JulianH Posted July 21, 2010 Share Posted July 21, 2010 OK, the HGs went on my wife's 98 Forester, so I pulled the engine, pulled the heads and sent them off to be cleaned and decked. I've got them back now, cleaned them up again, greased the contact surfaces, and torqued the outer cap to 84 in-lbs(7 ft-lbs), inner caps to 174 in-lbs(14.5 lbs). The issue I have is the exhaust cam on the passenger side does not rotate as freely as the intake does, it feels tight. When I loosen the outer cap, it rotates freely, but as little as 3 ft-lbs on the cap bolts and it starts to drag again. The exhaust cam on the driver's side rotates freely when torqued. Does anybody have any ideas as to what might cause this? Thanks, Julian Link to comment Share on other sites More sharing options...
Fuzpile Posted July 21, 2010 Share Posted July 21, 2010 Ouchers. The possibilities are what you don't want to hear like bent cam. Sounds like an alignment issue and good you caught it. You only can reflect back on how hot the engine got before. The possibilty a valve is slightly bent or seized disappears because it is something with that cam. Cap wrong way or mixed with another. That's just neophyte to these engines talking. If it is in the process, it would serve you to put the cam "between centers". That can be a few minutes on a lathe or inspection device. There are machined divots on both ends which are suspended-(sorry if you know all this) A dial micrometer can be placed across each cam bearing landing to see they don't vary. Link to comment Share on other sites More sharing options...
WoodsWagon Posted July 21, 2010 Share Posted July 21, 2010 How were they cleaned? If they soda-blasted them, that can pit the bearing surfaces in the head. When the bearing gets pitted, it creates raised spots where the displaced surface metal bumped up. That will reduce bearing clearance and cause it to bind. It's the same theory as nurling valve guides, you're displacing metal to reduce clearance. Check to make sure nothing got bent or dinged. Parts can and do get dropped, and often it's easy to dust them off and say "that didn't happen" than to check and replace what got damaged. Also check the cam with the buckets removed off of all the valves, so there's no spring preload on the cam. That will let you adress just the bearing issue. Make sure to check valve clearance after you're done, I've had the shims get mixed up and had to chart out clearances and figure out where each shim should go. Link to comment Share on other sites More sharing options...
Fuzpile Posted July 21, 2010 Share Posted July 21, 2010 Jullian you have your way to an answer with 91's post. He knows this engine. Perhaps it doesn't bind with the buckets off and the torque correct as before. Priceless about a cap being effected . A Hi-spot Dykem or similar may help find that area and relieve it. Link to comment Share on other sites More sharing options...
JulianH Posted July 21, 2010 Author Share Posted July 21, 2010 Thanks for the thoughts, guys. I don't know how it was cleaned, but he specifically told me before they did anything they don't remove the cams, caps, etc. He also said he checked the valve clearance and it was "good", but I didn't get a specific number. I'll go pull the shims/buckets and see what happens. Link to comment Share on other sites More sharing options...
davebugs Posted July 21, 2010 Share Posted July 21, 2010 My place steam cleans them. Locks them into a gizmo that runs some kinda "cycle". Of course they are bare heads. I mark, disassemble, and lay things out. One old oil box for each head. When I re-assemble I use assembly lube. What ever method used to clean (if any) could have removed whatever lube was there. Could be as simple as that. If not dis-assembled and machined, well, are you nuts? Shavings could be anywhere/everywhere. Link to comment Share on other sites More sharing options...
JulianH Posted July 21, 2010 Author Share Posted July 21, 2010 OK, I took the buckets out, torqued the caps back down(and they are in the proper position+orientation) and the cam spun freely. I then put the buckets back in and torqued it back down again, and the cam spins freely... maybe one of the buckets wasn't quite seated fully or something?!? I spun the cam around fully with a wrench a couple times, and it still spins freely, so I guess I'll just double check the valve clearance and put it all back together. Thanks for the help guys. Davebugs, I lubed everything up before reassembly, so that wasn't the issue. Where would shavings come from? Link to comment Share on other sites More sharing options...
davebugs Posted July 21, 2010 Share Posted July 21, 2010 Davebugs, I lubed everything up before reassembly, so that wasn't the issue. Where would shavings come from? If they did any machining at all. Making sure the mating surface was "true" for instance. Didn't notice where you had lubed things on re-assembly. Just looking for a solution. Link to comment Share on other sites More sharing options...
