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Throttle body rebuild

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I am rebuilding a throttle body which I did not strip. The butterfly itself has a bevel on the edges and I’m wondering which is the correct way to assemble.

I have done a drawing, where the bevels are exaggerated, but it’s gets across what I need it too.

Also this engine has an idle air control valve and has an idle screw in the throttle body for adjusting idle. What do you recommend should be the minimum/maximum clearance there should be on the butterfly?


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The top one.

When assembling it, back off the idle stop, if fitted, and loosely fit the screws. Then wiggle the plate to ensure it's sealing against the body as well as possible, VERY lightly tighten the screws and work it a few times, before holding it up to a light - you should see no light past the edge of the closed butterfly, or at most a VERY small amount. Then tighten them fully, recheck it's closing fully, and stake the fasteners.

Some people just use a locking product, but I've always been nervous about them and I use a punch, or drift, in a vice as an anvil, have one person carefully position the heads of the screws on the 'anvil', and stake, or deform, the threaded end with a punch, small chisel, or centre punch so the screw is mechanically prevented from loosening and dropping out and into the engine.

Others may have other techniques, but that's what works for me.

I'll just add that idle motors don't necessarily have sufficient range that you can run the plate shut.

You often need to use the throttle stop to get some of the air, leaving the IAC to deliver the rest.

Thankyou for getting back to me on this!

This is a similar system that i have attached.

I have an adjustable stop on the butterfly, an idle adjustment screw that controls the restriction on either side of the butterfly and an IAC that also bridges both sides of the butterfly.

How do thee components work in conjunction with each other? What would you typically set the gap too on the butterfly to the body of the throttle body for this type of set up? Would you set it to .001" just so it doesn't stick and then let the idle adjustment screw and IAC take care of the rest.

Am i right in saying, you screw the idle screw in or out to control idle speed and the IAC will control any fluctuations in this speed?


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The total air mass required for cold idle should be supplied by the throttle stop setting plus a little more air from the idle valve so when higher idle is required the idle valve still has more range to increase airflow.

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