While looking for photos of "parallel" 1bbl-to-2bbl intake mods, I stumbled across this page. What got my attention was the very last photo, down at the bottom, with the Dell'Orto DRLA 40.

https://www.overdrive.fi/forum/threads/ ... bl.309176/

I searched Dart 67's posts to see how it worked out. I learned two things:

(1) He put a turbo on it.
(2) Google translates whatever they call barrels (Or throats? Or throttle bores?) in Finnish to cucumbers:
"Maybe we had too big cucumbers but equally all that adjustment work was really deep."

That's what she said?

Those carburetors are meant to have one throttle-bore per cylinder. They are calibrated for the pulsing stop-start air flow of a single cylinder. Put such a carb on a plenum manifold that shares both barrels with six cylinders and you are in for a lot of recalibrating. The venturis are almost certainly too large which will complicate the calibration and may even keep it from ever working well. Imagine topping a 4 bbl intake on your 225 with an 850 double pumper and you get the idea. The Weber book says you need 28-30mm main venturis for a 2 bbl feeding 6 cylinders in the 3.7 liter range. This means using one carburetor of the two that were originally fitted to a 4 cylinder in the range of 1600-1800cc and still working very hard on the calibration.

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Joshua

Yup! I believe that's what they were getting at with the "big cucumber problem" (*snort*). I found some other posts in that forum mentioning the 1:1 barrel:cylinder relationship. That certainly explains why I haven't heard of other Dell'Orto 2bbl slant conversions.I wonder if the guy expected the forced induction to help with the big venturi issue. (I assume it wouldn't do anything to fix the lack-of-cylinder-pulsation part.)

Forced induction doesn't make anything about a carburetor easier.

I have a Lynx single DCOE intake manifold, but it really needs a DCOE 40 with 28-30 mm main venturis (chokes in Weber-speak), but I have a DCOE45 and a DCOE48. Knowledge on calibration for use on a plenum manifold seems to be closely guarded. Jets are easy enough to change, but the emulsion tubes give me pause. I'd much rather tune the Lynx SU manifold.

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Joshua

Indeed! I just meant that he may have thought forced induction would allow the engine to take a bigger carb.The Lynx M020, M022, and M024 were all on my "maybe" list for the LG stroker, but I found an Offy 5041 at a very low price, so I jumped on it.

40 DRLA is the proper size carb for our engines (used with three carbs or one). Pretty common on small 4 cyl engines, not sure what venturis were installed when bought new but 28mm and 30mm are available. There was a 36 DRLA available but didn't have smaller venturis available that I know of.

Better question is why would someone use it? It can be made to work very well but I'm sure it would be a pain to get all the proper jets and emulsion chosen. Not to mention lack of cold start circuit. Also there are widely available 2bbl carbs from weber that are already properly sized with cold start. 32/36 DGV has a 26/27 venturi (little on the small side) and 38 DGES already has the 30mm venturi and close jetting out of the box. That is not even mentioning that the DGV/DGS carbs are 2/3's the price of the IDA/IDF/DRLA carbs.

I was considering a 5041 offy manifold with two 34ICH (29mm vent) carbs. They don't quite match the manifold pattern but could be made to work. It's a shame that they don't make a larger ICH that we could use on a slant six as a single carb. Biggest 1bbl I have been able to find is a Kadron with a 44mm throttle plate and a 34mm venturi, pretty sure it flows a lot more than a BBS. There are some type I Volkswagen's making 170+ hp on dual modified Kadron's. Because they are only feeding 2 cylinders a 6 cylinder should in theory be able to get the same power out of one carb. Would be another carb that is a pain to dial in though for sure.

Brandon

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https://www.flickr.com/photos/162600228@N03/

Dividing an I-6 into 2 cylinder groups 1-2-3 and 4-5-6, especially an engine with a long duration cam, should considerably increase torque at all speeds except at the top of the RPM range. The reason being is that the intake strokes will not overlap and compete with one another. It probably won't quite match the throttle-per-cylinder setups for torque, but I'd bet it gets quite close. This makes the medium-long-runner South African intake manifold with 2 progressive 2 bbl carbs quite attractive. The next best bet may be a Hyper-Pak intake divided into 2 plenums. I do believe Doug Dutra tried this, but I've not spoken with him about it. The extra torque would make street driving more fun and allow use of a lower stall torque converter. Richard/Fopar in fact gets away with running a stock torque converter in his dragster with the six-motorcycle-carb intake.

I designed a tapered-runner twin-plenum ram manifold that was also to use a Helmholtz resonator. Maybe one day I finish it.

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Joshua

Joshua,

I would sure like to see your design for that manifold sometime.. I bet Lou would love to try it out as he is an intake freak.


Cheers,

Greg

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http://www.youtube.com/hyperpack

D

That sounds awesome. Is it something one could feasibly print?

See the parallel 2bbl setup article. Photo documentation of a very well done such conversion is here.

That single Dell'Orto modification to the stock intake is nifty but appears to be faulty. The carb mounting pad is not supposed to be parallel to the top surface of the intake manifold plenum!

As for unusual intake/carb setups, here are pics of a twin-carb dual-plane Slant Six intake from South Africa (with photobomb by an orange-painted twin-Weber intake also from South Africa).

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Too many people who were born on third base actually believe they've hit a triple.

I downloaded that one a while back. The one I was looking for is...that one! Thank you.Hmm. Looks like I've got some reading to do. (I don't intend to try it; just looking to understand the mounting pad thing better.)I love those. I tried to track down 68barracuda after finding threads like this one scattered through a few forums, but I had no luck. I wonder what became of the recasting projects.

Fer sher, fer sher.
Easy: the engine, as installed in the car, does not sit level front to back; it's higher in front. So the carb mounting pad is a wedge, thicker at the rear, so the carb will sit properly level when the engine is installed.
Donno; haven't heard from him in forever. ¯\_(ツ)_/¯

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Too many people who were born on third base actually believe they've hit a triple.

Aluminum 3D printing exists, but it's very expensive. The orange South African manifold would get you probably 90-95% of the way to what I hoped to achieve.

My one-off manifold was being fabricated from mild steel. Not as sexy as aluminum, but I can weld steel with the equipment I already own. I bought aluminized exhaust tubing for the plenum and runners. I made the tapered runners and the air horns to fit inside the plenum. The air horns would need to be changed for use with carburetors. I started on the head flange and it's under the bench. The next step is to make a mandrel to form the round tube runners into the intake port shape.

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Joshua

Can you tell us more about what the Helmholtz resonator would do for the intake?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.