Hey guys, need to know the cruising RPM for my 1954 3600. Put larger tires on so my speedo is way off. Put a tach on and I can get my speed off my GPS (TOMTOM). Also what would redline RPM be? Thanks.
As I said in your other post is what type of transmission are you running? Are there speedometer adapters available for it? I'm running a SM420 and got a speedometer adapter since I changed the rear end gears. With my 3.55 gears, I cruise at 60+ running at 2200 rpm.
Craig
My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
if it helps answer your redline question, i've attached an image of a typical power curve from a chevy engine test report for a 235 cu this image is from 1948 publication i've been told not to run 235s beyond 4000 rpm as that's "destruction in minutes" territory, but could be wrong or not remembering correctly. -s
Just for the heck to of it, here are power curve graphs for 1954 235 and 261 trucks (high-pressure engines). Improved versions of earlier engines, and compared to engine/graph posted above.
RPM = MPH × Final drive ratio ÷ Tire OD ÷ .002975 To get an answer, you need data on those three.
I've read references to 4,000 as the upper limit, but there are several possible reasons: 1. valve float - the intake valve will strike the piston (but should occur higher than 4K) 2. with the splash oil system reliable delivery to the rods is decreased by chaos in the pan 3. refers to iron pistons? Lots of weight flying around on that skinny rod 4. 2,500 f/m piston speed is an industry recco for sustained speed, it's 3,810 RPM for that stroke length
Assuming you've got an original-equipment engine and drivetrain, I'd suggest a max cruise RPM of around 3000, assuming the lower end is in very good condition and the oil pressure is good. Be aware that the engine will be a little noisy, mostly from the fan being wound up pretty tight. The 54 235 engine should have aluminum pistons and insert-type rod bearings, so pounding Babbit bearings out with cast iron boat anchors shouldn't be a problem. Short runs above 3K shouldn't do much damage, but most folks just can't bring themselves to run a stovebolt that fast.
Back in my college days, I ran a 58 Chevy Delray coupe with a 235 regularly at 70+ MPH with a 3 speed and a 3.70 rear end, and 14" wheels. Yes, it sounded a little stressed, but it stayed together for a long time. 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!
Took truck out yesterday and hit the back roads. Cruising at 60 engine was at about 2800 RPM's. Tire size is 235/85/R16. Main concern is if the engine can handle these RPM's for an extended time. Truck is all stock 1954 Chevy 3600 with a 4 on the floor trans. Thanks.
Only about 3 days past forever! These engines were designed to run wide open for hours at a time in the big rigs, pulling full (or way over) maximum gross weight loads. It's only been a recent trend for snowflakes with lace on their drawers to get a case of the vapors when they hear an engine turning RPM's even a little above idle speed. For the past 2-3 decades, manufacturers have been putting high rear end gear ratios and overdrive transmissions in their vehicles, and running engines at just above idle on the highway. My 04 Dodge Ram 1500 is only running 2,000 RPM at 75 MPH! Jump on that loud pedal and enjoy listening to an engine actually earn its keep for a change! 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!
A 55-62 motor can take more then 4000 rpm. Heck, the mechanical advance is not all in until 3500 rpm but yes, the springs would be a limiting factor. With good springs, or double springs, a 55-62 235 motor can go to at least 5200-5500 and I have one motor still in the back of my garage that I ran into those numbers on a regular basis on the street and race track, and once or twice into the 6000 range for 25 years. The issue in those rpm ranges is that the head really does not breath much past 4800 or so even in modified form, and probably not that deep in pure stock form, and it gets a little squirrelly when you are in the 5500 and up range with those rods. That and the harmonics start to play a part over 5000 rpm (read that loose flywheel bolts for example). So really your best bet is to keep rpms under 5000 rpm, but yes, no real problem 4000-4500.
Hi Tim, I don't believe there will be any gas mileage to discuss at that rpm, but I also don't think it will hurt the engine as much as some do. After all, running the engine at that speed you will be pulling off the highway at every exit to refill the fuel and oil tanks (not to overlook refilling the radiator and allowing it to cool down) so your engine should enjoy a nice rest period while that's happening.
