250 carb selection

[JACK250]

Hi all, after toying with the idea of tri-power, I have decided I would rather run something more simple and economical. The specs of the engine will be: 250 log head, 264/274 110* Classic Inlines cam, around 9.5:1 compression, elec ignition and C4 auto with 2000 stall. I intend on doing the 2v head conversion (hogging out the hole and adapting a 2v to the log). I am intrigued by the 32/36 weber but after reading the tech on jetting I am utterly confused. Does anyone know a jet combination that will require minimal testing etc as I am inexperienced in this area, and is there a carb choice more suited to my application? For example a holley 350 2 barrel or perhaps a small vac sec 4 barrel.

Thanks, Jack

 

[powerband]

The progressive 2Bbl Weber 32/36 or H/W5200 derivative series typically would be too small (low CFM) for a stout 250. With jetting and other mods may be usable but for simplicity , the Holley 2300 ( 350 CFM 7448 or 500 CFM 4412) are inexpensive, widely available as well as jets and mods for it. I experimented with 2BBls. as well as large 1bbl's on my tri-power 250. The 2300 was the simplest tuned setup but I did eventualy get three Holley 1904's to work after many fun hours of tuning and testing. Two or three 32/36's have been on my mind to try...

HAve Fun


PS: If you are building a complete performance package 250, I would strongly suggest using a previously known good running carb for initial startup and cam run-in. Initially I used a YF 1 bbl with outer tri power ports blocked until a few unrelated issues like ignition and cooling were worked out. "Borrowing" a carb from a good running car if possible .



>< <<> <>

 

[MPGmustang]

I agree with powerband, use a good running carb to break in the engine. I am alittle confused, I think you're building a 250 but you have chosen a cam for a 200, if you want to go mild on a 250 you'll want one with a grind of 284 or higher, with a very tight lobe center (108) as the 250 is more of a torque monster.

I think a holley 500cfm might do the trick for you with a 250, if you're building a 200 then stay around 400cfm. jetting is really easy, and holley jets are readily availible at o'rielys and other speed shops. it's really trial and error, luckily there are several on this forum that have already tuned and posted thier findings.

Good luck and let us know more of the build, like what block

 

[JACK250]

Oh right, I confused myself, didn't realise the cams would be different for 200/250. The engine is an aussie 250, not the 2V though, just a 71 log head, I'm not sure if the aussie 71 log head is equivalent to your big or small heads?

Thanks