Small-bore downdraft carb choices, for multi-carb setup..

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I've got a Rambler 195.6OHV motor (old Nash design) that's got a single Carter WCD 2bbl. It's got the same intake design as the Ford six, eg. cast-in-head with a plate over the top, with the carb bolted to it.

Lucky for me, the plate is literally flat stock, carve it out with a jigsaw! Naturally I'm thinking of making my life more difficult with two or three small carbs.

This is a long stroke, slow-turning motor; 3200 - 3500 is has fast as I'll ever spin it; 3000 is practical maximum. My spreadsheet calculates that this motor is pumping 127CFM at 3000, 150CFM at 3500, assuming 75% VE.

Pretty much all american carbs that I know of are too big. Weber probably has the right one, either 3 * 50CFM, or 2 * 75CFM, that sort of scale.

Any suggestions?
 
If you didn't want to make your life so difficult, how about one of the many small, progressive-opening 2bbls from Jap cars in the local junkyard? But I am all too aware that sometimes one feels it necessary to make one's own life difficult. And this is an old Rambler, and an engine that don't get no respect, so it's WORTH the effort!! Very cool idea, forget I said anything.
 
Seattle Smitty":vfgpprml said:
If you didn't want to make your life so difficult, how about one of the many small, progressive-opening 2bbls from Jap cars in the local junkyard?

Thanks for ruining my fantasy!! :) But you're probably right, I should poke around on the 'net and work up a list of possible donors.

Due to the low revving the pumping is really low; though the Rambler motor is 3200cc, I think I should use sizing rules of thumb that assume 1800 - 2000cc with the idea that it revs about half the max. of "modern" japanese cars. Sound about right?

Know of any flow data source on non-performance carbs?

Seattle Smitty":vfgpprml said:
And this is an old Rambler, and an engine that don't get no respect, so it's WORTH the effort!!

It is a fine old thing, if you keep in mind its ancient lineage. It sure is easy to work on, and torque feels flat from 1200 - 2400. Nice to drive!
 
I'm a fan of keihin carbs (stock HD). I've seen them on cars before. You can buy them off ebay all day long as many cycle enthusiest replace them only to find they were better off with what they had. I installed a DynoJet carb kit in mine and it was wonderfully fantastic.

http://www.keihincarbs.com/home.html
 
LaGrasta":3re12a25 said:
I'm a fan of keihin carbs (stock HD).

Those look nice, but when I try to run them pointing up and down I imagine I'll have a hard time setting float level.

Sorry, I'm making a bad joke at your expense -- I should have stated clearly that they need to be downdrafts. I guess most bike carbs will be sidedraft.

Here's some pictures of the intake with carb. Sorry, the images are a bit large. Everything in red paint is the cyl head casting; the carb plate bolts onto the head.

(There's no exhaust "carb heat" from the manifold or in the head.)

http://wps.com/AMC/1963-Rambler-America ... -motor.jpg
http://wps.com/AMC/1963-Rambler-America ... e-plug.jpg
http://wps.com/AMC/1963-Rambler-America ... umbing.jpg
 
If you ever wear the engine out to where you need to rebuild, you actually can get substantially more power out of it. I made some comments about this on Johnny Zoom's thread, but I want to stress that you can improve those horrible combustion chambers enough that with the right pistons and tight squish you should be able to build in enough more compression to get the car launching noticeably harder. You're going to be considered a bit daft for developing that enigne anyway, so you might as well put in some of Somender Singh's Astounding Grooves! Boil out your entire cooling system, maybe get the radiator rodded-out, then use 20% ethylene glycol antifreeze, one bottle of Water Wetter, and the balance distilled water. This should lessen the formation of hot-spots in your higher compression heads. You don't want to have to burn the expensive octane gas, after all. Oh, and balance the engine. When I was young and a cheapskate, I got away with omitting balancing my engines, but then I built two in a row that vibrated. Never again.

