Engine/Transmission (1994 - 1998) Head Gasket Job, and questions

[Vaughn MacKenzie]

I recently acquired a '96 12-valve with a slightly leaky headgasket (small coolant residue visible on right side near cyl #1).



I want to pull the head, possibly port it, but my initial plan is to stick with a stock headgasket replacement. I heard that the gasket has been improved considerably over what Cummins was using back in '96.



Here are the questions I have:



1) I see some shave their heads . 010" is this necessary? What is the point of doing this, to achieve better injector position when going with a thicker head gasket?



2) How much boost can a stock gasket maintain? I don't want to fool with O-ringing and don't plan on running more than 40-45 lbs.



3) What are the pros and cons of doing 12mm studs? I read in a thread there is a risk of block distortion using studs, how much of a concern is this? Do stock bolts (planning on new ones) hold reliably to the above mentioned boost pressures?



4) What is the main reason going with thicker gaskets to drop compression? Reduce peak cylinder pressures? What are the drawbacks? What about going . 010" thicker gasket? I heard the copper ones are a poor choice for those who don't want to mess with gaskets every 50-100k miles (I want to do it once and forget it).



Studs would be nice, would rather not spend the bucks though, and I don't want to risk distorting the block & cylinder bores and create more oil usage and blowby or accelerate wear. We are talking about an engine with 352,000 miles so I don't want to upset well-established wear patterns.



I am going to assess the health of the internals when I pull the head so I'll know how sound this motor is, and if it's up to some "bombing. " It runs good and has very little vapor coming out the blowby. When the engine is fully warmed up and I block the vent hose it doesn't build pressure very fast. I suppose I could mic the bores to see how much wear there is. Is there any accepted wear limits?



My plan is to go with about 350-375hp to the rear wheels and call it good. No plans to go hog wild or put twins on or the like. Still would like to get another few hundred thou out of it.



Thanks all,



Vaughn



ps it's a '96 4x4 CC longbed, 215hp 5-speed

 

[willyslover]

Vaughn... e-mail BPine. . Blair is running a stock gasket with twins and 12MM studs. . all is well at 50/55lb of boost. . this is what I would do if I was you also... just re-check the torque of the studs after initial heat cycles. . maybe a time or three on the re-check IMHO. . keep them in check as there will be a stretch when new and fresh gasket will also settle after heat cycles.



thicker gasket needed after head shave job and also injector washers [from Piers] as the injectors are out of alingment to the bowl. . just be sure to see if the head needs a truing, as it seams 12 valvers like to warp a bit. . copper is a PIA if not racing and using extream pressures don't use them IMHO if your not O ringing.

 

[JoshPeters]

My thought would be... . at that milage you have a very seasoned block. I personally would run the studs. Your still torquing the bolts down to the same torque. They just don't give like the bolts do. I've seen pictures from Benz where they put a piezoelectric plate between the head a block, and used each. The bolts did pretty good, studs did even better, and then streach bolts were the best. Benz uses one time use streach bolts. They are MAXED out and littereally streach so the torque is identical across the entire deck surface. Since they changed... . I haven't seen a bad headgasket... .



I don't know about the head shaving... the big boys will have to answer that one for ya. It sounds to me like your on the right track though. Get a better burn out of the fuel because the injector pattern is better.



With that kind of boost, I don't think I'd worry about a stock headgasket. Those are peak pressures, you don't sit there for extended periods. I've been running about that much boost, running my truck HARD for almost 70,000 miles. No problems so far. (knock on wood) But when Mine goes, I'm fire ringing. Oo.



Good luck!

Keep us posted on how the project turns out!



Josh

 

[Vaughn MacKenzie]

Thanks Willy and Josh. Studs I saw them at $450 a set, gotta feel like it's worth spending the $$, otherwise I will replace them with the stock bolts.



Willy I will PM or email Blair. Thanks for the tip.



First thing is to see if there is a complete upper gasket kit with head gasket, t-stat, etc. parts needed for the job, and the KDP will be killed at the same time using the tab method. If I was really getting into it I'd do a cam too but only have so much $$ to do so many bombs at a time.



