someone82

First posted this in the dual idf post

Speaking of Dual 40's... I just purchased 2 Dellorto 40 side drafts... and I'm interested in a dual setup for my 12a street port that's comming my way soon from Revolutionary Rotoary for my 79. All the links u guys could provide for like the manifold, linkage, vacume routing etc.. (gonna be running a points dizzy) would be great... what should i start the jetting at?
Also how would this be for street use... I know fuel economy won't be all that great
THanks,
matt

79 rx7
Suspension tech springs, RB Street port Exhuast (header to muffler), mazdatrix alum shifter bushing, cut down and welded shifter, and a blown motor

82streetracer

iTrader: (1)

www.tmwinduction.com

thats what Ill be running on my 4 port 13b.

someone82

Cool.. read the message in the idf post too. Just one question, how do u set up the linkage?

SilverRocket

I think you'll need to be doing more than just setting up the linkage. I'm no expert, but on my 48 DHLA, there are several mods performed by RB that would not be easy to replicate. I think you might be asking for a lot of work and trouble here, but I'd love it if you proved me wrong.

82streetracer

iTrader: (1)

Are you talking about OMP mods. I figure Ill just start premixing when I get this setup. I plan on breaking in my new engine with my okd nikki, that way I have a fully broken in engine to tune the carb with.

someone82

Yeah I know there will be more then just linkage.. I wish that was my only worries.. Jetting the carbs.. etc.. etc.. but that's a good Idea to break in the motor with the nikki. I think I'll do that as well... won't give me a reason too really get on it as well.
What do you mean by OMP?

SilverRocket

No I am not talking about only OMP mods. This goes way beyond making linkages and playing with jet sizes.

I don't think you guys understand what you're getting into. There are several more or less "secret" mods that RB did to allow the Dell to run properly on a rotary. There is no information on how to do these mods available on websites, etc, that I know of. Moreover, RB will not tell you anything about these mods if you call them or email them.

I don't know too much about it, but here's what I do know from experience with my RB 48DHLA. Firstly, regular emulsion tubes will not work, they will be much too rich on the top end. RB drills a series of tiny holes in specific places in the emulsion tubes. Good luck trying to do this yourself on a different carb setup.

Secondly, RB modifies the accelerator pump for greater travel. The gasket they use to do this is no longer available anywhere. This is a crucial thing, because if the proper travel is off by only a little bit, the carb will run like ****. Even with the RB mods it is hard to get it right when adjusting the carbs.

Thirdly, of course, they install inlets for the OMP lines, and a means for the OMP rod to be hooked up. Ditto the choke and throttle cables, but I'm sure you could figure those out pretty easily.

See, the thing is, I'm not sure if anyone really knows if those are the only mods or not. It's possible there are other mods that aren't well known.

Basically, what I'm saying (from my limited perspective; I am definitely no expert), is that you are going to be all fucked up trying to do this. Even if all you wanted to do was take a regular 48 DHLA and turn it into an RB-spec 48 DHLA, which you would have to do if you wanted it to run right on your rotary, it would be very difficult. You would need to have an RB spec Dell on hand to examine; the mods we're talking about are intricate and subtle. Even then, it wouldn't be easy. And if you had an RB spec Dell on hand, hell you'd just save yourself the trouble and run that wouldn't you?

Anyways, I don't mean to **** on your ideas, and I am certainly not an expert. But what I'm trying to say is, you certainly are not taking into account what will need to be done here, and you had better do some research (although good luck doing that) if you want to have a chance in hell of having a carb that doesn't run like ****.

We need a Dell pro to chime in here and clear this up.

peejay

As I understand it, running twin carbs allows the carb set-up to be remarkably similar to a boinger setup, so he might not have problems.

Then again, it is downright impossible to find tuning parts for Dells so good luck...

82streetracer

iTrader: (1)

Are these mods true to jsut dellorotos, or do they apply to webers also.

Peejay, i think you are correct because if you run two carbs the vaccume is seperate between the two carbs, like a "boinger setup" thats one of the many reasons I chose to go this route.

SilverRocket

Yeah, I was wondering if the dual carbs somehow changed the situation. The stuff I said above definitely applies to the 48 DHLA, but I'm not sure at all about anything else. I just wanted to make you guys aware of that stuff, in case you hadn't heard about it before.

Also, hit www.cbperformance.com for Dell parts. There's others as well, but cb is pretty good.

ItalianFedRotary

to get your jetting info go to www.gruntled.com and follow the links they more than likly have the info you need.

