Stock TBI Intake Coil Bracket Bolt Size
12-26-2022, 12:22 PM
#1
Stock TBI Intake Coil Bracket Bolt Size
I can't seem to find a bolt that threads into the coil bracket bolt holes on the later style stock TBI intake (the one that takes the distributor that has a separate coil) I'm planning on using for the time being, so I'm wondering what size it's supposed to be. I think paint got in the holes when I painted it so that's why I can't get either a metric or SAE bolt to thread in. I need to know the correct size so I know what size thread chaser to chase the threads with to clear out the paint without ruining the holes.
Thanks.
Thanks.
12-28-2022, 10:45 PM
#2
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Car: '86MCSS
Engine: 396 .030"
Transmission: M20
Re: Stock TBI Intake Coil Bracket Bolt Size
Sorry no help here...I don't even own a tap and die set so I don't have the accompanying tool to check the thread pitch either. I do have a stock oe tbi intake that's been sitting in my driveway for years exposed to elements covered in a layer of powdery white dust. I took a known sae carburetor stud and tried to thread it into the coil bolt hole. I got it to grab the first few threads but then it got tight. I have another complete tbi intake with throttle body and purdy much everything else bolted up to it but that thing is buried in the farthest corner of my parts room. Meaning it inaccessible at the moment. 
12-29-2022, 07:17 AM
#3
Junior Member
Re: Stock TBI Intake Coil Bracket Bolt Size
I can't seem to find a bolt that threads into the coil bracket bolt holes on the later style stock TBI intake (the one that takes the distributor that has a separate coil) I'm planning on using for the time being, so I'm wondering what size it's supposed to be. I think paint got in the holes when I painted it so that's why I can't get either a metric or SAE bolt to thread in. I need to know the correct size so I know what size thread chaser to chase the threads with to clear out the paint without ruining the holes.
Thanks.
Thanks.
you're talking about these guys, right?
If I recall correctly, these take a 1/2" socket, so I believe that's a 5/16" coarse thread. Pretty standard. They're pretty shallow holes, I had to stack a washer or two to be safe.
12-29-2022, 08:10 AM
#4
Junior Member
Re: Stock TBI Intake Coil Bracket Bolt Size
But honestly they could just as easily be 9/16" like mostly everything else on the intake.
It's one or the other.
It's one or the other.
01-02-2023, 12:18 PM
#5
Re: Stock TBI Intake Coil Bracket Bolt Size
Turns out they are just 5/16"-18 holes, the same as the mounting holes for the throttle body. I figured out the throttle body hole size and thought the coil hole size had to be the same since they are so close together and so I chased the coil holes out with this size, and after I got the chase started on them it thread fairly easily.
Seems like the Chevy V-8 engines pretty much stuck to SAE threads on this generation of V-8 even though the engines went in cars that had already gone to metric threads by this time.
Seems like the Chevy V-8 engines pretty much stuck to SAE threads on this generation of V-8 even though the engines went in cars that had already gone to metric threads by this time.
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