Inliners International Forums General Discussion Engines Rochester 2 Barrel

Anyone ever run one on a 235/261? I'm definitely considering this swap onto my 60 Pontiac with a 261/PG. I'd be using parts on hand, a 63 Roch. 2 bbl. off of a same year 283. As Curt B. has demonstrated in a previous post(hogging out), his prowess at building an adapter is excellent. I'm a neighbor, so to speak, in the same city, and I would be very likely using that adapter. Mods are limited to hopefully a split manifold and duals and a Pertronix igniter. Possibly a reground cam down the road. Thoughts?

I'd suggest one of the Holley-Weber progressive 2 barrel carbs off of a Pinto or Vega. They have a better metering circuit and will give better mileage.

Ron

How are they progressive? I am completely unfamiliar with these carbs. Does one throttle plate open, with the other following on heavy acceleration/passing/WOT?

There is a primary & secondary throttle, like 1/2 of a 4bbl, secondary starts to open (mechanical linkage) after primary is open above around 50%.
A singal carb from a pinto / vega isn't going to be enough for a 235 (vega were 140 cid), most folks run them w/ 2 carbs.
I had a Holley 2305 (no longer made, progressive version of 2300 2bbl) rated at 350 cfm and it was a little small for the 235. Now running a Rochester mobel B off a '67 292. Runs better & better fuel milage.
I like the rochester 2G, never ran one on a 235 but should be able to find one that would work well without too much tweaking.

Stovebolt Engineering has been selling the holly/weber progressive 2 bbl with an adapter for the 235 for many years. I have not read many (1-2?) complaints about the setup. Most comments are quite positive. I do know that Tom Langdon (Stovebolt Engineering) does not recommend the Holly/Weber for the 292. I would call Tom and run your engine build by him and see what he says.

Larry

I run a Rochester 2G on my 250 six for now, just with homemade adapter to the original intake. It runs pretty good, and milage hasnt gone up much, if i keep the foot of the pedal.....
It give a lot more power in mid/top range, but not much more in the lower parts, properly because the bigger carb ports than the original. I´m working with another intake,intake matched to the carb, and supposes different gains then.

I´d tried the Holley/Weber on a similar engine, and wasnt happy. Great lowend/milage on cruise, and ok on the top. BUT, midpower nearly did go dead!! On a smaller engine (218cid Dodge) it did function well, even if some midrange also dissolved here too.
Trouble seems like the small 1st port is ok on idle, but lacks power in till the 2.nd port opens, aka. to small carbed on midrange..

I am working on a conversion now. The Holley 2305 progreesive 2 bbl is too hard to find. It came in 350 and 500 cfm sizes and tunes like any Holley carb.
The conversion being developed will allow a standard 2300 series carb (350 or 500) to be turned into a proggressive 2 bbl. This would allow for much better tunability and carb sizing.

I put a little one bbl Stromberg(?) off of a Crosley on a 194 once, never ran it out of the driveway- the sucking sound it made at idle scarded me too much to drive it. I think it was the sound of a throttle butterfly bending from a great manifold vacuum.

It was probably the air passing the throttle plate at supersonic velocity.

Tom, when would this new setup be ready for consumption?

Almost done now. Want to do some testing with it.

It can be had as a complete base kit to bolt in place of your old base or as a do it yourself add on. Tom

Sure! I'll email you and get details.

several years ago I split a Pontiac rochester 2bbl's shaft at the middle and added a linkage tab to the pass end of the pass. shaft, then ran a short rod back to a "jackshaft" arrangement located about 2" behind the carb. Both the carb and the jackshaft were mounted on a common alum plate which was drilled to mount on a four bbl clifford intake. The jackshaft was a way to arrange the primary one bbl (driver's side) to be continuously operational and let the pass. barrel to be brought in at approx 2/3 throttle at a rate that would make both wide open at the same time as in a progressive tri-power set up. Mods to the "secondary side would only be the elimination of that side's idle mixture screw (passage filled with lead) and additional spring to bring back secondary butterfly. I worked on it only long enough to prove the linkage would work-never ran it. Would only be feasible on large rochester,stromberg(mopars),or the big two bbl holleys, as the small roch. 2 bbls ran ok on even the stock 194's.

I originally thought of trying to somehow index the shaft, to bring in secondary- but could not figureout how to make both be at wide open at same time. My method worked, but needed to be condensed in size. Gave up interest

I have a 2 bbl on my 250 . It runs fine but looks terrible with two adapters. I have the holley version of the 2gce or whatever it's called it basically a stock replacement carb made by holley with holley tune ability and it doesn't even leak yet.

PN for the adapter? Any pics?

No part number right now, I went to a carb shop to have my Gm 2g rebuild and he said he had a replacement carb basically same price,I 'll see if I can figure it out. And it too two adapters. One from offenhauser(adapts to holley square bore,one from mr gasket adapts spreadbore to gm two barrel.

I think the carb I used is the economaster. I will into it further though.

http://cgi.ebay.com/ebaymotors/NEW-HOLLE...sQ5fAccessories

Weird.

Tom, I sent you an email about the Holley...

Tom did your 2300 to 2305 conversion ever work out?

Made one and it works.Like most projects or ideas it is more work than I want. I will dig it out to get pics.

That would be great. If I can sort out the details, I might try the conversion.

If I can ever come up with a junk head I am thinking about making my own 2 bbl intake for a 235,I want a 2 bbl but not with a modern carb since I want it to look old. I was thinking about a 2 bbl carb from a Buick or Pontiac straight 8 but this will be a few years down the road.

Which one? The Carter WCD or the Stromberg AAV 'aero style' . . .

Not sure what carb I would use and would depend on how the linkage would hook up,I do have a Stromberg from a mid 50s dodge that looks like I might be able to make it work. I am in the planning stages of building a full pressure early 235 and have a 56 235 that will donate its crank and rods so it would leave me a extra head and exhaust manifold to use to make the intake.

Tom,

I know this is an old post, but I for one would like to see the pics.

I am thinking of doing this on a pair of Economasters and would like to see how you did the progressive linkage.

Thanx,


Bruce

I would too. I am just not that sharp to sort out making a 2300 Holley progressive like the 2305. Although I have tried to turn one of those 2305's up used, no dice so would be very interested in how Tom did it. I am with the others, I put a single Holley/weber on a 235 and it is not enough carb. I have two on my 235 and they run a lot better than two singles but still pretty small. Three might do it but two holly 2300's would be easier to deal with. The 350's are probably about 280cfm at the four barrel rating for something like 560 cfm in a two x two configuration. Not too shabby and to have them progressive would go a long way for drivability.

Thanx Panic,

I envision a different arrangement since the carbs will be mounted with the throttle shafts parallel to the crankshaft. The 1/3 - 2/3 primary opening to secondary opening is good info and gives the range of adjustability needed.

Bruce

Some of the commercially available 2 × 4 linkage is good for donor parts, including lever arms with staggered hole patterns to make whatever ratio you want.