The impact of wind resistance at 95? Seems to me it would be secondary to the problem of safely steering and stopping one of these trucks at that speed.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
I had the opportunity about a year ago due solely to my own fault to have to drive a 650 mile day home from the stove bolt get together . By coincidence it was the same distance to the event the only difference being I had an over drive gear that kept the rpm on my stock 62 235 at around 2200 rpm. at 70 mph. the trip home with no overdrive had me traveling at around 60 mph give or take and a fairly constant 3000 rpm. The only difference I noticed is that it pulled up the hills without lose of speed or the need to downshift. The truck weighs in at about 6000 lbs, and has the aerodynamics of and apartment building . I check mpg with every fill up and fuel mileage remained the same at 14 mpg. in both directions. Both trips were done none stop other then many MANY stops for gas. I noticed no difference in temp. oil consumption or engine noise. That being said I will be returning this april. along with new overdrive gears. John
Safe cruising RPM is something I have wondered lately as well, since I am about to install a fresh rebuilt 261 into my 53 1/2 ton. I was curious to the max cruise speed that these engines can handle. I figured 55-60 mph would put the engine in the 2,500-3,000 rpm range, which might be a fast as I would comfortably run one for a 10+ mile trip. My truck is stock configuration and the furthest trip I ever foresee making in it is a one-way highway trip of about 85 miles. I know "in theory" my truck will run up past 80 mph and 5,000 rpms if pushed to the max, but at what RPM do these engines enter the "danger zone" pertaining to lubrication, etc when run for an extended period of time?
Last edited by Green_98; 02/14/20197:07 PM.
-Patrick 1953 Chevrolet 3100 261 / 4-speed / 4:11 / Commercial Red
Looking at the factory maximum HP ratings of several mid-1950's 235's, they're specified at 3700-4200 RPM for various year models and transmission/rear end combinations. Since the 261 has the same stroke as a 235, similar figures would probably apply. I don't have 261 factory specifications handy at the moment. A 261's big advantage over a 235 is increased torque, not a lot more top end horsepower. Above those speeds, HP begins to drop off pretty dramatically as the "curve" goes above maximum. Torque tops out about 2000 RPM for most applications, so the "safe" operating range for best performance seems to be in the 2K-4K speed range. 4500-4800 won't hurt it- - - -but you're just spitting into the wind, power-wise.
While it's possible to make a stovebolt engine run above 4K RPM, it seems to be pretty pointless unless modifications such as camshaft changes and cylinder head and valve upgrades are done to move the HP curve to a higher RPM range. Then you end up with an engine that loses massive amounts of torque and pulling power in pursuit of a rather mediocre HP gain. 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!
Hi Patrick. You can get a slew of opinions on this subject. Here's mine: They cruise well and economically at 2000~2300 rpm...smoothly and effortlessly as long as you're on relatively flat roads and not in a headwind. At 2500 to 3000 rpm, you can drive your engine all day long but gas mileage will decline steadily the closer to 3000 you get. Trust your ears and your sense of feel. There is a big difference in driving one of these engines at 3000 to 3500 rpm versus driving a Honda, Subaru, Toyota engine at 3500 rpm. The harmonics are altogether different.
I had an uncle who was a cotton farmer. His analysis of the 235 (very similar to yours) was "run these at the right rpm and you can depend on them almost forever. Run these too hard and fast and you can depend on them for a little while. It is your choice." He used them to run irrigation pumps and some of his were still going after almost 20 years the last time I saw them.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
I run my '46 with a '54 235 / 3:55 gears and 16x7.00 tires at about 60-62 on the highway. Engine now has over 80,000 on it since it was rebuilt in 1986. It'll go faster, but you can tell she don't like it. You can feel when you're pushing them too hard. Also, it almost goes without saying that regular maintenance is key, and not using motor oil made for modern car engines. Been using Valvoline oil for diesels forever and not a hint of smoking or oil burning (of course it leaks some, but that's a feature, not a bug).
It is all well and good to say the speed that you will run it and I think yours is a wise choice if everything else is stock. In my case my 54 has 2.73 gears, I have on many trips said that I will run at 55 mph but when the traffic around me is running 65-70 I soon find that I am running at the traffic speeds. Good luck.
Ron, The Computer Greek I love therefore I am. 1954 3100 Chevy truck In the Gallery 2017 Buick Encore See more pix 1960 MGA Roadster Sold 7/18/2017
Back when I was using a 1959 3800 like a truck, not a pampered toy, I could cruise the slow lane of the interstate at around 60 MPH with no problems. That rig had a 4.56 rear end and 18" tube type tires. Yes, the engine made some noise, but it didn't hand grenade, and I drove it that way on a regular basis. The 58 Chevy Delray coupe that I drove in college in the mid-1960's, with a 235 3 speed setup, a 3.70 rear end, and 14" tires had no problem running 70 MPH or more virtually every time I drove home, 150 miles each way. 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!
