Engine/Transmission (1994 - 1998) Head Bolt Question

[Mag]

A friend of mine had the head gasket go on his 95 with about 120K miles. The head was shaved . 008 to true it up. He would like to know if he should be going to a thicker head gasket now?His next question is, should the head bolts be replaced? In my 2001 shop manual it tells me the max. length the bolts should be but we don't have that info for his 95.

Thanks for your help. Greig

 

[Andy Redmond]

head bolt length spec

Cummins sells a plastic go/no go gauge / card to tell if your head bolts are in spec. 3823921. . less than $10.



Ok here we go Max capscrew free length:



Short 71. 5mm or 2. 815"

Med. 122. 1mm or 4. 807"

Long. 182. 9mm or 7. 201"



Good luck

Andy

 

[Todd T]

my question would be what was done to it to cause the gasket to go the first time. if he's been flogging on it and running high boost then i would change them. if its just a daily driver that had a failure of some sort them reuse them. 120K is not a lot of miles ut what kind were those miles? follow me

 

[Mag]

Thanks for the bolt lengths Andy.

Todd, My buddy is only 20 years old and his truck makes about 40lbs of boost, so the answer to your question is, Hell ya he's been floggin on it. I've never seen a kid go through a set of tires so fast in my life. So if the bolts are not stretched more than the specs Andy gave me,we're alright to use them?

 

[Joseph Donnelly]

I've reused the bolts on my Ram several times, take them up to 115-120 ft lb in several steps following the sequence in the manual. I recommend 3283339, the . 020 over head gasket.

 

[Mag]

Joe, could you please tell me the reason to use the . 20 over gasket. Thanks Greig

 

[Jim Fulmer]

I agree with the gasket but I really like my studs, I had 7 or 8 stretched bolts.



Jim

 

[Joseph Donnelly]

Stock compression calculates to be 17. 5 and that is kinda high if you run high boost and fueling. You need . 010 over just to get back to stock after milling the head, and the other . 010 will cut compression about . 55 giving you just under 17:1. It will still start fine in the cold but you have less chance of blowing the gasket from cylinder pressures. --not much less, but since all three thicknesses of gasket cost about the same, why not go in that direction.



All my head bolts are original and I confess I have never used the gauge on them. So long as they came up to 115 ft lb quickly, I assumed they were ok. Studs work fine, but a real hassle since you have to remove them after removing the nuts so you can get the head off and on.

 

[Jim Fulmer]

Studs work fine, but a real hassle since you have to remove them after removing the nuts so you can get the head off and on.



Again I will have to agree, if memory serves me correctly I had two medium bolts that were stretched and the rest were the short ones, good post on the compression numbers Joe. I haven't had any weather here below 30 since I put the . 020 gasket on but it starts just fine.



Jim

 

[Mag]

Thanks for your help guys.

 

[Sled Puller]

Originally posted by Joseph Donnelly

You need . 010 over just to get back to stock after milling the head, .

How does milling the head change the compression ratio?

 

[Andy Redmond]

It allows the "dome" (recess for the valve train on the bottom of the head) for combustion to get closer to the piston top.



The thicker head gasket "shims" the head higher returning the oe compression ratio or lowering to depending on how thick one goes.



Joe can probably give you a better explaination than I can, since he's the hp master!



Andy

 

[Johnboy3]

Um.........

Andy and Joe, I know I'm a lowly Ford guy, but aren't the bottom of the heads flat?? You could shave away till the valves hit the pistons, and the compression ratio would not change.



Mag, all your friend needs to do is make sure the piston/valve clearance is ok. He could then put a stock head gasket back in with no problems. Going to a thicker gasket to lower to ratio for high boost isn't a bad idea. Your ratio will be a little different then Joe's figure though.

 

[Joseph Donnelly]

Sigh! The head is basically flat but has recesses for the valves. Valve heads are down about . 055" so cutting the head . 008 maybe is about like a . 005" thicker gasket. I'd still go with the . 020" thicker gasket. Lots of us have done so without shaving the head. I hope the shop put a super fne finish on it. As a rule of thumb, if you can catch a fngernail in the surface scratches, it is too rough.

 

[Johnboy3]

Why the sigh Joe?

 

[HVAC]

Sigh

Because Johnboy3, you and Sled corrected the former horsepower king (I'm gonna beat him).



I wouldn't think cutting the head would affect compression much. However, possibly a greater concern may be injector height. Changing the spary pattern may yield negative results.



So, if the head is cut . 008, then you go to a . 020 gasket, you deffinately want to change to a . 020 washer on the injectors. And that still leaves you off by . 008.

 

[Johnboy3]

Oh, I understand now. I suppose it's not easy being the king.

 

[Joseph Donnelly]

Come to May Madness and you'll see who is the king Right now HeberRam and HVAC are flexing their muscles on another thread. Sickly is cringing.



The sigh was because of two extremely vocal sled pullers who lose no opportunity to claim midwest superiority in knowledge and power, yet apparently never looked at the deck side of a Cummins B head. I can forgive a Ford guy, but Sleddy?????

All in fun though

 

[Johnboy3]

I only claim PA superiority. I can't speak for the midwest, they are too far ahead of me to be able to give an honest opinion.



I have perhaps seen a couple of B heads. I might even be smart enough to figure this whole compression mystery out too.



Sorry, no Vegas for me. I hear there are hookers, crooked dealers, and rigged dynoes out there. No place for a god fearin guy like me.

 

[83 crew cab]

per the service manual you only need the thicker head gasket to make up for the deck hight of the pistion, if you deck the block.



You have shims to make up the injector hight and adjustable rockers to make up the push rod lentgh, and I cant see the one or two cc around the vavles making any significant differnts in compresson ratio



Just my 2 cents on the thick head gasket if you not trying to drop compression Geroge