Keihins could be cool, once you got 'em balanced to each other. LaGrasta, don't some of those have accelerator pumps? The problem I see with a multi-carb set-up is that it becomes a lot harder to fabricate an aircleaner box and snorkel with a tube to draw air from outside of the hot engine-well, AND a tube to feed heated air to the snorkel valve for quick warm-up. You could probably omit this last feature if you install a plug-in engine heater. But to use side-drafts, you have to saw off the manifold, braze stubs to the head, and so forth. Maybe the tractor guys know of some little downdrafts; ask LazyJW. Maybe early Volkswagon carbs? You want something with an accelerator pump.

Why on earth would you want an ordinary engine?

Saw a Citroen 2CV go by last week! Outrageously cool! H*ll, even a senior citizen like me could pick up young lovelies with a 2CV! Snort!!!
 
Seattle Smitty":1alx8ni3 said:
If you ever wear the engine out to where you need to rebuild, you actually can get substantially more power out of it. I made some comments about this on Johnny Zoom's thread, but I want to stress that you can improve those horrible combustion chambers enough that with the right pistons and tight squish you should be able to build in enough more compression to get the car launching noticeably harder.

...enough to take all the teeth off the T-96 trans? :)

Seriously, it's really the weak spot on this car. The U-joints look like they're out of a steering column. It's a great car, incredibly fun to drive, handles surprisingly well all considered, but a speed demon, umm, well, ... but you can lug it in 3rd at 10mph and just mash the throttle (ignition lead? whaassat?) and it GOES! Did I say it has an 8.5" clutch?

The motor I think would take some hop up mods fairly easy; there's a lot of low-hanging fruit! I'll go look for Johnny Zoom's posts on the matter. I've always been drawn to this motor for some irrational reason, and the aluminum version (that also contains parts from the modern 64-up six).

This weekend I will pull the plugs and check compression, now that I've put 600+ miles on it. We'll see how even etc it is. That will tell me what project I might be doing all winter...

You said it best here:

Seattle Smitty":1alx8ni3 said:
Why on earth would you want an ordinary engine?

I was very lucky with this car - the motor seems to be in great shape. When I did the head there was zero ridge detectable in any cyl with a fingernail and all had visible crosshatching; there's a REBUILT tag on the motor.



Seattle Smitty":1alx8ni3 said:
Saw a Citroen 2CV go by last week! Outrageously cool!

A month ago I saw one pulling onto I5 South here in Los Angeles. A guppy jumping into the shark tank! Nervy driver!!
 
Seattle Smitty":11zvrska said:
.... Maybe the tractor guys know of some little downdrafts; ask LazyJW. Maybe early Volkswagon carbs? ....

VW used those tiny 28 mm Solex carbs on their 40 hp engines for years. They are a bit rare nowadays but still obtainable. Lots of 30 mm carbs around, I would avoid the 34's for this project.

I am unaware of any bona-fide tractor engine using a downdraft carb; most of them used UP-draft, the old two-cylinder John Deeres used a side draft type. Most of them had no accelerator pump but rather used an accerating 'well'. It seemed to work fine that way.

I like those old Ramblers, they were closer to what most folks really NEED for transportation; long stroke, slow turning torquers with good manners.
Joe
 
Well after poking around with what appears to be my practical options for small carbs I decided to blow this project off for now. The Carter WCD is sized pretty well, and carbs small enough to have N of them and ordinary enough to drive daily on are far between.

Instead, I did a nice cold air induction system, and switched to a more common filter element at the same time. Good air supply and a well-tuned WCD is probably not a lot worse than something more exotic.

http://wps.com/AMC/1963-Rambler-American/Cool-air

Thanks all for the suggestions, it really helped clarify things.
 
Nice work! And if you live in a place with coolish winters, you can disconnect it each Fall.
 
shoot, that brings back memories. has several of them cars in the very very early 70's, free, or $50 each. Beaters, but unkillable. Always start, always stop, got you there, & you could stuff a motorcycle in the rear or a junkyard 6 banger in the trunk.
Got me thru a few Boston winters, back then.
Simple. Dependable. Fixable. I want one......
 
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