shadesh Posted June 18, 2009 Share Posted June 18, 2009 I think I have done it this time. I am rebuilding my cylinder head (N42). I was in the process of torquing down the cam bolts with my torque wrench. The manual says 25-33 foot lbs. This is my first rebuild and I totally miscalculated and set the torque wrench at 38lbs. I ended up stripping the thread in the cylinder head for two of the cam bolts. Is the head usable? What can I do to remedy this problem?. Can this be fixed? I am about ready to kick myself for such a foolish mistake. Any help on this will be appreciated. Thanks. Shadesh Quote Link to comment Share on other sites More sharing options...
johnc Posted June 18, 2009 Share Posted June 18, 2009 http://www.mcmaster.com/#thread-repair-inserts/=2dd04s Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 http://www.mcmaster.com/#thread-repair-inserts/=2dd04s John, Thank You. I have virtually little to no experience when it comes to engine rebuilds and obviously using the torque wrench. But Thank You. that helps.... Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted June 18, 2009 Administrators Share Posted June 18, 2009 If you are referring to the bolts that go down through the cam towers... torqued to 25 ft lbs?!?!?!... those 8mm bolts, (12mm wrench size) only get torqued to 12-13 ft lbs!... Good news is that those threads are repairable. Bad news is that all the bolts you torqued past 20 ft lbs are no longer any good, stretched, and ALL the the threaded holes in head probablly need to be repaired. I might have an extra set of cam tower bolts, if I do you can have, just cover shipping. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 If you are referring to the bolts that go down through the cam towers... torqued to 25 ft lbs?!?!?!... those 8mm bolts, (12mm wrench size) only get torqued to 12-13 ft lbs!... Good news is that those threads are repairable. Bad news is that all the bolts you torqued past 20 ft lbs are no longer any good, stretched, and ALL the the threaded holes in head probablly need to be repaired. I might have an extra set of cam tower bolts, if I do you can have, just cover shipping. I followed this book to determine what to set my torque wrench at. "How to Rebuild Your Nissan & Datsun OHC Engine (Paperback)". It states to torque at 25-33 ft lbs.. yikes.. did I misread something here? Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted June 18, 2009 Share Posted June 18, 2009 I have the same book. Just looked. It says 10-12 ft-lb. I agree with Paul. Toss all those bolts and fix the holes. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 I have the same book. Just looked. It says 10-12 ft-lb. I agree with Paul. Toss all those bolts and fix the holes. This is going to be silly but can you tell me what page number you are looking at. Please.. Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted June 18, 2009 Share Posted June 18, 2009 Its in the chart in the back, right before the index. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 If you are referring to the bolts that go down through the cam towers... torqued to 25 ft lbs?!?!?!... those 8mm bolts, (12mm wrench size) only get torqued to 12-13 ft lbs!... Good news is that those threads are repairable. Bad news is that all the bolts you torqued past 20 ft lbs are no longer any good, stretched, and ALL the the threaded holes in head probablly need to be repaired. I might have an extra set of cam tower bolts, if I do you can have, just cover shipping. If you have the cam tower bolts, may I have them? Please. You can email me at kaviti74@yahoo.com. I really appreciate your generosity. Quote Link to comment Share on other sites More sharing options...
bobbyc Posted June 18, 2009 Share Posted June 18, 2009 so the cam and towers were off the head? were they marked when they were removed? this is not an area where someone learning a torque wrench should be assembling. i would take this to a machine shop. if you continue with the assembly, when torquing down those bolts...work your way around, make sure there is no binding and the cam turns freely the whole time. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 so the cam and towers were off the head? were they marked when they were removed? this is not an area where someone learning a torque wrench should be assembling. i would take this to a machine shop. if you continue with the assembly, when torquing down those bolts...work your way around, make sure there is no binding and the cam turns freely the whole time. I actually marked the cam towers before removing. and yes, I checked for binding while I was torquing the cam bolts down. I screwed up when i set the dial on the torque wrench... a really foolish mistake. I should have double checked to see I set it at the right # of pounds. Let this be a lesson for all that follow. Double check your torque wrench and also get familiar with how the numbers are marked on your torque wrench.. Quote Link to comment Share on other sites More sharing options...
bobbyc Posted June 18, 2009 Share Posted June 18, 2009 i reread what i wrote...ididn't mean to come across jerkish...it's just a sensitive area with tight tolerances, and it doesn't take much to mess things up...ive been there! Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 18, 2009 Author Share Posted June 18, 2009 i reread what i wrote...ididn't mean to come across jerkish...it's just a sensitive area with tight tolerances, and it doesn't take much to mess things up...ive been there! no worries.. I know what you meant... Quote Link to comment Share on other sites More sharing options...
