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420A ITB Information & Interest Thread

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BLACK'98DSM

5+ Year Contributor
4,470
1,905
Feb 9, 2019
Alabama
I have conjoined a few ways, and we are soon working on designing/producing an assembly of ITB's for the 420a. The purpose of this thread is partially to gauge interest, as there is a possibility to mass produce these if the demand is there. At a minimum, one or two assemblies will be produced for my personal 420a experiment. If we can get 10+ gauranteed orders by the time we reach a final product, then production of the first lot would begin.

A few things to note.
1: This is still in the pre-production stage, meaning I cannot present a finished product yet. A digital model is still being created, the initial raw ITB will be CNC machined of billet aluminum stock, and further modified with a synchronized throttle linkage, and possibly made as compatible with the stock throttle cable but I forsee an aftermarket cable being used. I will return to this thread to post blueprinting and production of the first unit.
2. Please keep in mind this should be considered for aggressive/racing applications only. This assembly will not be designed for use of an IAC, so Megasquirt is required. This assembly also will not be equipped with any vacuum ports, so vehicles with deleted accesories only, unless an aftermarket vacuum pump is to be added.
3. With enough time, I can release the flow values of this product as compared to a stock intake manifold and also a ported intake manifold. We have a flow bench. I do also wonder about the KSR sheet metal manifold but am not willing to invest $750 into that at the same time as this investment. I can also release the dyno results once we have achieved a final product. Average of 3 pulls with modified stock manifold then average of 3 pulls with our ITB setup, only variable being this intake change, and corresponding tune of course.

I honestly do not expect 10 members to step forward with this. But will be prepared if it does happen. I'm not sure how many people actually still race a 420a car, most of that ended 15+ years ago. But if a group is still out there, a new opportunity awaits. Even if no one is on board, I will still use this thread for project updates and results. I'm not really sure what results to expect with this experiment, but we have reached a point where I need to find a modification to truly maximize the 420a, I've always hated the shape of our intake manifolds.

It's late at night and I've obsessed over this a little too much today, so I'm sure someone is left with questions. Ask away and I'll get back with you.
 
We just cut the first flange over the weekend... (not using any stock components)

I will update with pictures once the first assembly comes together.
What size are you going with the ones I posted were Mark Bullett's that I got from him with the car. But there only 52 mm and I believe there too small for a drag app compared to other platforms.
 
What size are you going with the ones I posted were Mark Bullett's that I got from him with the car. But there only 52 mm and I believe there too small for a drag app compared to other platforms.
We're going to try multiple sizes and see what works best throughout the powerband. I don't think 52mm is too small. It would be senseless to have each body be significantly larger than the intake port. I want the size as similar as possible to not reduce the air speed.

This is something that will be produced and modified multiple times to get right but I have a good idea of which direction to go.
 
What size are you going with the ones I posted were Mark Bullett's that I got from him with the car. But there only 52 mm and I believe there too small for a drag app compared to other platforms.
I also just realized you bought Bullett's car. That's awesome man. I never heard that he sold it, but that isn't surprising after all this years.
 
Not to get the thread off topic but I always wondered what happened to that car!
Me too. And seeing how well that car performed with stock intake runners, I'm excited to see where we'll end up with a totally performance based product! The casting quality of the stock intake manifolds and cylinder heads is honestly terrible. Too much noise but not enough flow.
 
Any updates to this I may be interested in another setup to add to my collection

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may sounds really dumb but is this going to be a stand alone only thing or is there going to be some way to piggy back onto factory engine management?
 
I have thought about doing ITB's on my car, but honestly IDK if it's a good move. Intake at the rear that's a hot low pressure zone, not good for power. Unless you are going to put a scoop and an air box on it. I had planned on doing a slide valve. A butterfly gets in the way of the air and forces you to run a larger dia port and upsets the efficiency of the port. Many things that were itb have gone to plenum and single TB. But one shouldn't speak in certainties, so maybe you will find power.

Have plenty of experience with ITB stuff, and you can in fact run speed density and use a IACV on them. It's not gonna act like grandmas buick, but it's not that bad.
 
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