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Offy dual carb manifold with TBI
https://www.slantsix.org/forum/viewtopic.php?t=49049		 Page 2 of 3
Author:  Matt Cramer [ Wed Sep 12, 2012 8:29 am ]
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I've seen a couple guys put TBI units on dual quad manifolds on a V8. They generally don't seem to have much difficulty, particularly since EFI doesn't care quite as much if the throttles aren't synced perfectly when you have a balance tube. I've also seen a couple side-draft dual throttle bodies on other inline sixes. Sounds like this could be an interesting project.
Author:  Tim Keith [ Mon Sep 24, 2012 7:26 pm ]
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What might be a good single barrel TBI unit to use? Some S10 trucks had TBI with the 2.5 four cylinder, like this one on Ebay http://tinyurl.com/8ut44l5

I could find a couple of these at the Pick N Pull if these are okay.
Author:  Matt Cramer [ Tue Sep 25, 2012 9:34 am ]
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That could work - IIRC the trucks were around 100 hp, so two of their TBIs could feed a 200 hp slant six.
Author:  Reed [ Tue Sep 25, 2012 9:44 am ]
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Other than the novelty factor, I don't see the point of running dual throttle bodies. There is no way a slant will ever spin fast enough to "out breathe" a single throttle body. I think dual throttle bodies is just lots of work for little benefit.
Author:  Tim Keith [ Tue Sep 25, 2012 3:35 pm ]
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Two TBI units is to help with fuel distribution without using port injection. I prefer to retain the traditional look. TBI is simple enough for a novice to build (very important for me). The GM TBI requires 14 pounds fuel pressure so that the plumbing is less costly.

Hopefully TBI will be practical. I don't intend to make a lot of power but hope for better driveability and fuel economy.
Author:  Tim Keith [ Sun Sep 30, 2012 9:03 pm ]
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I got a throttle body from a 2.5 liter Iron Duke. This cost $28 at a salvage yard. I don't yet know the Rochester model number. The base plate throat diameter is the same the Holley 1920 from my '64 Valiant. I have read that the GM single barrel TBI is the same design family as 2 barrel TBI used on the 4.3 V6 with easy availability of parts. An adapter plate must be fabricated as the bolt pattern is different, which will enable me to orient the linkage to best work with two of them. The throttle body has a minimum of wires, it is simple in appearance. If this works okay for the slant six I may also use these on my 265 DeSoto flathead.
Author:  Sam Powell [ Mon Oct 01, 2012 4:05 am ]
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What year is your Desoto? That sounds like a cool projects. Tuning is going to be a challenge I think. Keep us in the loop.
Sam
Author:  Tim Keith [ Mon Oct 01, 2012 6:35 pm ]
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The DeSoto is a '47 S11 Club Coupe with Tip Toe semi automatic 4 speed. The car has got a good body with no rust or dents. It has its original 236 six but I have a '52 265 crankshaft and rod set that I want to use in the block. There aren't many 265s around as they were built as the entry price motor in the early Hemi era for the Chrysler Windsor. The Chryslers were putting on weight and the 265 was built to produce higher torque. The 265 also was used in some trucks and industrial equipment. A good place to find a 265 is at a farm equipment salvage yard. Many use two one barrel intakes on the flatheads to help with the fuel distribution. I don't know that anyone has used TBI on a flathead six. I thought I'd do one (or rather two) on the slant six first.

This is what the TBI looks like compared to a Holley 1920. The bolt pattern is different but they are both 1-5/8-inch. I am sure I can get another 1920 for less than what they are going for on Ebay, but the TBI is dirt cheap. I could sell the 1920 on Ebay and get enough to pay for the Megasquirt controller. I wish that the Megasquirt were easier to configure. The TBI has a minimum of wires and tubes, it doesn't look too bad. For $28 it might not be a bad start.

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Author:  kesteb [ Fri Oct 12, 2012 11:36 pm ]
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GM made two different models of 1v TBIs. The 110 model which is basically half of a 210 2v unit and uses the same injectors. The other model doesn't and they don't interchange. The 110 was used on pre 1990 4 cylinder FWD vehicles.
Author:  Sam Powell [ Thu Oct 18, 2012 4:25 am ]
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Very interesting info on the DeSoto. Thanks. I had a '56 with the small hemi, but the car I had most like your DeSoto was a 39 Plymouth with a similar flat head. What a great engine and car that was for its day. It ran rings around the more popular Ford flat head V-8 powered cars, even though it did not sound as cool.

I think you can make that 2 TB EFI thing work. I had no idea old holley one barrels were getting rare and valuable.

Sam
Author:  Tim Keith [ Tue Jun 01, 2021 8:21 pm ]
Post subject:  Re:
Quote:
Very interesting info on the DeSoto. Thanks. I had a '56 with the small hemi, but the car I had most like your DeSoto was a 39 Plymouth with a similar flat head. What a great engine and car that was for its day. It ran rings around the more popular Ford flat head V-8 powered cars, even though it did not sound as cool.

I think you can make that 2 TB EFI thing work. I had no idea old holley one barrels were getting rare and valuable.

Sam
Since this is my old post I'll re-open it. I still have the Offy 2 x 1 manifold and GM throttle bodies. I know that its possible to make this work, but has anyone done anything like this? I don't have a huge amount of time to fiddle with optimization.
Author:  Dart270 [ Thu Jun 03, 2021 9:33 am ]
Post subject:  Re: Offy dual carb manifold with TBI
Sync idle throttle opening and TPS voltages (even decently) at idle and you should be good to go. It should not be sensitive except around idle, and only unless the TPS's or idle openings are quite a bit off.

Lou
Author:  Tim Keith [ Thu Jun 03, 2021 6:55 pm ]
Post subject:  Re: Offy dual carb manifold with TBI
Quote:
Sync idle throttle opening and TPS voltages (even decently) at idle and you should be good to go. It should not be sensitive except around idle, and only unless the TPS's or idle openings are quite a bit off.

Lou
I don't understand what you just said. I've got a little studying to do. I'm sure somebody has used two TBI units. I think the Corvette crossfire system was two TBI units. I'm not aiming for a lot of power - just turn the key and go. I figure I can insulate the system so gasoline doesn't boil away as often happens with a carb on a slant six.
Author:  Dart270 [ Fri Jun 04, 2021 3:14 am ]
Post subject:  Re: Offy dual carb manifold with TBI
I suggest you read the MegaManual for megasquirt. If you do not know what a TPS is or what it does, then you need to do some reading for sure before getting into this.

Lou
Author:  Tim Keith [ Fri Jun 04, 2021 4:58 pm ]
Post subject:  Re: Offy dual carb manifold with TBI
I recently replaced a TPS on my Honda.

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