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OK Guys ,I thought I saw on this site that somebody says torque the head bolts to 125 & stop. Is this correct ?
 

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OK Guys ,I thought I saw on this site that somebody says torque the head bolts to 125 & stop. Is this correct ?
In my opinion this is not correct. The Cummins shop manual give a Torque Plus Angle Spec for head bolts. And also gives a spec for head bolt length to be sure they have not yielded.

Cummins spent millions to design these engines and come up with proper service specs derived thru Lab Testing. To disregard the published specs and come up with our own specs is not prudent, in my opinion.

Paul
 

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Thanx Paul, I'm doing it "By the Book" but it says to tighten all capscrews to 66ft-lb, then tighten the " long capscrews only" to 89ft-lb . There are 3 lengths of capscrews . I'm not sure about tightening the middle length screws to the 89ft-lb or just the 4 longest screws. Any help , Thank you.
 

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Some people's sites claiming to know the ft lbs value of the angle spec used a torque wrench to find pressure which the angle breaks. This is not consistant on every journal or bolt. An easy way out for those who are in a hurry IMO.

Manuals state procedure for good reason. Funny story to illustrate. Guy was selling an NV4500. He said "shifted and ran great til I put Royal Purple in it". He couldnt figure out why the trans went bad. He chalked NV making bad transmissions instead of his disregaurd for the only approved lubricant. Royal Purple amkes good products......its in the application.
Anyway......by the book is the way to go.
 

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Thanx Paul, I'm doing it "By the Book" but it says to tighten all capscrews to 66ft-lb, then tighten the " long capscrews only" to 89ft-lb . There are 3 lengths of capscrews . I'm not sure about tightening the middle length screws to the 89ft-lb or just the 4 longest screws. Any help , Thank you.
My Cummins 4B series engines use 14 head bolt cap screws. Two of my Cummins Parts Manuals show these cap screws as follows;

Qty 10 M12x1.75x120 Part Number 3903939
Qty 4 M12x1.75x70 Part Number 3903938

Also looking at a 4B series head ( just now) the pads for the (10) M12x1.75x120 are all at the same height and the same is true for the (4) M12x1.75x70 cap screws. To further check this out, I measured my head bolts removed from the 4BT now on my bench and they are as above.

I am confused when you mention medium length head cap screws. By chance are you working on a 6B series ? I have never opened a 6B

The max length spec for the long cap screws is 7.201"
The max length spec for the short cap screws is 2.815"

Anything longer than these specs should be discarded as it has yielded.

Paul
 

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Paul,
In my Cummins book Bulletin 3666087-02 printed 10/99 for both 3.9 and 5.9,
It talks about a medium length capscrew of a max length of 4.807, page 2-11, I'm guessing it applies to someting else besides cyl head cap screws, but it's listed in the cylinder head group? Its not listed in the crank group either.

Steve
 

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Paul,
In my Cummins book Bulletin 3666087-02 printed 10/99 for both 3.9 and 5.9,
It talks about a medium length capscrew of a max length of 4.807, page 2-11, I'm guessing it applies to someting else besides cyl head cap screws, but it's listed in the cylinder head group? Its not listed in the crank group either.

Steve
Steve;
Yes, I have Bulletin 3666087-1 10/99 and on the same page as you mention it lists a Medium Length Cap Screw and the 4.807" length.
But it does not say where it goes. I have no idea where it goes. I wish they gave a part number for the medium cp screw. Then 'maybe' we could find it in the parts book and know what they are refering to. It is strange its mentioned on the Cyl Head section ???

Paul
 

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Discussion Starter #8
I've got 18 bolts total . 4-long ones in the rocker pedestals , 10- medium length ones (between valve covers & they go thru the head kind of behind the exh ports ) and 4- short ones right next to the exh ports . So I'm not sure Cummins wants me to torque the 4 long & 10 medium bolts to the higher torque setting or just the 4 long bolts only.
 

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I've got 18 bolts total . 4-long ones in the rocker pedestals , 10- medium length ones (between valve covers & they go thru the head kind of behind the exh ports ) and 4- short ones right next to the exh ports . So I'm not sure Cummins wants me to torque the 4 long & 10 medium bolts to the higher torque setting or just the 4 long bolts only.
Your right, the long bolts are for the Rocker Pedestals/ head bolts. I have my pedestal bolts in bags with each pedestal and thus did not count them with the head bolts. Open mouth, put foot in ha ha.

The Shop manual is vague at best, in fact my shop manual only shows torque sequence for 6B series. I will be in Plattsburgh, NY tomorrow and will stop at Cummins and see what information I can get. If I can get a torque sequence picture, I will also scan it and post it.

Its my belief that all head bolts except the short ones go to 89 foot Pounds + 90 degrees and the short ones to 66 foot pounds + 90 degrees. But I will verify that and post back here tomorrow evening

Paul
 

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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
 

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Thanks for the help, Paul!

That shouldn't be a problem on the head torque sequence. As you know the whole purpose of the exercise is to prevent head warpage or overcome minor warpage that alread exists. As long as one starts in the center to pull head down in the area that's most likely to have the highest warpage crown the 6BT method should work fine.

It's my guess that the reason no torque sequence is given specific to a 4 BT is because it's exactly the same, until you run out of bolts to tighten. Some other engine patterns start in center and then use alternating X patterns but these are usually much smaller V8 heads. The larger Cummins head is torqued from side to side because of its size/mass.

Torque specifications don't usually vary because of a bolt's length, but rather in repsect of bolt diameter, metallurgy and thread root/pitch. If these were torque-to-yield bolts that's different, but they're not, right? Resuseable head bolts?

I always use at least 3 stages of torque increase to get to the specified number. I heard there are aftermarket high strength head bolts available but haven't researched who produces them. Possibly that mfgr. would have further info?
 

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4bt sequence

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
hi paul any chance you could eme that jpg pick of the head sequence? i cant read it on the site maybe if you e it to me direct it would come through better
and is the 92 lbs + 90 degrees right?
thxn Harry
 

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hi paul any chance you could eme that jpg pick of the head sequence? i cant read it on the site maybe if you e it to me direct it would come through better
and is the 92 lbs + 90 degrees right?
thxn Harry
Harry; PM me with your regular email address. I dont know how to attach pictures to PM's. If anyone else requests these 2 pictures, would you go ahead and send them out. I am on a 24.4K dial up, pictures take me forever. Thank You

Paul
 
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