The Stovebolt Site Forums The Shop Area The HiPo Shop Hi-po-ing a 270

Hi guys Building a 270 for 48 GMC panel.Would like to have mucho torque and as many ponys as makes sence. I plan on driven this panel everwhere. Would set aside ponys for dependability. If I could have it all would even like 15 + mpg. No Iam not smoking anything. Any input ? any good links. The running gear has already been update ie. borg warner 4 speed to an 12 Chevy diff with 373's
Thanks

Is cost an issue?

You mentioned MPG and the first thing that came to mind was fuel injection. I seem to remember some discussion about do-it-yourself EFI kits a while back, and that will help both power and MPG.

I think there's even a "build-it-yourself" kit if you're good at electronics, called Megasquirt . You buy the kit and the software to tune it, and can customize for your application. Search th

Beyond that: headers, exhaust, port & polish, high torque cam grind, etc. etc. etc...

-Boyo

Well I might as well put in my $.02. I had one "back in the day" in a 48 Chevy coupe. Of course then you could buy speed parts for them. IIRC I got some about 9.5/1 lightweight pistons, a Racer Brown roller cam and lifters, cleaned up the ports of all the nasties, The valve sizes escape me now, but they were larger. Then the bolt on stuff. I fabbed up an intake out of tubing with a box and drilled and tapped it for a Carter AFB. Also fabbed up some tubing headers. The trick was to build the complete flange and when everything was set up to bolt it to the head and weld up some 1/2X1/2 to it just to hold all the intake tubes and conversely all the exhaust tubes together before cutting it apart. The only downfall I experienced was not having a high volume oil pump. If I pumped up the pressure it would wash the bearings and if I left it alone it would beat them to death. Lots of fun back in the late 50's and early 60's. I'm sure when Proffitt gets back he will have all the new tricks. Or maybe go to the Inliners board. They have some GMC type gurus there.
Regards
Dennis

A Jimmy can still be made to perform. Cams, pistons,intakes, headers, etc are available from Patrick\'s or Stovebolt The 270H big port head is a rare find but the small port head would be better for MPG. Warning, building a Jimmy isn't cheap these days. Pistons are the major expense. Do check out the Inliners site , a lot of this old Jimmy stuff is traded between members.

what about milling the head a bit
I have heard that it works good

jim carter used to carry cast iron dual header's

My feeling about head milling on GMC heads is, only cut enough to ensure a flat surface. My reason is that these things are getting a little hard to find these days, and the more you cut off the more you increase the chances for warpage and cracks in the exhaust seat area (Achilles heel of GMC & 235 heads). Yes it used to be common to take .090 or .100 off these heads but they were cheap and easy to find. Pro head work on a GMC can easily run $1000 or more, why take a chance on trashing it? Plus you introduce problems with the pushrod cover holes not lining up. Pop-up pistons are expensive but a much safer way to go.