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domed piston question

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dennnis79
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domed piston question

Postby dennnis79 » Sat Nov 20, 2004 7:44 pm

Greetings folks.

I stumbled across this board while searching for information on cubs. I’ve visited lots of forums, and this one has the most knowledgeable and friendly folks that I’ve had the pleasure of reading in a long time. Lots of class folks here.

Also, our thoughts and fervent prayers are with Rudi. He has already helped me more than he will ever know.

I'm rebuilding the engine on the 49 cub. Oil pressure was failing and compression kept dropping off until it refused to run anymore.

The cylinders will require re-boring so I ordered .020 oversized pistons from the dealer. (That may have been my first mistake).

I neglected to look in the boxes before I got them home, and when I did look, I see that they gave me domed aluminum pistons. I've searched and read about others on the forum that ground out the head a little to make clearance for the dome, but I'm curious how that affects performance. Increasing the compression ratio can be good, but can't that cause problems with detonation? Can that be compensated for by adjusting the timing? Will the increased compression cause a problem with the head gasket?

Also I've searched and read about the wear sleeve on the front crankshaft pulley. I understand the tricks to get it on, but what's the method to get it off? Can it be safely cut off or should I try putting it in the freezer and then heat the sleeve with a torch?

I’m sure I’ll have lots more questions, but I’ll try and research as much as I can before pestering y’all.

Thanks
dennis
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John *.?-!.* cub owner
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Postby John *.?-!.* cub owner » Sat Nov 20, 2004 7:53 pm

Never tried the domed pistons myslef, but compression on a cub is so low to begin with that I doubt detonation would be a problem. Don't forget to get your head checked while you have everything apart. Warping is not unusual. Never tried to remove one of the pulley wear sleeves, but as thin as they are I would think that if you could get a small spot started they would probalby just peel off.
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Postby dennnis79 » Sat Nov 20, 2004 10:54 pm

Thanks John.

That sleeve peeled like a banana. Thanks for the tip.

The head appears to have some warpage. I can slide a .005 feeler gauge under a straight edge at the middle of the head. I guess the head will go along when the block goes to the machinist. I hope shaving the head won't change the compression too much.

And I guess I'll take a chance and stick with the domes.

Thanks again.
dennis

"Hey, I didn't get a harumpf outta that guy!"

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Postby nosih » Sat Nov 20, 2004 11:57 pm

What is the part number of the pistons that you purchased?? There is a change in the connecting rods & pistons, so you may want to make sure you have the right parts before you do anything more!!!! Case IH will not warranty anything once you install it (unless you are an authorized service center).. A customer of mine found out the hard way when he put in pistons & sleeves, gaskets, etc in an MD, and his case IH dealer sold him the wrong head gasket (long story on the differences in headgaskets), needless to say, the tractor ate a sleeve due to this, and he ended up having to buy all new parts at retail, as he was the installer (I was surprised the dealer wouldn't give him a break considering the dealer supplied him the wrong head gasket)..

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Postby dennnis79 » Sun Nov 21, 2004 12:03 pm

The part number on the piston box is 405008R1. This wouldn't be the first time this order was messed up.

Now I'm contemplating returning the standard bearings I got for some undersized. I thought the crank was fine, but my neighbor thinks that while the thing is apart, a re-grind would be appropriate. Oh well, it's only money.
dennis

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Postby nosih » Sun Nov 21, 2004 12:31 pm

Those pistons are only to be used with connecting rod part number 527457R11, so you may want to check your connecting rods. I would assume that you actually have connecting rod part number 251246R3, which would require the piston (0.020) with the IH part number of 352183R94.

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Postby dennnis79 » Sun Nov 21, 2004 9:39 pm

The connecting rod has a part number of 251246R1. Not sure what difference is between the R3 and R1, but I for sure have the wrong pistions. I'll start my search for 352183R94 and matching pins and pin bushings.

Thanks.
dennis

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Postby Jim Hudson » Sun Nov 21, 2004 11:02 pm

I think Jim Becker will say that means revised 1, 2 or 3 times. Does that mean same part and will still fit the application just made better? I think so.
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Postby Jack Donovan » Mon Nov 22, 2004 8:40 pm

As long as the block is going to the machine shop, be sure to send the pistons with , for fitting purposes. Some one on the board here put in Alum. dome pistions, a year or two ago and the engine only ran for 5 mn. and quit. when cooled down it would restart. Turned out that clearences have to be more for Alumn. Pistons. I wouldn't turn the crank unless you have to. The machine shop will know and I doubt that they will lead you astray. Good luck "Jack"

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John *.?-!.* cub owner
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Postby John *.?-!.* cub owner » Tue Nov 23, 2004 2:31 pm

I just had an email from Lombard. He reccomended making sure the head clears domed pistons without the gasket installed. That way you will have a minimum of .050 clearance when the engine is assembled.
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Postby dennnis79 » Tue Nov 23, 2004 5:20 pm

I think I'll make sure they clear by exchanging them for some flats, if they're even available. I was waiting to get all the parts before I took anything to the machine shop.

Thanks.
dennis

"Hey, I didn't get a harumpf outta that guy!"

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John *.?-!.* cub owner
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Postby John *.?-!.* cub owner » Tue Nov 23, 2004 10:32 pm

I was just corrected, the .050 is with the head gasket removed, but you have that taken care of.
If you are not part of the solution,
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