What carb to use with my 250 2v head?

[michael_cini]

Hey Everyone,

I finally got my shipment from OZ (thanks for the shipping help Mike!). Anyway, I already have a Weber 38 DGEV carb that I was planning on using with the head and my US 250 engine. Is this a good combo, or should I go with something else? Any help would be appreciated, thanks.

BTW, I ended up getting two 250 2v heads, after I purchased the first one on OZ ebay I found another listed for a decent price, so I got that one too! Had them both shipped over here to me in Cali. So, after I have both heads magnafluxed to confirm all is well I will be selling the extra one.

Oh, one head is a '72 and the other is a '74 is there any difference of preference?

Thanks,

Michael

 

[addo]

So you have a 72DA and a 74DA manifold, or the actual head castings are different? That would be picture time. Manifold internals (AFAIK) remain unchanged. I think they just batched a whole lot, then maybe changed a minor detail and recast in '74.

Seeing as "Made in Japan" was recorded in 1972, that would be my pick. Paint the head Deep Purple in recognition of this.

Without spilling the beans on too much tech detail, #5 gets a bit sooty in the manifold runner, at the final bend before the head. #6 not so bad; just a shade of grunge buildup. I think this is from the accelerator pump and the direction of throttle blade opening. A small deflector might benefit here if you get into fine tuning. Look into the plenum and you'll notice not all is as it first apears; there are offsets and reductions in the runners where they meet up.

Carb must be synchronous, not progressive. As you have a 250 the standard Stromberg "WW" series would be a good start but is a little thirsty. Otherwise the BG or Holley 500 might do ya.

You know I'm not a fan of the port divider.

Really, do consider a $60 Colortune kit. It's a good empirical measuring tool.

Other than that - dial your cam (somehow) and kick it in the guts. Don't fret too much or be too precious; get out there and get on it. ³ I've only heard of one cracked 2V head, and that had an odd history.

You can compare notes with Evan as his motor is all 'riginal in hookup of senders, fuel lines etc.

 

[SONNY]

350 holley works well you will need an adapter plate or make your own,saves butchering the manifold.

 

[Danielson]

Addo I am curious as to why the carb has to be synchronous and not proggresive?? I was going to adapt my ADM34 to mine .
Cheers Daniel

 

[michael_cini]

Adam, thanks for your detailed reply. Answers to your questions are below.

So you have a 72DA and a 74DA manifold, or the actual head castings are different? That would be picture time. Manifold internals (AFAIK) remain unchanged. I think they just batched a whole lot, then maybe changed a minor detail and recast in '74.

I just looked at the numbers on the intakes. Glad to know the innards are the same!

Seeing as "Made in Japan" was recorded in 1972, that would be my pick. Paint the head Deep Purple in recognition of this.

Good record, but I think you are dating yourself'' Purple would be great, but not with a blue car.

Without spilling the beans on too much tech detail, #5 gets a bit sooty in the manifold runner, at the final bend before the head. #6 not so bad; just a shade of grunge buildup. I think this is from the accelerator pump and the direction of throttle blade opening. A small deflector might benefit here if you get into fine tuning. Look into the plenum and you'll notice not all is as it first apears; there are offsets and reductions in the runners where they meet up.

Carb must be synchronous, not progressive. As you have a 250 the standard Stromberg "WW" series would be a good start but is a little thirsty. Otherwise the BG or Holley 500 might do ya.

I was not planning on using a progressive. But how is the Weber 38, or should I use a Holley like everyone else? I also have the original Stromberg, is this of any use?

You know I'm not a fan of the port divider.

There seems to be alot of discourse about this one, not sure where I stand.

Really, do consider a $60 Colortune kit. It's a good empirical measuring tool.

What exactly is this?

Other than that - dial your cam (somehow) and kick it in the guts. Don't fret too much or be too precious; get out there and get on it. ³ I've only heard of one cracked 2V head, and that had an odd history.

You can compare notes with Evan as his motor is all 'riginal in hookup of senders, fuel lines etc.

 

[michael_cini]

Thanks. everyone seems to like the Holley, there must be a good reason!

350 holley works well you will need an adapter plate or make your own,saves butchering the manifold.

 

[addo]

Dating myself? Well, I guess I get to pay for the meal and drop myself home afterwards, too.

The Stromberg is not the most economical carb. A 350 will be better on fuel. Progressive carbs will release less fuel to the runners closest to the secondary butterfly under normal operation; that's their issue. Manifolds built for a progressive 2-barrel have the secondary barrel more offset as once sufficient demand exists for its output, there is enough airflow happening to keep the mixture turbulent in the plenum - and thus fairly even in spread. That said, it may not matter as much as I suggest!

Quite honestly I believe a lot of change was for change's sake and that "gains" as were felt to be had often came from miscarbing; the good old bog followed by recovery being perceived as an extra boost in power, not a deficient fuel curve. Not saying it didn't make any difference, but simply that it could have been better again!

I have seen manifolds remilled with the carb angle preserved. This is to lower the total height of the carb into the engine bay another 3/8" or so. Try to run the water jacket if you can. It is not so much for heating or cooling but temperature regulation.

The Colortune is a glass-bodied spark plug. When fuel/air mixture is equal per cylinder, the combustion flame has an identical colour. This plug lets you observe the colour of fuel burning, one cylinder at a time.

Hope this helps!