kickdown?

2) Go with the single plane intake that came on the car? Or go with what appears to be a much more common dual plane that came with the setup I picked up?

3) Then questions of 0.040 over piston selection and perhaps cam.

This car is going to be driven exclusively on the street with this engine - I want to enjoy the experience of driving it around town. Before I killed it, the 225 wasn't a speed monster but was certainly no dog.

Other info:
7.25 SBP rear with factory 3.23 Suregrip and 14" wheels
904 Torqueflite with factory high stall torque converter
Either Holley 2280 or Carter BBD
Would like to reserve the possibility of adding a turbocharger at some point in the future

 

[diymirage]

to the best of my very limited knowledge, there are no dual plane intakes for the slant six
do you mean the difference between single and dual barrel carbs?

 

[66fs]

Go with the smallest over bore that will clean up the cylinders. I'd run the factory exhaust manifold and kickdown linkage, otherwise you are looking at some form of cable kickdown. Use at least 2.25 exhaust. Main thing is to up the compression through milling the head, decking the block, or both. High compression is not to be used with a Turbo, I'd figure what you want before compression is decided. I would not try to go both ways with the same engine.

 

[RustyRatRod]

No dual plane exists for the slant.

 

[RogerRamRod]

"I would not try to go both ways with the same engine." 2nd that. and, If you are thinking turbo, go manifold. If you decide N/A, I'd go header, but add manual valve body & do away with the kickdown, one large single exhaust, don't try to run duals on a six.

 

[slantsixdan]

There is a true dual-plane intake for the slant-6. It's an aftermarket piece from South Africa that takes two 2bbl carburetors. The car in question here almost certainly doesn't have one. Here're some pics. The orange intake in some of the pics is another South African piece, part of a long-runner twin Weber setup.

As for exhaust: Dutra Duals with a Flowmaster wye connector into a single 2-1/4" pipe.

 

[Dan Stratton]

you could go with aftermarket 4 barrel intake and a blow through carb for turbo with lokar throttle and kick down cables I would not go manual valvebody as then you have to shift it manualy every time

 

[RogerRamRod]

But it's only like 3/4 of the shifting the 4-speed guys have to do. Literally. And your leg doesn't have to do a damn thing.

 

[Trevor B]

My mistake - not dual plane at all. It's that one of the intakes has the two barrels divided and one doesn't! I just looked more closely and see that the divider doesn't extend to the floor of the intake. Sorry about the crappy picture - lights are no good in this part of the garage!

 

[slantsixdan]

Undivided one has been modified. If you're using a stock(ish) carburetor, the divided one is probably going to give you slightly better driveability.

 

[RustyRatRod]

There is a true dual-plane intake for the slant-6. It's an aftermarket piece from South Africa that takes two 2bbl carburetors. The car in question here almost certainly doesn't have one. Here're some pics. The orange intake in some of the pics is another South African piece, part of a long-runner twin Weber setup.

View attachment 1715009107




View attachment 1715009108


View attachment 1715009109


View attachment 1715009110


View attachment 1715009111

As for exhaust: Dutra Duals with a Flowmaster wye connector into a single 2-1/4" pipe.

Holy intakes Batman! That's badass!

 

[slantsixdan]

Oh, there's more...an octopus (okeh, hexapus) 4bbl intake with damn near equal runner length, that was another South African item.

 

[RustyRatRod]

Oh, there's more...an octopus (okeh, hexapus) 4bbl intake with damn near equal runner length, that was a factory Chrysler South Africa item.

I would love to see that.

 

[slantsixdan]

This looks to me like a really smart 4bbl intake design for the Slant. Most others (Offenhauser, Clifford, Weiand, etc.) have the two centre runners (#3 and #4) running directly from the plenum into the head. The obvious problem there is that the inner cylinders get fed more than the outer cylinders. This intake seems designed specifically to provide even mixture distribution.

 

[Valiant50]

View attachment 1715009303

This looks to me like a really smart 4bbl intake design for the Slant. Most others (Offenhauser, Clifford, Weiand, etc.) have the two centre runners (#3 and #4) running directly from the plenum into the head. The obvious problem there is that the inner cylinders get fed more than the outer cylinders. This intake seems designed specifically to provide even mixture distribution.

And would you know it busy being 3 D scanned - the plenum on this thing is quite interesting, with the dividers going deep in to plenum - plenum is from flat side to flatside - outlined in red - blue more or less indicates dividers