Torquing Perkins head

Tracy Brown · Jun 30, 2022

I have to put a head back on a 236 Perkins Diesel engine and looked up torque specs on the web. It shows tighten sequence and says to torque to 128 ft/lbs on round one. On round two it says to turn each 120 degrees more. Does this sound right to u real diesel mechanics? Thx

larbear · Jun 30, 2022

No. I put the head on my Dad's dexta years ago now probably 20 years. I don't know where I got my specs from, I think I finished out in the 90 pound range. What you're saying is going to snap a bolt. I'm not a mechanic but I have put a couple of heads on.

Billy Shafer · Jun 30, 2022

The English have some funny ways of doing. Talk to others or do has they say. I have done some English generators. Each has an odd(to us) of doing things.

Roger Tomfohrde · Jun 30, 2022

Can be if torque to yield

jm. · Jun 30, 2022

Tracy I just checked TWO perkins manuals and that is exactly what they call for. Using the old bolts I sure would be very carful and not go over the 128 before I start the last part.

Dieseltech · Jun 30, 2022

Does not sound right to me, main thing I recall on older Perkins is they wanted a hot re-torque. Not sure on the later engines though. Older engines with 1/2 inch fine thread hardware 128 FT/LB is enough with no rotating afterward.

Eric in IL · Jun 30, 2022

I believe most torque to yield applications require new bolts before assembly.

Gary Reif · Jun 30, 2022

Torque to yield is not unusual but usually specifies new bolts.

used red MN · Jul 1, 2022

The attached chart by Mahle whos name I have seen on gaskets agrees with those who are suggesting you are going to be snapping off some bolts. On page 100 and 101. What this shows is for MOST engine spec groups in the Perkins 3.9L 236 CID family the head torque is called out as 100 Ft lbs or 88 for bolts with integral washers. The two on page 100 are a bit different one calls for 96 Ft lbs and the other oddball that has specs per bolts size. I think personally for something this critical I would call your local MF dealer and see what their book says. Hopefully you have bought a few parts from them along the way and they will share some info with you.
Mahle torque

Dieseltech · Jul 1, 2022

What MACHINE is the engine in that you are working on? I'd use THAT repair spec for the head torque. Most 236/248 four and 354/372 with 1/2 inch fine thread hardware did not even go to 128 FT/LB. Perkins did spec a HOT retorque though at least in MF applications in the books at the dealer I worked for.

Tracy Brown · Jul 1, 2022

Its in an Allis Chalmers 715 backhoe.

ptfarmer · Jul 1, 2022

Torquing Perkins head

Tracy Brown

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larbear

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Billy Shafer

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Roger Tomfohrde

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jm.

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Dieseltech

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Eric in IL

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Gary Reif

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used red MN

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Dieseltech

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Tracy Brown

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ptfarmer

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