Extra credit if you show your work. 55.1 with 235-6, standard 3 speed trans, 3.9 rear end, 16-inch tires. I don't have a 6-volt tach. At 60 mph what are my RPMs?
I believe we need the "overall" diameter (tread surface to tread surface) of the tire you have. The rim size doesn't allow us to do the proper math.
If the tires are nearby, maybe provide the specifics like brand name, dimensions as found on the sidewall and any other specific identifying info so we can know all needed details?
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
The two stock sizes are 6-16 (28.5" tall) and 6.5-16 (29.9" tall). Based on your original post, I am going to assume you have one of them. If not, post the actual tire size you have (such as 235-75R16) and we can calculate the height from that.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
No I don't. I mean about 2600, Show your math for extra credit.
"Insert-bearing 235's (1954-61) were horsepower-rated from 3800 to 4200 RPM, depending on year and application. The torque specifications were measured from 2,000 RPM to 2200, also application-wise. The Corvette 235's had different camshaft and carburetion, and were rated at higher RPM for both HP and torque.
Most engines cruise best at or near their torque peak, or slightly above it. I'd consider 2,500 RPM to be a very good cruise RPM, with moderate use at or above 3,000 well within the normal running range without doing any damage. That's assuming that such things as rod bearings and oil pressure are up to normal standards. A trashed-out piece of junk with excessive clearances everywhere needs to be nursed along, obviously. Jerry"
Last edited by bartamos; 09/10/20231:39 AM.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
BTW - Now that we have gotten this far, I have moved the thread to the Driveline forum for further fun and conversation.
Dan
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Upon what I have found max horsepower, 105 NET, is approximately 3600 rpm, assuming that's "RED LINE" what speed would I be going before I find parts on the highway?
Using the OP's stated 90.25" tire circumference (28.74" diameter) I calculate 2737 RPM at 60 MPH, just like MikeB..
Last edited by Bill Hanlon; 09/10/20234:08 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Mph x gear ratio ÷ tire diameter ÷ .002975 = rpm. My truck... 60 mph x 3.9 gear ÷ 28.7 diam ÷ .002975 = 2740 rpm. Confirmed by my dwell tach.
Last edited by Jethro in Va; 09/10/202311:07 AM. Reason: Add
~~ Jethro 1954 3100 Back to Life In the Dity Gallery 1951 3100 (gone) / 1956 4400 (still in the neighborhood) / 1957 6400 with dump body (retired) / 1959 3100 panel (in the woods junked) / 1978 Custom Deluxe K10 / 1993 S-10 4.3 / 2004 Chevy Crew Cab / 1945 John Deere H / 1952 John Deere B / 1966 John Deere 2510 / 1967 John Deere 1020
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