Hello again everyone, it's been quite a while.

I've got a 67 D100 I plan to modify this summer, and my goal is to end up with a reliable truck with very good gas mileage, or at least as good as it can get. Top end power isn't much of a concern. I'm looking to get maximum efficiency between 1500 and 2800 rpm. I've been planning and collecting parts for this build for a couple years now, so I hope I'm not too far off base with what I've got so far.

My question is: which intake manifold should I go with? I've managed to collect the following three:

- stock 1 barrel (I have 2 of these now)
- cast iron super six
- Offenhauser 4bbl

What effect does plenum size have on the mid-range torque? At first I was excited to find the Offy at a really good price, but the more I look at it, the more worried I am that it is too big for what I want. Also, I've been reading about splitting the plenum, and I'm curious about everyone's opinion on if it will be worth the effort or not. If so, which manifold should I modify?

The rest of the build I have planned as follows:

- The engine itself will be an Industrial 225 from a Versatile combine. (As a side note, does anyone have any information on the camshafts used in industrial engines? Were they different than automotive cams?)

- I will be converting to HEI.

- I plan on using an Autolite 2100 carb, mostly because I've had good experiences with them. For this build, I've managed to pick up the smallest (190 CFM) version. I realize it is on the small side for this engine, but I don't expect to be revving much past 3000 rpm anyways. If it doesn't work out, the larger cfm versions are much easier to come by.

- The rest of the drive line will be stock for now: a 3-in-the-tree and a 3.91 rear. At some point, I would like to change to 3.55 rear, but again, that can wait.

Thank you for your thoughts and opinions,

Roger

Aussie Speed 2 BBL
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

I think you answered your own question about intakes, you will need to use the S.Six or Offy, along with an adapter plate in order to run that carb.

The big question is one of carb oreintation and getting the best fuel distribution... trouble is that the "forward vs sideways" carb mounting on a SL6... has been a long term debate... with no clear answers.

So for max. MPG it is best to set-up the engine for the most torque, so you can operate it in the lower RPM most of the time.
Getting good fuel distribution in the "wet" intake manifold is also key, along with having a well working carburetor. (correctly calibrated, on the lean side).

On good "trick" is to apply a lot of heat to the intake air & intake manifold, that helps get the fuel fully vaporized but it can also cause heat soak problem / carb "boiling", upon shut-off.

How about fuel injection??
DD

The Aussie Speed 2bbl intake is set up for the larger 2 bbl carbs from the factory. Were I to use any of the ones listed I would use the super six.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

I would also recommend the Super Six intake, but if you can find an aluminum one that doesn't leak, I would use that.

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Casually looking for a Clifford hyperpak intake for cheap.

My truck is similar to yours. I used a cast iron super six manifold with a Motorcraft 2100 carb (the 1.14 model, third smallest). I "hogged out" the intake to match the bores of the carb and used an aluminum adapter. The thing started right away with the stock jetting for a 289 Ford, but the carb lacked vacuum ports for the distributor. Something to check for on yours before you get too far. It ran OK but tended to overheat and suck fuel like a jet!

I switched to the Holley 350 carb and actually get better gas mileage than the stock 1 bbl did! Plus, the adjustability of the Holley made it super easy to tweak the pump shot, etc.

As for optimum mileage though, I think a Weber 32/36 would be best.

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If it was easy, everybody would be doing it.

Thank you everyone for your responses. I'll be checking the swap meets for that Aussie Speed manifold for sure, but for now is sounds like the Super Six is my best bet.

coconuteater64, I'm unclear what you mean by this. Can't I just pull vacuum from the manifold, or am I missing something? Regarding the carb jetting, I pulled it from a 221 V8, so I'm hoping it will be pretty close. I'm going to do some more research on the Weber carb you mentioned though.

Thanks again everyone

You must have ported vacuum from the carb to the distributor, not full vacuum which you get from a manifold port.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Righto! My carb only had full-time vacuum, not ported. Therefore, I had no vacuum advance. You need that for fuel economy.

I still think the Weber 32/36 is best for overall compromise for fuel economy and performance (over a 1 bbl). But if you have a decent Autolite with a ported vacuum source, won't hurt to try it out.

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If it was easy, everybody would be doing it.

If you are going to go with the super six and want to let that Offy manifold go, I would be interested in speaking with you.

~RDE~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Whoops! I missed that you already had the Offy. I would change my vote to the Offy. I once had an Offy intake and I measure the ports. They were actually smaller than the stock intake manifold ports. The smaller ports would help torque at low RPMs. I say run with the Offy and make an adapter plate to put a one barrel carb on it like I did.

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Casually looking for a Clifford hyperpak intake for cheap.