Fullpull2019

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I have an Allis G262 stock bore that I had done some work to,installed 235 chevy pistons[flat top]and some carb work.It had 0.195"from top of piston to top of head and head gasket was 0.175" head gasket bore 3.75".I was wondering what would the compression ratio be? I have been told various numbers[which may be correct]from 11.67 to 1 and higher just looking for more opinions.With this setup I have started the engine after I stalled it on a pull with a snowmobile battery 320CCA.I am wondering how this would be possible.It does not seem to have the power we figured it would have.
 
Figure the piston swept volume, bore x bore x stroke x .7854 = CID, x 16.39 = CC. Stock 3.5625 bore, 4.375 stroke is 43.6 CID, 714.75 CC, for example. With a piston at TDC and BOTH valves closed you could MEASURE the CCs of ATF it takes to fill the chamber through the plug hole. Divide that CC number into the swept volume CC will give you the actual compression ratio. Stock gas is 8.0 to 1, or head volume 89.34 CC. LP is 9.65 to 1, head volume 74.06 CC. You MAY have more head CC with piston at top than you think, filling with measured ATF will tell for sure.
 
Go to diamondracing.net, they have a good comp. ratio calculator. Also a good place to do business with.
 
Calculating compression ratio is only as good as the numbers you put in.

Is your .195" dimension from the piston to the block or to the head?

And the gasket is .175" thick compressed? That s a very thick gasket.

I come up with 12.2:1 without accounting for the volume in the head from valve recession or protrusion and the spark plug cavity volume.
 
The .195"is from the top of piston to top of block and the head gasket is copper and steel shim.The head is flat.My concern is with the compression ratio being around 12 to 1 how is it possible to start with a snowmobile battery with 320 CCA.
 
(quoted from post at 19:24:33 11/25/19) The .195"is from the top of piston to top of block and the head gasket is copper and steel shim.The head is flat.My concern is with the compression ratio being around 12 to 1 how is it possible to start with a snowmobile battery with 320 CCA.
You are correct. A snowmobile battery will not crank over a warmed up engine that is in good shape with a 12:1 compression ratio.
 
It has a stock cam and no head work.I did start it numerous times with a 320 CCA battery,I would like to know what I did wrong I am working on the engine now and would like to fix it.
 
(quoted from post at 18:24:09 11/26/19) It has a stock cam and no head work.I did start it numerous times with a 320 CCA battery,I would like to know what I did wrong I am working on the engine now and would like to fix it.
Troubleshooting over the internet is a guess, but here are some steps that apply to any engine.

Check engine ignition timing, must be an accurate check. What do the plugs look like, light gray? Shouldn't be totally black or real oily and wet. Goes without saying, shouldn't be white with the tips starting to melt.

If provided information is accurate, static compression ratio is right at 12:1. As mentioned in a previous post, if the numbers are incorrect, comp ratio is unknown.

So, guessing it is correct, the 1st step would be to perform a compression check. Warm the engine up to operating temp, shut down, pull all the plugs, then with a good stout battery, crank the engine over rapidly and read the compression gage at its highest pressure for each cylinder. For a fresh engine all cylinders should be within 5% or less of each other. For a 12:1 motor, guessing cylinder pressure will be in the 225-260 psi range.

If pressures are very low or inconsistent, a leakdown test on all or the suspect cylinders can be performed. I use 100 psi, not the 30-40 recommended, it's much easier to listen for escaping air in the intake manifold, exhaust, or oil pan. Also look in the radiator for bubbling water. If not familiar with this test, find someone with a set of gages and how to use them. It's not complicated, need to back off all the rocker arms, pressurize each cylinder, comparison of input pressure to pressure a cylinder can maintain, should not be more than 10% loss, preferably not more than 3%. Will be able to hear escaping air thru either valves, going by rings, or seeing bubbles in radiator. Have seen a brand new engine where the valve seats weren't true and the valves wouldn't seal, valve job corrected the problem.

If those things check out, check camshaft health. Put a long travel dial indicator on the valve spring retainer, hand crank the motor thru a full two revolutions (do not crank with starter), write down max valve lift for each intake and exhaust. Compare to each other and the engine specifications. If they vary more than a couple %, there's camshaft problems.

If the cam checks OK, need to check what intake centerline deg it is installed. Should be somewhere between 99-104 unless engine specification says otherwise.

Eventually the problem will surface.
 
