wondering if 7720 pistions will work with a 7.6 head? February 14, 2011 11:55AM
wondering if 7720 pistions will work with a 7.6 head???? any help would be great thanks !!!!!!!!!!!
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Re: wondering if 7720 pistions will work with a 7.6 head? February 14, 2011 11:56AM
head is from a 4955 john deere!
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Re: wondering if 7720 pistions will work with a 7.6 head? February 14, 2011 10:59PM
Compession Ratio will be very low.......10.5 to 1
There is a low ring piston used in some applications like a 4960 and OEM power units where the top ring is dropped down about 3/8.
Compression Ratio would be about 15.8 to 1 with these.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 15, 2011 04:05AM
Ag Tech.. you could trade him heads.. haha..

We just had this conversation a few days ago...
Just a few specs.. These are the two that were were offered.. The first is the one that Ag Tech was talking about.. (I'm sure there are others.. but these were the ones we were looking at the other day.. ) From a 4960..
RE60297 (liner kit) piston # RE57731 (16.38mm from the top to the first ring.)
RE60294 (liner kit) pistons # RE57512 (3.96mm from the top to the first ring.)

Bryan
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Re: wondering if 7720 pistions will work with a 7.6 head? February 15, 2011 09:28AM
i have 4455 high ring pistons and the 4955 low ring pistons just didnt want to take bottom end about yet had other plans when i did a cash flow is low with milk price down was trying to get by this year with one in it til next year if they will work thats what im asking i know 4955 are the way to go but i just need to know if 7720 one will work without harming the motor lowering the compression really doesnt matter to me doing damage to head or block is what im trying to prevent!!!!!!!!!!! thanks
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Re: wondering if 7720 pistions will work with a 7.6 head? February 15, 2011 01:09PM
fire ring it kept an eye on your exaust temp & boost,use water (if aloud)good luck,
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Re: wondering if 7720 pistions will work with a 7.6 head? February 16, 2011 04:07AM
Ag Tech what would a 10.5 to 1 comp ratio cause. Would it just take away the low end or is there other problems with this low of compression. I helped a friend put together a 466 40 series pistons no valve clearance cut due to using stock cam, we put a 55 series head on it and he runs d3-d4 in a 3000 rpm class. It does seem to drop down quick in rps when the sled hits. It seems to run real well in the top halve of the class but it doesent seem to hang in long enouph. Thanks to anyone with thoughts on this.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 17, 2011 03:27AM
THE 466 HEAD AND THE 7.6 HEAD BOTH DO NOT HAVE A COMBUSTION CHAMBER SO THERE SHOULD NOT BE NO CHANGE IN COMBUSTION RATIO
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Re: wondering if 7720 pistions will work with a 7.6 head? February 17, 2011 03:50AM
The 466 head is flat on the deck surface, were as the 7.6 has domes that recess upwards in the head. I am told that the 7.6 head will lower the compression ratio around 3 points.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 17, 2011 10:06PM
that what i was told also but it will work so im going to try it and see if i can run down them red guys!!!!
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 03:20AM
Good luck running down the read ones they have more stroke out the gate and wont be hidered by low compression. If ya get your water rite and run enouph fuel and get your timing correct you should be able to run d-3 and d-4 with cut tires but will run out in the end.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 04:14AM
With a 10.5:1 compression ratio, you'll be lucky if it even starts. That'll eat ether like there's no tomorrow. At that compression ratio, you'd almost be better off converting the head for spark plugs!
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 04:35AM
Make sure you take the ether!! If your going to the trouble to put pistons in it why not put the right ones in? They are not that expensive.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 04:50AM
If you can afford some machine work then all you need to do is have the 7.6L head planed and be done or of coarse run the 7.6L pistons. Some of these 7.6L heads are being planed over .100" to make up some of the compression loss.
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 10:43AM
time will tell the story !!!!!!!!!!!!!!!!!!!!!!!!!
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 11:25AM
Hate to tell you we told you so!!! Spinning
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Re: wondering if 7720 pistions will work with a 7.6 head? February 18, 2011 01:42PM
Heck, I have a gas motor in my car w/ more than 10.5:1 compression, there's no way a diesel will fire on that combination!! Forget water injection, you'll need constant ether injection!
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