3.5" over bore kit

Matt L · Jan 10, 2011

I kinda struck out on the whole .020 over idea when my parts supplier said pistons are discontinued.

So I got a wild hair and bought a 3.5" bore kit. Not that i needed the extra couple hp. It was cheaper buying .020 over pistons from this site.

So whats the actual bore on this kit? Is it 3.500 or is it the same as a the 144 diesel @ 3.562?

Whats the new compression ratio supposed to be? Im prolly screwed far as having to much with these pistons. Plan is to mill the dome off and have ~ 8:25:1 ish.

Blindhawg · Jan 11, 2011

Assuming you have a 134 ci NAA, Jubilee or hundred
series-original is 3-7/16, overbore sleeves/pistons
are 30 over or 3-1/2" I have it in my 640 with the
domed pistons. I haven't noticed any problems that
may have been caused by the domed pistons. I think
compression ratio was probably so low before that
you could run it on gas way with octane rating way
below today's pump gas. Don't over think it, use it
and enjoy.

Matt L · Jan 11, 2011

(quoted from post at 17:40:10 01/11/11) Assuming you have a 134 ci NAA, Jubilee or hundred
series-original is 3-7/16, overbore sleeves/pistons
are 30 over or 3-1/2" I have it in my 640 with the
domed pistons. I haven't noticed any problems that
may have been caused by the domed pistons. I think
compression ratio was probably so low before that
you could run it on gas way with octane rating way
below today's pump gas. Don't over think it, use it
and enjoy.

Stock bore is 3.4375" .0625 over is 3.500". Ive heard varying things on what the 3 1/2 bore kit is and makes for cubes.

Im wondering on compression since Ive already taken a bunch off the head. Stock compression is 7:5:1 Im prolly in the 8:25 range plus already. This tractor does see hours and hours of heavy brush hogging and heat.

Blindhawg · Jan 11, 2011

Meant to say 60 over, bad math! Use mine for heavy
bush hogging too. I use a 5-1/2' Sidewinder and
have had nagging overheating in the heavy stuff but
I don't think its because of the over bore. I've
found that the radiator gets full of chaff. I'm
probably lugging it though.

Matt L · Jan 12, 2011

Eh bad math happens ...

I only have a 5' hog that I pull- Trying to step up to a 6'er. I might be taking on lots of acreage to mow this next year.

Im gonna rebore my sleeves more then likely - I decked the block and dont wanna redeck it. The sleeves were all the place. Its FLAT now 8)
Might stick the head on the flowbench and play with the chambers to get some more flow outta it, then Im getting the cam ground to gain some lift to take better advantage of all my mods.

My 641 only gets hot when the radiator gets plugged up. Its even dirty inside and the block had 1.5" of sludge in it too.

Dean · Jan 12, 2011

A 6' rotary cutter is too much for a 134, over bore or otherwise, except in nearly ideal conditions.

Dean

Tom-TX · Jan 12, 2011

Wow. Why 1 1/2 inches of sludge? What brand and weight of oil have you been using in it? Tom

Dave in MS · Jan 12, 2011

Since they're talking cooling, I'm thinking he meant sludge in the water jackets.

Matt L · Jan 12, 2011

I have a howard transmission that needs to be installed in it yet. Should take care of my going to fast at times.

3.5" over bore kit

Matt L

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