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| | | | Joined: Oct 2019 Posts: 7 New Guy | | New Guy Joined: Oct 2019 Posts: 7 | I’m looking into getting a set of headers the exhaust manifold is cracked in a few places and is in terrible shape the listings I find don’t list a 270. My question is this engine the same as the other inline sixes of this era I’m thinking it’s a 48 gmc 2 ton model any help or suggestions would be greatly appreciated | | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | The exhaust port size and placement, and the flange bolt pattern is AFAIK unique to GMC (228, 236, 248, 256, 270, 302) and definitely different from Chevrolet stovebolt (which is similar in appearance but smaller). I suspect the exhaust port size (but not the position) differs between big port and small port GMC heads. AFAIK a 270 may have either.
If the primary opening in the backside of the flange is the right size (not smaller, slightly larger OK), a "foreign" header (but probably still from a 7 port engine with individual #1 & 6 exhausts and siamese 2-3 and 4-5 exhausts) can sometimes be adapted (lots of work) by splitting the flange (in the center, or between every port) to move the primary positions closer or apart. Engines with similar bore pitches are probably the best candidates. | | | | | Joined: Sep 2010 Posts: 1,706 back yard wrench turner | | back yard wrench turner Joined: Sep 2010 Posts: 1,706 |
Wayne1938 1-Ton Farm TruckStovebolt Gallery Forums1989 Silverado 1996 Mustang GT convertible When I die, I hope she doesn't sell everything for what I told her I paid for it! | | | | | Joined: Oct 2019 Posts: 7 New Guy | | New Guy Joined: Oct 2019 Posts: 7 | Any suggestions as to where I can purchase a set of headers or an exhaust manifold? | | | | | Joined: Oct 2019 Posts: 7 New Guy | | New Guy Joined: Oct 2019 Posts: 7 | Any suggestions as to where I can purchase a set of headers or an exhaust manifold? | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | In the swap meet, here.
Or, on OldGMCtrucks.com | | | | | Joined: Jul 2014 Posts: 892 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 892 | You can make or have made a flange kit using the old exhaust manifold as a pattern. Then you or a competent welder can make up a set of custom headers based on the flange you have made. This is how I made a set of headers for a 53 Cadillac V8 sitting in a 53 Chev coupe. In those days I was a competent gas welder. I could not do that now but someone can. I had given up trying to adapt a set of Olds V8 headers and started from scratch. It helped that I was working in a welding shop at the time.
1951 3800 1-ton"Earning its keep from the get-go"In the DITY Gallery1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971. | | |
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