630 to much compression

[jd 530]

I overhauled a 630. it was bored 90 over and i found a used set of m&w pistons . It knocks. we put in e-85 less knock but still knocks. we took a compression test and it was at175-180 psi. what did we do wrong?? did we end up with high altittude pistons??? with out having parts books [m&w]and #'s how do you know what you putting in ? what is the cure? Should our mashinist have caught this before it was together?Does it have to be pulled apart and different pistons put in? Thanks Henry

 

[Duane Larson]

Can you provide the casting number from the inside of a M&W piston? I have some M&W piston numbers. What is your timing set at?

 

[buckeye brierhopper]

is that rollover comp or is thatrunning comp? did you check timming? posibly to much,may need to back down, posibly to arround to 20 degrez check what oct fuel you ar useing. timming maybe you biggest problem

 

[Machinery-Man]

I know your problem. I put a set of supposedly Hi altitude pistons in a 520, they looked the same as LP and that tractor had 160 PSI and would not run properly. I have overhauled a 620 using the hi altitude pistons, the dish was a little less but that sucker has tons of power but no knock problem. The 520 pistons were flat top in design. I would say you"re going to have to get back to a jd design piston, obviously there is no 90 over but should be some with similar design.

 

[730-LP]

Try 93 octane and play with the timing.Had a B with a Power Block and hysler head that was 190 and run fine on 93

 

[jd b puller]

If you're knocking with E-85, you're probably about 2 turns too far in on the carb. You have to run a ton more E-85 otherwise it will be lean and you'll get knock again.

So, when you put these pistons in, how far from the top of the block did they come?

 

[buickanddeere]

As previously stated. The mixture is too lean and the timing is likely too far advanced.
Even the metering jets for an all-fuel 720/730 transplanted into the 630's will be too lean for the use of E-85.
The "jets" will need to be approx 1.3.to 1.5 times larger in diameter than for gasoline.
In the mean time, try the 630 on some 100LL aviation fuel.

 

[gtx1967jewison]

u people baffle me! all u need is colder plugs & set timing back some. get gasoline back in there as its too difficult to get rich enough mixture with e85. thats not even very high for compression & should run fine on 87 octane when right plugs & mixture. u can run over 200psi ok.

 

[jd b puller]

(quoted from post at 13:28:05 11/23/08) u people baffle me! all u need is colder plugs & set timing back some. get gasoline back in there as its too difficult to get rich enough mixture with e85. thats not even very high for compression & should run fine on 87 octane when right plugs & mixture. u can run over 200psi ok.

Hi gtx1967jewison, out of curiosity, what tractor are you running 200psi on?
What's your timing set at?
Bore/Stroke

Thanks,

 

[Machinery-Man]

While I"m not a tech guru but have had a lot of experience on 2 cylinders. I think with extreme hi compression you"re picking RPMS but you"re cutting you burn time. For the old two cylinders to function properly you need an adequate amount of burn time for torque or lugging. This is why you time advanced to start the burn through the full stroke...you loose this will hi compression...

 

[Anonymous-0]

A cure, pull the pistons back out and machine the cup deeper, this will decompress it a little. We got a 70 gas that is around 180 psi, that runs on 50/50 E85 and 93 pump gas and runs like stock. Its jetted up, and it will run enough to run rich, and it loves its timing! Had to notch the one side of the distrbutor housing to get more adjustment! it should run like its got a slight load on the engine at idle, like a car with an automatic transmission sitting in drive with the brakes on,, make sence? put it up at bout half throttle and turn the distributor to see if the knock quiets down, it should idle with a more aggressive, deeper "putt" to it. Sure fire way to know if its better is if it shuts off and doesnt try to keep running. Hope this helps. Chad

 

[Glen D Anderson]

To get ANY engine to run on pump gas at 200 psi compression and yet keep the "little man with the hammer" at bay is an accomplishment in itself............

Care to share?

 

[Anonymous-0]

I've seen both 60's and 620's (not modified) knock rather stoutly if timed with their Delco distributors at or near 0° static. They're supposed to start out at 5° AFTER TDC static. Like the others have said, you're likely lean and you're likely way too far advanced as was easy to do with those tractors anyway.

As to the E85... Had a '51 G on the dyno last fall. With gas it sat there steady at 50 HP. He switched to the big tank full of E85 and it started to roll off in HP and knock. By the time it was fully on E85, it was down to 35 HP and knocking rather stoutly.

Owner wanted to "re-adjust the carb" as somebody told him to.

Barely noticed a difference.

I asked him how much did he open it?

They told me no more than a quarter turn.

I suggested another turn and a half or maybe two. At two turns MORE than gasoline (I don't know what octane he used) we were barking back up the original tree with 50 horse. You shouldda seen the turbulence in that sediment bowl!

When he went back to gasoline, it smoked like a Reeves and would barely run but a twist o the wrist fixed that.

I was amazed at how well it ran on the E85 even though is was very very lean.

 

[gtx1967jewison]

already did. set timing to 0 or later, cold plugs.

 

[jd b puller]

gtx, what JD did you run 200 psi on?
What did it make for HP with ZERO advance? Model/Bore/Stroke please.