C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

LT1 header thread size

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Old Mar 31, 2008 | 01:07 PM
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Default LT1 header thread size

What size threads are these on the AIR tubes? I bought so 2061 headers, and need to hook up the AIR tubes. It looks like a fine thread.

The '87 stuff won't fit/is different.

-- Joe
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Old Mar 31, 2008 | 01:15 PM
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My '95 uses an M21 thread for the air injection ports on the headers.
I was struggling to find a fix for this myself, but on another site, someone had suggested using an M21 oil drain plug for it. Or you can find a plug/disc/etc that can block the hole and then cut the old fittings off the air pipes and use those to hold it down.
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Old Mar 31, 2008 | 01:29 PM
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Originally Posted by F1Fan
My '95 uses an M21 thread for the air injection ports on the headers.
I was struggling to find a fix for this myself, but on another site, someone had suggested using an M21 oil drain plug for it. Or you can find a plug/disc/etc that can block the hole and then cut the old fittings off the air pipes and use those to hold it down.
M21 drain plug? Sounds good. I'll dill out the center and weld a 90* to it.

Thanks a bunch!

-- Joe
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Old Mar 31, 2008 | 10:19 PM
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Originally Posted by F1Fan
My '95 uses an M21 thread for the air injection ports on the headers.
I was struggling to find a fix for this myself, but on another site, someone had suggested using an M21 oil drain plug for it. Or you can find a plug/disc/etc that can block the hole and then cut the old fittings off the air pipes and use those to hold it down.
The left and right are a different size on a '94 LT1 or is it the tube size that's different?
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Old Apr 1, 2008 | 09:58 PM
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It ended up being 22MM on both sides.

-- Joe
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Old Apr 1, 2008 | 10:57 PM
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Default drain plug

I got mine at oreilly auto in the area where they have all the generic stuff like window cranks vacuum tubing etc. The application is a cummins diesel dodge.
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Old Apr 2, 2008 | 06:56 AM
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Originally Posted by C4forlife
I got mine at oreilly auto in the area where they have all the generic stuff like window cranks vacuum tubing etc. The application is a cummins diesel dodge.
Good to know! I searched through a bin of fittings for 10 minutes. They didn't end up charging me for them.

-- Joe
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