Rx7carl

2bbl wraparound side draft.

Pros- good in autox, road racing, street use no stumble. easy to access jets for tuning. Some are equipped with a "choke" or more correctly a cold start assist.

cons- parts not easily availible, some carbs are totally out of production.

Rx7carl

2bbl down draft

pros- see wraparound, probably better hi rpm power over wraparound

cons- see wraparound, no choke/cold start assist AFAIK. Probably worse in the low end.

Rx7carl

Sterling-

pros- cheapest of all, uses stock replacement parts, matches flow of the Holley without the stumble problem. Autox, Road race, streetable. No choke but fast idle retained for cold weather warm up. Good all around performance

cons- less total flow potential than the others without a manifold to match.

DriveFast7

iTrader: (1)

Carl, input on the Rotary Engineering dual 36 DCD setup? I just bought one.

pros - Real nicely curved intake manifold with longer primary runners and shorter secondary runners. Jets, floats & rebuild kits still available (same jets as DGV). Supposed to make very good low and midrange and some people say they make great top end too. Standard setup is 25mm primaries, 32mm secondaries. Mine has 28mm primaries. Flow potential?

cons - must synch carbs but once synched they stay set for years.

jjlrx7

have holley and its nice for 1/4 mile but corners and mid range rpms sux. go weber or injection.

FB II

holleys are one of the best carbs to use ever... but you HAVE TO UNDERSTAND THEM! on our rotaries changing the boosters is almost a must. it gives better signal and atomization of the fuel delivery. there is no holley too big either. a 750 can work beautifully on a stockport 12a. just gotta know what your doing.

Rx7carl

Sounds well engineered, the choke sizes are pretty good. The long wraparound runners will definately aid in low midrange power. Is it an true IR manifold? That might limit the top end but not necessarily. I've never flow tested that manifold, nor a 2bbl downdraft so its hard to quantify compared to what I know as fact.

Hows the linkage setup? I imagine like any multiple carb setups any slop translates into big time sync problems. Unless they got something tricked out, keeping them sync'd may be more than a yearly chore. As it wears, it'll go out of sync. I used to love my 4-1bbl setup on my flat 6 vair, but talk about a PITA to keep sync'd? Like once a week! But that was a poor design.

Rx7carl

Yea just block off the secondaries LOL.

Maybe I'll put an 1100 Dominator on my wheezing stockport 12A thats in my DD.

Cmon Zac, you know that the booster signal would be crap on a 750 no matter what you use. And the low end? Might as well get out and push it up to 40mph. Bigger is NOT always better, at least in this case. V-E-L-O-C-I-T-Y is king, velocity without restricting top end power is the name of the game. Lots of ways to get there though.

FB II

exactly. that's why there are so many boosters and venturi setups that can be used with any cfm carb. basically you use the booster that gives you the most gain, thereby keeping low end power of a smaller carb but all the top end you can use

check this out: http://popularhotrodding.com/tech/05...arb/index.html

i already tuned a 600cfm double pumper on a stockport 12a and it actually cranked up, idled, and cruised slightly better than my nikki. got better gas mileage as well. i need a new carb hat tho so it won't be going back on for a while. and the power difference is rediculous.

FB II

oh and CSU carb shop does rotary holley setups.... and the ONLY one they use is a 750 double pumper. perfect idle, drivability, and amazing power.... especially when blow-thru i'm talking anything from stockport 12a - PP 13b turbo.

Rx7carl

You still will have no intake velocity unless you put in smaller venturis, and then you now have a smaller carb. Have you ever changed boosters on a Holley 4150/60 3310? They dont come out like the Nikki. Special tools are required to change them. And the venturis are not removeable, they are part of the body.

Ive seen a 750 on a stock port FC at an autocross. Of course it will work, doesnt mean its optimal.

I believe you about CSU. If you know what your doing you can make anything work. Thats why they are specialists. Oh and Im not pickin on you bro, I just disagree with you to a point. Technically like I said, anything can be made to work, so you have a point, but theres easier ways than hacking up a carb.

FB II

agreed... it definitely by far isn't easy. that special tool is a pain in the ***. i guess i'm still looking at it in more of a boosted perception. i can run the bigger carb and make gobs of power up top under boost, but still achieve the drivability of a much smaller carb. but ofcourse it is way easier to just get a smaller carb and tune from there

but it caaaan be done. my point is mainly to all the holley haters in the world

DriveFast7

iTrader: (1)

The R.E. mainfold is Independant Runner. One runner per choke. One runner per intake port. Benefits.........limitations..........affect on top, mid, low end?

The linkage has two heim joints for the throttle shaft which rotates and moves 2 levers. Levers are attached to throttle shaft on one end, carb throttle body on other end.

aussiesmg

iTrader: (1)

Interesting thread, great info Carl

Rx7carl

My guess would be that low end should be strong with a lower overall torque peak. The mid and top would depend alot on the inatke tract lenghts. If they are tuned for more midrange, then thats where your peak will be.


Well make sure you keep any slop out of the linkage. Do you have a unisyn or some other sync gauge? Your gonna need one.