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No low end torque

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North Dakota H

12-16-2006 07:18:01

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I have a farmall H, we have done an aggressive grind on the cam,a super H head and maifold and a M carb and have a oil free air intake. The dyno shows 40 H.P. but we are still powering out when we pull, no low end torque. Any ideas? We are still running flat top piston's and was wondering if we could use a domed piston with the aggressive grind on the cam without the piston hitting the valves. Chad S. could you please respond. Ideas from anyone else also welcome.

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ChadS

12-16-2006 11:52:44

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

Junk the cam and go to a 350 camshaft. Best one your gonna find for the best power. What kind of pulling are you doing with the H?? That engine, even at 40 hp, is good for tractors that have more of a stock hitch setup. The closer you move the hook point to the rear axle, the more power it takes to keep moving. Try to get a #23 for the venturi,,,, that will give you the best low end power, if your running racing fuel, go back to a good pump gas, that stuff does not belong in a low rpm engine, period!! The timing likes to be retarded on these engine, tune it in onthe dyno if you can, while its at 500 instead of 540 pto,, since your rpms are in the lugging range, thats the rpm range you need to focus on to tune it. That cam has to go, it was doomed from the start,,,, sorry, thats the reality of it,,, your not running a large stroker that requires anything beyond the best upgraded parts from the factory,, and even then, custom cams may hinder the engine instead of helping. Only better cam option would be just a step above the specs of the 350 cam,,, still,, 40 hp aint bad for a H with an overbore kit,,,, So,, think of the hook point and maybe move it back farther away from the axle, that may help it without changing parts,,,, Let us know what style pulling you do,,, weight classes,,, tire size,,, etc etc,,,, More info coming soon! ChadS

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North Dakota H Puller

12-16-2006 17:03:03

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Re: No low end torque in reply to ChadS, 12-16-2006 11:52:44

We have been pulling the 4500 pound class. 13.6 X 38 tires. The cam that is in it has high lift and about the same duration as a stock H cam. It has great power going down the track until toward the end, then it just slows down and stops right away. It is still competitive. I turned the RPM's up to like 2250. I only have about 110 pounds of compression in each cylinder. I was thinking that it would maybe help to get a little more compression? What do you think?

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ChadS

12-17-2006 11:14:13

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Re: No low end torque in reply to North Dakota H Puller, 12-16-2006 17:03:03

Do you knowwhat the lobe separation angle is on that camshaft?? What you have is the typical low compression engine,,, More compression will surely wake it up torquewise. You need to be in the area of 150-175 psi at cranking speed. Its gonna be hard to do with flat top pistons. Id look for a set of high domed pistons, that will help alot, if the engine has been recently rebuilt,, you can drop the pistons in the sleeves it has already,, just hone them out once more, unless they are really super worn,,, then replace them. Id also bet, it may have cast iron pistons,,,,, very heavy in weight,, with low compression, it will die off quicker when the load is heavy. If it was higher compression, it would help make some extra torque with the heavyweight pistons,,, but still,, no subsitute for aluminum pistons. Id think about pulling apart and upgrading the piston/sleeve kit,, fairly inexpencive to do,,,, One thing I have done in the past was to put the thick H sleeves in another block, and sent it to be bored,, and remove them and put them back in the engine you have,, that eliminates having to remove the engine from the frame and be done inframe,, which saves time,,,, Did that to a Super H and went up to the 350 pistons,,,, the H wont go that big,,, and still have sleeves,,,, Ive seen 300 pistons in sleeveless H blocks with a little honing of the block,,,,, Chad

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North Dakota H Puller

12-17-2006 13:16:16

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Re: No low end torque in reply to ChadS, 12-17-2006 11:14:13

Not sure about the lobe separation angle. Seem to have lost the cam card. Yes they are the flat top pistons. We have installed a 300 head for more compression and bigger valves. Not sure about domed pistons. The cam may have too high of lift for clearance. I know my machinist has redid a cam in a super M diesel and put valve reliefs in the pistions. I am wondering if I can do the same.

