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09-03-2014, 07:11 AM | #1 |
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Highway speed rpm
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 tranny (with overdrive) and the stock rear end.
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09-03-2014, 07:40 AM | #2 |
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Re: Highway speed rpm
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...!
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09-03-2014, 08:04 AM | #3 |
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Re: Highway speed rpm
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)
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09-03-2014, 08:06 AM | #4 |
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Re: Highway speed rpm
2500 rpm is not pushing it too hard.
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09-03-2014, 09:30 AM | #5 |
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Re: Highway speed rpm
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
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09-03-2014, 09:57 AM | #6 |
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Re: Highway speed rpm
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09-03-2014, 09:58 AM | #7 |
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Re: Highway speed rpm
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.
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09-03-2014, 10:37 AM | #8 |
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Re: Highway speed rpm
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.
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09-03-2014, 06:24 PM | #9 |
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Re: Highway speed rpm
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.
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09-03-2014, 07:15 PM | #10 |
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Re: Highway speed rpm
Lucky you have overdrive!
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09-03-2014, 07:46 PM | #11 | |
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Re: Highway speed rpm
Quote:
R |
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09-03-2014, 07:47 PM | #12 |
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Re: Highway speed rpm
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/f...0to125late.htm looks like a '53 239ci is about 194 @ 1900 to 2100.
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09-03-2014, 07:49 PM | #13 |
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Re: Highway speed rpm
Running 14s will equate to having the 3.92 ratio, I would think.
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09-03-2014, 07:56 PM | #14 |
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Re: Highway speed rpm
Don't think so. If the seats start receding, it closes up the clearance to the lifters, until finally they never close. MASSIVE loss of power when that happens.
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09-03-2014, 09:57 PM | #15 |
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Re: Highway speed rpm
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.
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09-03-2014, 10:00 PM | #16 | |
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Re: Highway speed rpm
Quote:
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. Last edited by JSeery; 09-03-2014 at 10:07 PM. |
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09-04-2014, 05:11 AM | #17 |
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Re: Highway speed rpm
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!
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09-04-2014, 05:45 AM | #18 |
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Re: Highway speed rpm
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.
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09-04-2014, 06:07 AM | #19 |
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Re: Highway speed rpm
Thanks Vic!
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09-04-2014, 08:05 AM | #20 | |
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Re: Highway speed rpm
JSeery
Quote:
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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