Best Speed/RPM for long engine life ?

[Greg out west]

Hi Guy's


What would be a good Speed/RPM for long engine life..I wouldn't drive my modern car full throttle,,,But you can with the A...It's a long stroke engine & a lot of Mass going up & down


1800 RPM ???


Greg out West

[Tom Wesenberg]

A long stroke engine lives better at lower RPM's. I try to stay 2000 or less and 2200 is my upper limit. If the Model A was a stationary engine running a generator or compressor, I'd like about 1200 RPM.

[Kevin in NJ]

No good answer.

Seriously.

The primary factors limiting the A engine is how well it was built and how well you can set the timing for the driving conditions.

So how well built was your car?
What are the specs for your crank?
How well centered are the mains and how well is the flywheel located?
How good are you at setting the proper advance for the driving conditions?

A well balanced engine with properly poured babbitt you can run hard and put it away wet. It will be happy to do the next run.
So long as you do not have the timing set to far advanced for the driving conditions.

It all comes down to a well balanced system just spinning happy all day long vs imbalanced system beating itself to death.

[1wonton]

If you will calculate based on miles per RPM you're better off running the engine at a high RPM, lugging any engine is harder on it than high speed.

[hardtimes]

Hey Greg,
Two things govern , IMO. First, do not 'lug' engine either when driving around town (short trips). Second, do not lug engine when on the long run, i.e.- find/use the right gear to ensure not lugging at speed (say uphill, etc) and keep rpm at, say 55 to around 2200. Now second thing is done with gearing thru overdrive (better/more expensive)and rear end and tire combinations. Good luck

[Tom Wesenberg]

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To make the engine last longer you should add counterweights to the crankshaft, or buy the new Burlington crank.

[Dusty]

Originally Posted by Tom Wesenberg

To make the engine last longer you should add counterweights to the crankshaft, or buy the new Burlington crank.

I have a Burlington coat...will that help Having said that I just completed the install of a 39 tranny(go ahead guys hammer away I have my new flame suit on) and its is a dream compared the the original transmission. I find now I will shift to 2nd instead of plodding along when I know I should not. Slipping it into second is a breeze and you don't have to deal with the howling of the old tranny and you can actually hear the engine turning now

It has changed the drive ability of this car so much it is unreal(at least for me it is)


dusty

[Dave in MN]

Originally Posted by Tom Wesenberg

To make the engine last longer you should add counterweights to the crankshaft, or buy the new Burlington crank.

FYI: The Burlington crank is discontinued...unless someone has a stock of them.
Good Day!

[hardtimes]

Originally Posted by Tom Wesenberg

To make the engine last longer you should add counterweights to the crankshaft, or buy the new Burlington crank.

Hey Tom,
Yeah, Burlington, if you can get one ! Now long ago , here on this site, the Burlington maker explained that he would no longer make a crank for us...due to lack of sufficient demand(do file search) ? What that means, is obvious, but does not compute..IMO. As there are still guys here who will want such.

Now, there is good/bad to this situation. Bad is....that Burlington only made Model A size crank, but NO Model B size...bummer,eh! I and IMO a lot of others would buy B size Burlington cranks ! Why they did not make a B size was not known,
Good is...that SCAT still makes us an A size and a B size crank....Bad is that scat cuts the rod journals down to A size (1.500), but keeps mains at 2.00. I just spoke to scat rep and ask...'why would I buy a B crank (bigger/stronger) and use A rods with small (weaker) rod journals
Well, he said that that's the way it is !! But, hey you can get it drilled or no. With cut down rod journals...I said no, as needed drilled crank , but not weakened drilled crank.
I settled on a henry C crank that is drilled AND beefy !

BTW..cost of a new Scat $1550 +/-

[eagle]

My A is completely stock and nice and tight, I usually run about 50mph as it runs nice and smooth at that speed. Different cars vary. Pay attention to how it feels/sounds.

[H. L. Chauvin]

Advice in Reply #10 sounds like very good judgment ........ attention to "feels/sounds" ........ different cars do vary.