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ChadS

12-18-2006 10:41:48

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Re: No low end torque in reply to North Dakota H Puller, 12-17-2006 13:16:16

Bout anything is better than the ol flat top pistons. Here is whats going on in your engine,,,, Big cam, big valves, bigger carbs, and low compression pistons,,, your creating way to much air flow than what your pistons can draw in. When the air freeflows too much,,, you lose the most important characteristic that goes with low end torque, and thats manifold vacuum. Its losing its ability to draw in the air charge when the load is applied. The pistons mechanical compression is not pulling in enough air to compliment the modifications, and doesnt pump up the cyl properly,,, so,, you have to look at ways to increase the vacuum pressure in the manifold. Actually going back to the OEM H carb would be the best choice at this time, until you do something in the short block. Its not going to increase compression,,,, but its going to move your torque range from high rpms, to low rpms. Slow that air flow down enough to help put a better draw in the cyl, it mixes better, and builds more low end power. Too big of breath,, and it falls on its face on the low side. Its very possible to make your engine better with what you have now,,, just change the induction system to help the low compression feed the engine more efficiently in the lower rpm ranges. In this case, smaller carb is best. Chad

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North Dakota H Puller

12-18-2006 10:59:42

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Re: No low end torque in reply to ChadS, 12-18-2006 10:41:48

We plan on doing some modifications to the engine this winter. Just not sure what. Right now we would like to try to increase compression if possible. Will this help the too big of breath problem at low end or would I need to do something else to help this.

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ChadS

12-18-2006 13:16:21

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Re: No low end torque in reply to North Dakota H Puller, 12-18-2006 10:59:42

More compression will help draw more air into the cyl, it will increase vacuum pressure cause you are moving a bit more air,, a faster air flow to be more precise,,, See,, a certain amount of vacuum pressure will mix a certain amount of fuel,,, lower levels will have alot of air, and less fuel,,, where the higher pressure will have more ability to draw fuel and air mixed in better which gives more tunability on the dyno. As far as what to do on a buildup,,,, there are litteraly 100's of options to choose from. Ill tell you about some of the engines we have done for ourselves,,, we built a 350 rowcrop this summer,,,, 175 ci, (3-5/8 bore) we took it a step further,,, we used H rods, made a bushing, and then offset drilled the wrist pin bushing higher on the rod,,, that pops the piston up more out of the bore,,, and then we remachine the piston so it fits in the head. That engine is 55hp, has a torque curve of 65 when lugged down,,,, Lots of low end torque added,,, If that was in a H frame,,, you would have a H that can run 4000,4500,5000,5500 low gear classes and have power to pull it. Then theres the stroker options,,,, Chad

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Brian in Ne

12-16-2006 11:42:39

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

I experienced this a few years back with a friend's H. Only he had used the SH/300 cam and timed the engine for max power at high engine speeds. Same thing when the engine pulled down it fell on its face. We talked about it and I suggested to time the engine back to stock so it would have its higher horsepower down in the RPM band so when it starts to lug it kept pulling.
It worked. Remember that engine on an antique (unless its a Div4 or 5 NATPA) is only going to stay at high idle for a short time down the track. If you are pulling Div1 or 2 and maybe 3 use the SH/ 300 or 350 cam. Don't port the intake too much just clean it up a little or you will loose your ports air velocity.Don't polish the intake. Do match the ports and manifold. Port and polish the exhaust, not too much again! And LEAVE the stock valves in the head! On my H, I have the 350 pistons. The engine flows 83cfm @ 1950rpm. My carb flows 88. And it pulls awesome!

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ChadS

12-16-2006 12:11:32

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Re: No low end torque in reply to Brian in Ne, 12-16-2006 11:42:39

Brian, does that H have firecrater pistons? That design does alot of good, the extra turbulence created inside the cyl really mixes things up alot better than stepped head pistons. Especially on the exhaust stroke,, where the air is more of dead headed path, where the crater creates a spiral shooting towards the valve to help evacuate the cyl. Makes a world of difference in my opinion. Ive got a Div 4-5 H Farmall Im putting back together, (finally) With such high compression that it had, was running a flattop style piston,, and opted to go with a dished piston, which is a firecrater,,, I had built one earlier this year with a smaller stroke,,, same piston,,, and had less compression than the exact duplicate I have in another tractor,,,, That engine had 40 psi less inthe cyl pressure, but still had 4 more hp at 540 and about 10 more on the low end torque curve over the flat top piston with higher compression. It has to be the firecrater design,,,, Stock IH performance,,,, what more can a guy ask for!! I cant wait to get that H going again,,,, Chad

