RPMs

[P-12 Tommy]

Does anybody know the redline on our flatties? Just curious.

Tom

[Jim Yergin]

Check out Tod Fitch's web site: http://www.ply33.com/Misc/speed

"Thus it is reasonable to assume 3200 to 3400 RPM, as a maximum sustained RPM for the engine."

Jim Yergin

[greg g]

Well the Hudsonater regularly pulled his pulling tractor motor to 5 K or so, though it was highly modified for its purpose. max HP is at 3600, so spinning htem faster, doesn't get you much. I would thing 4200 would be plenty for a stock engine in good condition. don't imagine it would be happy there for along period though. Long stroke engines do't like high rpms.

There was a guy on the HAMB that was trying to build a 200 hp flattie, he was doing dyno pulls at about 4200. Don't know if he ever got his 200 hp. he was at about 180 last i heard, but again a highly modified engine.

[TodFitch]

Check out Tod Fitch's web site: http://www.ply33.com/Misc/speed

"Thus it is reasonable to assume 3200 to 3400 RPM, as a maximum sustained RPM for the engine."

Jim Yergin

That's about the maximum for my "I just want to get home" or "the tour starts a long ways from home speed". Works out to about 60 MPH in my 1933.

When I was much younger I took it up to around 70 once which would be a bit above the 3600 RPM where you get maximum BHP and was definitely "over speeding" the engine. I would not recommend that foolish young behavior. On the other hand, the car was only 45 or so years old then while it is 76 years old now. And we all know that you are more capable of physical exertion at 45 than you are at 76. Probably holds for cars too.

[Dodgeb4ya]

Had my 51 Cranbrook to 5200 Rpm back in 1970 during high school days.That was in 1st gear-thats what my Dixco tach was showing me and my buddies. Had it ported and 8 to 1 CR with a Mallory.-Scary! It still is running well to this day though. My 1st car.

Bob

[P-12 Tommy]

Thanks for all the info guys!! Appreciate it.

Tom

[Andydodge]

With or without a tailwind?..........lol.........the original engine in my P11 coupe, the 201cube lump of throbbing power doesn't like much over 3200, and thats with the tailwind and me leaning forward in the seat, window down whipping the door like a jockey...........lol........now when I finish(if I ever finish) the 230 cube monster I'm building I intend to have it ballanced, hot cam, lightened flywheel, edgy head, twin carbs, split exhaust, bigger sail, larger whip, more angle on the seat......lol.........then go hunt me some Frods.......err......Fords..........now where did I put my meds?........lol.........andyd

[james curl]

A friend and I took my P-15 on a 4600 mile trip from central Texas to Reno, then to Grass valley Ca. From there to Bonneville. Drove everything from secondary roads to Innerstates. Ran 70 for hours on end at just under 3200 RPM. I had some issues when I got home, mostly my own doing. I timed the engine at 10 degrees before TDC at idle. The manual calls for 0 to 2 degrees before TDC for a reason. I thought the vacuum advance would be out of the equation at higher RPMs but I have since run the car at a steady 70 mph and am pulling 11 to 12 inches of vacuum which is equal to about 12 to 14 degrees advance added to the 20 degrees from the mechinical advance equals to 42/44 degrees before TDC which is too much advance. I had broken top ring on both #5 and #6 cylinders. I ran the engine as high as 3600 RPM for several hours in west Texas on I-10 where the speed limit is 80 mph and most drive 85-90 mph. If your engine is in good condition and timed per the manual you should be able to run at 85% of the rated RPM with no problems. I have read that MoPar ran the engines at 3600 RPM for 50 hours to test for endurance.

[moose]

thats what my Dixco tach was showing me and my buddies.

Bob

I just got this tach. Does any body know how to wire it? It's a Stewart Warner 960 series. From what I could figure out it's a '69 model and for 12 volts, and does not require a sender. One of the posts needs 12v and the other goes to the distributor lead. Anybody know which goes where?

[greg g]

The black wire is for the light, the white looks to be ground as it attached to one of the mounting studs. as for the others one should have been a red wire (to ign on power) and the other red (to points side of coil) pretty simple, how ever with the low rpm it may not be an automotive tach, may be Marine. Also if it was for a 8 cylinder, it probably won't count correctly for a 6 cyl application. Many not transistorized tach from the 60 were cylinder count specific. I'm suprised that is not marked. SW has a pretty extensive FAQ and tech support o their site.

[p24-1953]

Okay 15 years ago when i was less wise... i told a few budies that i could get my car to 95. they didnt belive me so we took off down a baren west texas road. that was straight for about 5 miles and took off. we got it to 95 and they said it was afluke and that i had a tale wind. so we did it the other direction. so using the RPM calculator based on tire size and gearing i had to be turning about 4500 rpm. and the engine is still running to this day. I know now that my speedo is about 10% off, but those guys never need to know that. 85 is good enough. its amazing a rabbit didnt jump out , or tire blow out , or something failed and we get killed.

[p24-1953]

also i commonly run 70+ on the free way and that ='s 3500 rpm (final gear of 1:1 w/ 3.73 gears). still running strong with good compression

[Andydodge]

James.........you mention that mopar ran the engines @ 3600rpm for 50hrs..............lol............did any pass?......lol..........andyd

[TodFitch]

James.........you mention that mopar ran the engines @ 3600rpm for 50hrs..............lol............did any pass?......lol..........andyd

The book by Carl Breer about the birth of Chrysler Corporation had that bit of info: All engine designs had to pass a 50 hour test at max BHP, which for the L-6 engine would be at 3600 RPM, before the design was approved. There was at least one story in the book about what they found and had to do with the old Maxwell engine design when Chrysler took over management there to get it to having a chance to pass the test.

Now, just because the engineering prototype survived the test does not mean that all engines coming off the production line would fair equally well. But I suspect that after the Plymouth L-6 engine had been in production for over ten years (first version released in 1933 for Plymouth), the production engines probably could do pretty well on the dynometer running flat out for 50 hours.

[greg g]

An item I read suggested they took random engines off the line and tested them during the production runs. If you figure that 3600 rpm is apx 70 mph over the road. Thats a 3500 mile test, but I guess we don't know if there was any load or if it was just a free run with nothing simulating the over the road HP loss.

[TodFitch]

An item I read suggested they took random engines off the line and tested them during the production runs. If you figure that 3600 rpm is apx 70 mph over the road. Thats a 3500 mile test, but I guess we don't know if there was any load or if it was just a free run with nothing simulating the over the road HP loss.

If you are testing at max BHP you pretty much have to put a load on the engine. (HP is basically RPM times torque (load)) so if you have no load you aren't running at max BHP.

I haven't heard before your post that they pulled production engines for testing...

[Andydodge]

My understanding was that US engine horses were rated under the SAE banner which meant all power robbing things like fan,generator,etc were disconnected and that European engine horses were rated DIN, which supposedly included all the extras........in the mid 70's US engine power ratings dropped dramatically when they went from the SAE to DIN method of measuring horses.......andyd