Highway speed rpm

Kevin - Illinois

Kevin - Illinois

Senior Member
I'm new to the V8 flatheads. I picked up a 53 Ford Mainline 239 and was curious what a good rpm would be for highway driving. It runs at 2500 rpm @ 65 mph. Is this pushing the 239 too hard? It has the stock engine, 3 in the tree ****** (with overdrive) and the stock rear end.
 
Is that 2500 rpm at 65 mph in O/D? Usually, at least in my case, I have found that a Flathead will let you know its 'sweet spot' out on the highway. If it objects to that rpm at that speed, you'll hear about it...!:eek:
 
This should help, it assumes stock size wheels / tires, sounds like your in the range for the 3:77 range rear:

Gear Ratio of 3.92
Speed Engine RPM
30 - 1300
Torque 250 ft/lb @ 1700
40 - 1750
50 - 2200
60 - 2600
70 - 3050
75 - 3270
HP 135 @ 3400
80 - 3500
90 - 3925
91 - 3969
Maximum RPM 4000
92 - 4012
110 - 4797 (Maximum on Speedometer)

Gear Ratio of 3.77
Speed Engine RPM
30 - 1260
Torque 250 ft/lb @ 1700
40 - 1680
50 - 2100
60 - 2510
70 - 2930
75 - 3150
80 - 3350
HP 135 @ 3600
90 - 3775
Maximum RPM 4000
100 - 4200
110 - 4614 (Maximum on Speedometer)
 
Where did we get 250 ft of torque @ 1700 RPM? A stock flathead would have triuble maling 150 ft lbs if torque at 1700 RPM
 
The primary thing I'd worry about is that a '53 EAB engine wouldn't have had hardened valve seats from the factory. Those RPMs for extended periods on gasohol can lead to very short seat life. Ask me how I know... :mad:
 
Yep, max torque should be around 2200 rpm and in the 170 ft-lb range (if you use Fords numbers). A lot of people seem to like the way the engines runs on the highway in the 2000 - 2200 rpm range, most likely because that is in the max torque range.
 
My 53 Victoria runs 2000 rpms @ 70mph in overdrive, I run at 75 mph seems like a good crusing speed, the engine runs without effort. I have al heads that may help. At the rpms you stated sounds like its not going into overdrive.
 
The overdrive is working and I'm certain the rear end is 3.77. The comment on the valve seats from Ross is spot on as I think this would explain the puffs of blue smoke at start up and at decelerating. The car has 14" wheels which aren't helping. I have hesitated to replace them with 15's as the tires are brand new BF Goodrich TA's... I think I'll just bite the bullet and move to 15's and get off the throttle. I have also noticed a very slight rumble of "sucking" in the exhaust after running at 65 mph when I let up on the throtle.

Thank you all for you replies!
 
JSeery said:
Yep, max torque should be around 2200 rpm and in the 170 ft-lb range (if you use Fords numbers). A lot of people seem to like the way the engines runs on the highway in the 2000 - 2200 rpm range, most likely because that is in the max torque range.
Click to expand...

Using those figs it would equate to about 71 hp that would be realistic.

R
 
Your r.p.m., axle ratio, and overdrive don't add up. Using stock Ford axle ratios for 1953 (3.31, 3.54, 3.92, and 4.10) and the overdrive ratio of 0.7, the only combination that gets up to 2500 r.p.m. at 65 m.p.h. is a 4.10 rear axle with 25 inch tall tires. Since 4.10 was the factory ratio for most cars with overdrive and you have 14 inch wheels, it might be true. I run 28 inch tall tires on my 53.
 
AnthonyG said:
Ole Ron, your right 250 @ 1700 is too high. I'm not sure where I got that chart. Was in some old research from when I was building mine last winter. I just rechecked the torque on chart from Vanpelt.
http://www.vanpeltsales.com/FH_web/flathead_specs-90to125late.htm

looks like a '53 239ci is about 194 @ 1900 to 2100.
Click to expand...

Would it be possible to post a copy of the torque curve you are reading, I have never seen one with that high a torque value for a flathead, would be interesting to see.

Edit: I see, you pulling it off of the spec sheet and not a torque curve chart. Not sure where these numbers are coming from, but think they are way to high. The 170 ft-lbs off of the torque curve is to high, but it was what Ford published. A more realistic value would be around 150 ft-lbs in the 2000 rpm range.
 
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Didn't mean to turn this into a gearing debate. It's a fact I don't know what ratio the rear end is, and that the car does have 14" wheels, and that the overdrive is working fine, AND that the engine is running at 2500 rpm at 65 mph. The question was is driving continuous at that speed and rpm too much for the old flathead... Interesting posts have resulted, and thanks to all that responded!
 
Kevin, like I said in my first post, the Flathead will let you know at what sustained speed it is comfortable. I run my '39 CS stock 85 HP Flathead on the highway all the time at speeds between 65 and 70 mph and my '51 F-1 with a 255 Merc Flathead and 3.92 rear at the same or faster speeds. The only real way for you to find out, and get to know your car, is to take it out on the road and give it a try. Have fun with it.
 
JSeery
I see, you pulling it off of the spec sheet and not a torque curve chart. Not sure where these numbers are coming from, but think they are way to high. The 170 ft-lbs off of the torque curve is to high, but it was what Ford published. A more realistic value would be around 150 ft-lbs in the 2000 rpm range.
Click to expand...

JSeery, true, was just getting the # off of the spec. sheet I posted from Vanpelt, but I did find several other published spec. charts indicating close to the same but chose Vanpelt as he is well respected on FB.
Here's another, http://www.secondchancegarage.com/public/406.cfm. Haven't been able yet to find an actual torque curve test chart. It would be interesting to see if you have or know of one?
 
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