Thanks forty40,I guess I should have asked these questions before I took the engine apart and have send parts away to get worked on.My plan now is get the compression to 13.5-14 to 1,head work,custom cam,bigger carb,custom intake and see what results I will get.
 
if the numbers .195 and .175 are correct,the compression is way low,taking off.040 - .050 is alot and will raise the compression several points,ccing the head volume with a berate is the only way to know,then the whole cylinder volume,add em up,divide by combustion chamber volume,like diesel tech said,but no spilling,no wasted drops of liquid,a stock older tractor was in the 7-8 to one range,head needs to be cut a lot to achieve 14- 1 with flat top pistons.stroke helps a lot,my pistons have a .500 inch dome to get to 13-1.cranking pressure with a gauge only gives you a slight idea of actual compression,it is meant to check rings,scoring and valve seal,not compression,as every gauge is different and just squirt some oil in and recheck,very much more gauge pressure,on a good gauge,13- 14 to one is around 280 - 300 plus,as just an indication,not accurate,when using a berate to check a smaller bore and stroke,several drops wasted,spilled or misused is a lot off on real ratio.And with an angled plug on the side,head installed,-- no way to know if an air bubble is present,and head needs to be off,flat and level to accurately check that volume, or else every thing is just a guess.good luck,many smaller engines lug better in the 9-10 to one range,without cam work,bigger stroke,bigger carb you are just chasing your tail stock.
 
The 262 has a flat head, no combustion chamber in the head. Milling the head, other than truing it up won t do you any good.
 
The Allis G262 engine has a flat head so would I gain any compression with dome pistons? My gap from top of piston to top of block is .195,with a thick head gasket I was going to get a new thinner head gasket to get my compression up to 13.5-14 to 1.Iam also doing head,cam work,bigger carb and custom intake.
 
Were the stock pistons dished? If they were you ve made your engine a quenchless engine, this could really effect how it runs. Ford gas engines have a flat head with a dished piston.
 
(quoted from post at 08:40:52 12/01/19) The Allis G262 engine has a flat head so would I gain any compression with dome pistons? My gap from top of piston to top of block is .195,with a thick head gasket I was going to get a new thinner head gasket to get my compression up to 13.5-14 to 1.Iam also doing head,cam work,bigger carb and custom intake.
Sort of thinking out loud, not sure an engine without quench will run right. 235 flat top pistons have no outer rim and being .195 in the hole, there is no means to prevent the flame front from rebounding back into the combustion area...detonation. A 235 piston is inexpensive but may never make satisfactory performance and custom dish pistons would be needed to provide a better combustion area. With zero piston to deck and a .060 T head gasket, a 50 cc dish in the piston is required, that's a deep dish, 3.00 dia x .400 deep. A piston mfg would have to be contacted, definitely not off-the-shelf. Maybe 235 pistons will work, just haven't seen a flat top that far in the hole. Automotive high performance with flat top pistons, zero deck and .030 head gasket with 47 cc comb chamber. Attached is a picture of a typical dished piston, as shown not at TDC
mvphoto46068.jpg
 
The engine runs good,works good I am wanting to up the Hp so was thinking higher compression,head and cam work, custom intake would bring up the Hp.I was told by a guy that works on these engines that it would be a very small difference.
 
Have you ever dyno d what you have now and seen where the hp/tq were in the rpm bands? That would also be an opportunity to tune the engine as well, we ve picked up 5 hp on tractors with a slight timing adjustment and some carb tweaking.
 
You can gain maybe a little. But to really make power. Have to turn it 7000 rpm. Or make it 450 or so cubic inch.
 
Iam wanting to get to 100+/- Hp which Iam told well happen with the stuff Iam doing to the engine.Can not dyno it I removed the pto_Other pullers may notice 7000rpm when the max I can run is 3000.Not sure it is possible get a G262 to 450 ci.
 
4" x 6" makes 415cu. There is a lot of small (honda) big end rods out there for small block Chevys and Fords. Some a little bigger than 4" I have used cheap smog pistons in a AC. Had to cut the dish out round. Cut a dowell rod same size as main bearings. Then cut another one to fit inside your honda big end. Cut a 1/8 x 1" flat iron 3" long. See how much you have to grind to get it to turn. Don't forget the cam. I've seen some pretty radical cuts on cams. On my AC I've ground on rods and the cam. Plus ground block 12 times. Cc your combustion chamber, so you know pin height and rod length. Or go to a tractor puller engine builder. I've worked 3 yrs on my D17 and Had engine out 3 times and getting ready to do it again.
 
There is very little room inside a G262,I have heard some go to 5.25 stoke but not reliable.I will go with the build I have planned and hopefully be more reliable.
 
I have read that Mike Lepard makes custom pistons for these engines, hope he still is been thinking about getting some myself. An old post on here listed his phone # as 716-308-5987 and email is [email protected]. Let us know what you find out.
 
I have talked to Mike,and those are the contacts that I used.Good guy to talk to,has worked on lots of G262s and knows lots about them.
 

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