Xnke Posted July 25, 2008 Share Posted July 25, 2008 Well, I went to check out my first E88 head, (got two now) and found what looks like detonation damage or something. (maybe some rocks in the cylinder? who knows?) Can this be fixed, or is it time to look over the spare head? Quote Link to comment Share on other sites More sharing options...
woldson Posted July 25, 2008 Share Posted July 25, 2008 Two questions: 1 Is this reflective of all the combution cambers in that head? 2 Why is it important? Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 25, 2008 Author Share Posted July 25, 2008 1. No, this chamber (#3) is the only one that looks like this. 2. Because this head is in overall better condition, regarding stripped out bolt holes, cam and valvetrain wear, and port sizing. (Head was ported in the past.) The PO was running this head with two headgaskets stacked, flattop L24 pistons, and a stock exhaust manifold/carbs. (I don't believe it was a turbo motor...could be wrong though. Why else the two headgaskets?) Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted July 25, 2008 Share Posted July 25, 2008 Yes, the head can be saved. It can be fixed and improved, if you want. Do not get rid of it. First get it cleaned (glass blasted is best). Have them then weld up the area that showed the damage (welding on that metal can be done). They will weld it and machine/clean the weld area. Then have them do a three angle valve job (also it would be a good time to add harden valve seats or replace them, if needed), also get new valve stem oil seals and install them next. The one thing you would want to do, is also port and polish the intake/exhaust ports (costs a lot of money, but is good for higher rpm usage)(is not really needed for the street). How far you go with this, will depend on money and time. Good Luck, Rich. Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted July 25, 2008 Share Posted July 25, 2008 After looking at the picture, if I am looking at it right. You may be able to have the valve areas reworked (i.e. unshrouding the valves) may be all you need to do to repair it. Just look at where the head gasket metal ring is marked on the head. You should be able to grind the area down where the damage is. It looks like you have enough area to do it. Don't know where you are from. But take it to a head shop or machine shop and have them look at it. They should be able to give you a answer to what they can do or not do. You would lose a little CC from the head. But you also may help the flow in or out of the head. They should be able tell you every thing that can be done. Rich. Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 26, 2008 Author Share Posted July 26, 2008 Well, about the valve unshrouding, yes, that portion is correctable. I was more worried about structural concerns about the valve seat area. I can weld aluminum, MIG/TIG/Torch, just didn't know about the durability of the welded area around the valve seat. It's getting N42 valves anyway... Quote Link to comment Share on other sites More sharing options...
Devilcat Posted July 26, 2008 Share Posted July 26, 2008 If you going N42 then you can go out a bit. When you weld that head the best way is to stress mount it first to avoid structural deformation (warped head). Too much heat will kill no matter what (mostly). When you TIG the head, make sure you don't cheap on the aluminum rod and keep the gas pressure up. For the cleanest weld cold dip the head and clean with starter (eather) fluid and then wash with mild detergent and then water. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 27, 2008 Share Posted July 27, 2008 I can weld aluminum, MIG/TIG/Torch, just didn't know about the durability of the welded area around the valve seat. Being able to weld aluminum, and being able to weld an aluminum head casting are two different things altogether. Preheat, post heat, stress relief, preload bending, bending to true the head afterwards... It's not just zapping the thing with your TIG and letting it cool down...do that and the chunks will fall out of the chamber onto the piston crown while the engine's running... Many L-Heads have been extensively reworked (including in the valve area) without any problems whatsoever (same with VW heads and etc...) But you want to take the head to a place set up for welding large aluminum castings and heads. Have them repair all the corrosion extant around the water passages as once you're done with the welding, top and bottom surfaces likely will have to be trued anyway, so they may as well have nice properly shaped water passages as well as nice new looking high-quench combustion chambers... Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 27, 2008 Author Share Posted July 27, 2008 I cast aluminum at home, and have welded castings before. That's not a big problem, but if you look closely, you can see that the pitting in the combustion chamber area is in deep around the valve seat. Portions of the top edge of the exhaust valve seat are exposed. I do not know if this is a problem or not, I can see the valve seats on all the other exhaust valves as well, but they are not pitted like this. The "corrosion around the water jacket holes" is leftover gasket and dirt, I have since cleaned the area and there is no pitting or other nastiness. The head will be used with dished pistons, so a high quench chamber is a moot point. 9.0:1 compression is the target, and maximum usable valve unshrouding is a goal as well. If the pitting is really that bad, then I'll just get another head. the spare head has these pits as well, in both #3 and #4, around the exhaust valves. the other chambers look to be in good condition on both heads...it's really weird. Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 28, 2008 Share Posted July 28, 2008 I am thinking that the head is probably trash to you, (in that it would take too much effort to use for your purposes) but it could certainly be used as more than a boat anchor.... But, that was my first impression, and I didn't mention it the first time I viewed this thread because I don't really know too much for certain regarding this subject. However, everything I have read that others say seems to support my first impression, in my mind. Quote Link to comment Share on other sites More sharing options...
Devilcat Posted July 28, 2008 Share Posted July 28, 2008 It is that there is a lot that comes in to play when repairing a head. The pitting around the valve opening is not a harsh as it look but it will take a skilled hand to restore this head. If you have not done this type of TIG welding then I believe we all would recommend taking it to someone who knows this type of work. At least its not cast iron, that's even more delicate. Just take the time to call around the local Nissan clubs and you will find a special person to help. Good luck Quote Link to comment Share on other sites More sharing options...
1 fast z Posted July 28, 2008 Share Posted July 28, 2008 I would recomend a very powerful mig welder, and not tig. Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 28, 2008 Author Share Posted July 28, 2008 Hey, No offense taken. If I was as sure of my skills as I must've sounded, I'd already have welded up the head. As it stands, I'll be buying another (mostly) complete L28 this weekend, that already has an N42 head on it. Missing the Dizzy and damper. 1 fast Z, why the MIG? better fill characteristics? Lets just say I were to repair both of these heads (I have two like this, pitted around the exhaust valve seat on cyls #3&4) Would installing the larger exhaust valves and seats (this would take out most of the pitting around the valve seat area, combined with unshrouding the valve) make it worth trying to repair the pitting on the "quench pad"? Quote Link to comment Share on other sites More sharing options...
1 fast z Posted July 29, 2008 Share Posted July 29, 2008 A good hot mig, will work just as effectivly, as well as weld better to corroded areas. With Tig, you have to get the head so hot, that it warps terrible, even with pre-heat, post-heat, and clamping. With Mig, you can clean it good, grind it, whatever, then weld, pein then you can litteraly take your hand and touch the weld, pretty much no heat involved. If you were to tig it, you would have egg shaped seat bores when you were done, etc. Mig and Tig both have there places in the industrial world. Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 29, 2008 Author Share Posted July 29, 2008 That makes a lot of good sense. I think I'll keep the E88 around, practice porting with it, practice welding the chambers, maybe build a hot L24 sometime later for another Z. (We all know these cars are like potato chips, you usually can't have just one.) Quote Link to comment Share on other sites More sharing options...
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