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#1 |
Registered User
Join Date: Mar 2018
Location: Fort Wayne
Posts: 106
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exhaust manifold question
So my truck is a 1968 with a 307 in it. I have the ram horn style of exhaust manifolds and I need to address an exhaust leak from one of the exhaust manifolds. I can see where the bolts attach on each side of each port.....but mine also has these funky square bolts on each port. What are these and what is their purpose? These don't seem to go all the way thru and into the block.
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#2 |
Registered User
Join Date: Sep 2011
Location: Ark City, Kansas
Posts: 3,333
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Re: exhaust manifold question
They may be pipe plugs. Some engines that year came with what was called a smog pump. It pumped clean air into the exhaust to help burn fuel that had not burned in the combustion process. Many folks did away with that setup, early. It caused problems, needed maintenance, and could be a pain....
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#3 |
Registered User
Join Date: Mar 2018
Location: Fort Wayne
Posts: 106
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Re: exhaust manifold question
Interesting. So if I bought new ones, I could buy ones without those plugs and all would work just dandy?
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#4 |
Registered User
![]() Join Date: Apr 2017
Location: Boise, ID
Posts: 856
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Re: exhaust manifold question
Definitely. I just did this on my 68 327. I bought the already ceramic coated manifolds that many parts vendors sell.
__________________
1968 GMC C2500 Long Bed Fleetside |
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#5 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,397
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Re: exhaust manifold question
Provided that one of the plugs is the leak. If they have square heads, they are probably 1/4" taper pipe plugs, but the threads in the manifold are for 5/16" B-nuts like one finds on an inverted flare line. If one of those is leaking, just remove it, clean the hole and put in a 5/16" B-nut plug. If the threads in the manifold are toast, use a little JB Weld on the threads. Note that the 5/16" refers to the tubing, not the thread. I forget what the thread actually is atm, but if you go to the parts store, they can sell you that B-nut plug. Common as dirt.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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