Archived Head bolt streach spec

[JoshPeters]

Well I blew my headgasket again... . I just installed new bolts, but I want/need to know the bolt streach spec so when I go back together this time the bolts are still ok. If they aren't I need to replace them again! I will be doing this ASAP, as I'm supposed to be leaving for Chicago tomorrow!



Josh

 

[MMiller]

If you buy a headgasket kit from cummins it will have a gauge in it too measure the bolts with, HOWEVER, it was recommended by PDR to me to replace my headbolts during the replacement of my second head gasket. Are you going to mill the head? Did you have it milled on the first repair of the head gasket? It was also recommended to mill the head for a good headgasket repair. The heads on our trucks are pretty light for the application and subject ot warping.



I replaced all the headbolts on mine except the ones that hold the rockers on(forgot those) and they was about $70 from cummins. If you have the head milled then cummins has thicker gaskets. It was cheaper to buy the standard head gasket kit, then buy a . 010 over head gasket for my truck. The standard head gasket kit(includes all gaskets, seals, orings for head gasket repair) was about $170. For the same kit with a . 010 over head gasket it was about $400, but the . 010 over head gasket was about $80 or so. Don't ask me why.



Good luck

Michael

 

[JoshPeters]

Well I replaced the bolts on the first headgasket. Do I need to again? I'm going to check the head for straightness and get it milled if need be.



Josh

 

[MMiller]

That is a good question. Why did the head gasket fail this time? Have you got that far yet? I would have to say from PDR's standpoint repairing a customers bombed truck, reliability is the utmost importance. $100 for new bolts to ensure a better repair. I know that I do not enjoy doing the headgasket on my truck that I rely on. I just wish I had the funds at the time to put in a stud kit.



Call and talk to the guys at PDR, they will listen and give you good suggestions.



Michael

 

[JoshPeters]

I believe it failed due to my torquing the head incorrectly. I got a couple different torque specs. One was the cummins spec, the other a max torque of 120ftlbs. Since everyone says to "retorque" the head after it warms up..... I was confused and ran the 120ftlbs at first... . till I broke a bolt. Then I backed off the 2 I had torqued and retorqued all the bolts to the cummins spec..... except I didn't understand that I needed to do a 90* turn on the short bolts. It was totally my error. I just want to make sure all is ok this time around. Last time I was short on time.....



Josh

 

[MMiller]

I believe the cummins spec is just fine for a stock motor. With one that is running at twice the boost as stock then stock won't do. I wish someone with some more head gasket experience then me would step up here. My cummins isn't as modded as others are.



Michael

 

[Jim Fulmer]

The last stock head bolted motor I worked on I did 100 on the short bolts and 120 on the long ones, if you can swing it I'd spend the extra money and go with studs.



Jim

 

[Joe Mc]

Josh - Understand the fault on the gasket was yours due to confusion on the specs. - sorry you had problems. I had head to block sealing problems with a much lesser engine than ours (4 banger jap) and finally had to have the block decked. I doubt that you have this problem but, when you get the head off and everything cleaned up get hold of a Machinist's straight edge that will span the lenght of the top of the block and check for flatness - check the head too. I'm sure in the shop manual there are specs as far as how much gap is allowable. Since the 1st gasked didn't seal there's always a possibility of something not being in spec. If it's not in spec or really close to the end of spec. that 0. 010 thicker gasket might be worth looking into???



In my case, w/the 4 banger, it leaked between cylinders and wore away top of block between them. Of course I didn't mill the head the first time, and it still leaked after I milled the head - as they say third time's a charm (block decked). Finally got it to seal then a wrist pin seized %@#$!&**. One more head gasket, piston & wrist pin later it ran great . . . I sold it for a song. Funny how we sometimes have time to do it wrong 3 times, yet not enough time to do it correctly once? Nature of the beast.



Hope all works well for you this "last" time - good luck.

 

[JoshPeters]

Josh - Understand the fault on the gasket was yours due to confusion on the specs. - sorry you had problems.

The problem I'm having now is a lack of understanding. I have 3 different size length bolts. Short. . lets say 4 inches. Medium, lets say 6 inches. Then really friggin long for the rocker towers. Which ones get torqued to which spec? This is probably where my confusion has stemmed from in the beginning.



Josh

 

[Joe Mc]

Josh, Just responding to help keep this post up on top for ya. I don't think the spec's in my shop manual would be the same as your 12V. I'm sure someone will chime in that knows soon, especially with the weekend coming up and all. I can understand the difficulty with all the different lengths and what not. Good luck man. Joe Mc

 

[crabman]

Torque Specs

This info is from my 95 Chrysler book.

First, the holes are numbered from the center of the head. #1 on d/s, #2 on p/s, toward firewall #3 on p/s, #4 on on d/s toward firewall. Then, #5 is on the same side as #4, only toward front, etc.

1) Use clean engine oil to lubricate the cylinder head bolt threads and under the bolt heads.

2) the cylinder head bolts are 3 different sizes. Install the bolts in the proper hole. Tighten the bolts as follows:

Step 1

Tighten all bolts, in sequence to 66 ft/lbs

Step 2

Tighten all long 12mm bolts (Nos 4,5,12,13,20 and 21) in sequence to 89 ft/lbs.

Step 3

Tighten all bolts in sequence an additional 90*



Rocker lever pedestal bolts 18 ft/lbs

Valve covers 18 ft/lbs

Good luck!!

crabman

 

[Joe Mc]

I knew it wouldn't take long Josh. What a great site!