engine horsepower

I am building an engine with a '45 crank and 4.125" WD pistons with around a 10:1 compression ratio and a D17 governor spring. I think it would be 240 cubic inches. What would be a good estimate for horsepower?

yeah i would say cotncrazy's estimate is pretty close, depends on a lot of things, not just bore and stroke, what kind of pulling are you building it for, stock class? high speed? 

My farm 17 dynoed 64 with only 6 hours on it. 41/8 17 kit and big head.

But, also a thing to consider, 540 power will be less in a wc-wd-wd45 than a d17 because of the rated rpm difference. If memory serves 540 in a WC is 1300 RPMS while 1650? is D17 rpms. It had certainly make more power with 350 more RPMs. Its all relative to your desired rpm range and chassis.

Another thing to consider is this, Id defiinitely install at least a d17 cam in that engine while you have it apart. Its a better grind.  Not as old ( less wear, possibly)and designed around a motor that is certainly closer to what yours will be than a '45 or wc EVER was.

A stock D-17 (not a series 4) was rated at 52.70 HP @1650 RPM by Nebraska test. If you installed a real set of M&W pistons and sleeves (4 1/8" bore with 7.5 to 1 compression) they claimed 57.1 HP @1650 RPM. There's no way a set of 4 1/8" pistons with farm gas compression makes 64 HP.. I'm sorry, it ain't real regardless of what the dyno says. This of course assumes a stock carb and camshaft are being used. The 1/8' overbore only gained 4 HP by M&W's specs, not 11 HP.

here's what i would do (and will do this winter when things slow down) my grandpa's friend has a dyno, so it is readily available to use. we are going to dyno the tractor before we tear it down, than after we rebuild it do all that fun stuff (for once i actually want it to snow) we are going to dyno it again, on the same dyno, that way even if the dyno isnt accurate it will at least show how much power we gained. if you dont have acces to a dyno use another method of testing it, like was previously done, you could haul a load of corn up a hill before and after, you could pull a disk or a plow or something like that before and after, i dont know what class you pull in, but i pull in farm stock, which is a class where hp is just a number, i prefer lug and torque, love to listen to that allis pull way down and then hit that sweet spot, where it doesnt lug down any more for a ways, until i finally choke it out to where the only reason the engine refired when i hit the clutch was because the pistons were still moving, but thats just me, and what i would do to measure your improvements 

Horsepower is a simple number right? (torque X speed)/ 5250= hp

What makes horsepower? A chemical reaction, it's the burning of fuel.

How do you burn more fuel? You carry it in the cylinder with more air.

As your engine slows down, the cylinders get more time to take a breath of air. They are already restricted so giving them more time to take that breath will help them to fill better. The more air they can take the more fuel the engine can burn. But the speed has dropped now hasn't it, for the horsepower to stay the same the torque output has to rise. Torque is made from airflow. Unlike many believe that stroke makes torque, it's really the increase in airflow. The stroke length is part of the equation, but weather you have a 4.5" stroke or a 5.5" stroke, you only use part of that for the actual "lever". Meaning that a 4.5" stroke crankshaft only has a lever of 2.25", or half stroke length. The real kicker here is that the effective stroke length of say that 4.5" stroke crank isn't 2.25", it's much less than that. Why?

The power stroke is only for a few degrees of crankshaft rotation, this all happens when the piston is pushing off of TDC for a few degrees of rotation, so your "stroke" has became almost useless, as it's only pointed straight up. Effective stroke length is the same on a 4" stroke crank as it is on a 6" stroke crank WHEN the piston is at TDC, as the piston is pushed down and the crank rotates, the stroke length becomes a tangent of the angle that the crankshaft is at during it's rotation. Now a 6" stroke crank has a more useful or a longer lever than a 4.5" stroke crank for this time. But this is only true ATDC (after tdc). Now when you light your fuel charge BTDC, (before tdc) lets just say 20 to 25 degrees of crankshaft rotation this force is negative. It's only useful ATDC when the piston is pushing down on the crank that the increased stroke length is useful.

None of this matters if the cylinder doesn't have much fuel to burn, or much air to burn it with. The speed is going to drop until the point where it can take in enough air to make the torque to maintain the speed and load that it has to or it will kill. How can you increase your torque output? Increase your airflow.

