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| | | Joined: Jan 2021 Posts: 5 New Guy | | New Guy Joined: Jan 2021 Posts: 5 | I have a 60 model 261 engine with 3.55 rear. According to my calculations I am running about 3100 rpm at 70 mph. This a daily driver and some time on the highway. I guess I am concerned about what kind of highway rpm's the engine will tolerate without damage. The engine is stock.
Thanks, Pete | | | | | Joined: Mar 2014 Posts: 4,482 Moderator, Electrical Bay | | Moderator, Electrical Bay Joined: Mar 2014 Posts: 4,482 | Hi Pete and welcome to the place. That's a bit higher than I like by 500 to 800 rpm, but should be ok as long as the engine is in good nick.
~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
| | | | | Joined: Nov 2020 Posts: 366 'Bolter | | 'Bolter Joined: Nov 2020 Posts: 366 | I would run it at 65 max personally. Then again, I started out with babbit bearings and iron pistons and max @45mph. Your 261 is probably much more stout. But I am on the safe side with these. Nice combination BTW.
'38 1.5ton; "The stuff is as tough as woodpecker lips"
| | | | | Joined: Mar 2004 Posts: 6,214 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,214 | The 261 was the big truck 6-cylinder and was governed at 3600 rpm which is where max HP is made. Back when they were being worked every day they would run them wide open all day long so don't be afraid to step on it! Mike B  | | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | 3,100 RPM is only 2,034 feet per minute piston speed, well below the informal 2,500 f/m suggested for sustained cruising.
Don't worry about it. | | | | | Joined: Feb 2004 Posts: 29,771 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,771 | "Drive it like you stole it"- - - - -these old engines are a lot tougher than the snowflakes with lace on their drawers think they are. The cylinder head design won't allow much over-revving unless maybe you're running wide open in granny gear on a SM-420. Any cruising speed under 4K RPM in high gear isn't likely to do much damage to an engine with a good lower end, particularly one with good oil pressure and rod bearing clearance under .002"
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: Jan 2021 Posts: 5 New Guy | | New Guy Joined: Jan 2021 Posts: 5 | Thanks for all the input. Much knowledge here. | | | | | Joined: Jan 2021 Posts: 5 New Guy | | New Guy Joined: Jan 2021 Posts: 5 | Panic, Where did you get this information? Looks like some good data.
Thanks, Pete | | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | | | |
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