I joined a couple years ago but just recently acquired a running 1956 Mercury 312 that I plan to put in a 1954 Customline.  The engine is stock and for now it will just be a driver/cruiser.  I tried searches and found mention that using an adapter on the A intake to use a later holley would require some blending.  Additionally I know that the B intake has larger ports than my ECZ-C heads so I assume that I would need to port match the heads if I switch to the B intake.  (I will be using a later distributor from a 1958 parts motor)  So from a drivability/power standpoint, would it be better to just use a WCFB, use an adapter for later Holley, or switch to the B intake?

Given the fairly low CFM requirements of the engine, has anyone ever done a comparison between a small 4bbl and a large 2100 2bbl?

One more question:  I am currently using the 1954 3spd standard, but will be changing to a later model 4spd.  Would it be better to use the original 54 flywheel, or the flywheel from my 1958 pickup truck engine?

Thanks in advance for your help.  James

I don't have a WCFB, I was just wondering whether I should look for one, but it looks like the B intake is the best option.

When installing the B intake on the ECZ-C heads, which intake gaskets should I use, 1956 or 1957?

Do you know whether anyone has done a dyno comparison between a small 4bbl and the later model 2100 2bbl?  A 1.12 2100 would flow close to some smaller 4bbls.

Thanks for the help, James

I dont have access to a dyno, so no figures in that regard.  Remember that 2V carb cfms are rated at a larger pressure drop than 4V, so if that is considered a 300 cfm 2V carb would flow around 250 cfm if rated at the same vacuum as a 4V. 

2100s didnt come in a 1.12 version.  For a 312 the 1.14 at 300 cfm should work well, or a Holley 350 cfm.  However either one would still need an adapter plate on top of the B, of the type used in flat track/circle track racing.  And the 4 bores in the intake should be slotted out.  There is no provision on the Autolite carbs for a PCV attachment.  The circle track plate can be drilled and tapped for fittings.  IMHO it would be better to get a Holley 4V 390 cfm.

I used a 1.14 2100 last year, and this year there is a 1.08 on top of my 292.  They are simple, economical, easy to work on, with good throttle response.  But the real reason I use them is to limit HP, and protect the '46 transmission.

I plan to go with the B intake and a small 4bbl Holley or 4100.

Regarding the 2bbl, I meant when used with the later model 2bbl intake.  Based on "seat of the pants" I remember one of my previous Y-Blocks, a 272, seemed to perform better with a 2100 than a 4bbl.  Of course it was also 40 cubic inches smaller than the 312 so it didn't need as much cfm.

James

Depending upon which 4 barrel and how it was set up given the smaller displacement, the little two valve very well may have given a better sense of performance.

In the 4100 series, make sure to go with the smaller venturis, 1.08 vs. 1.12.  If the ID number has C5Z.... , or C6Z..., grab it if the price is right.

Mike 

James, i have found responsive success with replacing the old 320 cfm 2 bbl holley ( 4 hold down bolts) with 350 2bbl with external float adjustment.

Bill,  I have a couple 350cfm and a 500cfm center float Holley 2bbls that we used on circle track cars that I had even thought about using.  I guess the 4bbl would theoretically give better fuel mileage as long as I cruise on the primaries and don't kick in the secondaries.  But what fun is that?

James

Re your second question, the '54 flywheel is most likely drilled for a 9 inch clutch, the truck would have had a 10 or 11 inch.  Otherwise they will interchange.

Since the ECZ-C intake ports are smaller than the B intake, should I use intake gaskets that are specified for the heads (1956), or for the intake (1957)?

James

The ‘57 and up intake manifold gasket would be preferred.

Thanks for the response.  Is there much issue with the port mis-match if the heads are not port matched to the manifold?

James