Lehman 120 torque specs for bolts

[markmclain]

Hi, I have the FL 120 manual but can't find any bolt torque specs, specifically I need the flywheel bolt specs. Can't seem to find them anywhere and hoping someone might have them. Thanks!

 

[OldDan1943]

and torquing pattern too.

 

[Comodave]

Call Brian at American Diesel. 804-435-3107

 

[SoWhat]

Typically 80-90 ft lbs but it depends on the grade of bolt being used.

 

[Cigatoo]

Typically 80-90 ft lbs but it depends on the grade of bolt being used.

So What is pretty darn close

Service Manual Page 66 states flywheel bolts are 75 to 90 ft lbs

 

[OldDan1943]

Typically 80-90 ft lbs but it depends on the grade of bolt being used.

You really should use new factory approved bolts incase there has been 'thread stretch'.

 

[Comodave]

I believe that Bob Smith said to use new head bolts each time on the 120s, but I don’t know about these bolts.

 

[Alisske]

I believe that Bob Smith said to use new head bolts each time on the 120s, but I don’t know about these bolts.

I believe they are reused and not the stretch type.

I am sure AD can confirm. But i believe thats who i learned from.

 

[psneeld]

There are stretch bolts and those that are not...If you don't know.... I believe there are indicators that might tell you.

Here is one example - https://usefulcarstuff.com/can-cyli...etch once torqued to the proper specification.

"How do you tell TTY bolts from regular bolts?
TTY bolts also known as stretch bolts are identified by a section of the bolt shaft just above the threads dedicated to elongate. Stretched bolts are easily identified by the portion of the shaft that is a smaller diameter than the rest. Some TTY bolts are nearly impossible to distinguish unless labeled by the manufacturer."

When I redid my head gasket about 6 years ago, American Diesel said the chances stretch bolts were used on a Lehman 120 were slim and just reuse the ones on the engine. They did have replacements, but at something like $40 a bolt for 26 bolts....I went with reusing the ones I had..

 

[Alisske]

[When I redid my head gasket about 6 years ago, American Diesel said the chances stretch bolts were used on a Lehman 120 were slim and just reuse the ones on the engine. They did have replacements, but at something like $40 a bolt for 26 bolts....I went with reusing the ones I had..[/QUOTE]

Haaa! I got the same exact response and sticker shock from the bolt cost!!! (I forgot until you posted)

 

[jleonard]

I doubt those are stretch bolts
However if they have lock washers I would consider new ones of the same style.

 

[catalinajack]

I believe that Bob Smith said to use new head bolts each time on the 120s, but I don’t know about these bolts.

Perhaps he did but when I asked Brian about it he said no. It is also why, when adjusting the valves, the head must be retorqued before setting the valve lash. On a FL135, the head does NOT get retorqued.

After I adjusted the valves, my two 120s ran noticeably more smoothly and quieter. Brian told me that the valves should be adjusted at no more than 1,000 hour intervals. No doubt there will be someone out there that will say that a 120 will run just fine "as is", but my experience says otherwise. So does the manual.