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Old 11-25-2018, 02:38 AM   #1
aussie merc
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Question maximan revs

how fast can a stock 24 stud rev before you start stretching the frendship believe eng was rebuilt around 2000 has good oil pressure idles at 30psi and peaks and maintains 45 psi above 1000 rpm hot compression is good with only 3% variation across all cylinders and a cylinder drop test averages about 30 rpm at idle across all cylinders but vehicle dosnt have a factory tacho [none did] and dont seem to be able to find any literature from ford as to recommended max rpm or vehicle speed Last thing i want to do is damage an otherwise good eng due to over revving reason i ask is 70mph not a problem and still got more pedal left than used and it sounds happy
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Old 11-25-2018, 08:30 AM   #2
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Default Re: maximan revs

In my experience, you cannot over rev a flathead; it'll run out of breathing before it gets into self destructive revs.
I understand a stock standard 35 Ford was supposed to be able to do 85 MPH.
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Old 11-25-2018, 09:24 AM   #3
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Default Re: maximan revs

Stock Ford torque curves go to over 4000 rpm. Because of the design of a flathead it would be difficult to damage them with too high of rpms.
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Old 11-25-2018, 01:35 PM   #4
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Default Re: maximan revs

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In my experience, you cannot over rev a flathead; it'll run out of breathing before it gets into self destructive revs.
I understand a stock standard 35 Ford was supposed to be able to do 85 MPH.
I have always heard that a flathead cant suck enough air to hurt its self!!
Our Bonneville truck ran 4300 at the 1 mile, 4300 at the two mile and 4300 at the three mile. I knew at that point i needed a bigger air pump!!!
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Old 11-25-2018, 04:00 PM   #5
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Default Re: maximan revs

You don't say what your banjo ratio is, nor your tire size, but 70 mph in any case is not a problem. My 59L will run all day long pedal to the metal on the Nevada desert at 78 mph flat out with a 3.78 ratio and 6.00 16 tires. At that speed, it does get a single misfire once or twice a minute, never have found out why, but the engine seems happier down closer to 70 mph where my heart rate goes down.
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Old 11-25-2018, 06:10 PM   #6
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Default Re: maximan revs

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In JWL's Book, max torque of the stock engine comes in around 2000, However, it still produces some usable torque up to 3200. Depending on carbonation. Installing a Max #1 cam raises this up to 2500. Max torque of the stock engine is 150@ 200 HP is 80 at 3000. Without gen abd fan.

Last edited by Ol' Ron; 11-25-2018 at 06:24 PM.
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Old 11-26-2018, 12:07 AM   #7
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Default Re: maximan revs

Is anybody running with a tach on these flatheads to see just how fast the engine is turning at speed? It would be interesting to know. My 52 Merc (automatic) sounds fairly relaxed at 55. I'm not sure I have pushed it any higher as I don't get it on paved highway very often but have no doubt I could get a speeding ticket out on the open highway here in Sask.
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Old 11-26-2018, 12:46 AM   #8
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Default Re: maximan revs

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Is anybody running with a tach on these flatheads to see just how fast the engine is turning at speed? It would be interesting to know. My 52 Merc (automatic) sounds fairly relaxed at 55. I'm not sure I have pushed it any higher as I don't get it on paved highway very often but have no doubt I could get a speeding ticket out on the open highway here in Sask.


My tacho is 2900 rpm with a 3.78 rear end at 60mph.
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Old 11-26-2018, 01:00 AM   #9
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Default Re: maximan revs

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Originally Posted by BUBBAS IGNITION View Post
I have always heard that a flathead cant suck enough air to hurt its self!!
Our Bonneville truck ran 4300 at the 1 mile, 4300 at the two mile and 4300 at the three mile. I knew at that point i needed a bigger air pump!!!

dang, that is impressive.


Over revving a motor will let something go. A rod etc. Something has to give. If all is in order then more is better, right?

