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Index > Engine/Drivetrain > Thread: Side draft or down draft...
Thread: Side draft or down draft...
top1usa


Redlining
Posts: 264
posted October 11, 2011 08:41 PM

Side draft or down draft...

Hey guys, need advice from you guys.

I'd decided to go with Weber 48 IDA on my engine rebuild but not sure the differences, pros and cons between side draft and down draft manifolds. Engine is 13B street ported. Someone told me side draft has better high end and down has better low end....what should I believe and ultimately which should I choose???

Thanks in advance....


Tim
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Brad


Rotorhead
Posts: 1671
posted November 14, 2011 05:15 PM


Hi Tim. Just the opposite. Sidedraft with the carb ontop of the motor has a long intake manifold which makes a better lowend.

Weber IDA downdraft makes better top end. The short manifold with one gradual bend plus the carb's ability to move a lot of air and fuel makes it a top end performer.

The biggest question is do you want a cold start assist system? IDA does not have one and it's cranky when cold. ONLY OEM DCOEs have a cold start asisst, the typical DCOE's from the speed shop to not.

Dellorto DHLA has a cold start assist that works extremely well.

       
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spokanerxdude


Hauling
Less cubes... More balls
Posts: 181
posted November 16, 2011 11:16 AM

There are actually two types of side drafts one is the over the engine like Brad is talking about and the other has very short runners and the carb stick straight out towards the shock tower. Not sure which is which but one had a stronger top end and the other has a stronger bottom end (power wise). I'm sure someone on here can tell you which one dose what.
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Brad


Rotorhead
Posts: 1671
posted November 16, 2011 02:50 PM

the short manifold with the carb sitting above the headers has much better throttle response and top end. atkins sells these, they were originally made by "Lake Cities Rotary".

the long mani with carb sitting on top of engine has better low to mid.

       
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top1usa


Redlining
Posts: 264
posted December 25, 2011 11:11 AM

Thanks guys!

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74' Mazda Repu-Flare
yellow
85' Toyota ae86-Red-SOLD
88' Toyota ae92-Gray
14' Toyota Prius

       
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