I was lookin around at different sites for any new parts and I noticed that RB and Mazdatrix offer a downdraft manny w/IDA, but Atkins offers the manny w/IDF. They look the same. What's the difference between them? Is one better than the other on a rotary?

 

Ok, in case I'mnot the only moron that asks this question, I've been reading/searching and from what I've found there are a couple differences. IDA is primarily a race carb, IDF is more "streetable". IDA has mech. pump, IDF has vaccuum pump. There is also a difference in the progressioin holes, which is deigned to make the IDF "smoother" in transition than IDA, But IDA will flow more, therefore providing a better top end.

If this is wrong or there is more to add feel free to chime in. I own neither, but am debating one or the other.

 

More or less. It's also possible to get really big IDAs, but I don't think anyone makes an IDF bigger than 48mm.

I still think my ultimate carb setup would be dual 44 IDFs.

 

I was wondering if that would work on a street ported 12a? (dual IDFs) And where would you get a manifold for that? I found a kick *** deal on a pair, but don't want to drop that dough and not be able to use em anyway. LOL

 

I don't know, dual 44s might be a bit much for a 12A. Dual 40s would probably work great.

As for the manifold, you'd have to make one yourself.

 

Japan 12LA has dual IDF manifolds now. I'm on the edge of buying one.

No the IDF has a rubber pump jet circut and the IDA has a metal on metal one. The only benifit to the IDF pump jet circut is it's repairable when it goes bad. The IDA carb is toast once the pump jet dies, but that usually takes 300-400,000 miles to kill one.

 

**Japan 12LA has dual IDF manifolds now. I'm on the edge of buying one.**

Nope, says he's out of the 12a's, just has 13b's now.

 

Who still has a 12A these days? LOL!

 

Ok, all you knowledgeable weber guys. I need to be schooled a bit on the sidedraft. Whats the "E" add on the DCOE? I ask because while perusing carbs and fantasizing about possibilities I of course can't afford, I was noticing that the dcoe's seems to predominantly be 40 and 45's. But I missed an e in my search and found that the "DCO" has up to at least a 58mm! It looks like the same carb from the outside, whats the difference? The mount is the same, well, if you don't count having 13mm larger port. Also, since I'm playing in left field here, anyone ever try to put one of the "porche" style triple webers on a rotary? Thats a mean lookin carb.

 

Triple webers would work on a 20B, I guess. What's the size of them?

 

triple weber 40mms. Hmmm.... wonder if it would work to take the center one and have the plenum open at the top and split to the center intakes ina a12a? Naw, nevermind, the synch would have to be "perfect" on all three or you'd end up ******* up somethin. Remember the old flathead motors? wonder if you could use a dual stromberg or holley 97 or 94 setup, like they used to put on those? That would be pretty cool too. I don't remember those being all that hard to tune either. Hmmmmmm.............

 

The E stands for starter circut.

 

Cool! so the dco just doesn't have a "choke"? that would be fine.

 

Correct. The choke on the DCOE was considered to be a common failure point on those carbs.

If worse comes to worse, you just need to give the motor a little gas until it warms up enough to idle on its own. About a mile of driving usually did the trick.

 

Remember the old flathead motors? wonder if you could use a dual stromberg or holley 97 or 94 setup, like they used to put on those? That would be pretty cool too. I don't remember those being all that hard to tune either. Hmmmmmm.............

Anyone ever done this? Or heard of it being done?

 

I haven't heard of those particular carbs being used. Holleys have been used on rotaries before. They suffer from the problem that the manifold they mount on mounts the carb 90 degrees from how they would sit on a v8. The problem with this is the floats will bottom out on cornering. The solution is to use center hung floats, but those will bottom out on straight line acceleration.

My 2 cents? Just use a weber. Theres a reason why those style carbs are the most popular choice on a rotary.

 

FYI it's not actually a choke on the DCOE it's a starter circuit. Most 4 barrel carbs have starter circuits that are chokes, but the DCOE circuit is a fuel enrichment circuit not a choke. Either way it sucks and gets blocked off on all DCOE's I use. LOL!

 

Is this on a tutorial somewhere? I'd like to remove mine too, but don't want to make things worse. LOL I've got an "old school" 45 dcoe 9, from the 70's

 

I'm sure there are alot of reasons. Among them ...
1. the r&d has been done and bugs worked out
2. they are readilly available and well liked
3. they are versitile ?sp
4. intakes etc. are already made to accomodate these

However, considering the number of carburetors out there, and the different "styles" and uses, I can't help but think that there are other carbs that would be "suitable", even "beneficial" on a rotary. The Hurley "SU" carb setup is a great example. I haven't ever heard of anyone using those till now either. But they have and according to thier r&d it nets good mileage AND awsome power. I'm not looking to "pioneer" rotary carburetion, I just don't like to discount the possibilities on the basis that " If it could be done, someone else has already done it. " and it obviously didn't work cause noone else does it. Now in the case of the Holley's etc., there are known issues in design, and that I understand.(though ironically they are apparently worth the effort to modify, since they also have a large following on the rotary) If there is any other carbs that have specific problems when applied to a rotary I'd love to hear them. Like the weber, the 97 was used on many different cars and engines, in fact many of the same ones. So, versatility doesn't seem to be an issue. Also like the weber, it is a "simple" carb.

I'm just trying to learn. That can best be done through exchanging information/ideas. The whole " do this because everyone else does " mentality leaves little room for improvement or change. I'd just like to know what the reason is for some carbs not working well, not just that there is one. Know what I mean?

 

all you do is unscrew it and make a block off plate. Simplz...