Engine: Two barrel carb vs. two one barrels

[studeluvr]

On the flat head sixes all I see are two one barrel intake manifolds is that just for the wow factor or is it better than a two barrel carb set up. What would be the rule of thumb as per cfm on a stock 170 with headers or a 185 with headers? I'd like to put a two barrel on my stock 170 for now. I have a couple of Stromberg 2 barrels that would work as far as linkage etc. any ideas?

[PackardV8]

I'd like to put a two barrel on my stock 170 for now.

What do you expect to gain for the effort? Yes, the 2x1-bbls have much better fuel distribution than a single 2-bbl. Most converting to a 2-bbl take the CASO route and just bolt on an adapter. The extra airflow of the 2-bbl is trying to squeeze through the original 1-bbl hole and the performance gain is miniscule. I spent quite a bit of time doing a 2-bbl conversion for my '56 Flight Hawk 185" and not sure it made any more power.

A bit OT, but the best carburetion setup I ever did for the Champion was three SU sidedraft carbs as used on the MG engines. The manifold stubs were easily made from exhaust tubing and they really worked. Today, I'd probably go with motorcycle carbs.

jack vines

[Skybolt]

Take a look at these two albums for ideas.

https://plus.google.com/photos/116673105435250958898/albums/5798866509243560337?banner=pwa

https://plus.google.com/photos/116673105435250958898/albums/5797488889404169441?banner=pwa

In the first album there is a four barrel Holley, based on a Weber design, that I ran on my OHV six and the second album was a Holley 1940 single I had on a 170 Flathead.

I tried singles, two barrel, progressive two barrels, and four barrel carbs on my six cylinder engines.

The biggest hurdle is what jack mentioned about trying to get the air needed for the larger carbs to work efficiently and effectively through the small single sized manifold.

The best compromise I found was the Holley 1940 single. It was a smooth and more powerful setup. I could never get the progressive two barrel to work right and the four barrel was a blast on the OHV six. Down low it hesitated just a bit so I had to give it a few more RPM than normal but once pat that it was so good I never took it off.

Food for thought.

Len.

P.S. What Jack said about the triple side draft motorcycle carbs is the ultimate setup. I just didn't have the money to put it together but it would have been the bees knees.

[gordr]

Another thing with the triple motorcycle (or SU) carbs: you could put them on tuned ram tubes. Look at the length of the intake runners on modern multi-port EFI engines. They use those long runners because a mass of air that size has inertia, and once moving, tends to keep moving. This ram effect works best at lower speeds, and really boosts your torque.

[LeoH]

Where did you get those manifolds Skybolt? They are pretty.

[RadioRoy]

What about using the carburetor from a Commander six?

[studeluvr]

The most I'm expecting out of the 170 is drive ability so I can keep up with traffic safely at 65 plus mph. The altitude is about 4600 ft so more air into the intake the better. I've always wondered about choking off the intake with adapters so the two carb system makes sense. Being a true CASO I plan to make my own intake and exhaust manifolds so I'm leaning towards the two carb system. We have a motorcycle wrecking yard here maybe I'll go bend their ears a little. Thanks for the input good points to consider.

[Skybolt]

Keihin or Mikuni carbs can be used for your 170 like in the link below, especially if you can get them cheap.

http://prirace.com/page/triumph-tr6-mikuni-flat-slide-

[Reggie]

Well, what I'd suggest is using a slightly larger one-barrel carburetor.

[RadioRoy]

If you go for two carbs, be sure to design the linkage and set them up properly. I have never seen a home made dual linkage setup that worked properly. Don't forget the choke system.

[Skybolt]

Where did you get those manifolds Skybolt? They are pretty.

All the intake and exhaust manifolds I used on the Flathead and OHV six were stock. All were sandblasted cleaned of casting slag and painted with heat proof ceramic paint.

All the adapter and spacers were bought on eBay and modified to suit. I did however make a spacer out of phenolic to enable the use of a PCV valve on the Champion six.

Len.

[Skybolt]

If you go for two carbs, be sure to design the linkage and set them up properly. I have never seen a home made dual linkage setup that worked properly. Don't forget the choke system.

I made a linkage for a triple 2bbl stromberg WW on a Smolgen for a modified Studebaker V8 I had back in the early 90's. The center carb worked from idle on up to it's WOT then the outer two kicked in. It was an amazing ride. I made it out of an automatic spring loaded linkage to operate the center carb and the other two were linked together and when the spring loaded linkage stretched wide open, as for kickdown on the automatic, it pulled the others into play. Homemade but worked flawlessly.

[LeoH]

All the intake and exhaust manifolds I used on the Flathead and OHV six were stock. All were sandblasted cleaned of casting slag and painted with heat proof ceramic paint.

All the adapter and spacers were bought on eBay and modified to suit. I did however make a spacer out of phenolic to enable the use of a PCV valve on the Champion six.

Len.

Why the added PCV valve? As for the manifold, sure doesn't look like my 170, that's why I'm asking. The manifolds are both rounded stock on mine and shorter and not squared like yours.

[Skybolt]

Why the added PCV valve? As for the manifold, sure doesn't look like my 170, that's why I'm asking. The manifolds are both rounded stock on mine and shorter and not squared like yours.

You must be looking at the OHV manifolds and not the Champion manifolds. They are not interchangeable, but the carbs are. The Aluminum colored engine is the original one from my 1959 and the black is from 1962 that had 1963 engine I swapped into my 1959. You should be able to see the yellow OHV valve cover, that should have given it away.

[64Wagonaire]

In the first album there is a four barrel Holley, based on a Weber design, that I ran on my OHV six and the second album was a Holley 1940 single I had on a 170 Flathead.

Skybolt-I have a freshly rebuilt OHV 6 in my 64' Wagon I am restoring (rebuilt by previous owner) this thing runs great but the previous owner never got his carb setup dialed in. He left me with the stock carb which I am not using as it will barely hold idle and I have a 1bbl Carter AS core that I am planning to rebuild to have a nice simple setup to use to make sure all of the kinks are worked out. Once everything is dialed in I am planning to throw a few small modifications at this motor to see if I can crack the head not really just want to get some more low end out of it for pulling a small trailer and just moving off the line faster than a VW bus. We have toyed with the idea of running a carbureted turbo from a 79' Buick 3.8, with low boost, and throwing an adapter plate (similar to your modification) and a 4-barrel Holly on top of it. My step-father (Drrotor) has used this setup on other sixes in the past and says the improvements may be modest but would be a nice improvement over stock. Obviously I am worried about cracking the head as these motors are so known for but think that low-end power and not over-revving the 170 will keep things in check. Do you have any thoughts on this type of setup. Maybe just putting a 4-barrel on it as you did is all I need to do. Any other modifications to head, cooling, etc. that you did to make the 4 barrel happy?