Visit to Cummins for Info
I Stopped and talked with the service manager of Cummins while up north this afternoon.
While I was with him, he looked at 8 Cummins Service Manuals for the 3.9 and the 3.9/5.9.
Not one showed the Torque Tightening Sequence for a 3.9 engine. In all cases the manuals showed the 5.9 head sequence as illustration. So, we have nothing at this time that shows the proper tightening sequence for a 4B Series 3.9 Engine Head ! He suggested to use the 5.9 tightening sequence as a guide on the proper sequence and then tighten the corresponding head bolt positions as close as possible.
The picture is a photocopy he made for me taken from a 1985 4B Series 3.9 Shop Manual. Note that the head shown in that manual is still a 5.9 head. The remarkable thing is the torque specs given in the 1985 3.9 Manual (Bulletin Number 3810206-01) ! You can see in the picture that the torque specs are all given in Foot Pounds ONLY, not Torque Plus Angle. And also remarkable is that ALL head bolts are torqued to 92 foot pounds. The service manager told me that in the
1990's (he forgot the exact year) the torque changed from Torque Only to Torque Plus Angle.
Further the present manuals have an error ! They show the short bolts only getting 66 foot pounds + 90 degrees rotation, and the rest getting 89 foot pounds + 90 degrees rotation. The error is that ALL bolts need to be torqued to 89 foot pounds + 90 degrees rotation. He said the final step was left out by accident and if you dont bring the short bolts up to 89 foot pounds + 90 degrees rotation, you have a head that is not evenly torqued and probably will blow a head gasket on the short bolt side. This does make sense and is in keeping with the torque specs given in the pictures of 92 foot pounds for ' ALL ' head bolts.
Now, digressing, somewhere out there in the world is a shop manual with the proper head torque sequence and torque specs. We need to find that to verify, back up if you will, the information I learned today. What I believe we need is for some of you guys to visit your local Cummins and Try to get a Photocopy of the Torque Sequence and Torque Specs, both for the old engines and newer where Torque Plus Angle is used. I live very remote and have no other Cummins to visit.
PLEASE !! dont kill the messenger. I am just bringing forward info I learned today at Cummins.
Paul