A Tale of 6 Carbs- Holley 1940 is the winner!

[MercuryMarc]

I rebuilt my 1969 250 block and 1980 head on my 63 Comet. I have tried 6 carbs so far (yes I know I am a little bit crazy but I like to try to fix these things myself instead of handing them off to Pony Carbs, etc.). I have been tryning to get a smoother ride and a stronger top end so I have experimented a little (OK, a lot...).

1st carb: Holley 1940 (1 7/16th bore), Auto Choke. Ran fine, not much power a top end.

2nd Carb: Holley 1940 (1 11/16 bore), Maual Choke. Ran Fine, lots of top end power.

3rd Carb: Autolite 1101-could not get it to idle even after I rebuilt it- I suspect vacuum leak somewhere

4th Carb: HW 5200- from eBay then I rebuilt - terrible low range bog.

5th Carb: NOS HW 5200, always idled very rough, then it died.

6th Carb: Remanufactured Holley 1940 (1 11/16 bore), Maual Choke- this thing runs great! Smooth as silk idling, I can set the choke/idle speed with the choke cable every time I start it. This is the carb for me!!

So for now, I am sticking with the larger 1940. I think it was used for 240 and 300 ci truck engines so it should be able to handle the CFM needed for my 250.

Could it be that the other carbs were just too restictive for my 250?

Thanks!

 

[ASMART]

The HW probably needed some adjusting for your engine. The low RPM bog may have been helped by adjucting the accelerator pump shot. It has been along time since I messed with them but if I remember right you can adjust the amount of fuel by moving the pivit point for the pump arm up and down on the side of the carb. Also, it would be common to need different jets than the ones you have since no HW was ever bult for a 250. There is a sticky at the top of this forum that goes into detail about jetting those carbs. AS I understand it, the Holley Weber will give supperior service once tuned for the appropriate engine. Many have said it is a good compromize between performance and mpg.

 

[LaGrasta]

I'm very happy with my 1946. Starts with the pull choke, no problem. I get great top end out of it. At lower cruising speeds though, I do get a bit of stumble.

 

[MercuryMarc]

The first 5200 stumbled like crazy with a slow and gradual throttle movement as well as a rapid throttle opening, so I assumed it was not related to the acceleator pump dischage, but I could be mistaken. I have tried 150-180 jets without much luck but I have not messed with the idle jets. Basically I just gave up after a while. With the new setup (Manual choke on the 1940) I have lots of control over the cold idle speed and no longer screech the tires backing out of the driveway on cold mornings due t a very fast idle setting to prevent stumbling and stalling.