Test Question: If one has a radio in one's Model A, (fixed, or portable battery operated), with all windows rolled up, while driving on a paved highway with little or no traffic, at what incremental RPM's and/or at what incremental speed(s) does one have to re-set & increase the radio volume to hear the hourly news? LOL

[700rpm]

Jeez Dusty! Don't you crackers know anything? A 39 Trans in an A? Well, no surprise, I guess, with green fenders. I bet you'd put a Buick auto in it if you could. Criminy!

OK, just kidding. But I thought I should take advantage of your "flame suit," and, while I wouldn't do it, your fenders actually look pretty cool.

[DougVieyra]

Like has been said ; a number of factors come into play when judging the 'correct' speed of your Model A. Things like how the engine was built, the rear end gear ratio, the body weight of the car (i.e. - '29 Roadster vs. '32 Town Sedan), over-drive unit, tire size, etc. etc.

However, that being said - with all things being equal, with a basic Ford Factory built car, my experience has been that each individual cars has it's own 'sweet spot'. Of the ten or so Ford Model A's that I have driven over thousands and thousands of miles during the last 50 years, my cars seemed to have a 'sweet spot' of between 50 to 55 miles and hour. My light weight '28 Phaeton was 'comfortable' between 55 & 60 miles an hour. However, I was NOT comfortable in driving it at 60 miles an hour (brakes, modern traffic, etc.). My '31 Dlx Coupe has a 'Touring' engine, Mitchel Over-Drive, over-sized Firestone tires, etc. - it too likes to run about 55 to 60 miles an hour. Because the Coupe has better crash protection, I don't mind driving at 60 miles an hour in it.

All of these cars were perfectly capable of doing faster speeds, But I always liked to go the speed that my car felt 'comfortable' with - the 'sweet spot'.

[V4F]

40 mph @ 1800 rpm for a stock motor .

[Ron/IA]

If you technically want the "best speed/rpm" for a Model A engine; it would be zero rpm and only coast down hill with the engine off for speed.

Sorry, I just had to say that.

[Sixseven]

Originally Posted by V4F

40 mph @ 1800 rpm for a stock motor .

I think this answers the question best. Bearing life depends a lot on speed and load. If you are just driving with normal acceleration and also not pulling or otherwise hauling heavy loads, then keeping the RPM at around 1800 max will give you longest engine life. Other things not withstanding like routine oil changes and decent warm up.

[Dusty]

Originally Posted by 700rpm

Jeez Dusty! Don't you crackers know anything? A 39 Trans in an A? Well, no surprise, I guess, with green fenders. I bet you'd put a Buick auto in it if you could. Criminy!

OK, just kidding. But I thought I should take advantage of your "flame suit," and, while I wouldn't do it, your fenders actually look pretty cool.

Thanks, I need a good slap back to reality The only problem is now you got me thinking about that damn Buick Auto transmission

Now as to engine RPM, I give up After reading here for many years I have come to the conclusion that I need to get rid of the "A" before for she blows Don't lug, don't go past a certain RPM, keep it under 50, "I run 55 all day", to be safe put it in 2nd gear around town so that is no chance of stressing the engine at low RPM, make sure the advance is set right for this or this,or that Than after all this you still hear a lot of stories about the engine crapping its self one way or the other as did mine last Summer so I guess its because of not following all the do's and don'ts or maybe I made the mistake of just starting it

After reading all the don't do's over the year it seems to me this engine is very, very fragile I think for you to be able to enjoy just driving this car you need to install an on board computer from one of the abandon Shuttle space crafts just monitor things so you won't blow it up...no wait a minute forget that, shuttles blow up to

Saving money in WV for a new engine...its sure to blow up any day now.

dusty

[jkcrosson]

Originally Posted by Dave in MN

FYI: The Burlington crank is discontinued...unless someone has a stock of them.
Good Day!

When were the cranks discontinued. Did something happen?

[eagle]

Dusty. You hit the nail on the head! These are tough old critters and if you use some common sense will serve you faithfully. All of the must do and must not do get to be comical after a while.

