Engine/Transmission (1994 - 1998) help with head gasket job

[BLeinart]

I have a leaky head gasket on my 95 cummins and have been trying to decide what mods I need to do. I don't plan to get to radical with this truck. I plan to put some 50 or 75 horse DDP injectors and get a new fuel plate, hoping for 250 or 300 horse. Do I need head studs or will a set of new bolts be ok? Got a set of ARP studs and realized I have to mill pedastals and it says the studs may still be to tall so you have to measure height of stud off block. The studs sound like a lot of trouble. I read many threads of people having to retorque several times. Also, I'm going to have my head milled while it's off, but not sure if I should use a thicker gasket. Sounds like some people have not liked the results of the thicker gaskets.

 

[GAmes]

If you are absolutely positive that you will be satisfied with 300hp you may as well stay with the stock bolts. The Cummins headgasket kit has a gauge to measure the old bolts for length. I've had no problem with mine after replacing the gaskets at about 195k. If you are planning on a 3 or 4k GSK or an exhaust brake, now would be the time to install 60 pound valve springs. As for the milling, I was lucky. I didn't have to resurface the head and used a stock thickness gasket. From what I can determine, there is no advantage to increasing the compression ratio by milling the heads like there is on a gasser.

 

[hsmith]

Agree with Gary. New stock bolts are good unless you want to get radical. Also do not need the several re-torque as the studs. I went with the thicker gasket, stock head, as it is supposed to handle advanced timing a little better.

 

[BLeinart]

are the valve springs necessary for the 3k gsk. How will the heavier springs effect the engine?

 

[fest3er]

are the valve springs necessary for the 3k gsk. How will the heavier springs effect the engine?

Some say yes, some say no. I had the 3K GSK installed several years ago and kept the stock lighter valve springs. I've had no problem. But that's because I don't exceed about 3200 RPM. I got the 3K kit because I wanted full fueling up to 3K RPM, not because I wanted to rev the engine up to 3500 or more. For me, the stock 35# springs are just fine.



Some might say you *have* to go with 60# springs because you *might* rev the engine too high and float a valve or three. When a piston meets a valve, the valve and pushrod are the bigger losers. If you don't expect to exceed 3200 RPM or so and expect to stay under 35# of boost at top RPM, I think the stock valve springs will be just fine.



As to head bolts, unless they are damaged, there should be no reason to replace them. They are almost never installed torque-to-yield.

 

[Forrest Nearing]

stock valve springs will handle 4,000rpm if the boost isn't insanely high. I recomend 3500rpm or less on stock valvesprings.

 

[WilsonF]

Some very good moderate advice, I get tired of reading that you have to get this wazoo part and that high buck widget thingy, when If you do, all you have done is spend twice the money to get the same performance. Very refreshing.

Floyd

 

[cro-magnum]

The valve springs are very easy to do later if you feel the need. Just compress your spring until the valve goes into the motor about a 1/4 inch. (BUT DO NOT REMOVE ANYTHING YET) I found turning the engine backwards easiest till the piston lifts the valve back up. Then your new parts can be installed. I did the 60#ers for a pac brake and I would also like to get the 3200 gsk to help with the spread from 3rd and 4th gear
Travis

 

[GAmes]

The valve springs are very easy to do later if you feel the need.

I have to disagree that replacing the springs with the engine in the truck is "very easy". Envision a two handed job under the windshield cowl with low light and limited work space. Yes it is doable, but compressing the #5 and #6 springs while leaning over the engine and removing and reinstalling the keepers would be much more difficult than replacing the springs while the head is on a workbench. It is also a good time to replace the valve seals, not that easy in the truck.



The heavier springs will not affect the engine performance and could save you a bunch of dollars. IMO cheap insurance, but not a necessity for a 3k GSK. Cummins believes they are a necessity on the exhaust side with an exhaust brake though, and I have no reason to disagree.

 

[fest3er]

... Cummins believes they are a necessity on the exhaust side with an exhaust brake though, and I have no reason to disagree.