Vaughn

 

[Bandit1]

get the studs, they provide a more even holding force on the block and wont stretch with higher boost, also i lost my head gasket with only 32 lbs of boost. something to think about.

 

[1dslram]

Vaughn:



I am glad to see you are only going to 375 HP, remember that a year from now. He He I said only 250 - 300 HP, well I was wrong!! Definately go with the studs. You can get them from Summit for the Cummins for about $350. 00 for the ARP studs Summit #ARP-247-4203. Use the stock gasket and it will be good to at least 60# with studs. If you get the cam from Piers they are very inexpensive but the install is a job, just check out the threads for hints on the install to make it easier. While you have the head off be sure to match port your ATS manifold and if you don't have one already be sure to install one, it is very important with any high milage engine. You dont want to break the ears off the head, from a shrunk manifold, I have seen the results and it is ugly.

 

[Vaughn MacKenzie]

Originally posted by 1dslram

Vaughn:



I am glad to see you are only going to 375 HP, remember that a year from now. He He I said only 250 - 300 HP, well I was wrong!!

LMAO dslram! I just KNEW someone was going to say something like that!!



I hadn't thought about the exhaust manifold, I do want to change it out but not right away, so I think you're right about port matching.



Thanks for the PN for the studs, I like that price a lot better!



Vaughn

 

[Jim Fulmer]

Vaughn MacKenzie



I bought a new head, brand new that needed 7 thou to make it straight before O-ringing, I think that flatness had more to do with it than anything.



BOTW, there are two of us as 80 psi with a PDR Stage 2 head, . 020 gasket and a single O-Ring and 12mm studs and no issues.



Jim

 

[CDegner]

Vaughn,

Having just done a head gasket job on a 12V (with probably more miles than yours), the issue is in truing the surfaces. They had to take off 0. 008 to get mine flat. Called cummins to ask about the agsket and they told me to go with stock thickness.



The distortion issues with studs are from 14mm studs. I have heard of no problems with 12mm.



When you start checking the internals, I think you will likely be impressed. at 249K, all hone marks were highly visible and there was no ridge at the top of the cylinders.



Carl

 

[Vaughn MacKenzie]

CDegner that's good to know. Did you do studs or stock bolts?



2 other basic questions. . . I assume you remove the injectors before pulling the head. What about the pushrods or do you lift straight up and clear them? Can the head be lifted with 2 people?



There is a good machine shop here in town that I trust, I will take it to them to check for flatness and true it if needed. Sounds like more than likely it will need it.



249,000 miles? My rig passed that a couple years ago. . . it shows 351,997



Hey come check out NW Bombers sometime, we have gatherings & events fairly regularly. www.nwbombers.com Have Diesel Thunder coming up in September and a campout in August as well as drag racing & truck pulls and so forth.



Vaughn

 

[dpuckett]

Vaughn-

I forget the part number offhand (I can only memorize so many p/n), but there IS a kit from Cummins with the HG, all manifold gaskets, about 5 sets of injector washers (keep the 9-7mm adpators for some 1st Genner that wants to upgrade), valve cover gaskets, exh manifold gaskets, valve seals, and everything else you may or may not need. I still have some things left over that I didnt use.



2 people can get the head off IF they are pretty stout. I used a tractor front end loader with a chain through the two loops, and it was easy. I dont think I would want to try to lift it off with just 2 people reaching 2-3ft over to lift 160#. 3 maybe.



Daniel

 

[willyslover]

Vaughn. . my guess is that with as many miles as you have on it it will need a head shaved at the least. . but don't be to suprised if you have to replace do to serious cracks as many high mile 12 valvers have discovered with head removal.



suggest you use a cherry picker to remove as it's a big back tweek to get that damn thing out LOL and yes I would remove the injectors. . you can leave them in but never know what Murphy has instore for you and yes remove the pushrods and check for true also... roll them on a piece of supported flat glass for true testing

 

[Gary - K7GLD]

HMMmmmm - everyone checks and trues up the head - but what about the block surface - and what if the head actually matches any curvature between the two that has ocurred over time and use?



