Hi Everyone:

Ok - I know that the first recommendation from every one is going to be 'don't...just...don't' and I completely agree and understand. The situation that I find myself in, is that I can't for the life of me seem to be able to source a 2 bbl manifold and carb (though I know that you sent me a possible carb suggestion, Dan and I appreciate it). The 2 bbl Super Six manifold seems to be as extinct as the dodo up here in Canada. If anyone has a lead on one, please let me know, as this is my preferred configuration. Dan also forwarded me a build link for a manifold modification, which is interesting, and that may be my way out of this 2bbl manifold shortage I find myself in.

However, that may not happen...so....

If I had to opt for the 4bbl manifold and carburetor, does anyone have any suggestion as to which setup would be my best way forward?

Alternatively, I'm not opposed to keeping the stock 1bbl carburetor and manifold and working with a newer cam (again, thanks Dan). I wonder what the benefits would be of having the stock head worked on by the local shop, then mating that to a lower-end factory rebuild. Again, an upgraded cam would be utilized.

Just spitballing.

Thanks,
Shawn

4bbl intake manifold: Sure, that's an easy "buy right now" item. The one you'd want would be an Offenhauser № 5270. A Google search will show you numerous vendors.

4bbl carburetor: Don't. Just don't. Put a 4bbl-to-2bbl adaptor plate on that intake (another readily-available part) and proceed with the Motorcraft 2100 as per PM, and see this thread for kickdown options.

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

Thanks Dan:

As usual, your advice is always appreciated. You should write a slant six book! You have an ability to grasp the "Gordian Knot' solution when I can't even see it! At the risk of sounding like the complete newbie that I am, what is the advantage of mounting the Motorcraft 2100 22bl carburetor on the Offenhauser 4bbl manifold, as opposed to going with a 4bbl carburetor? Would it have something to do with low speed efficiency of the carburetor mated to the 6-cylinder engine?

Alternatively, is there an interesting build matrix for the stock engine with the 1bbl carb and stock manifold? I'm not opposed to having something 'different' and if the original parts can be utilized....

Thanks,
Shawn

Most 4 bbls are simply too large for a 225 cubic inch engine. Here is a simply cfm calculator below to help buy the correct carb for your needs. Even at 6000 RPM, a full race prepped 225 engine only needs 398 CFM. A mild or even relatively stock engine needs much less, and most any 2 bbl will be a great choice to provide all the engine needs.

http://www.carburetion.com/calc.asp

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There's no such thing as too much cam....only not enough engine!

Thanks for the link and for the clarification!

Shawn

It exists, sorta. Hit [Search] on here and put SlantSixDan in the Author blank. Twenty-five kiloposts, no waiting.
You get to spend most of your time driving and smiling instead of tuning and tweaking and cursing and swearing and spending way too much on gasoline.

The 1bbl carb is a serious bottleneck; upgrading is a very fine idea. But a 4bbl is too big and too much hassle.

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

You might consider running a four barrel intake with a four barrel carb but lock out the secondaries. Run the four barrel like a two barrel. That would give you the tune-ability of the modern carbs but the airflow of a small two barrel. I plan on trying this on my truck with a Holley 4360 (450 CFM small four barrel carb).

Put a BBD on an Offy and call it a day.

Unless you are going to bump the compression, do a some head work, better the exhaust, and upgrade to the RV style cam, the 4 barrel isn't worth it.
(I'm putting this type of build together for the Aspen Project I'm working on)


Going to a 2 barrel, and putting the feather duster style exhaust pipe Dan recommends makes a good bolt on upgrade both for power and mileage.

Because your car is a heavy A-body, you could keep the 1 barrel, upgrade the exhaust and change the rear ratio to 3.21... it'll feel like a whole new car...

…or go to the 2bbl, upgrade the exhaust, and put in 3.2 rear gears. Then it'll feel like an even better whole new car.

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

Yep. Depends.

Best fuel economy I ever got out of a slant was with a 390 Holley. With a lot of work. But that was with 8ish to one compression. Though the factory states 8:1, it isn't, and the dynamic compression isn't going to play well with it unless you have some cam.
To run big cfm flows, you need compression, cam and head flow. Just be real careful cutting a head. Chevy machinists will hit water 9 times out of 10.
Don't go with oversize seats. Don't cut big ports. Keep at it, and look around here for info on ports and what to do. A big cut will result in poor performance. There is a knack to it. The average engine builder will be completely lost. Worse, he will screw up your parts.

Four barrel slants have built engines. You can leave the long block alone and run a 2 barrel super six. There are variations there, but the 500 cfm Holley isn't one of them. That's reserved for boost or built slants. Even the 350 cfm Holley really should be reserved for higher compression builds.

CJ

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Part of Tyrde-Browne Racing

Want a small 4bbl........

Get one from an old Mazda rotary engine..............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I worked on my buddy's RX-7 back in the day... just beware of the hooter valve....






Being a long term junkyarder and from what I see locally in the here and now, the choice of carburator should be weighed by availability of parts... in the PNW we are about to pass beyond ready availability of BBD's (or pay wild cat $150 for one....), the Motorcraft still has a fair following due to the amount of Fords built with one, the Holley 350 is compatible with all 2300/4150/4160 carbs so it will have the most over the counter parts available... but will require some time reading one or two books on how to tune one to make the best use of them....

IMHO...

I will be doing this to my Aspen Project... to the Holley 8007... It is interesting that the newer Ford Mustangs come with 2 sets of Keys....
One for normal operation, and the other with a different FOB signature unlocks the "GT" function in the PROM....

Thanks for the tips, everyone....I guess I'll have to make a decision and stick to it. I like the idea of keeping the 1bbl carb, but upgrading the exhaust and rear end gearing. For daily summer driving applications, I think that makes sense (and will be easiest on the wallet). The car will never be raced. Is there a straight swap out gear set, or would I have to change the differential? I'm not sure what the stock setup is, but are there varying stock differentials? I could start with the rear end work and I could then shop at leisure through swap meets, etc for the 2bbl manifold and carburetor...

I kind of like that idea.

Cheers!
Shawn