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I have one for a 13B I'm going to use on a future engine, I used it before with an adapter I made for a 6 port, which ran terribly.
The air chose to go through the secondary and aux ports only, it could idle without jets in the barrels for the primary ports.
For the future 4 port I'm planning on doing it the old fashioned way and drilling jets incrementally.
I have one for a 13B and I have a big chunk of plate to make a 12A adaptor. I could probably port it together to smooth the transitions/convergence angle, but I really bought the manifold for my bridge ported engine. With the Holley 750 as a throttle body on a RB 4 port manifold, looking at datalogs it is starting to become a restriction on the bridge ported 13B over 7000 and by 10000 it is a roughly 5kpa restriction. I was hoping that dual 45 throttle bodies would fix that Not that it needs any MORE power.
But I also wanna make the 12A make more power. With this car's weight and a stock 12A I SHOULD be able to get it into the very low 15s. My deep competition in that car's class is an NB Miata and I could probably get more power/weight to make up for the reduced handling. (More power has never served me wrong yet!)
The nice thing about the dual DCOE manifold is that it is like half the length of the Lake Cities/Atkins style manifold. There is barely any room for an air filter with the Lake Cities, and the trumpets end up right up against the strut tower. I tried sitting my DHLA on it and the lack of clearance was concerning. Even with an adaptor plate, the dual DCOE will be a lot shorter.
I have quite the collection of manifolds I have a Pro-Jay for a 6 port, a Racing Beat for a 4 port, a Lake Cities for a 6 port, and the TWM for a 4 port. As well as Racing Beat DCOE uppers for both GSL-SE and Series 4/5... that one I bought new and they were removed from the website shortly thereafter.
I also have a dual DCOE manifold for a VW 8v engine, that has HORRIBLE transition from the carbs to the ports. I'm half tempted to adapt THAT to the 12A, because the port layout and spacing is similar, and it has a nice maybe 10-15 degree up angle, which would be awesome for strut tower clearance.
I also planned to make an adapter for my current 12A, but then I found a Lake Cities manifold.
I didn't think there was enough metal on the 13B manifold to slot the holes for a 12A engine and with a bolt through adapter it looked like there wasn't enough room for the bolt heads, so I CADed up a 2 piece adapter.
I dunno, maybe I over complicated it.
Trying to find info on a good starting point for jetting dual 40 DCOEs on a stockport 12A.
so two DCOE's? i can tell you that a stock engine likes a 55-65 idle jet. the IDA doesn't use the air bleed like the DCOE, but a smaller one helps, not sure what F number that is. the main jet can be 140-180, with the air corrector being ~20-40 smaller than that and like an F7 E tube. oh and 38-40mm venturi
i have no idea how having two carbs would change things, half the air flow should actually help the idle and transition circuits though, usually the rotary is wanting enough air that its idling on the transition circuit
07-13-21, 06:07 PM
Not that it needs any MORE power.
I have a Pro-Jay for a 6 port, a Racing Beat for a 4 port, a Lake Cities for a 6 port, and the TWM for a 4 port. As well as Racing Beat DCOE uppers for both GSL-SE and Series 4/5... that one I bought new and they were removed from the website shortly thereafter.