[Purdy Swoft]

I agree.I've still got my first one that I got in 1960. It still has the original babbitt and has run with non detergent oil for most of its life. I changed to detergent 20w50 in all of mine a few years ago. I run the hell out of it when I was a teenager. I've wound it up until it screamed many times with no i'll effects. I've overhauled the engine twice in the past 54 years and the original babbit is still good. when the shims were all removed I filed the caps. It has an easy life now and I expect it to run for the rest of my life and beyond.

[fiddlybits]

I can find a tachometer in my car.... I guess my engine is always at zero rpm.

but... since I know that I roll 91.75 inches for every turn of the tire and there are 63,360 inches in a mile, so I know my wheels go around 690.6 times per mile allowing me to quickly calculate my engine speed at any time by factoring in the rear end ration plus the gear ration that I am in, the current speed down the road (after converting to furlongs per fortnight), accounting for the wind cross angle, cloud cover and phase of the moon and ..... what was the question again?

(low tech = sweet spot at 45 indicated/ 50 actual)

[Dave in MN]

Chris Robbinson has decided to discontinue the production.
I spoke to him a few months ago and he mentioned the cranks would not be available after his stock was depleted.

Dave

Originally Posted by jkcrosson

When were the cranks discontinued. Did something happen?

[gary635g]

A friend has one he put the high compression head on and drove it 65mph to Wellton from Yuma he did not make it, it got to pounding and smoking (oil on exhaust from knocked out rear main) so bad he had shut down and got a lift home on a tilt bed truck.

[vermontboy]

I think people tend to baby them way too much. Thank about all the old AA log trucks spending an hour or two at wide open throttle in low (or low-low) with a full load uphill over the old mountain passes. The "air conditioning" was standing on the running board and steering through the window.

[SeaSlugs]

Got me thinking, there's a few engine RPM calculators out there. Heres one i used:
http://www.powerblocktv.com/resources/

I did for the AA worm drive high speed rearend (5.17:1 ratio) with the standard stock 600X20 tires(given diameter of 32.2") and also in 3rd gear (1:1 ratio for 28/29):

30mph 1619rpm
35mph 1888rpm
40mph 2158rpm
45mph 2428rpm
50mph 2698rpm
55mph 2968rpm

now if you bump it up to the also common Firestone size of 650X20 which has an overall diameter of 34.6 inches:

30mph 1506rpm
35mph 1757rpm
40mph 2009rpm
45mph 2260rpm
50mph 2511rpm
55mph 2762rpm

I think im going to get the slightly larger 650-20 tires to make it slightly less of a traffic obstacle and also what Ive heard is true: AA's are most happy at about 35-40 mph cruising.

For S&G i tried what the low speed worm (7.25:1) rear axle would do with standard 600x20 tires:

15mph 1135rpm
20mph 1513rpm
25mph 1892rpm
30mph 2270rpm
35mph 2648rpm
40mph 3027rpm

aint going anywhere fast but could climb up a tree if you wanted!

Anyone got what the ratios are for 1st and 2nd gears in the standard 3 speed tranny?

Could calculate absolute max speed or what rpm your at at a certain speed in a certain gear. (like on my modern pickup i know about every 10mph increase in speed the engine is at about 2100 rpm)

[tbirdtbird]

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Become intimate with automotive engineering. Look at the torque/HP curve, study it, and figure out what it is trying to tell you. It is plain as day.

[stouchton]

Here is an old rule of thumb - 2/3 Redline RPM or RPM of peak torque - whichever is lower.

Ok... that is for marine engines. And I've got no idea what the redline RPM is of a stock A motor, nor do I know of a dyno curve. If SeaSlugs numbers are representative of MAX rpm, then I would keep my cruising RPM at 2000.

[modelAtony]

Originally Posted by jkcrosson

When were the cranks discontinued. Did something happen?

Some of the cranks were having bad quality problems , like breaking on end. Have fun modelAtony Lafayette,LA

[tbirdtbird]

dyno curves:
http://www.modelaparts.net/dynosheets.htm/dyno1.htm

you can get anything you want on the internet

[Tom Wesenberg]

Notice where the spark advance is on the chart Tbird listed.
It's 30*, which is NOT full down.
Full down is 40* and IMHO is too much advance for most of our Model A's and especially if you have a higher compression head, which requires even less advance.

