boxboy Posted June 17, 2010 Report Share Posted June 17, 2010 I have a recently purchased 520 with a J13. Runs great, but leaks oil out the rocker cover so bad I can watch it happen. So I got a gasket kit for it and thought it wise to adjust the rockers while I am in there. My question then is, should I also re-torque the head while I'm in there? Fears: That re-torquing may move something I don't want moved and I will end up with a leaky HG. That I my pull a stud or something and have made things worse rather than better. Benefits: I would know that my head is torqued correctly. In my experience with motorcycle engines, it is also common to loosen the headbolt slightly and then torque to spec one at a time in sequence. Theory being that it is harder to start a tight bolt than a loose one, so just checking torque without loosening would be a false reading. Thoughts? Quote Link to comment
datzenmike Posted June 17, 2010 Report Share Posted June 17, 2010 Fears: That re-torquing may move something I don't want moved and I will end up with a leaky HG. That I my pull a stud or something and have made things worse rather than better. Benefits: I would know that my head is torqued correctly. Generally I would think that head bolts don't get tighter with age, if anything the gasket compresses initially and may further compress from the thousands of heat cycles over time. It's safe to say that the older the head gasket the 'looser' it will be. This is not to say that there is risk of failure. To address your two concerns: I would think tightening to specification would properly clamp a head to the block and prevent a leak from happening. I don't think you are going to pull a stud from the block as you are, after all, only tightening to the stock specifications the stud was designed to hold. example: It's generally accepted that the Z24 motor blows it's head gasket every 100K miles. I know of some that have a quarter million Km on them with no problems but it seems that this is not the norm. The iron block and aluminum head expand differently and at different rates as they heat up and cool down. Because each surface of the gasket is held immovable against block and head there is a sideways shearing force inside the gasket itself. Over many thousands of heat cycles this can force a failure. Nissan's cure for this problem is on a cold motor, to loosen each head bolt one at a time in no particular order and re-torque to specification at every tune up!!! I know of no other motor where this is stressed as much as on the NAPS Z24 motor. I also know of no one who does this... and the gaskets keep failing. Indeed most Z24 owners would know nothing of this as the vehicles are 30+ years old and never go to the dealer for work on them. Quote Link to comment
boxboy Posted June 17, 2010 Author Report Share Posted June 17, 2010 Ah, the aluminum head! But my head is iron is it not? So there should be less movement as they would heat and cool at roughly the same rate? Anyway, what I hear you recommending is the re-torque. Quote Link to comment
boxboy Posted June 17, 2010 Author Report Share Posted June 17, 2010 To add to this question, what is the proper installation for the rocker cover gasket? I have an OE gasket set with some sort of cork composite gasket. NAPA says use high tack on it. But that means a new gasket every time I tune up. Advise please. Quote Link to comment
Pumpkn210 Posted June 17, 2010 Report Share Posted June 17, 2010 Re tourque is a recomended process by the manufacturer! I have had a head gasket go (alot of work) could have been prevented by a simple re-tourque! I looked around for a rubber gasket for my valve cover, cause the cork ones SUCK! The rubber ones dont "require" RTV but I usually put on a thin smear of it after its been off and on a few times! I would recomend to retighten them after the engine is warm and dont be affraid to get em fairly snug! Happy Wrenching! Dave Quote Link to comment
Braden Posted June 20, 2010 Report Share Posted June 20, 2010 the fel pro head gasket i just got says to not retorque right on the gasket Quote Link to comment
boxboy Posted June 21, 2010 Author Report Share Posted June 21, 2010 I retorqued and set my rockers. All is well after about 50 miles. Quote Link to comment
datzenmike Posted June 21, 2010 Report Share Posted June 21, 2010 You did this on a cold motor, right? Did it tighten up much or about the same? Quote Link to comment
boxboy Posted June 21, 2010 Author Report Share Posted June 21, 2010 Yes, I did it cold. I didn't notice that any bolts were particularly loose. There my have been one that turned a slight bit more than the others, but all in all not much movement. I would say maybe the most increase was 1/8 turn. Quote Link to comment
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