compression ratio

[jdo]

can anyone tell me what compression ratio would be on an A powerblock with G pistons and a heisler head, i am looking for 10:1 or 11:1 will this combination be close

 

[johndeereman]

too much im running the same block set up with factory head shaved 325 thousandths and i have too much

 

[Dblair]

what's your static compression ?

 

[Drew]

Without having all the details on how much the block/head has been surfaced, how exactly the pistons were cut, how much the valves hang out of the head into the chamber, etc., I come up with +/- 9.75:1

 

[Big Jugs]

well, we've ran the same setup on 2 different tractors with heisler heads, and none taken off top of piston, just sides to fit into compression ring. Runs great, no complaints. As for a head being shaved .325.....wow.....just find it hard to believe.......but if he did it, ok.

 

[buickanddeere]

There is compression ratio and compression pressure which really matters. Cam timing is a major factor.
You can build a 8 to 1 engine that needs premium fuel and a 10 to 1 engine that runs fine on regular. Just by changing cam timing.

 

[Dblair]

are you over 220 psi turning the engine with the starter ?

 

[Anonymous-0]

(quoted from post at 16:01:06 02/05/10) There is compression ratio and compression pressure which really matters. Cam timing is a major factor.
You can build a 8 to 1 engine that needs premium fuel and a 10 to 1 engine that runs fine on regular. Just by changing cam timing.

MM sounds like the difference in static comp. ratio and dynamic comp.ratio. dynamic cr. always dictates the motor octane rating needed to prevent detonation

 

[Drew]

I dont have a tractor with this particualar combination, but I have measured all these components at one time or another and have enough information to get pretty close to what the static compression numbers would be (not accounting for how much the head/block have possibly been machined)

I have no idea what the cranking compression would be. And like buickanddeere said, the camshaft has a huge infulence on the cranking compression numbers.

 

[CJ_1080]

I have a buddy with a 6-3 powerblock, .125 over running G high compression piston made to fit a powerblock, and an all fuel head. I was wondering about compression also. Any John deere gurus on here know head cc numbers, or the size of the ring in the powerblock? Wanted to figure compression ratio, but didnt want to take the engine appart. Sorry for hyjacking this post, just was thinking about it while reading.

 

[johndeereman]

i havent done a compression test on mine yet i cc'd the head and it hold 115 cc's of water with the plexiglass method from the top of piston to top of block is 1/4 inch but its a powerblock so theres where its tricky to mathematicaly figure it out jdbpuller run my numbers and he came up with 12;1 a couple other guys here ran my numbers and came up with 13 and 14;1 im waiting for my cam to come back and get it back together then i will compression test it and yes we do take 325 thousandths off the heads take it down so far you have to grind that oil slot into it again its not real far from a flat head now

 

[CJ_1080]

Is there a different size in combustion chaimbers in a JD like there is in, say farmalls? Difference between gas, all fuel/distilate, propane...ect. Also there are aftermarket like heisler and johnson, are they worth the money or can you mill/modify factory ones to be just as good?