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04-19-2011, 02:28 PM | #1 |
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Location: devine texas
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Flathead highway speeds
ive heard diffrent stories on how fast these flatheads will run.i would love to hear about others.mine is a 1935 ford pickup,rebuilt 37 flathead with aluminum heads and stromburg carb.37 three speed trans and 40 rear banjo.i do not know the rear ratio.here in texas speed limit is 70 mph and i can pass most people.impossible to read speedo as it bounces around too much..thanx everyone and keep on truckin
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04-19-2011, 03:18 PM | #2 |
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Re: Flathead highway speeds
80 is in reach for many, some can go faster stock. Engine speed you want to run is probably the main limiter for most, within the range below arrest. Your likeliest rear ratios are 4.11 (engine really buzzing on the highway) and 3.78, fairly busy but not too high. Lube your speeedo cable!! If that doesn't do it' I can send you how to lube speedo bearing ideas.
Ford Service bulletins had a "Performance" road test section. This gave measurable standards for speed, acceleration, and economy, so if a customer complained that his car wass too thirsty or too slow, the dealer had a check to see if car was running to spec. On the level road speed test, a '35-'37 85 should be able to hit in the 84-86 range to pass muster. A '40 Merc 239 with 3.54 standard seems to be the fastest of the period. It was expected to hit 95 flat. My '48 could indicate 160KPH/100MPH, but who knows with what accuracy at the end of the speedo scale. |
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04-19-2011, 03:21 PM | #3 |
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Re: Flathead highway speeds
We have several Flatheads ranging in years from ’39 to ’53 and we drive all of them locally and on the highway. Depending on the way the Flathead is set up, the rear gear ratio, the tire size, etc., each one performs differently and each one will find and let you know its “sweet spot” at highway speed. Remember that most of these cars and trucks were not built with driving on super highways in mind however, that does not imply that they can’t. This past weekend we drove our ’39 CD down to Long Boat Key from Odessa, FL (Just 100 miles each way), half of the trip on I-75 where the slower traffic does a steady 70mph. For the most part we kept up with the slower traffic, even passed a few. The car mellows out at between 65 and 70 mph with a stock 221 c.i. Flathead and 3.78 rear.
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04-19-2011, 03:22 PM | #4 |
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Re: Flathead highway speeds
that should have read '39 CS... the fat finger got me again.
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04-19-2011, 03:42 PM | #5 |
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Re: Flathead highway speeds
I had to mount a magnetic placard on my 40's dash that reads, "CAUTION: Do Not Lower Windows at Speeds in Excess of 120 MPH!"
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04-19-2011, 03:46 PM | #6 |
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Re: Flathead highway speeds
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04-19-2011, 03:50 PM | #7 |
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Re: Flathead highway speeds
That same placard is on the inside of the glove box door on our '63 Avanti, from the factory. apparently the rear window could/would blow out at that high a speed...
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04-19-2011, 03:53 PM | #8 |
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Re: Flathead highway speeds
We're getting ready to install the Columbia in the Zephyr, should make a big difference in highway driving as the Zephyr came stock with a 4.44 rear.
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04-19-2011, 03:55 PM | #9 |
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Re: Flathead highway speeds
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04-19-2011, 04:39 PM | #10 |
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Re: Flathead highway speeds
I run my original '35 fordor (with rebuilt 221) at 55 to 60 MPH on the Interstate highways. I took it up to 70-75 once for a few minutes just to see how it handled that speed. I think I could have gone faster but did not want to rev the engine any higher.
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04-19-2011, 04:57 PM | #11 |
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Re: Flathead highway speeds
When I was a teenager many years ago I had a 50 ford cv. 3 speed with overdride and drove it all over the east coast of the USA and on the open I ran 70-75 and never had a problem. I am fixing to do coast to coast with the one in the picture and am planing on running the same speed.
sp1ke
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04-19-2011, 05:09 PM | #12 |
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Re: Flathead highway speeds
We have just been up to Rocky to visit a friend in the 34 3w,stock eng with 3.54 rear gears,sat on 50- 55 mph all the way and back (120klm each way) no problems.
But the hyway was BAD and lots of B doubles, single lane each way. Lawrie |
04-19-2011, 05:10 PM | #13 |
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Re: Flathead highway speeds
and thats all i have to say about that.thanx
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04-19-2011, 05:37 PM | #14 |
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Re: Flathead highway speeds
yo Vic, how come different font sizes show up with your different posts? Damn, this thread is difficult to follow.
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04-19-2011, 06:25 PM | #15 |
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Re: Flathead highway speeds
36 PU wiith probably a 4:11 rear downhill with a tailwind maybe 45 mph
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04-19-2011, 06:41 PM | #16 |
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Re: Flathead highway speeds
O K to all you speedsters, Here is the next question: You are pushing your flathead to 75 on the interstate and suddenly the car entering the road cuts in front of you. To what speed do your old brakes slow you before you hit him?? Without your air bag and shoulder straps how severe will your injuries be?? hmm
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04-19-2011, 07:11 PM | #17 |
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Re: Flathead highway speeds
Ya got me??? That's a computer tech question... I have no idea Vic
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04-19-2011, 07:16 PM | #18 | |
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Re: Flathead highway speeds
Quote:
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04-19-2011, 07:17 PM | #19 |
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Re: Flathead highway speeds
Why does this question/subject keep reappearing without any one knowing what R.P.M. their engine is turning? That should be the limiting factor: A late '30s car with a 4.11 rear end will be buzzing the engine a lot harder than a car with a 3.78 gear at the same highway speed. The guy with the '49-'53 car with O.D. (even with a 4.11 or 4.27 gear) is only turning 70% of the R.P.M. his gear would normally dictate. A cruising speed which spins your engine no more than 3200 R.P.M is probably the max for comfort and reliability-regardless of the roadspeed.
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04-19-2011, 07:49 PM | #20 |
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Re: Flathead highway speeds
Trucks & cars are somewhat different. My 34pu has a flat grill, flat windshield etc. which equals a lot of wind resistance. It has 4:11 rear gears and at 55mph, I'm in the 2800-3000rpm range. I ran it up to 65+ once but a lot of wind noise, shakin and rattling, vibrating from unbalanced tires and somewhat wobbly wire wheels reminds me that a 45-50mph is more sensible and safe.
I have early hydraulic brakes and my wife insisted on shoulder type seat belts so she would feel safe. You must also realize that the narrow tires have a very small footprint so emergency stops can lock up the wheels but forward momentum is still maintained for some distance. I built a 34pu restorod some years back and it was much more comfortable at higher speeds. Lets face it, these old flatheads have a lot of low end torque but high speeds are not safe on most vehicles made in the 30's. So we enjoy them even with their limitations. Just my opinion. Jack 34pu |
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