Need info on Holley 94 carb setting on Merc engine
 

Hello Barners. I need some assistance.

I would like to replace the stock 855 carb and manifold on my 1950 Merc flathead (4 inch crank) engine, completely stock, with a completely rebuilt1950 Ford Holley 94 8BA carb and manifold.

Merc is 255 cubic inches and 1950 Ford was 239 cubic inches.

Any changes that I should be aware of for the change?
What jet numbers and power valve numbers should I use on the 94, in order to compensate for the increase in cubic inches?

Any other things to take into consideration?

Thanks for assistance. Bill

Re: Need info on Holley 94 carb setting on Merc engine
 

I'll bet it'll work fine. If it's in good shape, put it on and run it. It's pretty close to start with and if you notice any minor problems, you can correct them down the line, like any carb tuning regimen. You may want to consider putting a small base Rochester 2G on the Merc manifold. The throttle bores are a little larger, but if you put it on backwards, everything lines up, fuel line, throttle linkage, and even the automatic choke. It's basically a better carb to start with and parts and availability are much better.

Re: Need info on Holley 94 carb setting on Merc engine
 

People have to realize that a carburetor meters fuel dependent on the air flow through the venturi. They are pretty much self regulating unless the carb is totally mismatched to the application. If you have to make major jet changes, the carb is misapplied. In your case I would not expect any problems.

Re: Need info on Holley 94 carb setting on Merc engine
 

I used an 8BA/ 8RT intake with a Holley 94 on a '50 Merc engine for years and found it to be a direct bolt on. Ran great. Notice location of vacuum fitting for Load-A-Matic distributor. Distributor shown is mechanical advance but I did use the OEM distributor for years. Engine was in 40 Ford. Used stock Holley # 51 with Gross Jet later on as they last "forever".

Re: Need info on Holley 94 carb setting on Merc engine
 

if you don't want to swap the manifold, Charlie NY set me up years ago with a late 1940s Lincoln Zephyr 4-bolt carb base to fit the Merc manifold and that bolted up to a 8BA carb. Trick set-up from back in the day. Worked great!

Re: Need info on Holley 94 carb setting on Merc engine
 

If changing to a 3 bolt carb type intake on the Merc 255, why not opt for a '55 or '56 Ford 272 Y-Block 2110 (94) carb ? They have the 1 1/16" venturi for more air flow, and the 1956 model had larger throttle bores too (may require boring the two throttle bore holes in the intake though). The 1956 model also had an auto choke like the Merc originally had too.


Sal

Re: Need info on Holley 94 carb setting on Merc engine
 

On the subject of automatic chokes, I have done two when putting Rochester 2G's on Mercury manifolds, so I have found out a couple of things. The first one I did had the choke stove (the round "thingy" with "rich-lean" on it) mounted on the carb. There was about a 5/16 hole in the Merc manifold about halfway up the side of the manifold. On the Mercury, there are some fittings and a tube that goes to the choke stove. Putting a Ford manifold on a Mercury and utilizing an automatic choke of this type would be quite simple; just drill the proper sized hole in the appropriate place in the Ford manifold. The second one I did was on a '51 Mercury manifold. These have a "divorced" choke where the choke stove is mounted on the manifold and a rod from it connects to the carb. Trying to modify the Ford manifold to use a choke like this would be near impossible.

Surprisingly, I have found that making the choke function properly is probably the most difficult part of changing from the original carburetor.

Re: Need info on Holley 94 carb setting on Merc engine
 

Not sure a 94 would perform as well as the 855. I had a 239 8ba with an 855 on it & an Isky Max 1 cam. The 855 woke that engine up noticeably. The 855 developed a vac leak so i went back to the 94. You could tell that the car ran better with the 855. Based on that, i think the 255 Merc would be somewhat starved for fuel. ? Just my 2 cents worth. mike