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> Throttle body, Hole in butterfly plate
Ron914
post Jan 18 2025, 02:10 PM
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Hi ,
A new question about my throttle body.
Should I remove this screw&nut now that I have corrected my vacuum leak ?

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sixnotfour
post Jan 18 2025, 09:21 PM
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Mikey, try it,,you might like it..
https://www.youtube.com/watch?v=vYEXzx-TINc
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technicalninja
post Jan 18 2025, 09:53 PM
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I would...

That is a "bypass" hole.

The reason for the hole is to allow the throttle to close enough to operate the TPS (idle position) and provide enough airflow for idle.

When they first set that up it didn't have a hole, and they had trouble adjusting idle.

They sized the hole specifically to improve idle adjustment.

When everything is "proper" and you don't have any additional air entering past that throttle plate you will need it.

If your throttle is worn out and you have excessive bypass air you won't need it.

Hole or not, having additional hardware that MIGHT come off of the throttle and get into a cylinder is BAD!

You are asking for a visit from the Reaper!

If I wanted to close the hole, I wouldn't use a nut/bolt assembly. I'd braze it closed or something similar.

I AVOID any additional hardware anywhere in the intake tract if possible.

If you still have vacuum leaks (throttle shaft bushing wear can be a BIG one) opening the hole will increase your idle speed maybe to the point of being a problem.

I'd leave it off and if I could not adjust to my idle, I'd tape it closed (aluminum duct tape) for test purposes.

If I decided to keep the hole closed, I'd pull the throttle plate back out and permanently braze it closed.

I wouldn't trust any epoxy there; too much heat cycling and vibration IMO.

Edit: there is a chance the hole was drilled larger to allow the bolt clearance. If so, you WILL need a new throttle plate. Maybe someone here can provide a size (drill bit that will fit through a stock hole). I will look to my T-bodies tomorrow for a size. My stuff is basically late 1.8l L-jet and may be different from yours.
There is also a chance that different years and displacements had different sized holes...
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Ron914
post Jan 19 2025, 12:32 PM
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@technicalninja
Thank you for your response .
After finding the source of my vacuum leak I now have to back out the idle screw a lot when the car first starts so I believe now I might need to open that hole for now. Funny how you correct one issue and another one pops up ( I have determined I have a faulty decel valve also) . I think I will not try to close up the hole permanently until I get everything sorted out and pass my smog test .
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brant
post Jan 19 2025, 12:58 PM
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With the butterfly installed in the TB
Can you see any light around the butterfly?

99 percent of these cars have air leaks around the plate
Look in your TB and see if it has wear ridges where the butterfly clloses

Most TB are worn
Need new bushings and when bored slightly to be round again will need a new plate also to fit the new bore


When I had my TB rebuilt the person that did the work also fabricated is new butterfly to correctly fit the remanufacturing
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Ron914
post Jan 19 2025, 03:22 PM
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QUOTE(brant @ Jan 19 2025, 01:58 PM) *

With the butterfly installed in the TB
Can you see any light around the butterfly?

99 percent of these cars have air leaks around the plate
Look in your TB and see if it has wear ridges where the butterfly clloses

Most TB are worn
Need new bushings and when bored slightly to be round again will need a new plate also to fit the new bore


When I had my TB rebuilt the person that did the work also fabricated is new butterfly to correctly fit the remanufacturing


Interesting you asked that question. Yes I took a photo a couple of months ago . Looks like what you mentioned .

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Do you know who I can find that will rebuild this one for me ?
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JeffBowlsby
post Jan 19 2025, 03:49 PM
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Check with Mark Kinnaman Bartlett 914
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Ron914
post Jan 19 2025, 04:03 PM
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QUOTE(JeffBowlsby @ Jan 19 2025, 04:49 PM) *

Check with Mark Kinnaman Bartlett 914

Thanks Jeff
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brant
post Jan 19 2025, 05:35 PM
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So that is another vacuum leak. Unmetered air getting in
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Ron914
post Jan 19 2025, 07:17 PM
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QUOTE(Ron914 @ Jan 19 2025, 05:03 PM) *

QUOTE(JeffBowlsby @ Jan 19 2025, 04:49 PM) *

Check with Mark Kinnaman Bartlett 914

Thanks Jeff


I checked and tried Mark Kinnaman @Bartlett 914 but nothing comes up. Maybe he does not offer these services anymore .
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emerygt350
post Jan 22 2025, 01:47 PM
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He did mine back in April of last year.
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rjames
post Jan 22 2025, 02:23 PM
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I'd love to know what the original tolerances were. Anyone have a new old stock TB tucked away somewhere?
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Ron914
post Jan 22 2025, 03:09 PM
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QUOTE(emerygt350 @ Jan 22 2025, 02:47 PM) *

He did mine back in April of last year.

Hi Emery,
I have tried all means to search for him . How did you reach him? He might just no longer providing this service, (IMG:style_emoticons/default/sad.gif)
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JeffBowlsby
post Jan 22 2025, 04:46 PM
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Look here:

http://www.914world.com/bbs2/index.php?showuser=4707
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emerygt350
post Jan 22 2025, 06:28 PM
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Have you sent him a PM?
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Ron914
post Jan 23 2025, 08:57 AM
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Thanks You Jeff and Emery . I just sent Mark a PM.
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SirAndy
post Jan 23 2025, 11:52 AM
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QUOTE(Ron914 @ Jan 22 2025, 01:09 PM) *
I have tried all means to search for him


Y'all know we do have a member search?
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