Phlebmaster Posted June 18, 2009 Share Posted June 18, 2009 I wrote this how to from experience... http://forum.ratsun.net/showthread.php?t=10971 I did this on my L4...but it it the same for the L6. I have pulled my cam towers on many occasions, So I thought I would share what works for me. The reason not to do it is simple...binding your cam will wear it out the towers and send metal into your motor. Not good at all. But if you are very careful you can put everything back together without incident by doin this: #1. number your rockers in the order they sit in your head. carefully pull the rockers, springs and retainers keeping them as sets. #2. Put your motor at TDC and chock your chain tensioner and pull the cam gear. Don't lose your chain or you will be pulling your timing cover. I use a 1" dowel about 10" long. #3. loosten the 10mm allen head bolts that are holding your towers first and pull them out. Better be sure you have your torque wrench handy for re-installation. Re-torque can be tricky....you need to snug the head bolts back in first, then go in three to four steps tightening them down. Head bolt re-torque Try like 10lbs, 15lbs, 20lbs, 35lbs, and no more than the standard torque for the final step. Check your owners book for that last step. Then do a quick check on all head bolts at the top setting, being careful not to over torque them. Iv'e done that. #4. Now your cam should spin freely. Then take out all of the other cam tower bolts. They are 10mm socket. #5. Pulling the cam towers can be a bit tough at first..use a rubber mallet and tap very gently while you wiggle the cam towers. There will be several inserts that aid in lining up the towers and they get stuck sometimes. Be sure you DO NOT lose any of them. Your cam and towers should lift right off. Mark your towers 1-4!! Re-install #1. putting everything back in is pretty strait forward...just do the opposite of the steps you took to get it off. If using new cam towers 1-4 according to where they go on the head. #2. Now the tricky part.....getting the towers to line up takes some finesse. If the head is in the car, then you will need to insert the cam into all of the towers making sure you have the right tower on the right cam bearing before you install them. If you don't, you will be pulling them again I promise. Use assembly oil like Lukas or something in the cam towers and on the cam bearing races. #3. line up the cam towers on the head and get the inserts I told you about lined up and gently set them in. Then you take the cam tower bolts and set them in and get them started, but don't tighten them. #4. Now put in your head bolts you pulled and get them started too leaving them loose. #5. The allignment..... now you take your cam and turn it many times as you make the bolts tighter and tighter. This will ensure your allignment and you will know if the towers are off before you finish. #6. once everything is tightened and torqued down, you put your rockers and springs back in. The trick with this part is making sure your cam does not move backward in the towers....keep it lined up!! Line up your timing marks and you are golden. Do not turn your cam with the motor at TDC...otherwise you could bend your valves on the #1 and #4 pistons. Thats about it. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 19, 2009 Author Share Posted June 19, 2009 I wrote this how to from experience... http://forum.ratsun.net/showthread.php?t=10971 I did this on my L4...but it it the same for the L6. I have pulled my cam towers on many occasions, So I thought I would share what works for me. The reason not to do it is simple...binding your cam will wear it out the towers and send metal into your motor. Not good at all. But if you are very careful you can put everything back together without incident by doin this: #1. number your rockers in the order they sit in your head. carefully pull the rockers, springs and retainers keeping them as sets. #2. Put your motor at TDC and chock your chain tensioner and pull the cam gear. Don't lose your chain or you will be pulling your timing cover. I use a 1" dowel about 10" long. #3. loosten the 10mm allen head bolts that are holding your towers first and pull them out. Better be sure you have your torque wrench handy for re-installation. Re-torque can be tricky....you need to snug the head bolts back in first, then go in three to four steps tightening them down. Head bolt re-torque Try like 10lbs, 15lbs, 20lbs, 35lbs, and no more than the standard torque for the final step. Check your owners book for that last step. Then do a quick check on all head bolts at the top setting, being careful not to over torque them. Iv'e done that. #4. Now your cam should spin