Carby for 250 2v
- Thread starter JACK250
- Start date
aussie7mains
Famous Member
Wouldnt agree, thats too big for the big cam your talking about, Id err for something smaller, in my experience a big single carb on the 250-2v with a big cam is very soggy down low, and since your talking about a slushy trans Id be keeping as much low down torque as I could.
The idea you have is fundamentally wrong, a 250 isnt a big rever and as such your better off trying for increased torque, the 2v head will move your torque peak up about 500 -750 rpm and increase it quite a bit, but you wont get peak power much above 5000rpm even with a big cam, so keep your cam under 220 degrees (even thats probably too big) run a smallish carb and since Im assuming youll use the stock 2V intake manifold a smaller two barrel should work well .
So overall where looking at a cam around 215 (25-65) and exhaust port work, the inlets are almost too big stock, a bigger inlet valve will help a little, a good set of headers with a divided centre exhaust port, something around 350-500 cfm carby, 350 is very streetable, 500 gets a bit wobbly with the cam, is OK with stock cams.
This will give a you a good solid torquey thing which will work well with a stock type auto box. I hate loose comvertors and would say they are only suitable for drag racing, far to wastefull on the street.
If this is in a light car, say under 1200kg it will go rewally well and not too heavy on fuel.
All the best
A7M
The idea you have is fundamentally wrong, a 250 isnt a big rever and as such your better off trying for increased torque, the 2v head will move your torque peak up about 500 -750 rpm and increase it quite a bit, but you wont get peak power much above 5000rpm even with a big cam, so keep your cam under 220 degrees (even thats probably too big) run a smallish carb and since Im assuming youll use the stock 2V intake manifold a smaller two barrel should work well .
So overall where looking at a cam around 215 (25-65) and exhaust port work, the inlets are almost too big stock, a bigger inlet valve will help a little, a good set of headers with a divided centre exhaust port, something around 350-500 cfm carby, 350 is very streetable, 500 gets a bit wobbly with the cam, is OK with stock cams.
This will give a you a good solid torquey thing which will work well with a stock type auto box. I hate loose comvertors and would say they are only suitable for drag racing, far to wastefull on the street.
If this is in a light car, say under 1200kg it will go rewally well and not too heavy on fuel.
All the best
A7M
stevexysupersix
Well-known member
I agree. I found the 350 holley works really well, alot better than the wws. Goes great and is surprisingly economical. Some good dyno comparisons (2bbl vs 4bbl) on the CI site, but i think they ran on or close to a stock bottom end. I think mine is now being starved by the 350 so going to try a 465. Not really concerned with economy though it already takes a little 'coaxing' off the line(231@50), A7M makes a good point, I hadn't considered that the 465 may make it worse.aussie7mains":cki8trxy said:
That's about where my head is, these days. The EFI "daily driver" has only failed to proceed due to user error (insufficent fuel! 
) - all the mysterious gremlins people cite as risks with an EFI car, have their parallels in carbies/points.
My diagnostic costs so far - used laptop $300, cracked software £25 - the final link is maybe $200 (or less) in specific test cables. When you have the sort of information this provides, questions about stumbling, pinging or low power are significantly easier to diagnose.
I suppose whether this relates to the OP's posing, depends on his interest about setting up a manifold for multipoint EFI.
) - all the mysterious gremlins people cite as risks with an EFI car, have their parallels in carbies/points. My diagnostic costs so far - used laptop $300, cracked software £25 - the final link is maybe $200 (or less) in specific test cables. When you have the sort of information this provides, questions about stumbling, pinging or low power are significantly easier to diagnose.
I suppose whether this relates to the OP's posing, depends on his interest about setting up a manifold for multipoint EFI.
Exactly, Addo. There is really no excuse anymore to put up with a motor that runs poorly down low and guzzles heaps of juice. If done right, efi can be had for around the same money as a carby setup, too. Plus, emissions out the tailpipe will be less (think 'green') and you'll pickup extra power and torque.
(On the subject of emissions, I was following an old V8 mustang the other day, and it stank - miles too rich. Big carby = fail.) The old argument about 'what if it breaks down' is a load of bs also, since it's less likely to break down than a carby/points arrangement. It's more about peoples' fear of the unknown, I feel. (This is with the utmost of respect for the OP.) Go efi, lads : the only carby stuff you'll own will be your mower & brush-cutter!
(On the subject of emissions, I was following an old V8 mustang the other day, and it stank - miles too rich. Big carby = fail.) The old argument about 'what if it breaks down' is a load of bs also, since it's less likely to break down than a carby/points arrangement. It's more about peoples' fear of the unknown, I feel. (This is with the utmost of respect for the OP.) Go efi, lads : the only carby stuff you'll own will be your mower & brush-cutter!
sorry, i won't be convinced on EFI on these motors.
Its a 40 year old head design for gods sake. My theory is set it up oldskool, carb, cam, maybe a little help with some elec ignition, but appreciate it for what it is and what it was back then.
8)
^^werd.
I'm running a holley 500 with a 214deg cam (110l/c). Pulls easily to 5000, but doesn't make much power above 4800-4900.
Will soon be converting to a 465 with a 222deg cam (108 l/c) 28/68. The holley 500 runs out of puff at around 210-220hp, while the 465 is capable of 270-300. I'll never have that much power - target is 220-230 flywheel hp, so i think the 465 will be perfect for me and no soggy bottom end. All in a 1200kg TD cortina, manual, lsd, should spell some fun.
Economy isn't an issue for me though, as its not a daily driver.
Its a 40 year old head design for gods sake. My theory is set it up oldskool, carb, cam, maybe a little help with some elec ignition, but appreciate it for what it is and what it was back then.
8)
aussie7mains":21x78co7 said:
^^werd.
I'm running a holley 500 with a 214deg cam (110l/c). Pulls easily to 5000, but doesn't make much power above 4800-4900.
Will soon be converting to a 465 with a 222deg cam (108 l/c) 28/68. The holley 500 runs out of puff at around 210-220hp, while the 465 is capable of 270-300. I'll never have that much power - target is 220-230 flywheel hp, so i think the 465 will be perfect for me and no soggy bottom end. All in a 1200kg TD cortina, manual, lsd, should spell some fun.
Economy isn't an issue for me though, as its not a daily driver.
aussie7mains
Famous Member
Just a little comment on the EFI vs Carby, there is no "clean green" gaurentee with efi, certianly its easier to achive but its just as easy to make it worse.
A big part of reduced emissions is down to the combustion chamber and aftertreatment catalysts, which a 250-2v doesnt have.
The other thing is how do you get it to fit that engine, wyou would have to make all your own manifolds etc.
A7M
A big part of reduced emissions is down to the combustion chamber and aftertreatment catalysts, which a 250-2v doesnt have.
The other thing is how do you get it to fit that engine, wyou would have to make all your own manifolds etc.
A7M