The Stovebolt Site Forums The Shop Area Engine Shop Gonna put dual Rochester 1B's on my 48

What do you guys think? Read an article in HRM that Holly will rebuild your Rochester 1B's so I called 'em and cost is ~$200/ea - they media blast, recoat zinc coated parts, and flow test. You can buy a rebuilt one for ~$200 from several online sites. Or a rebuild kit is about $50. Rebuild seems simple enough, but I can't come close recoating with zinc to look original. Is there a good paint that will last on a carb? Appreciate thoughts on options.

Eastwood makes paint for the carburetors, it looks decent but I have never used it.

I have tried all kinds of carb combinations on my 250 and have now settled on two Carter W-1's from the late '40s. I had three Rochester Model H, two Monojets, one Monojet, and have a Quadrajet rebuilt and ready to try.
Its a lot of time and money to set up dual or triple carb systems. I suggest spending the least amount on kits and cores and do it yourself rebuilding. Get them on the truck and running, then decide if you need professional rebuilds. Over the counter rebuilds are a mix of parts the rebuilder has on hand so its questionable what you will get. It may look good and even run, but getting two identical might be tough.

Be sure both carbs are identical, right down to the make, model, and date if possible. There are hundreds of different Model B, internal and external changes were made through the years. Once you have them in hand, verify they have original parts still inside them, jetting, metering rod, and power valves.

Even when you get a set ready to run, I will bet you find they are to big as a set. My Monojet's are sized for the engine cubic engine I had it on, when I added a second one, the air flow was cut in half in each carb. This created a lean condition since the air is what pulls fuel out into the air stream. Mine ran OK and looked really cool, but the fuel milage was horrid. The W-1's are much small carbs. The air flow through each one is high enough to pull fuel into the engine. Even these have problems with a off idle lean condition. If I adjust out the lean spot, fuel milage drops, so I settled for better milage and learned to drive through the lean spot.

You will never know till you try, so keep at it, but don't be shocked if it takes a while to get them sorted out. I have had the W-1s off four or five times now tuning on them. I hate to think how many times I had the three model H's off.

Joe

Allen, you may (or may not) find some of these links helpful:

http://www.thecarburetorshop.com/Dual1barrelcarbs.htm

http://www.thecarburetorshop.com/Triple1barrels.htm

http://www.thecarburetorshop.com/CarterChevroletW1.htm

Jon.

Great resources Jon. I've seen Professor Jerry post...ABC - always buy carter - are they really that much better than Rochesters? Why? If on a scale of 1-10 Carters are a 10, if Rochesters are a 7-8 that would be good enough for me. If they are a 2, wonder why so many are still out there?

Thanks Joe...great advice. So maybe the Carters are just better for doubling up? Would I have better luck with a 235 vs. your 250? That's not intuitive given the smaller CI's. I'm looking forward to the challenge of getting it lined out with help from guys like you. If I wanted it easy, I would just stay on the sofa,and watch football all day !

Another thing you'll need to get right is the intake manifold and to get antifreeze running thru it or not.
I did duals with zeniths on a Tattersfield w/water and it runs fantastic. It took a few tries to get it right.

I forgot about the heated manifold, even in Texas heat you should plumb water or exhaust to manifold. High heat keeps the fuel vaporized better.

Joe

I'm running dual B's that I rebuilt. No heat, starts right up. Runs pretty good, just have to do a little tweaking still to get rid of a little hesitation when I hit the gas. Threw in a set of .54 size jets.

[IMG]http://i148.photobucket.com/albums/s30/HoggerRC/ed2ff1e0-1b76-4964-a2e0-aeffc402a52c_zpsa5ce6cab.jpg[/IMG]

There you go, just shows what can be done.

No heat, starts right up = too rich.

One of the very first facts learned in "carburetion 101" is there are three major ways to improve fuel atomization:

(1) Increase carburetor air velocity
(2) Provide heat
(3) Throw additional fuel at the problem

This is even more true on an inline engine where the carb(s) are offset from the heat of the engine than for a V-8 where one has the heat from the engine right under the carb.