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Roger Mills

12-16-2006 08:46:00

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

I havn't done pulling with tractors just big engine 4x4s. I have a stock P60 (very long 20K# gross) frame flatbed 4 wheel drive Dodge from 1961 that has a 440 and 5.60 gears in it. It did very well but I wanted more so we tore the engine down and went agressive with the compression and cam. Big mistake!!! Power band was good only above 6-7k RPM and below that zilch. Put in what is called an "RV" cam for low end torque and the power band was great from 2500 to 5000. From what I have seen with old tractor motors 2000 RPM is very high. I suggest you call Engle or eq. and tell them what you want-ie max air at 2000 RPM. send them a cam to regrind. Next port and polish EVERYTHING! Match the ports, gasket too! Install the biggest intake valve you can. Finally dyno the dist. advance springs for max HP at all useable RPM's

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T_Bone

12-17-2006 06:46:35

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Re: No low end torque in reply to Roger Mills, 12-16-2006 08:46:00

Hi Roger,

I have a 70's 440 that's going to the scrap yard if I can't give it away. Needs rebuilt as it had 90psi when I pulled it 15yrs ago. It might be total junk by now.

SW of Phoenix.

T_Bone

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vally farm

12-16-2006 08:45:12

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

I "built" a little 2.3 ford in a fox body Mustang, to prove how much power it can make. She ran pretty strong until I put in a higher profile cam. Ran like a jet engine above 5000 rpm's, but couldn't hardley move until it could get to those rpm's. My guess would be the cam grind. Try a 305 cam and I think you'll be much happier. Just a thought, My neibour had a H and said it couldn't pull his spreader for dirt. I bought a Super H, and it can almost pull as much as Pop's Oliver 1600 with a moter job. 1/3 the fuel too. Mike

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LenRahilly

12-16-2006 08:20:14

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

I'm wading into territory I've never been in before (hopping up tractors and pulling), but I HAVE spent years on H's and the tractors in the same 2-plow category that preceded them (IHC 10-20 and F-20). I still like to sit around and think about the old girls, and I do a little armchair engineering from time to time (maybe it will be obvious that I am not an engineer). The older tractors had big engines that ran slowly. Lots of torque, a bit like a big, slow guy with a lot of muscle. They were almost impossible to stop, even if way overloaded. When I first got to do the same kind of work with H's, I was terribly disappointed in the lack of torque (my father first got a low-compression H, which we ran on gasoline, then later he got a "high-compression" gasoline model; there wasn't a lot of difference in the way they performed). It helps to compare the size of the engines: the H has about 152 cubes, if I remember rightly, and the F-20, about 221 cubic inches. The H gets its horsepower from running the engine quite a bit faster than the F-20 (1650 at full load, versus 1200 for the F-20). The F-20 on 36" rubber (low compression kerosene/distillate engine, but running on gasoline) would pull 2-14s in fourth gear at close to 5 mph, heavily overloaded and with the engine pulled way down, but it wouldn't actually die. The two H's I used over a good 15 years would pull a 2-bottom plow in sod ONLY in second gear, and if you tried to shift up even one gear, you would pull the engine speed way down and it would just stall out. Different design philosophy. No question that the H was a "sweeter" tractor than the F-20--lots more comfortable, lighter, more agile, but it just didn't have the moxie of the older tractor and its big, muscular engine. Well, this is just some fun musing over the good (?) ole days, and I hope it's at least interesting, if not really helpful.

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El Toro

12-16-2006 08:04:30

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

I would open that main jet adjusting screw to make sure the engine has plenty of fuel. Hal

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billde

12-16-2006 07:57:07

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

High lift high duration cams typically show poor low end performance. You need to keep rpms in the upper range to get the desired results. Have you matched the intake and exhaust ports? If you have access to a dyno try playing with the carb setting and timing.

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Doc Larry

12-16-2006 08:18:56

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Re: No low end torque in reply to billde, 12-16-2006 07:57:07

My thoughts exactly. Aggressive cams give better performance at high rpm only, and are much worse than stock cams at low rpm. In my experience, anyway.

Larry

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Janicholson

12-16-2006 07:27:59

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Re: No low end torque in reply to North Dakota H puller, 12-16-2006 07:18:01

Compression can always help a puller unless fuel restrictions limit the use of high octane. Using an old gasket, clay on the piston top to assess clearance, a good feel for rotating effort, and use of a die grinder/Dremel, can make it work well. Engine building is an artform. If you have flat pistons now, many choices can be found with little or no grief. A tall agressive cam may have much less torque at low speeds than you would imagine. Probably less than stock. Thus keeping RPM up will be useful. JimN

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