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| | | | Joined: Feb 2004 Posts: 29,834 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,834 | There's a saying that's about as old as hotrodding- - - - -"There's no substitute for cubic inches! With a little imaginative metal whittling, the 235 crankshaft can have its stroke increased to 4 3/8 inches- - - - -a whopping 7/16 inch increase over the standard 3 15/16" that the Chevy engineers thought was all they could manage. Of course, it requires some tinkering with connecting rod length, rod bearing diameter, and some oddball choices for pistons, but the majority of those parts can be substituted from standard parts of other engines- - - - -no pricey exotic custom stuff involved! A 216 with a set of .060" oversize Ford 170 cubic inch pistons, modified flathead Ford V8 connecting rods, rod bearings for a CJ-3 Jeep 4 cylinder, and the stroker crankshaft comes out to 261 cubic inches. A 235 with pistons for a Ford 223 six, modified original 235 rods, the same Jeep rod bearings and the stroker crank comes out to 270, and a 261 with the right piston/rod/crankshaft combination gets up to 300 cubic inches. That's approximately a 40 cubic inch gain for all three engines, with a corresponding increase in compression from the increased displacement. Add a Corvette/261 camshaft or the slightly hotter Melling clone of that cam and a little pocket porting of the head, and you've got some torque monsters that look completely original from the outside.
It's also possible to do some very similar modifications to GMC 248 and 270 engines, resulting in a much longer stroke, a bigger bore, and a lot more cubic inches.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Aug 2010 Posts: 605 'Bolter | | 'Bolter Joined: Aug 2010 Posts: 605 | Just curious.. if a guy had a GMC 301 'big six' already, could it gain more cubic inches as well?
1965 C60 school bus | 1967 GMC 6500 school bus
| | | | | Joined: Feb 2004 Posts: 29,834 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,834 | Just curious.. if a guy had a GMC 301 'big six' already, could it gain more cubic inches as well? Yes, the 301 has a 4" bore and a 4" stroke- - - - -with longer connecting rods and whatever 4" bore piston has the right compression height (Chevy, Ford, MOPAR, etc.) the 301 stroker shaft could go to 4 3/8" or maybe a little more. A 4 3/8" stroke and a 60 thousandths overbore on a 301 would give 340 cubic inches. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Aug 2010 Posts: 605 'Bolter | | 'Bolter Joined: Aug 2010 Posts: 605 | That would be pretty amazing for a six.
1965 C60 school bus | 1967 GMC 6500 school bus
| | | | | Joined: Feb 2004 Posts: 29,834 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,834 | It would definitely be a torque monster- - - - -and the GMC cylinder head responds better to porting and intake/exhaust system modifications than the Chevy six does.
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
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