1956 225 hp runs rich

[Al S.]

Runs great at plus 2000 rpms,loads up at low rpms,and the engine shakes at idle (500 Rpms). so far I've cleaned the plugs (they were black), set the needle valves,pulled the front carb top and checked the float settings. The front carb occasionally leaks from the primary shaft butterflies of the front carb.
i'll continue by pulling the top of the rear carb and checking the floats etc.
It's got to be something small that I'm overlooking.
Thanks, in advance, for your thoughts.
Al

[Clem Z.]

Re: 1956 225 hp runs rich

Runs great at plus 2000 rpms,loads up at low rpms,and the engine shakes at idle (500 Rpms). so far I've cleaned the plugs (they were black), set the needle valves,pulled the front carb top and checked the float settings. The front carb occasionally leaks from the primary shaft butterflies of the front carb.
i'll continue by pulling the top of the rear carb and checking the floats etc.
It's got to be something small that I'm overlooking.
Thanks, in advance, for your thoughts.
Al

air pressure check the needle/seat gaskets for leaks at the area where they screw into the carb top. a lot of the kits that come with a gasket that had too large of a inside diameter and leak there if not carefully installed.

[Roy B.]

Re: 1956 225 hp runs rich

If you just bought the carbs or had them rebuilt by some one not a NCRS guy it may have the wrong metering rods or there not adjusted correctly

[Al S.]

Re: 1956 225 hp runs rich

If you just bought the carbs or had them/
rebuilt by some one not a NCRS guy it may have the wrong metering rods or there not adjusted correctly

Roy,
I know how to set the rods but how do I find out what size they should be?
Al

[Roy B.]

Re: 1956 225 hp runs rich

Al ! I dont have the sizes but some one like people gave you thier names should know that.Ask them

[Al S.]

Re: 1956 225 hp runs rich

air pressure check the needle/seat gaskets for leaks at the area where they screw into the carb top. a lot of the kits that come with a gasket that had too large of a inside diameter and leak there if not carefully installed.

Clem,
I sent you an email asking if the low speed jet tubes are what you're describing. They go into the top of the center section and show no gasket.
Al

[Clem Z.]

Re: 1956 225 hp runs rich

Clem,
I sent you an email asking if the low speed jet tubes are what you're describing. They go into the top of the center section and show no gasket.
Al

no i am referring to the brass needle seat where the gasoline come into the float bowl.

[Clem Z.]

Re: 1956 225 hp runs rich

i replyed to your email. here is what i am talking about that sometimes the gasket has too large a I.D. and they leak fuel into the float bowl. pri jet .082 dia, sec jet .051, pri metering rod is 3 step .064 X .060 X .054 dia

[Al S.]

Re: 1956 225 hp runs rich

I think I've got it. The needle hangs from the float and usually has a neopreme tip. Right? Air pressure applied to the fuel inlet with the float up.
I'm German so sometimes it takes awhile to get thru.
Thanks,
Al

[Clem Z.]

Re: 1956 225 hp runs rich

I think I've got it. The needle hangs from the float and usually has a neopreme tip. Right? Air pressure applied to the fuel inlet with the float up.
I'm German so sometimes it takes awhile to get thru.
Thanks,
Al

just use about 6/8 PSI and spray some soap solution around the area and see if any bubbles show up. my mothers maiden name was HERTZOG i think that is german.

[John H.]

Re: 1956 225 hp runs rich

Runs great at plus 2000 rpms, loads up at low rpms, and the engine shakes at idle (500 Rpms). so far I've cleaned the plugs (they were black. Al

Al -

What plugs are you using?

[Al S.]

Re: 1956 225 hp runs rich

Al -

What plugs are you using?

I'm using AC 44s plugs.
But I seem to have solved the problem by closing all needle valves and backing them out less than one turn.
In addition, I used the needle valves on the side of the carb.
Th manual says to start with two turns.
Thanks for the advise.
Al

[Stuart F.]

Re: 1956 225 hp runs rich

You should really use a vacuum gauge (gage) when you adjust your fuel mixture screws at the front of the carb base starting with the recommended dry set. The screws on the sides of 56 Vette carbs, as you no doubt know, are for the air idle. 56's are a little more critical to adjust (something like those European multi-carb systems of the old days - SU's, etc). With the air idle screws, you idle with the primary butterflies closed or near closed which makes the fuel mixture screws that much more sensitive than on later models (57+) without air idle screws. It's been a long time since I set up a 56, but I recall they are more difficult to get them under control at low and idle speeds. They evolved from dual quad setups that did not use progressive linkage, rather ran both primaries together (2 stage vs. 3 stage).

Stu Fox

[John H.]

Re: 1956 225 hp runs rich

I'm using AC 44s plugs.

Al -

I've had three 2x4's over the years (two 57's and a '61), and could never get any of them to run cleanly at low speed with 44's without some level of fouling. I switched to 45's (R45S), and never had another fouling issue. Mixture distribution to the front four cylinders at low speed is lousy by design, as they're only running on the rear carburetor, so they're calibrated on the rich side on purpose to compensate. Of course, the idle mixture screws need to be set correctly with a vacuum gauge, not by "turns".