DriveFast7

iTrader: (1)

RB redrilled the emulsion tubes like mentioned already. Your guess is as good as mine if those same holes would work for dual carbs. And I bet duals wouldn't use the .8 e-tubes anyways. Generally speaking rotaries like lots of fuel, especially at the lowrpm range, so you'd have to try differnt e-tubes to get it right. So patience, practice and a good air/fuel meter are required for this.

Is there a dyno near where you live?

SilverRocket already went over the OMP, bent accelerator rod, and thicker accelerator pump gasket (which you can make yourself with some 1/4" thick rubber.) They took the two small rectangular weights out of the passages under the lid that I can't remember that I think control the accelerator pump fuel. Besides that theres nothing else I can see RB did to that carb besides jet it for rotary.

Top End Performance in West Hollyweird, CA designed and sold a dual 40mm Weber DCOE carb "convertion" using the TWM manifold years gone by, and that kit is still available if you have the $. Your best bet would be to call them and ask them for the jetting they use for that kit and cross your fingers they'll talk to you. Use that jetting on your Dellorto as a starting point. Weber e-tubes use different numbering system than Dellortos, but if you post it here I can convert it for you. It takes them a long time to reply to emails so just call them.

http://www.racetep.com/weber.html

These guys can also sell you linkage.

www.cbperformance.com sells lots of parts too, have great friendly service, and there are some more that sell dellorto parts.

PLEASE keep us updated on your progress so we can all benefit from this information! YOU can get it to work!

-bp-

someone82

Well I've never stopped my self from a challange.. and I figured if I could get a set of junkyard DRLA 40's too work on a 1835 vdub motor.. I'm sure I can do it on this motor with time of course... I'll still probably run the nikki for awhile until I get all the parts together etc.. but thanks for the help and I'll be sure to give u guys updates on all the pro and cons that come outta this project and I can say I am determined to get this running for street use.

matt

RXcetera

There's no reason why this couldnt work... it's been done before. Tunning this setup will be a royal pain in the *** though, but if your the patient type, you might just enjoy it lol. My biggest concern would be overkill. You really dont need that much carb for a SP engine. By the time you've choked those carbs enough that they will run properly, you'll have negated any advantage of running such a complex setup.

As far as RB mods to the DHLA 48, they've all been covered in the this thread except one... The accel pump diaphragm appears to differ from the original dell parts. It has a longer "rod" allowing for more pump action. Also, the oil metering pump mod isnt really a mod... You're simply swapping the venturi anchor screws with hollow nipple screws.

Have fun with your setup... I wish I was there to help you out. Sounds like fun .

82streetracer

iTrader: (1)

I dont think two 40s is too big for a SP, it think it will make great power. you are right about the tuning being a pain in the *** though. I know that

DriveFast7

iTrader: (1)

http://mrmazda.members.atlantic.net/mcarbs.html

Considering Racing Beat's Holley 4bbl 465 with 27.8 mm venturi in all 4 is designed for a 12a SP, and has total venturi area of 2425. And dual 40's with 30mm venturis (still too large for application) has 2827 venturi area, it could be said to be overkill, but also has gobs of potential.

I truly think dual 40's would best be used on a 12a BP with 31 or 32mm venturi. The RB Holley 600 was made for this application. The short intake manifold would work very well here since bridgeports don't need a long one, narrrow powerband.

Just talkin late at nite here.

Best of luck and keep us posted!!!

-bp-

someone82

Well I got a price quote on the manifold.. and here is what twm told me:

List price of 8-0048 is $420.00 for manifold with studs and nuts. Price for 0048 manifold with linkage for Webers is $522.50.

hmmmm maybe it isn't worth it... just yet... hehe I'm gonna still toy around with the idea.. and put it to the side until I get some much need funds heck I just ordered a new motor right..

how would the stock nikki perform on a street port?

I still really want to do it tho cause mainly it looks awsome and who else in my area has a Series 1 set up like this?

82streetracer

iTrader: (1)

atkins makes a single weber sidedraft similar to the TWM. Im am thinking of going that route to save time and money.

Is there a smaller dcoe than a 40. I have heard of 38s or something like that.

someone82

I've seen them on e-bay.. 38's
My dad suggested just to run a single 40, but I think that would be too small for a street port... let alone a stock port.. or would it perform better then a stock carby if I get it set up running smooth?

RXcetera

Just find a cheap used 48 somewhere.

82streetracer

iTrader: (1)

a single 45 is almost to small for a stock port, a single 40 would suck ***.

someone82

yeah that's what I thought... so where is a good place to get a cheap 48.... cause I really don't wanna run my nikki after the motor is broken in and I'm too cheap to by stuff brand new...