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270 exhaust question
#1336629 Fri Dec 06 2019 04:52 AM
Joined: Oct 2019
Posts: 7
F
Ford351 Offline OP
New Guy
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

Re: 270 exhaust question
Ford351 #1336657 Fri Dec 06 2019 01:13 PM
Joined: Dec 2008
Posts: 1,430
P
Shop Shark
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.

Re: 270 exhaust question
Ford351 #1336661 Fri Dec 06 2019 01:48 PM
Joined: Sep 2010
Posts: 1,538
W
Shop Shark
What he said!


Wayne

When I die, I hope she doesn't sell everything for what I told her I paid for it!

1938 1-Ton Farm Truck
In the Stovebolt Gallery
Photos that I have shared on Stovebolt via PhotoBucket are no longer available. Please contact me if you want a photo from an old post. malmwayne@hotmail.com
Re: 270 exhaust question
Ford351 #1336710 Fri Dec 06 2019 09:46 PM
Joined: Oct 2019
Posts: 7
F
Ford351 Offline OP
New Guy
Any suggestions as to where I can purchase a set of headers or an exhaust manifold?

Re: 270 exhaust question
Ford351 #1336717 Fri Dec 06 2019 11:22 PM
Joined: Oct 2019
Posts: 7
F
Ford351 Offline OP
New Guy
Any suggestions as to where I can purchase a set of headers or an exhaust manifold?

Re: 270 exhaust question
Ford351 #1336722 Fri Dec 06 2019 11:45 PM
Joined: Sep 2001
Posts: 30,014
ace skiver
In the swap meet, here.

Or, on OldGMCtrucks.com


Tim
1954Advance-Design.com [1954advance-design.com]
1954 3106 Carryall Suburban [stovebolt.com] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [1954advance-design.com] - part of the family for 15 years
Z-series (54/55) GMC 350 (2-ton) COE [1954advance-design.com] - now part of Dave's family
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engine are not "splash oilers" - this is a splash oiler. [chevy.oldcarmanualproject.com]
Re: 270 exhaust question
Ford351 #1336738 Sat Dec 07 2019 02:13 AM
Joined: Dec 2008
Posts: 1,430
P
Shop Shark
Compare different L6 engines by bore pitch (sorry, not port design) on my page here: http://victorylibrary.com/mopar/m-table.htm

Re: 270 exhaust question
Ford351 #1336967 Sun Dec 08 2019 09:16 PM
Joined: Jul 2014
Posts: 190
1
Shop Shark
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.


51 3800 PU, 55 235 (w/cam, headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.

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