looking to upgrade carb on stock 250
- Thread starter 79granada
- Start date
The Holley/Weber 5200 seems to be popular. Progressive 2 barrel in three cfm ratings 235-270. Needs an adapter and some mods. If you don't have it get a copy of the Ford Six Cylinder Performance Manual at classicinlines.com, covers all the important stuff.
Carter RBS might also be considered if you want something that's not a pain in the butt to tune properly. And mount. You have a throttle cable. The 5200 would require an orientation that puts it across the log rather than perpendicular like the older Mustangs with the accelerator rod.
The RBS should bolt right onto a '79 250 head. The YFA is usually considerd upgrade on 60's engine's and a rebuild or rebuilt YFA can be a good peformer. The RBS is a strange looking carb with the lower fuel bowl but is typically a good performer and I believe has the highest CFM ratings for 250 use.
The popular progressive 2 barrels are the pricey Weber 32/36 and Holley/Weber version - H/W5200. The 5200 series progressive is widely available inexpensively having been used on mostly small 4cyl. engines 70's/80's, but most available versions's jetting' are much too small (lower CFM) than the stock 250 YFA and RBS carbs. THe 32/36 and 5200 are easily re-jetted and if you search here you will find a lot of discussion on getting them tuned for different engine configurations. I run a H/W5200 on a 170 through a simple adapter and yields smooth idle and excellent performance and economy but it took two carbs and lots of tinkering to get there...
Another popular alternative is the widely available Holley 2300 series 2 barrel. Not progressive ,it's an option that can work well for performance on 170/200's and is avilable in a 350 CFM version (7448) which is not much bigger than the RBS's CFM.
Have Fun
RBS off 250:
5200 w/adapter on '77-250 head (HP170)
<> 
Holley 7448 / 2300 series 2X1 and Weber to Holley adapters:
<> 
Have Fun
The popular progressive 2 barrels are the pricey Weber 32/36 and Holley/Weber version - H/W5200. The 5200 series progressive is widely available inexpensively having been used on mostly small 4cyl. engines 70's/80's, but most available versions's jetting' are much too small (lower CFM) than the stock 250 YFA and RBS carbs. THe 32/36 and 5200 are easily re-jetted and if you search here you will find a lot of discussion on getting them tuned for different engine configurations. I run a H/W5200 on a 170 through a simple adapter and yields smooth idle and excellent performance and economy but it took two carbs and lots of tinkering to get there...
Another popular alternative is the widely available Holley 2300 series 2 barrel. Not progressive ,it's an option that can work well for performance on 170/200's and is avilable in a 350 CFM version (7448) which is not much bigger than the RBS's CFM.
Have Fun
RBS off 250:
5200 w/adapter on '77-250 head (HP170)
<> 
Holley 7448 / 2300 series 2X1 and Weber to Holley adapters:
<> 
Have Fun
Good point, I never thought about the RBS as an upgrade but it has more cfm than the YFA. I have one on my 250/Bronco and has been running fine. Should be an easier swap than the 5200 and someone on this forum probably has a good used one for sale.
"...never thought about the RBS as an upgrade..."
and it should fit on our 250 equiped bronks (hood clearence issues already due to the 250's higher deck) easier. It is lower than the others, not sure on how it duz on the gradients cars don't C tho...David around?
and it should fit on our 250 equiped bronks (hood clearence issues already due to the 250's higher deck) easier. It is lower than the others, not sure on how it duz on the gradients cars don't C tho...David around?
79granada":3f51ovx4 said:
Yes, one is a mirror image of the other. The 5200 is a US made Weber built by Holley, hence the Holley~Weber (or H~W 5200). It's choke, throttle and secondary barrels is on opposite sides of the 32/36 Weber DG- series, but ALMOST an exact copy of the 1978-1980 Ford Fiesta 32/36 DFV,but with 26 and 27mm venturis. In side,its the same, and most internals interchange with any other Weber DG-series. The Webers usually flow a few CFM more, but the quoted ratings vary due to Weber using a 1.83 " Hg flow drop, so its 227 cfm DG series could be 291 cfm rated at the industry standard 3"Hg.
The cfm rating varies between all the Holley Weber lists due to air horn changes, and there are a whole bunch of Chrysler Horizon or K-car based carbs, Chevette and Vega and Fox car/Bobcat/Mustang II/Escort versions, so that Holley Weber could be a 5200, 5210, 6210 or 6520 carb, with anything from 235 to 270 cfm, or if its a Weber, anything from 227 to 291, depending on how it was rated.
