‘51 H Engine Block Question

Tinman57 · Sep 3, 2020

I am rebuilding this tractor and the engine was seized pretty bad so I took it to a engine rebuilder to pull the pistons. They got them out but now they are asking what the parent bore size is for the pistons. I know they have sleeves but they want to make sure they are the uniform size. Also, is their an oversized sleeve to fit? If so what size should that bore be. Appreciate any help, thanks!

Longknife · Sep 3, 2020

(quoted from post at 15:24:04 09/03/20) I am rebuilding this tractor and the engine was seized pretty bad so I took it to a engine rebuilder to pull the pistons. They got them out but now they are asking what the parent bore size is for the pistons. I know they have sleeves but they want to make sure they are the uniform size. Also, is their an oversized sleeve to fit? If so what size should that bore be. Appreciate any help, thanks!

Standard bore is 3 3/8 over size bore is 3 7/16,,,,

https://www.yesterdaystractors.com/cgi-bin/store/model_parts.cgi?SearchArea=Farmall&&md=H&cat=Engine%20Pistons%20and%20Sleeves&r=mcats

Highwayman · Sep 3, 2020

Bore of the bare H block is 3 9/16”

fastfarmall · Sep 3, 2020

You can have special sleeves made,or you can bore it to accept the Super H sleeve, but you sure you want to do that?

Tinman57 · Sep 3, 2020

Wasnt planning on it. I just wanted to make sure that the bores where all correct while the machinists shop has it. All I need is the correct original bore size for the standard sleeves. Thanks

Tinman57 · Sep 3, 2020

Thanks but now im still confused because I have three different sizes

John M · Sep 3, 2020

Whats the measuremnts?

AlinMO · Sep 3, 2020

(quoted from post at 11:29:37 09/03/20) Thanks but now im still confused because I have three different sizes

I would think it would be the machinists job to figure this out.

Tinman57 · Sep 3, 2020

That’s what I am asking for!

John M · Sep 3, 2020

My bad. I thought you already had 3 measurements of the parent bore itself. The parent bore is 3 9/16 OD, as mentioned. Factory bore of the inside of the sleeve is 3 3/8 ID, the overbore sleeve is 3 7/16 ID.

John M · Sep 3, 2020

Sorry, thats 3 9/16 ID of the parent bore.

Tinman57 · Sep 3, 2020

(quoted from post at 13:20:23 09/03/20) Sorry, thats 3 9/16 ID of the parent bore.

Thanks, I appreciate that!

jal-SD · Sep 3, 2020

They make sleeves with the ID of Super H pistons that will fit an H block, at least they used to. We put several sets into several H blocks back when we farmed 800 acres with 4 H's when I was in High School.

D Slater · Sep 4, 2020

Failed to put down the parent bore that I can find, but sleeves installed way in the past I have the sleeve OD as 3.5625 for a thin wall sleeve and 3.5628 OD for a thick wall sleeve. If the bore is slightly smaller, even and round you should be okay. Probably thin wall sleeves is what you can find now. Some instructions given with those is to not have a heavy press fit in block. Some say they want a hand push fit around 1/2 the way in and say hone parent bore if needed.

Tinman57 · Sep 4, 2020

I appreciate that!

David G · Sep 4, 2020

I would replace the pistons and sleeves as a set, this site has them with early or late serial number breaks. I would question this rebuilder actually knows what he is doing.

‘51 H Engine Block Question

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