freely. Then take out all of the other cam tower bolts. They are 10mm socket. #5. Pulling the cam towers can be a bit tough at first..use a rubber mallet and tap very gently while you wiggle the cam towers. There will be several inserts that aid in lining up the towers and they get stuck sometimes. Be sure you DO NOT lose any of them. Your cam and towers should lift right off. Mark your towers 1-4!! Re-install #1. putting everything back in is pretty strait forward...just do the opposite of the steps you took to get it off. If using new cam towers 1-4 according to where they go on the head. #2. Now the tricky part.....getting the towers to line up takes some finesse. If the head is in the car, then you will need to insert the cam into all of the towers making sure you have the right tower on the right cam bearing before you install them. If you don't, you will be pulling them again I promise. Use assembly oil like Lukas or something in the cam towers and on the cam bearing races. #3. line up the cam towers on the head and get the inserts I told you about lined up and gently set them in. Then you take the cam tower bolts and set them in and get them started, but don't tighten them. #4. Now put in your head bolts you pulled and get them started too leaving them loose. #5. The allignment..... now you take your cam and turn it many times as you make the bolts tighter and tighter. This will ensure your allignment and you will know if the towers are off before you finish. #6. once everything is tightened and torqued down, you put your rockers and springs back in. The trick with this part is making sure your cam does not move backward in the towers....keep it lined up!! Line up your timing marks and you are golden. Do not turn your cam with the motor at TDC...otherwise you could bend your valves on the #1 and #4 pistons. Thats about it. Thanks guy. I am glad you put this write up here.. especially on the #6 with regard to not turning the cam due to risk of bending the valves.. I took the head to the machine shop yesterday and it will cost me 20 to fix that spun thread. Quote Link to comment Share on other sites More sharing options...
shadesh Posted June 19, 2009 Author Share Posted June 19, 2009 Its in the chart in the back, right before the index. I thought about this and yes it makes sense to not torque at 25 ft lbs. I saw the chart you mentioned and yes, it states 13-15 I believe. However, I would like to direct your attention to page 94 in that book. It specifically states 25-33 ft lbs. I looked at my torque wrench again and I did dial it in at 25 ft lbs for the first round of tightening. Did I misunderstand something? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted June 19, 2009 Administrators Share Posted June 19, 2009 If you have the cam tower bolts, may I have them? Please. You can email me at kaviti74@yahoo.com. I really appreciate your generosity. I will go out and check if I have some in a little bit. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted June 19, 2009 Administrators Share Posted June 19, 2009 If you have the cam tower bolts, may I have them? Please. You can email me at kaviti74@yahoo.com. I really appreciate your generosity. I found a complete set of 10 cam tower bolts, (5 long- 5 short), boxed and ready to go. If you PM me your shipping address in the next few minutes, I'll drop them off at the post office on my way into town this morning. These bolts do have some very light surface rust, but are functionally perfect. Just take wire brush to them and use oil during assembly. Quote Link to comment Share on other sites More sharing options...
Phlebmaster Posted June 19, 2009 Share Posted June 19, 2009 Thanks guy. I am glad you put this write up here.. especially on the #6 with regard to not turning the cam due to risk of bending the valves.. I took the head to the machine shop yesterday and it will cost me 20 to fix that spun thread. Glad you got it fixed!! Yeah...guess how I figured out about the # 6 thing. lol Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted June 19, 2009 Share Posted June 19, 2009 I thought about this and yes it makes sense to not torque at 25 ft lbs. I saw the chart you mentioned and yes, it states 13-15 I believe. However, I would like to direct your attention to page 94 in that book. It specifically states 25-33 ft lbs. I looked at my torque wrench again and I did dial it in at 25 ft lbs for the first round of tightening. Did I misunderstand something? Yeah, just looked. You are right. That's a major mistake. I've seen it too many times. Even in FSM's . Dam Porsche manuals. lol Quote Link to comment Share on other sites More sharing options...
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