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225 Exhaust manifold - 3/8" studs?
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Author:  GregCon [ Mon Mar 14, 2022 10:49 am ]
Post subject:  225 Exhaust manifold - 3/8" studs?

I have this manifold fro man '81 truck...I separated it from the intake today and noticed it uses 3/8" fasteners rather than the 5/16" I'm used to seeing on older manifolds. It this stock, or did someone modify it?

The stud closest to the cylinder head looks like an OEM stud, the other two look like all-thread that was cut to suit.

Thanks!

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exhaust .jpg
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Author:  Badvert65 [ Mon Mar 14, 2022 12:32 pm ]
Post subject:  Re: 225 Exhaust manifold - 3/8" studs?

OE would be (3) 5/16-18, minimun of 3 inches long.
jus sayin....

Author:  volaredon [ Mon Mar 14, 2022 7:03 pm ]
Post subject:  Re: 225 Exhaust manifold - 3/8" studs?

the last few I have dismantled, were 5/16 to outside of carb, 3/8 between carb and head. and 7/16 to hold pipe to flange on the exhaust.
70s Super 6, (X2), 80 D150 ( originally a 1 bbl) and also a pre EGR, 1 bbl exhaust stack. so about 4 manifold stacks. Wide variance of years they were off of.
On 2 of the exhausts, I had to send out to have busted thru bolts, lasered out. They did the 1st one (when I converted my son's truck to Super 6) and didn't charge him anything/ but the same guys, at the same shop, stuck me for $150 for the same job. on the same kind of manifold. about 8 months apart.
(I wasn't happy, still mad about that, when their shop's name comes up// nother story)
and yes the all thread was probably something done thru the years.

Author:  GregCon [ Tue Mar 15, 2022 5:33 am ]
Post subject:  Re: 225 Exhaust manifold - 3/8" studs?

Thanks. I'll operate on the idea they were a modification. It appears pretty well done, the threads are straight. I haven't looked, but I think these later manifolds (or this one, at least) have more meat on the bosses. It seems the earlier manifolds would get pretty thin if you oversized the holes.

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