Last edited by Tinker; 11-26-2018 at 01:50 AM.
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Old 11-26-2018, 01:06 AM   #10
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Default Re: maximan revs

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My tacho is 2900 rpm with a 3.78 rear end at 60mph.
Phil NZ
That's about where my truck was, so I swapped in a 3.50 9", now it's around 2400 +/- at 60. It seems to love to run around 2500-2600, really hits its stride.

Back in the day these engines were run at and above 3000 all day in the bigger trucks, and under heavy load.
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Old 11-26-2018, 10:02 AM   #11
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Default Re: maximan revs

I agree with Ross, the Merc in my '51 Ford seems to like to sit at 2700 (which is 70 on the speedometer) and cruise; any more than that and it's OK but the temperature goes up 10 degrees after 5 minutes or so. As an aside, after I had some break in time on my 258" new build, I ran it to 5500 just to see what it would do. I think it would have gone more, but I chickened out. That's with reworked Edmunds heads, a MAX-1 with 185G springs, a Mallory dual point, and a 2GC.

Also, the reason Zora developed the "Ardun" heads is said to be that he thought the flathead was limited by it's restricted breathing and the engine could be made to produce more revs and power. I've always wondered what he thought about only three main bearings.
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Old 11-26-2018, 02:20 PM   #12
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Default Re: maximan revs

Lawrie run his at 6500 rpm but for only 9 seconds at a time.
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Old 11-26-2018, 07:09 PM   #13
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Default Re: maximan revs

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Lawrie run his at 6500 rpm but for only 9 seconds at a time.
True
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Old 11-27-2018, 05:08 AM   #14
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Default Re: maximan revs

sorry neglected these details tires 600-16 rear gears 3.54 full steel 39 mercury on a diet of 91 octane
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Old 11-27-2018, 05:31 AM   #15
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Default Re: maximan revs

I use this formula to determine rpm.

RPM= mph x gear ratio x overdrive ratio x 336 Divide by tire diameter



Or, using the formula, leave out the overdrive and work the math as if in standard drive. Then multiply standard drive rpm by overdrive ratio for final result.
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Old 11-27-2018, 12:04 PM   #16
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Default Re: maximan revs

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sorry neglected these details tires 600-16 rear gears 3.54 full steel 39 mercury on a diet of 91 octane
All things being equal, 3.54 gears will push a car about 5 mph faster than 3.78 gears, so, mine tops at 78, yours at 83. There are always other factors to consider, that's just a ballpark number.
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Old 11-27-2018, 09:41 PM   #17
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Default Re: maximan revs

In another current thread, folks are discussing old flathead books. Roger Huntington in his book published by Floyd Clymer, ends his dissertation on hot rodding the ford V8 with a short poem. I quote:

A man is a man who will fight with a sword,

Or tackle Mt. Everest in snow,

But the bravest of all owns a '34 Ford,

Who will try for six thousand in low......
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Old 11-27-2018, 09:56 PM   #18
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Default Re: maximan revs

I am thinking a STOCK flathead will float the valves before reaching any RPM number that will hurt it. Those stock valve springs will act like a governor!
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Old 11-27-2018, 10:39 PM   #19
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Default Re: maximan revs

Quote:
Originally Posted by tubman View Post
I agree with Ross, the Merc in my '51 Ford seems to like to sit at 2700 (which is 70 on the speedometer) and cruise; any more than that and it's OK but the temperature goes up 10 degrees after 5 minutes or so. As an aside, after I had some break in time on my 258" new build, I ran it to 5500 just to see what it would do. I think it would have gone more, but I chickened out. That's with reworked Edmunds heads, a MAX-1 with 185G springs, a Mallory dual point, and a 2GC.

Also, the reason Zora developed the "Ardun" heads is said to be that he thought the flathead was limited by it's restricted breathing and the engine could be made to produce more revs and power. I've always wondered what he thought about only three main bearings.
5500 wasnt in high gear was it ??
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Old 11-27-2018, 11:33 PM   #20
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Default Re: maximan revs

You can make them breathe well enough to hurt themselves. I've run stock rods over 7000 rpm at the strip.
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