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| | | | Joined: Sep 2011 Posts: 131 Shop Shark | | Shop Shark Joined: Sep 2011 Posts: 131 | What is the safe RPM to run a 261 that is in good shape.
I just installed a tach and it is turning 2650rpm at
55mph. at 60mph it turns 3000rpm.
I normally drive about 55, not wanting to damage the engine.
The truck is a 1955.2, 1433 (canuck) one ton with 5:17 gears.
It will soon have a carrier swap to get a better ratio.
Some very informed guys on here. What do you think.
1 1955 Chev one ton. 261 engine
3 1962 Chev c-10 261 engine
4 1966 Plymouth VIP 5.7 GenIII Hemi
5 1966 Imperial Crown Coupe 440 engine
| | | | | Joined: Aug 2004 Posts: 1,418 ODSS Lawman | | ODSS Lawman Joined: Aug 2004 Posts: 1,418 | Drive the wheels off of it. You're not going to hurt a thing.
Get up to 5000 or 6000 rpm then you have things to worry about.
Wind resistance won't let you get that high.
SWEET Sergeant At Arms: Old Dominion Stovebolt Society BUNS?!?!?!Where we're going, we don't need no buns.....1950 GMC 450 1951 Chevy 1/2-TonThe GreenMachineIn the Stovebolt Gallery | | | | | Joined: Feb 2004 Posts: 29,881 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,881 | Depending on the year, 235's were max horsepower rated at anywhere from 3700 to 4000 RPM. A good condition 261 (same stroke as a 235) should cruise all day safely at 3000-3200 as long as it stays cool and has good oil pressure. These engines in medium-duty trucks would run all day at a governed RPM very near the HP peak. Most people are too timid to run 'em that way these days!
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 2004 Posts: 1,418 ODSS Lawman | | ODSS Lawman Joined: Aug 2004 Posts: 1,418 | Turn your sound down, Gort is loud on the Interstate I think this 261 hit 80 on the pass. 261 flyby
SWEET Sergeant At Arms: Old Dominion Stovebolt Society BUNS?!?!?!Where we're going, we don't need no buns.....1950 GMC 450 1951 Chevy 1/2-TonThe GreenMachineIn the Stovebolt Gallery | | | | | Joined: Sep 2001 Posts: 29,270 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,270 | I easily have gotten up to 90 mph on level ground with my 261 and 3.55 rear-end and 31" inch tires. But I try not to cruise at more than 65 mph (the gas mileage decreases significantly above 62/63 mph).
That (90 mph) would be a smooth/quiet 3500 rpm - no big deal.
My Suburban is quiet - we can talk at normal noise volume - saying something like "that's pretty cool".
It sure does impress my friends, though (as I immediately settle down to an even quieter 60-65 mph).
| | | | | Joined: Feb 2004 Posts: 29,881 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,881 | I drove a 58 Chevy Delray coupe with a 235, a 3-speed, a 3.70 rear end, and 14" tires for several years, back in my younger and wilder days. It saw high 80's and low 90's pretty frequently, and survived it. No tach, but that old stovebolt would scream along pretty well.
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: Dec 2008 Posts: 1,923 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,923 | A common recco for sustained cruising RPM with aluminum pistons is 2,500 feet per minute piston speed, which occurs in the 235 & 261 at 3,810 RPM.
The math: RPM @ 2,500 = 15,000 / stroke
The noise can be safely ignored, but if the engine feels "rough" (buzzy through the pedals, steering wheel etc.) it may be a bent fan blade, harmonic damper on the way out, etc. If it's still there when you depress the clutch it's in the driveline, not the engine (bent driveshaft, bad U-joint, wheel balance). Check it before it goes south. | | | | | Joined: Sep 2014 Posts: 385 Shop Shark | | Shop Shark Joined: Sep 2014 Posts: 385 | Not a 261 but my 235 on the highway. Highway drive | | |
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