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1963 Unimog 404
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26 Posts
Discussion Starter #1
On the 404 with the ndix carb,has any one tried modifying the insulating s pacer between the manifold and carb by changing it from 2 holes to one large slot(cutting out the divider between the two holes). This would not change the cfm of the carb but would make more cfm avalible to each piston on the intake stroke. this work great on some engines.the set up on the 404 is basicly 2 small 1bbl carbs sharing a float bowl as it apears,I have not taken the intake manifold off to check how it is made. thanks Voudoux
 

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1963 Unimog 404
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26 Posts
Discussion Starter #3
why,if it was equipted with a 1bbl or aprogresive 2bbl all cyl would draw from a single plenum.The air velocity through the carb would be slower possibly making throtle response not as crisp and the transition from the idle/off idle circuit to the main may be efected,nothing that can't be tuned out of it, but at wot you would get the effect of a larger carb.I am planing on trying it as soon as I get a spare plate.thanks for the reply Voudoux
 

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2015 Rubicon Unlimited (Let the shame be upon me!)
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3,823 Posts
A dual plenum intake with divided venturi carburetor is ideal for the low speed environment in which the 404 was designed to operate. With a modest cam profile and amazingly low compression ratio putting something that amounts to an Edlebrock Air Gap is not really going to promote performance. The split plenum as stated allows each half of the carburetor to provide high gas flow and high vacuum impulse to only half the cylinders. On throttle tip in your vacuum will stay much higher which keeps the mixture better suspended.

Improve the airflow through the engine with increased output until the manifold is the restriction and then you can start to talk about performance intake manifold tricks.
 

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1967 404 Unimog (Belgian), 2010 Ford Fusion Hybrid
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253 Posts
It's an interesting thing to try.

I assume you're looking for increased performance at high throttle opening. I would expect the high velocity at or near WOT would result in little or no impact under that condition; i.e. the mixture spends so little time in that short gap that it cannot easily change direction to feed the other set of cylinders. I would also expect virtually no impact at idle. As the other guys said, I would expect the greatest impact at low throttle openings.

Thus funky behavior in the transition between idle and low throttle opening and little change elsewhere.

However, this is an easy and cheap thing to try. It seems unlikely to damage anything if you're just trying it briefly. If it does not work you can just put the stock spacer back.

I say give it a shot and post the results!
 

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85' U1300L Holset Turbo VA A/C, 66' Propane 404.1 rock mog, 1975 416 Doka, G500, Volvo C303
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5,035 Posts
I suspect zero gain will be realized.
 
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