1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

side draft or down draft?

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Old Dec 11, 2012 | 10:48 AM
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side draft or down draft?

My question is pretty simple. Which do you think is better and why? Ida down draft or DCOE side draft. If you need to know its for an 85 GSL-SE street port 13b.
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Old Dec 11, 2012 | 01:50 PM
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Side draft == better streetability due to longer intake
Down draft == better top end performance due to shorter intake
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Old Dec 11, 2012 | 01:51 PM
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sidedraft more torque down low longer runners, downdraft. better for like brideports and up high flow.

thats my understanding but i could be wrong
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Old Dec 11, 2012 | 02:03 PM
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From: https://www2.mazda.com/en/100th/
the only real difference between a side draft and a down draft, especially Weber IDA vs DCOE, is the intake length.

the side draft has a longer manifold, so peak torque, and thus hp will occur at a lower rpm. the exact rpm depends on the ports and stuff.
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Old Dec 11, 2012 | 02:17 PM
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For a street driven 6port or 1/2 bridge, a 4 bbl makes a bit better choice. It isolates the large secondary ports at idle/low RPM for a better idle quality and off-idle throttle response, while allowing them to come into play above ~3000-3500 RPM, which is where they start to make more power.
Of course, getting the carb tuned right, no matter which type is used, makes all the difference in the world.

Racing application, and the 2 bbl weber carbs then become more desireable, since there's very little need for the lower RPM driveability concerns.

This is just my thoughts, and I do run a 4 bbl on a 6 port myself.
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Old Dec 11, 2012 | 07:02 PM
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Two down draft 36 DCDs give you the best of both worlds, plus you get to learn to syncronize carbs, which can be very satisfying.
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Old Dec 11, 2012 | 07:46 PM
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Is there slosh with side draft carbs?

My eldelbrock likes to lean/rich out on long sweeping turns. (inherient flaw in putting a carb on a car sideways).
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Old Dec 11, 2012 | 11:47 PM
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down draft all the way , how many cars that are not fuel injected have a 180 degree runner ? none .......
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Old Dec 12, 2012 | 10:25 AM
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From: Lake Wylie, N.C.
Originally Posted by Qingdao
Is there slosh with side draft carbs?

My eldelbrock likes to lean/rich out on long sweeping turns. (inherient flaw in putting a carb on a car sideways).
I think in general yes. My Dell has this issue on right handers sometimes.
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Old Dec 12, 2012 | 11:49 AM
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Originally Posted by Qingdao
Is there slosh with side draft carbs?

My eldelbrock likes to lean/rich out on long sweeping turns. (inherient flaw in putting a carb on a car sideways).
Any carb that has a float bowl will suffer from fuel slosh. Pretty much every carb has some kind of float bowl, unless it has been modded to become "floatless".
The harder a carbed vehicle is driven, the more apparent the fuel slosh can become, due to the effects it has on the engine's performance. Sadly, there is no "perfect" carb for any/all use.

I use an edelbrock carb on one of my FB's (6p 13B), and to minimize the effects of fuel slosh, I lowered the floats ~1/16" and installed the "off-road" needle/seat kit. I saw no ill effects of fuel slosh at last year's rallycross nationals after performing these minor mods. Not only were there plenty of tight turns, but it was also on rather uneven ground, made even worse due to the blown front struts on the car......
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Old Dec 12, 2012 | 02:29 PM
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From: https://www2.mazda.com/en/100th/
+1.

the IDA's do pretty well, but if you're in a turn @1g and hit a bump, it'll misfire... sometimes the sevensonly FD things run with us, and the exit of turn 15 is bumpy, and they all misfire at the same place...
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