[stouchton]

Tom - do you think 2700 rpm is the redline? Wasn't sure why the dyno test stopped at this point, although it was falling off the torque curve quite quickly.

[Tom Wesenberg]

2700 would be my redline. I'm not sure who or how the red line is determined, but going past the peak horsepower is more harm than good to the long life of an engine IMHO. These are long stroke engines and give good torque at lower RPM, than most of today's short stroke engines.

[stouchton]

Originally Posted by Tom Wesenberg

2700 would be my redline. I'm not sure who or how the red line is determined, but going past the peak horsepower is more harm than good to the long life of an engine IMHO. These are long stroke engines and give good torque at lower RPM, than most of today's short stroke engines.

Thats a good point - if the hydrocarbon burn is not being put to work as mechanical energy, it is toasting the motor.

With that in mind, 45 mph seems like a conservative "cruising" based on the HP curve and the 2/3 marine rule of thumb (assuming 3.78:1 rear and 4.75/5.00x19 tires).

50 mph would put it right at the end of the peak HP curve.

[fiddlybits]

I make 690.57 revolutions of the tire per mile and with a 3.78 rear end that should give me:

30mph - 1305rpm
40mph - 1740rpm
45mph - 1957rpm
50mph - 2175rpm
55mph - 2392rpm

It has a "warm fuzzy" feeling at 27mph, 40mph and 53mph (gps speeds, not indicated)

As for a redline, here's my take.

First, for most stock engines you do not want your piston speed to exceed 3500 ft/minute and piston speed is simply calculated by the stroke times the rpm divided by 6.

So: at 3000rpm our pistons speed would be 2125 ft/minute, which is still a 30% margin.

How about 55mph...or 2392rpm? well, that comes out to 1694 ft/min piston speed, or about half of what would be considered red line.

So, what's my redline? Frankly I'm not going to worry about it. I'm going to drive my car sensibly and enjoy it knowing that the car basically will limit itself.

[Gunmetal blue2]

Does any body make the counter balance weights to weld to the crank or have a drawing and measurements of one [so that you can make them].

[CarlG]

Originally Posted by Gunmetal blue2

Does any body make the counter balance weights to weld to the crank or have a drawing and measurements of one [so that you can make them].

Berts has them: A-6216 Counterweight for crankshaft $8.00
http://parts.modelastore.com/show_Product.asp?ID=3541

[tbirdtbird]

what, exactly, is to be accomplished after 2200 in a stock motor? Your HP is past peak. Your torque is long past peak. Your dynamic compression ratio has turned to crap. (dynamic ratio is always less than static ratio and gets worse with revs.) You have a non-counter weighted crank. You have a center main that is undersized for the job. You have a long stroke motor with a very high piston speed. Think about it.....

And Tom, I agree with your timing advance observation....30 is plenty for a stock A. In fact the FSI electronic dizzy maxes out at 26-28 degrees. A stock long stroke motor will not do well with a lot of advance...not enough 'burn' left in the chamber after the piston swings past TDC...you will actually lose some torque and risk knock

[Brother Hesekiel]

Which makes me wonder . . . how to advance properly on a flat road?
I start fully retarded, and then go pretty much to the 9 o'clock position. How many degrees would that be? Should I retard a bit when idling at a red light? When should I advance more, and where would the 30 degree point be?

[Tom Wesenberg]

Originally Posted by Brother Hesekiel

Which makes me wonder . . . how to advance properly on a flat road?
I start fully retarded, and then go pretty much to the 9 o'clock position. How many degrees would that be? Should I retard a bit when idling at a red light? When should I advance more, and where would the 30 degree point be?

A lot depends on the compression your engine has.
I have a stock head on a worn engine and have 50 lbs. compression.
I start the engine at full UP, which is 0*. As soon as it starts I pull the lever half way down, which is 20*, then leave it here for all around slow driving. When I'm driving about 30 MPH or faster I pull the spark lever down to 2/3, which is about 28*.

With a higher compression head I would need less advance. With a Snyder 5.5 head I might not have to go past half way down on the spark, and maybe 1/3 down for idle. If you pull the lever down and feel no increase in engine speed or power, then you might be advancing it too far.