Planning a moderately warmed over A14 build as stage 1 of the 120Y having just picked up a bunch of manifolds and carbs, and I've started thinking about my options. Obviously the factory Hitachis will be out gunned by the single 40 on the Lynx x-over manifold, but I have a left field thought... 40mm IDF on the big Rowland downdraught manifold. It might have some advantages:
1) It's further away from the heat of the exhaust
2) bigger runners than the Lynx manifold
3) less sharp bends than the Lynx
4) large plenum for intake pulse damping
5) constant draw on the carb - virtually eliminating charge stalling

I'm leaning towards the IDF being a better option than the DHLA. Am I missing something about single plenums not working as well at higher rpms?
Obviously on a stock manifold you wouldn't bother at all because they're tiny and don't actually have a single plenum feeding each inlet runner, but the big Rowland manifold is a different story... I'd be interested to hear some thoughts on the idea, or if anyone has some good links to articles on inlet designs for 4cyl or even V8s? I guess it's sort of similar to a V8 dual plane vs single plane manifold, but that's going against my thoughts on the constant draw issue...

Thought about the 38dges? Its certainly capable of 100+HP. One letdown with my manifold is you can't really port the inlets with these stock ones, under the adapter I smoothed out the transition but left the head and ports unported so I suspect that's where its holding me back from cracking
100rwhp

I've read a number of books and papers on the technical aspects of pressure wave charging etc. with IC piston engines. What I've taken from that is

-Max power/ torque is always individual runners/ throttle bodies. Changing nothing else the torque curve has one defined peak.
-Adding a plennum reduces the peak torque value and shifts it down the rpm band, but, it has the desirable effect of spreading it out. i.e. the total area under the curve doesn't change much
-As the plennum gets large the torque curve looks more like ITBs.

These are purely the effects of plennum/ no plennum.

Grouping 1&4 and 2&3 but keeping them seperate approximates an ITB since there's no time they are sharing the fluid path.

I can't speak to your other comments with any confidence but I'm sure others will have confidence.

Harry, Give the 40 or 44 DCNF weber a look as well. They are also a synchronous dual throat carb and from memory share the same or very similar stub pattern as the 32/36 DGV's asynchronous carbs. I have used a few over the years with good results. Much like the DCOE & IDA /IDF all components are tune-able to the specific requirements. I think I may have a spare one in the shed somewhere if you want to try it out. They look like the image below. Plenty of spares and calibrated parts.




One of my many side projects is a twin 40 dcnf setup.. [still not finished].

I was thinking IDF because they're readily available, and the design and tuning is basically identical to DCOEs. So I'd be comparing apples to apples and the only real variation is the manifold design.
38DGAS carbs aren't as tuneable with fixed venturis, and aren't really a performance carb in the same way as DCOE or IDFs. They're more for improved torque compared to a 32/36. And really on the stock inlet manifold you're not going to get anywhere even approaching 100rwbhp. Most seriously worked twin sidedraught A series struggle to get there using cams that simply will not run with the standard manifold design.
DCNFs - all I know is they were used on Ferraris, and that sounds expensive lol.

The Lynx x-over manifold may actually have an advantage over a twin sidedraught setup because you get a far more constant draw on each choke, halving standoff and time taken to get the inlet charge back up to speed after the valve opens. There is also effectively a plenumn for each pair of cylinders to dampen pulses.
It's downside is the 2 or 3 90degree bends in the inlet paths and the smaller internal size. But those bends should also help dampen pulsing. I reckon they should be within a few percent of twin dcoe peak power and probably be better everywhere else! But really I'm more interested in the two manifolds I have rather than ones I don't...

This is an individual runner manifold, sharing a large (for the engine capacity) common plenum. Massively different design to the factory manifold and capable of supporting much more aggressive cams.
If you ran a synchronous carb, you could weld a plate in there and split the manifold into a 1-4, 2-3 manifold like the Lynx design, but with larger runners and a better inlet path. I reckon it's worth the few hundred bucks it would cost to mess around with, just to satisfy my own curiosity...
1- dyno it on the 40mm Dellorto sidedraught
2- dyno it with the 40mm IDF on the stock Rowland manifold
3- dyno it with modified split Rowland manifold

My money would be on 3 for peak power, but the others would be interesting comparisons...

As a follow-up.
You make all very valid points regarding the manifolds. I think the Lynx X-over design certainly helps with maintaining the gas speed on the dual throat synchronous carbs, but as you say it has all sorts of sharp bends on the flow path to achieve the outcome. I think the performance edge may actually be with the Rowland manifold due to the more direct pathway and it may also retain more heat specifically at the base of the carb mounting point to contribute to better fuel vaporisation.

As for the DCNF's weber, yes they were and are typically standard equipment on Ferrari and Maserati, but have been proven to be very popular on VW engined cars. They can be had at very reasonable pricing. [There's one on Ebay US for $120] Calibrated parts are no more expensive than DCOE, IDA/IDF's and are tuned in the same way, three circuits. Idle, Progression and Main. I like them as they are extremely compact.

I think that since it is a warm A14 build, there wont be be much in the net difference between both induction setups.

On an aside, have you considered giving a 32/36 DGV5-a the formula Ford treatment. The kits are available to convert them to FF spec which essentially transforms them into a synchronous carb. There is a bit of literature on the web detailing what to do. They do have the capability to flow more than enough for a warm A14. This may contribute to keeping the cost down.

if I was going to the effort of testing the manifolds I'd get my freind to 3d print out a thick phelonic spacer that incorporated a dividing plate underneath. Should last a few runs on a dyno.

Did you order the manifold through Rowland directly? I heard there was a reseller here?

I like the IDFs better choice for velocity stacks
than the DCNFs but I like the 38DGAS if the primary
is on the outer or 1 a 4 runners as it will make
the primary equal and have more down low.
Depending on your performance goals bu the 38dgas
Asynchronous are good carbs and easy flow plenty
for 2ltr and over therefore you have many choices!
will be interesting to see if a divider makes a
difference but Im guessing the downdraft mani
will perform better than the single side lynx setup

I'm curious to see the flow figures of the manifold my buddy and I modified. If you were local I would loan you the manifold with carb.

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