Running with no heat on a street engine may be possible in Honolulu, San Diego, Miami or the high desert; but anywhere else asking for icing issues.

On a race engine where RPM continually exceeds 5000 RPM or so, there will be sufficient air velocity to not need the heat.

Jon.

Jon or Joe,
Can you guys recommend, a dual carb intake using exhaust for heat, would rather not use water unless you guys highly suggest it. Found a few links.

Speedway Offie Intake w/exhaust heat


Langdon site dual carb heat solution

I made mine, so I have no input on which is better. I have heard the Offenhauser is a smaller runner intake over the Clifford which should make more power at lower rpm. The Clifford is made for higher rpm. Small runners mean better throttle response.

Joe

That triple looks real nice Joe, guess you took that pic back when you had the 3 rochesters on it.

Any of the dual carb intakes can use manifold heat rather than coolant/water heat.

Offenhauser, Fenton, Clifford, etc

As long as the intake has the fitting for a plate under the intake, you can then plumb one or two heat tubes from the exhaust manifolds (depending on the exhaust manifolds).

Allen, the three Model H Rochester's I had on came off a 1961 Corvair. I never could get them to run like I wanted them to. The Model H is a very basic carb, the only way to add fuel is through jetting, no metering rods. I could jet for performance, mileage, or cruise speed, but not all three at once. I still have them setup and ready to run. At the time of the picture, the manifold was part of header / intake combination I made one winter. The header didn't make any difference other then add noise and I couldn't heat the intake with out some ugly modifications so I scraped the header and adapted the intake to a stock exhaust manifold.

Dual or triple carbs run smoother then the single carbs I have had when working correctly, so you should see some improvements once sorted out. Even the dual Mono-jets rans really good other then fuel mileage. Finding jetting is the hardest part. I was soldering the main jets shut and drilling to smaller sizes when trying to get the model H's running.

Joe

Carbking, referring to the admonition about "Running with no heat on a street engine ... is asking for icing issues," has me wondering. What is a guy to do? My Roch B on my stock '66 250 I6/Powerglide 2spd sits "far away" from the exhaust manifold, as you know. I always thought that this is a good thing because I read that Rochester put in those "slots/grooves" on some of their throttle bodies in an attempt to cool their carb in summer city traffic. Most of what I know about carburetors comes from guys like you and your website articles. But I find myself somewhat confused at this point. Though it sounds ridiculous, can it be that for those of us running Roch B's we need a carb configuration for summer and a carb configuration for winter? I am not referring to the routine need to adjust the idle for winter. I am thinking about whether I should somehow shield my carb from the manifold in summer and then take off the shield in winter. Or, (now please do not laugh) should the stock exhaust manifold have two carb sites: one for summer and one for winter? Before I get run out of town for that idea, please note that my research has not brought forth a better idea. Alternatively (and at the risk of sounding like an idiot) I wonder whether a small electric fan for the Roch B would be beneficial for summer city driving, the same fan being repositioned in winter so as to direct heat from the exhaust manifold to the carb. To my lay mind, it seems that Rochester agreed that their B was not doing well in summer city traffic congestion (hence the throttle body slots), while at the same time, empirical evidence from the consumer suggests agreement that the carb needs heating at most all other times. -Alden

Only the 1965-* Rochester "H" has a power valve system, and it's operated by velocity rather than vacuum.

The slots/grooves is the throttle body gasket have nothing to do with cooling. The slots alleviate internal pressure in hot city traffic driving that would otherwise create an overrich condition.

Repeat - the slots are to relieve pressure, not aid in cooling.

http://www.thecarburetorshop.com/Ventedgaskets.htm

The questions are valid, but you do not need an auxiliary fan or a two position manifold.

Jon.

Thank you, Jon. Of course, those slots relate to pressure.