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| | | | Joined: Apr 2005 Posts: 926 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 926 | Hi all; I installed a 292 in my '57 GMC F350,and am wondering what rpm the engine is safe with. I know the 230 and 250 were good with relatively high rpm,but I'm not sure about the 292. According to my number cruncher,I should be capable of 65 miles per hour at about 3675 rpm;is that safe for the 292? 60 mph would be about 3400 rpm. I've driven it a little,but still need to replace a wheel/tire that's in bad shape and can't get the lugs loose. (Yeah-I know about the left and right threads.  ) there's still some bugs to work out,but it seems to run fairly decent,outside of a finicky carb and a little wiring weirdness,but that'll be minor stuff. | | | | | Joined: Sep 2006 Posts: 2,393 Shop Shark | | Shop Shark Joined: Sep 2006 Posts: 2,393 | You are not going to hurt it at 3600 rpm except for long term wear, but your fuel mileage will drop. You might consider some tire size change or gear change in the trans or rear to help that.
Drew
| | | | | Joined: Feb 2000 Posts: 5,195 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,195 | Also, GM lug nuts are all standard thread, no left hand lug nuts.
Joe | | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | I was told by a mechanic that used to work on them that they are a long stroke motor and they don't like high RPMs. Those RPM figures seem pretty high to me. I don't think I would do that. | | | | | Joined: Sep 2008 Posts: 130 'Bolter | | 'Bolter Joined: Sep 2008 Posts: 130 | I agree with truckernix, I don't run mine that high. They are low tork motors.Under 3000 would be better. | | | | | Joined: Apr 2005 Posts: 926 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 926 | Beg to differ,Joe;
Already had wheels off this truck from both sides,left side is left hand thread,right side is right hand thread. I know one ton and smaller is all right hand,but this two ton is as I stated,and uses the same lug nuts as the OTR trucks use,but only six per wheel instead of ten.
Speed | | | | | Joined: Apr 2005 Posts: 926 Shop Shark | | Shop Shark Joined: Apr 2005 Posts: 926 | Drew; So I guess 75 mph @ 4250 would be a little over the top,eh? I'm actually trying to get some passable used 11.00R-22.5's for it now-it's my understanding that those would bring my rolling diameter from 38" to around 44",good for 75 mph @3665 rpm.  I hope that' s true! That's about the only viable option to gear it up. The rear is what it is-no optional gears for it that I'm aware of. (Maybe find a different 2 speed axle,but that'd likely mean different wheel lug pattern.) Maybe a change to a 5th gear over transmission,but then there's getting a PTO set up for it and possibly driveline mods. 3 speed Brownie,same problems,and a longer speedo cable. I think my stock six hole wheels with 11.00's will be about the tallest rubber I can install. And regarding fuel economy,I wasn't considering that an option,so-no harm,no foul. Speed
Last edited by speed 6351; 11/02/2011 5:39 AM.
| | | | | Joined: Dec 2008 Posts: 1,922 'Bolter | | 'Bolter Joined: Dec 2008 Posts: 1,922 | The usual guideline for highest cruising speed is 2,500 feet per minute piston speed.
F/M = stroke × RPM ÷ 6
2,500 F/M = 15,000 ÷ 4.12 = 3,641 RPM
Highest sustained speed is 1,500 feet per minute.
1,500 F/M = 9,000 ÷ 4.12 = 2,184 RPM
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