Oops. I forgot about exhaust brakes, which may be able to raise pressure high enough to exceed 35# springs' strength and keep the valve open enough to cause damage. This could definitely happen if one were to go directly from high boost to e-brake use.

 

[Vaughn MacKenzie]

I would just worry about doing the exhaust valve springs, for the exhaust brake reason, and because you don't have the interference risk with the intake valves like you do the exhaust side (because the intake valve closes as the piston is moving away from it, whereas the exhaust is closing as the piston is racing towards it).

 

[Forrest Nearing]

true, but high boost will tend to make it harder to close the intake valve.



if you're going to do any valve springs, do ALL of them.



my . 02

 

[Hammer]

I also concur with the others on the valve springs,not needed for 3k and below unless an exhaust brake is used or you run high boost applications. HOWEVER,that being said its also a pay me now or pay me later cost too I feel. If the head is off already why roll the dice on chance,change the springs and be done with it as the reward is better than a chance with excessive cost if something happens.



On the head studs...

You have two avenues here,

One,find a shop that has a set of rockers already turned down or swap the studs out for the one that need not be turned to install them.



OR



Just use a new set of head bolts and torque them properly. I have seen many 12v trucks with o-rings and headbolts live as long as a stud equipped truck. Its all in the job and doing it correctly the first time. Sleddy's old puller is still running the same bolts and o-rings which were installed some 7 years ago when he built the truck. The current owner has never had the motor down and never has had an issue with it.



One last thing...

To net a managable EGT 300hp you truely need little in the way of performance parts,If your money is spent wisely and on the proper parts for the job... ... Andy

 

[Joseph Donnelly]

I have successfully re-used stock head bolts in a number of different situations. They will be fine if they come up to torque (I use 115 to 120 ft lb) quickly, and they are not already too long (use the Cummins plastic gauge to check them—it is very rare for them to be stretched as much as the gauge allows). Definitely do a valve job and check the head and block for warpage. I recommend resurfacing the head to remove tching around the cylinders and other problems, so long as you find a shop that can put a very smooth surface on them—60 microinches or better. You cannot catch a fingernail in the surface at all. See how smooth your stock surface is for a comparison. High boost, usually over 60 psi, excessive timing, and high exhaust gas temperatures all play a role in failing a head gasket. Your horsepower goal should be far below the maximum capability of the stock Cummins gasket, 3283335 (the marine grade replacement gasket), or the . 010” thicker 3283337, or . 020 thicker 3283339.

 

[12Vmudder]

I blew my head gasket and just did the whole job in April... I'll recommend doing what I did which is go ahead and get some 60lb valve springs and then take your head in to a good machine shop to have them check it to see if its warped. Mine was warped . 009 so they ended up taking off . 010 and I bought a . 010 thicker head gasket from Cummins. Also while at the machine shop I had them pull all the valves and clean up all the seats and then install the 60lb valve springs when they put it back together.

I then had my local performance shop cut 0-rings in it and they had a set of new ARP studs that were about 4 years old so I bought them and all I had to do was dremel out the webs in the valve covers to get them to fit without leaks.

The performance shop told me to torque them up like ARP tells ya and then start the truck and let it idle until its up to running temp and then let it sit overnight and retorque them and call it good... been fine so far

For me one of the hardest parts of the job was cleaning the top of the block because you need it to be absolutely clean before you put the head back on.

Good Luck,
12Vmudder

 

[GOlsen]

Is there any other reason to use a thicker head gasket, other than to take up material lost by milling? I'm also doing a head gasket change. Already have a head cut for o-rings. Where's a good place to get the gasket and o-rings?

 

[Forrest Nearing]

a thicker head gasket lowers compression and keeps the piston to valve distance the same. the cummins head is a flat deck, so compression ratio isn't effected much by milling

 

[GOlsen]

So, I wanna make sure I get this right before I order some wrong parts. I'm thinking about a . 010 gasket. The head I am using is new, so it will lower the compression ratio. This will lower cylinder pressures, allowing me to run more fuel/boost? Also, if I effectively bring the head up by . 010", will I have to compensate for that with the injectors to get the right spray pattern? Any thing else that I'm not thinking of that might affect my decision?? TIA