wd flat top pistons in a g226 z code block

rsmn

New User
I will be overhauling my gleaner eIII engine that i use in my wd45 tractor, I was thinking about going with new 4,1/8 overbore wd flat top pistons and sleeves. just wondering if i will encounter any problems doing this. I read some people believe the compression is too high, while others say it will be fine, would like some more input if possible. the block number on the side is 17-79203-z. 8:1 compression now.

thanks

Rusty
 
The most compression ratio you can have and still use 87 octane fuel is 8.25 to 1, and even at that, your ignition timing needs to be 23 degrees BTDC at full throttle to keep from having detonation problems. The timing mark on a WD-45 flywheel is 30 degrees BTDC, so be sure to remark it while the engine is out. The only way you will know what compression ratio you have is to take a new flat top piston and connect it side by side to an old piston with a piston pin and calculate the difference in volume of each design, using water and a piece of Plexiglas on the bowl to measure the CC's and go from there. Why do you want so much HP for a WD-45?? If those 4 1/8" flat tops are 8.0 to 1, you'll have 70 flywheel HP at 1650 loaded RPM's. I believe some one makes 8.0 to 1 ratio four inch bore pistons/sleeves which would match your old ones. If you have more than 180 lbs cranking compression psi, you will have to use better gas than 87 octane.
 
Me and Dr. Allis have disagreed on this before and I will tell you its one of very few thing ive contradicted him on but theres a good many engines running 9:1 easily on pump gas. I have same as what you're talking about building in a WD. Old hot rod guys will tell you 12.5:1 is the line. If you can do that and turn 8000 rpm in a 350 I cant see a problem on a low rpm engine. I will tell you I do have problems turning it off if its been worked. I'm not entirely sure what mine is running for compression. I'm told 10:1. I do know they are flat tops and are taller than the original. I run 87 octane no problem with points ignition
 

Remember, if they get to smoking and loosing compression...it just may be the compression rings have shattered...

( I wonder why they DO that?.. )
 
It's easy to claim to be 10 to 1 compression, as it is a calculated number.. Actually running a cranking compression test verifies what it really is. 170 to 180 psi is what an A-C 170 or 175 gas actually have and is in the Service Manual and they are 8.0 and 8.25 to 1. I had a Customer bring me a D-19 LPG many years ago, and wanted it converted back to gasoline. The LPG engine was 9.0 to 1 compression ratio and had 210 psi on each cylinder when tested. I did the conversion and tried retarding the ignition timing from 25 degrees BTDC down to where it didn't detonate any more when idled clear down in road gear and cracking open the throttle when engine was at operating temperature. By the time I reached the "no-ping" zone, the timing was down around 15 degrees BTDC and the engine was really a turd. The Customer just figured he'd buy better octane fuel to solve the pinging problem, as it was a limited use tractor and never pulled a plow or disc. Good luck with whatever you do. A tractor engine that has to plow or disc all day long has to have good enough fuel or low enough compression to not be pinging all the time. That's a fact.
 
Ill agree with you that it cant be pinging and I
didn't claim 10:1 I said I was told that. I do know
I cant hook the a dyno to it because if you get
close to rated rpm it shears the bolt in the PTO.
If I remember correctly mine was around the
250psi Mark but its been to long for me to say
for sure. I can say for a fact ive had excellent
results with the combination he is asking about
and I'm running 87 octane on a working machine
Not a puller.
 

No matter what the actual measured Compression Ratio measures ( by actual Volume), the ACTUAL Operating Compression can be much Higher..

Take my old Ford Big Block with a Crane Cams 531" lift, but a 324 DEGREE Duration.( as used in the Ford "ThunderBolt" cars).. At Idle, it didn't have enough compression to keep running unless it stayed above 1,6oo rpm..BUT, from 4'500 to 7,500 it was a Rocket..
I still have the 427 Heads ( with Tunnel Port valves) + the Cam..

Anyway, IF the cam keeps the valves open at any time during the compression cycle, Measured cranking Compression will be effected..
 

Maybe I should add that as Duration increases, the Exhaust Valve is KEPT open farther PAST TDC on the exhaust stroke, while the Intake Valve is opening further Before TDC.

At the Bottom of the cylinder, as the Cam Duration increases, the Intake Valve stays OPEN increasingly farther PAST BDC...while the Exhaust Valve is opening earlier ON THE POWER Stroke..

THAT is why "Hi RPM Engines" (as in for Racing) have very high Compression ratios and cannot deal with being pulled down and laboring, like a Big Cubic Inch lower compression engine.. If Detonation doesent set in ( High RPM usually uses MORE Ignition lead time), the shear loss of BMEP at the lower RPM takes the power away..

So, this IS much different than the old Tractor Engine Cam timing of NO Valve over-lap at either TDC OR BDC.. which will actually GIVE you an accurate measurement of Compression Ratio at cranking speeds..
 
I'm unaware of any gasoline fueled American built farm tractor engine that was ever more than 8.25 to 1 advertised compression ratio. If there is some company who had a gasoline farm tractor engine with a higher ratio than that, I'd sure like to know who it was. So, with that in mind, if there was some way to actually build a farm tractor engine higher than that, say like 10 to 1, why didn't some Manufacturer do it????????? I would think out of the hundreds of smart Engineers that built all those engines, if it was practical to do so, they surely would have done it. Wouldn't you think ????
 
You have to allow for operator error. I'm sure
I'm running at least 9:1 probably 10 but I
don't lug it. I can pull rated load just fine but
if you get stupid bad things will happen. I
had a Ford 390 interceptor that was factory
10:1. Automotive and tractors are different
because of the way they are worked. My
neighbor growing up had a MM UTU that
had dome pistons and 4232 heads. Pretty
sure it was around 10 or 11. Someone with
more knowledge could tell you. We took the
heads off and de rated it because if you
pulled it down to far you would blow the
heads off of it. This was at the advise of the
local dealer who built many a pulling tractor.
I do good with the 226 hes talking about.
Lots of power. Just don't try to lug it.
 
I have flattops in my D17 with Petronix.
Over 210 psi cranking pressure
You will need 91 or higher octane or it will run on/ping.

Yes tractor has more power but I only use it for pulling and small jobs. It is far more temperamental with the flats.
If it was still farming, then put stock stuff in it and be happy for another 40 years.
 
Only issue is fuel u will need better fuel , and the higher compression will give u a little more top end power the difference shouldn't matter in this application but sometimes when ur compression is raised it will loose low end lug as it gains top end power
 
How convenient will that be to have to use "91" octane fuel for a tractor that's used on the farm?? For a tractor pulling tractor, no problem. I have to use 114 octane on one of my two pullers, but get by a whole Summer on only 6 or 8 gallons of fuel. That's not difficult to manage.
 

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