Question - 255 Flathead RPM's

Since power peak is listed by Ford as 3600 RPM, this should be a safe RPM even for extended running. Set the trans to shift at full throttle about 3800 so it will stay in the powerband when it goes into the next gear. This will give the best acceleration. If it shifts at a lower RPM, it will be a dog when it upshifts.
Then play with the governor and throttle valve to get the light throttle shift points you like. I always used to try for shifting into 3rd at about 30 MPH on older Ford-O-Matics, C4's, etc.
 
i read your hamb thingy 700r4 have you got a adapter for the trans to engine,,,,,4.27 gears i thought o/d flatheads had 4,11 :confused:
 
If you are going to race it the 200r4 is better.Flatheads like 2000 rpms or more.Thoses od are for ever down shifting.The idea of the od is to run low rpms.Its a flathead and works better with 3 speed c4.
 
In JWL's book he plots the torque curve for all the engine mods from stock to highly modifies. The stock 239 begins to fall off after 3500 and the addition of a 4" crank might start sooner. The camshaft timing will determine the top end of the curve at the expense of the bottom. By increasing the displacement and CR, can increase the torque in the curve which improves low end drivability. The biggest mistake most owners make is in tuning the engine, this has become a new science.
 
I realy don,t under stand the question.
If you had a car with 4.44 gear 3 speed with 710/15 tires at 58mph at 3000 prms.
You would NOT want to drive it very far.
My 255 . 060 over likes 2000 rpms with 205/75/15 I can do the same speed 58mph.
I have stock dist valcum and full advance is 2000 rpms.
Flathead as you have said 2000 rpms max touque.
Now knock it down 30% with od.
If you have ever driven a700 r4 they always are down shifting.
I only drive on street and when I want to get it going with the c4,
I.ll wind it up and shift it manualy.
I think a 700 is to much for the flathead.
They are highly overated.
 
40 Deluxe said:
Since power peak is listed by Ford as 3600 RPM, this should be a safe RPM even for extended running. Set the trans to shift at full throttle about 3800 so it will stay in the powerband when it goes into the next gear. This will give the best acceleration. If it shifts at a lower RPM, it will be a dog when it upshifts.
Then play with the governor and throttle valve to get the light throttle shift points you like. I always used to try for shifting into 3rd at about 30 MPH on older Ford-O-Matics, C4's, etc.
Click to expand...

Thanks, sounds like good info. I also got some good info over on the HAMB so I think I've got what I need.
 
George/Maine said:
I realy don,t under stand the question.
If you had a car with 4.44 gear 3 speed with 710/15 tires at 58mph at 3000 prms.
You would NOT want to drive it very far.
My 255 . 060 over likes 2000 rpms with 205/75/15 I can do the same speed 58mph.
I have stock dist valcum and full advance is 2000 rpms.
Flathead as you have said 2000 rpms max touque.
Now knock it down 30% with od.
If you have ever driven a700 r4 they always are down shifting.
I only drive on street and when I want to get it going with the c4,
I.ll wind it up and shift it manualy.
I think a 700 is to much for the flathead.
They are highly overated.
Click to expand...

I gave a bunch of info, but what I was looking for was what RPM to shift and max RPM the flathead can handle. I've had 700's in daily drivers and never really had complaints. I know they aren't traditional, but the first guy to put a nailhead into a merc wasn't traditional either. I consider it being true that I opted to keep the flathead and not put in a SBC. I think once my shift issue is solved, the 700 is going to be just fine.
 
George/Maine said:
If you are going to race it the 200r4 is better.Flatheads like 2000 rpms or more.Thoses od are for ever down shifting.The idea of the od is to run low rpms.Its a flathead and works better with 3 speed c4.
Click to expand...

I'm not going to be racing my 4-door boat much so I'm not worried about that. I'm pretty confident that the 700 will work out well once I get some bugs worked out. Around town it may not even get into OD or if it does start searching, I always have the D gear to go into. I've had someone very reputable tell me the 700 is the better choice with a flathead, so who knows. We'll see soon enough.
 
The Mercury cars with Dana 44 rear axles didn't have a lot of choices for gears. 4.27:1 would have been mountain gearing with an overdrive transmission and 3.91:1 for normal driving. The automatic (Merc-O-Matic) had the lowest ratio at 3.31:1 with higher one at 3.54:1 for mountainous use but these were only available for the Dana 44 since the smaller Dana 41 of 1949 wasn't set up for use with the automatic yet.

The 4.55:1 rear axle was for use with the Long Long Trailer like Lucy & Desi pulled back in the day.
 
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