... I hate to be a troublemaker...

 

[Bandit1]

i have wonderd the same thing, but the block is a big piece of metal to warp, my guesss is the head warps with the stretching of the head bolts, hence needed the better head studs. jsut a brain fart

 

[Gary - K7GLD]

Well, when an entire engine is "blueprinted", both the heads AND the block get trued to each other and the crankshaft centerline - and usually, there IS a fair degree of distortion in a block surface - after all, the block has lots more attachments to it and stresses applied to it in normal operation than the head does - so "truing" the head *only* MIGHT result in a greater mismatch than what ya started out with...

 

[Hohn]

Originally posted by Vaughn MacKenzie

I recently acquired a '96 12-valve with a slightly leaky headgasket (small coolant residue visible on right side near cyl #1).



I want to pull the head, possibly port it, but my initial plan is to stick with a stock headgasket replacement. I heard that the gasket has been improved considerably over what Cummins was using back in '96.



Here are the questions I have:



1) I see some shave their heads . 010" is this necessary? What is the point of doing this, to achieve better injector position when going with a thicker head gasket?



2) How much boost can a stock gasket maintain? I don't want to fool with O-ringing and don't plan on running more than 40-45 lbs.



3) What are the pros and cons of doing 12mm studs? I read in a thread there is a risk of block distortion using studs, how much of a concern is this? Do stock bolts (planning on new ones) hold reliably to the above mentioned boost pressures?



4) What is the main reason going with thicker gaskets to drop compression? Reduce peak cylinder pressures? What are the drawbacks? What about going . 010" thicker gasket? I heard the copper ones are a poor choice for those who don't want to mess with gaskets every 50-100k miles (I want to do it once and forget it).

1) the reason to deck the head is to remove irregularities, ensuring a perfectly flat prepped gasket surface.



2) Stock gaskets vary, but they usually will hold 50 on a 12V



3) 12mm studs should be just fine. MOre clamping force without block distortion. Distortion is only an issue with 14mm studs, imho. The studs from Don M are imho the way to go for the 50ish boost crowd.



Lower compression allows less strain on the engine for a given amount of HP. It's more efficient to run lower CR and higher boost. The drawback is lower efficiency off-boost, and it can be hard to start if it's REALLY low compression.



Copper gaskets ahve a bad rep because they are so often done improperly. When properly setup, a copper HG is a one-time proposition (maybe a re-torque). Copper HG will seal a LOT of compression force, to the point where the head won't lift and act as yoru safety valve. After that, the next weakest link are parts that are MUCH more expensive:{



Justin

 

[Vaughn MacKenzie]

Originally posted by willyslover

Vaughn. . my guess is that with as many miles as you have on it it will need a head shaved at the least. . but don't be to suprised if you have to replace do to serious cracks as many high mile 12 valvers have discovered with head removal.

I hope not, can't afford a head replacement right now



What causes cracking? High EGTs and/or overheating? Even on a stock-powered motor?



Vaughn

 

[willyslover]

all the above, and heat cycles with poor design ..... IMHO is the largest issue



well worth it if your going to pull it, save up a couple more weeks and do a stage II and or get our buddy on NWB to do it for ya. [HDM]

 

[Vaughn MacKenzie]

Originally posted by willyslover

well worth it if your going to pull it, save up a couple more weeks and do a stage II and or get our buddy on NWB to do it for ya. [HDM]

You're reading my mind Willyslover



Gary KJ, how about this for checking deck and head squareness: Thouroughly clean surfaces on both sides, then lay head back on block w/o gasket and check full perimeter by trying to insert a feeler gauge such as . 003"? If you can slip anything in then the head gets decked . . . sound reasonable?



Vaughn

 

[GAmes]

Originally posted by Vaughn MacKenzie





2 other basic questions. . . I assume you remove the injectors before pulling the head. What about the pushrods or do you lift straight up and clear them? Can the head be lifted with 2 people?





Vaughn

There are two rubber plugs in the bottom of the air plenum that need to be removed in order to get the rear head bolts and the push rods out. I lifted my head off with an engine hoist.