You want to put in a D-17 camshaft. Others always say on here they want a "170 cam". But very few know what it is, or how to phase it to the crankshaft to take advantage of it. You're trying to fill your cylinder with a cam moving the valves at the wrong time, and for not long enough no matter what cam you have laying in the shed or at the salvage yard. Some of them are better than others, but they are all like trying to fill a 5 gal bucket with a spoon. You need a bigger spoon, or more time to fill the bucket.

Your camshaft it timed to the crankshaft, it's currently a little late in getting the valves to move. It would help if the camshaft was moving the valves a little earlier in relationship to the piston movement. You can simply jump it 1 tooth, or advance the camshaft 1 tooth when lining up the timing marks. This isn't the best solution but it's better than nothing. Your stock timing marks are timing the cam a little late, jumping it would time it a little early, but it's better than being late. Ideally you need to be abut half way in between, but this is going to take a degree wheel, indicators and some knowledge to accomplish. If you can't do this, then advance the cam 1 tooth, it's simply better than where it's at but not quite optimum.

The camshaft is still to short of duration, meaning that it's not holding the valves open long enough to fill the cylinder. We can't hold the valves open to long though, as the engine slows down in speed we will loose the air we are trying to trap to burn the fuel if the valves are open to long. It takes time to get the air charge moving into the cylinder, if the cam opens one valve to early and closes the other one to late we loose what we are trying to gain. If the cam does this at the wrong time, there's no cylinder for the air to try and fill, or we open the exhaust valve to early and bleed off pressure pushing on the piston.

My point here is that you need a camshaft with about 20 degrees more duration or time to breathe than whatever is on the shelf at the salvage yard or laying in the shed . Much more than that and you will go backwards. Your stock cams timed in correctly will help, but not quite as much as having one ground correctly and installed correctly. It'll be more useful than any other thing you can do on your engine.

DrAllis wrote: That's a good idea. Just make sure you have the same air temp on each run. Humidity also plays a part in overall HP numbers, but 30 degree air versus 70 degree air makes more difference.

yeah i was thinking that after i had posted, that you can get more hp on colder days, didnt know about the humidity making a difference though

Its no suprise that Pank is the STROKE expert, Butch...judging by his posts on here it seems all he does is....well.....you get the pic

What happened to compression is king and Nitro is the fuel for power Mr Kinkrod??

Edited by Butch(OH) - 06 Nov 2013 at 11:26am

THE-MAN wrote: Its no suprise that Pank is the STROKE expert, Butch...judging by his posts on here it seems all he does is....well.....you get the pic

Theroretically, maybe. You will need to "time" the ignition later than 30 degrees BTDC with that compression ratio. I'd guess 20 degrees BTDC, but dyno tuning for the most HP is the best and fuel of over 100 octane will be needed.  Better make extra marks on your flywheel or have a timing light with degree calculator built into it.  And when you get it running, run a compression pressure test and see if it is really 10 to 1.  I'd expect more than 200 psi, probably 220 psi.

So with a D17 cam and rpms up 21.2% from 1650 to 2000 theoretically you would gain 21.2% more HP?

I guess ..in a d17.

But I dont think that is a solid enuf theory to build on, or apply generally.

Its like saying that my F250 makes 400 hp @2500. It will make 800 at 5000 rpm in the same form. Aint gonna happen no wa,y no how. Only in a Fantasyland.

These close to stock motors will make a little more hp if you turn them on, but who cares what it makes at 2000,  or even 2500 if it cant hold it there! Find where your power band is, figure what gear you run and what speed you need to be at and work on bettering it where you need it. I broke down and bought one of those Zack Peterson TRACTOR SPEED GUIDE spiral bound books. I can figure speeds mathematically, but its nice and easy to open the book up and get a close idea. It also helps you calculate based on loaded tire hight n stuff.

One way to look at it in perspective is to take 49.7 hp/240 cubic inches for. 207 hp per cubic inch. So a 6 inch stroke 4 inch bore 301 at 7.3 compression would have 62 belt hp. 400 inches at 7.3 comp 82.8. Now most 392 or 400 ci puller motors from a 226 go 100 hp. They have 10 to 12.1 compression to do so.