Rotary vs in line fuel pumps in old tractors

I've heard that in-line fuel pumps deliver better power and torque characteristics especially for pulling. I've also heard that the rotary pumps make for better starting which is why IH went with rotary until the late 5488s etc. If this is true, how much of a difference does it make? Is the in line pump in say a 4430 JD far superior to an IH 1066 rotary pump in terms of power output? And while we're at it, where does a Roosamaster in a 1256 fall into place as far as power potential in comparison

This post was edited by Farming Enthusiast on 06/20/2023 at 06:28 pm.

MOST inline pumps, but not all have more torque rise fuel capacity than rotary pumps do when the governor has a torque capsule installed. BOTH can be set up for good cold
starting depending on design. Injection pumps can be designed with constant beginning/variable end of injection, variable beginning/constant end of injection, and some
inline pumps have variable beginning/variable end of injection. With good filter care inline pumps can go 10,000/15,000 hours before needing service. The IH 1256
Stanadyne/Roosa pump has .370 inch rotor plungers. Serious pullers switch to an inline pump for more reliable higher output max fuel delivery than the simpler rotary pump
can deliver.

Thank you for your response. So that being said, the 4430 would have a better factory pump than a 1066 for power output or not necessarily?

If both pumps are stock, the 1066 M100 pump can have a higher max fuel delivery with it's 10MM head plunger. The 4430 inline pump has 9.5MM plungers, and they are limited
on max fuel delivery due to the retard start notch cut into the plunger top, which retards the timing at full rack travel to help with cold starting. The M100 pump has a
14 degree cam advance as engine speed increases for better cold starting. The Mack HD9126 11MM head is a bolt in, but pullers now also can get 13, 14, and 15MM heads for
the M100 pump. The largest STOCK Bosch A size pump plunger is 10MM, but larger custom pumps are available.

(quoted from post at 19:12:31 06/20/23) If both pumps are stock, the 1066 M100 pump can have a higher max fuel delivery with it's 10MM head plunger. The 4430 inline pump has 9.5MM plungers, and they are limited
on max fuel delivery due to the retard start notch cut into the plunger top, which retards the timing at full rack travel to help with cold starting. The M100 pump has a
14 degree cam advance as engine speed increases for better cold starting. The Mack HD9126 11MM head is a bolt in, but pullers now also can get 13, 14, and 15MM heads for
the M100 pump. The largest STOCK Bosch A size pump plunger is 10MM, but larger custom pumps are available.

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Good stuff. Thanks again

There are fuel injection shops that produce larger replacement cups and plungers for the in-line pumps to dramatically increase fuel delivery.

Here's an observation- if I am running something like a grain vac or forage blower with certain inline pump tractors (JD 4450, 4455), i'll
have much more uneven, surging power than with a rotary pumped tractor. (4020, 4320, 4240) It's like the governor tries to adjust for each
paddle full of grain or forage.

As for the inline pumps, one probably has 14k hours on, and runs smoother than one rebuilt 1500 hours ago.

I'm not saying one's better than the other, but just sharing experiences.

(quoted from post at 06:31:24 06/21/23) Here's an observation- if I am running something like a grain vac or forage blower with certain inline pump tractors (JD 4450, 4455), i'll
have much more uneven, surging power than with a rotary pumped tractor. (4020, 4320, 4240) It's like the governor tries to adjust for each
paddle full of grain or forage.

As for the inline pumps, one probably has 14k hours on, and runs smoother than one rebuilt 1500 hours ago.

I'm not saying one's better than the other, but just sharing experiences.

Click to expand...

Thanks again for the very good info guys. I've just started getting into tractors the last 5-7 years and am curious.