I'm pretty sure I have to do the head gasket on my truck. No coolant leaks, or other obvious signs except having the engine overheat and lots of air in the cooling system that I can never get rid of. I can check the head for flatness at work to see how out it is, but the closest machine shop is 4 hours away and I can't have the truck out of service for too long. How bad is it too just change the gasket w/o milling the head flat and checking for cracks??

Andrew

 

Check it. SOMETIMES (hardly ever though) you can get lucky and not have to machine the head.


As for the cracks.... run it!!!


If you just pull it off... then replace the gasket (surface prep is a given) you are IMHO playing roulette. I have done headgaskets over due to my trying to save a dime on machine work.

Again... JMHO
Mark

 

Save yourself a bunch of time and a headgasket and get the head decked while it is off.

 

If I'm not mistaken, once the head is machined, the valve seats must be machined a like amount (recessing the valves). Be aware, the OEM valve seats are induction-hardened and can only be machined a small amount before they have to be cut out and replaced. Not sure of he specs but it is well covered in the FSM.

Perhaps this is where a thicker head gasket comes into play. Those better informed will chime in I'm sure.

Hope this helps more than hinders.

 

Sooo, because its winter and I'll be doing this in my equipment shed (gotta move the manure spreader first) I don't want to have the truck down for more than a weekend, its my dd. If for now I just replace the head gasket, then in the spring when I can have it down for longer I can take the head into piers and have them do the work. Am I risking damaging something by just doing the gasket for now??

Andrew

 

If it holds until spring you will be good to go.


The problem is putting it all back together (80 bucks for a new HG) and two days later it pops again. (now you paying 160 for a head gasket job)


Its up to you.

Damages??? Wont hurt anything. Just like popping a head gasket. Keep an eye on stuff and make sure coolant stays put, oil stays put and cylinders squeeze.

 

I'm doing mine this week and now am seriously considering sending it to the shop....arghh, this is getting more and more expensive. I didn't want to put ANY $$ into the old style head, but I don't want to do this again untill I've got a 7mm head ready to go.

 

If it's flat enough, run it. The specs are no more than 0.0004" out of flat within any 2" diameter area, and no more than 0.012 end to end or side to side.

 

At's the way i went sept with studs. PRAY'N it will hold.
TOMMY

 

Maybe you should try torquing the bolts and see if you can get by until spring when you have the time to fix it?

 

In the engine manual it says that thicker HG's are needed when you deck the block. The distance the piston sticks above the deck is important.
There are different "grades" of pistons from Cummins. They have different pin heights.

 

If you have the head milled just a small amount to flatten it out you don't have to sorry about thicker head gasket or any valve train geometry issues. The valve adjusters have PLENTY of adjustability. Milling a thou or two off won't raise your compression ratio much at all either. I did the math at one time for a slant 6 that I took a 10th off the head, but I don't have the exact figures on the Cummins for head or deck milling and compression ration changes.
By the way, Milling a 10th on the slant six raised the compression ratio about a point, and the factory valve adjusters still worked perfectly.
I'm just saying...

 

Well to give you some idea, I just had Cummins replace my gasket. The head checked well within spec the first time they replaced it. After the 1st replacement blew they had the head decked flat, and put it back together. Now, in just 1 day, the second replacement blew! Now I haven't found out why this one blew yet, but deck the head, its worth the security, and make sure you re-torque the head at least 3 times...I'm gonna do 5 at this point.

 

Planing the head won't really raise the compression. It would a very slight amount do to the valves being a little closer to the deck. Nothing like a gasser.
BC847 is probably onto something with grinding the valves down.

 

Thanks for all the input!! I talked to piers and they don't mill heads but said I can ship it thru a local parts store to a good machine shop. This saves me from having to take it in myself.The shop will check the valve clearance after milling and can grind what's needed. Hopefully the head is in good shape and doesn't need much work. Does anyone have the torque pattern for the head bolts?

Thx again Andrew