DemonHunter

425 duel mixer adaptor

13 posts in this topic

does any one know of where to get one of these or at least get one made up at all?? lm running straight LPG on my xf pano , l have 2 425 mixers with the holey  throtal plates on them  but l want to run both instead of just the one.. the only place  cn find one is on evilbay an its from the states which is way costly as hell.... lm also waning  to run twin hi filters if l can an ideally would like to be able to get one made  so that the mixers sit alil further apart to do so...or  would that make it sit too close to the dizzy in the end??..Any help be great as this is the 1st time lve actually used the 425 mixer

s-l400.jpg

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If it's on a 4.1 crossy, a single 425 is more than adequate. They're a pretty good size on a mild V8.

Bolting another one on will be a costly, time-consuming, energy-sapping, giant ball of disappointment. You'll possibly see a drop in economy due to the loss of metering accuracy, also fuel curves, already a bit crude on gas, will be screwy because you may not get into the "power" section of the metering rod.

The main restriction on your engine will be in the valve size, porting and manifold, not the mixer. As valve size can't be increased much on a crossy, you're stuck with putting a big cranky cam in it, with all of the downsides that go with that.

On a vapour mixer setup (as opposed to liquid injection), LPG takes up roughly 25% more volume in the inlet tract than petrol does, hence the power drop. Barra 6s put out 182kW, but the Barra e-gas only put out 157.

The difference there is in how much fuel/air each one can gulp with the same valve/porting/manifolding setup. The LPG engine simply can't breathe as much fuel/air as the petrol one. Bolting on another mixer would have achieved nothing.

With that adaptor, the two mixers still need to feed into the single throttle at the bottom. Not much point to that really.

Another point: LPG vapour mixers operate on constant depression, just like CDs and SUs. Bolting on another one will still impart the same pressure drop across both carbies as having a single one because it's the diaphragm spring that determines how far the piston and rod rises. Having two will just mean that each one opens less, with the same amount of vacuum below. Sure, they will "top out" at a much later point, but honestly I don't think you'll reach it with just one on a 6 cylinder.

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2redrovers likes this

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A tunnel ram would work better if the front and rear runners don't join on the top part of the manifold!
https://www.ebay.com.au/itm/FORD-CLEVELAND-302-351-2V-TUNNEL-RAM-INTAKE-MANIFOLD-12-15912-200/132798569618?hash=item1eeb695c92:g:frwAAOSw3thbVrlv:rk:29:pf:0
Yowsers.... Can you order the one that's not gold plated?

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OK... Disregard my long-winded reply. Twins are the go, but on a manifold like this:

https://speedmaster79.com/ford-302-351c-cleveland-3v-4v-w-tongues-twin-carb-intake-manifold-satin/

OK it's basically a P__ C__p and quality is a lucky dip, but nobody else makes them, so this is it. It has a big plenum and gas likes that, more so than long runners (atomisation isn't an issue).

The design is actually for a blower mount (more recent ones have an open top and carby adaptor plate goes on that) so runners are very short. Might need some rounding off of corners/smoothing out of casting, etc.

Only drama would be build quality. From the varying stories I've read, some of them are rubbish and others have no problem.

Advantage of this low-profile design would be bonnet clearance: no need to cut holes.

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deankdx likes this

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