JulianH Posted July 21, 2010 Author Share Posted July 21, 2010 Oh yeah, I suppose milling the heads might create a few chips, huh? These guys come highly recommended, they are supposed to be the best cylinder head place in the area, so I imagine they know how to clean the heads after milling. I went and checked the valve clearances, and all the intake valves are perfect. The exhaust valves are a different story, only 3 out of 8 are .25 mm, and the other 5 I can't even get the .20 mm gauge in. I guess I'll be driving back to the dealer tomorrow to get some shims, that's what I get for not checking them myself. Thanks for the help, Julian Link to comment Share on other sites More sharing options...
Olnick Posted July 21, 2010 Share Posted July 21, 2010 Way to go, Julian! We're rooting for you! Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 21, 2010 Share Posted July 21, 2010 Oh yeah, I suppose milling the heads might create a few chips, huh? Head surfaces are not milled - they are ground and it's done in a "blanchard" grinder with flood coolant/cutting fluid which would carry away most of the grindings. It's possible there could be contamination but it's not real likely. Sounds like whatever it was it corrected itself. Though I would probably think about cleaning the heads again with bra-kleen, etc just to be sure there isn't anything that's going to cause a problem. GD Link to comment Share on other sites More sharing options...
Fuzpile Posted July 21, 2010 Share Posted July 21, 2010 Well i don't know all about that with aluminum but I'm glad our friend found something and is on his way to success. I'm thinking he woulda taken the cam out anyway because he just had to Know why it was binding. It was helpful I'm sure, all these fine folks here. What was really cool is that he took this real time info and applied it within an evening. Total salutes. Link to comment Share on other sites More sharing options...
davebugs Posted July 21, 2010 Share Posted July 21, 2010 Head surfaces are not milled - they are ground and it's done in a "blanchard" grinder with flood coolant/cutting fluid which would carry away most of the grindings. It's possible there could be contamination but it's not real likely. Sounds like whatever it was it corrected itself. Though I would probably think about cleaning the heads again with bra-kleen, etc just to be sure there isn't anything that's going to cause a problem. GD No idea of what the shop looks like. Do you? I've seen it happen from folks who took heads to a general machine shop. The two places I deal with want empty heads "just in case". And they use a grinder/resurfacer. Don't know the technical term. Just trying to help a fella out with where to look to resolve a problem. Sounds like he may have it straightened out now. Link to comment Share on other sites More sharing options...
Fuzpile Posted July 22, 2010 Share Posted July 22, 2010 Grinding. I was on another thread and they mention "grinding" these aluminum heads. Well actually you grind iron heads. What they use is called a "flycutter". It is large maybe 6-8" . The setup is the main thing. It is supposed to take off metal at one side and not the trailing side. It really requires a lot of care to get everything correct and level. Then "what" is level? On some cars the heads have to be torqued down to the table to represent the profile they will present to the gasket after they are torqued. That is why a shop that Really knows about these things is THE place. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 22, 2010 Share Posted July 22, 2010 Grinding. I was on another thread and they mention "grinding" these aluminum heads.Well actually you grind iron heads. What they use is called a "flycutter". It is large maybe 6-8" . The setup is the main thing. It is supposed to take off metal at one side and not the trailing side. Typically you don't use a flycutter (which is a type of milling head) to resurface heads. A blanchard grinder is a rotatry surface grinder that rotates the work against a counter-rotating grinding head that is generally cone shaped, etc. The grinding head is first "dressed" against a carbide tool that is attached to the work table - this causes the grinding head to be 100% true with the table and thus anything you bolt down to the table will automatically be parallel to the grinding head. Grinding produces the best and most consistent surface RA for head gasket adhesion apart from hand lapping of course - but it's MUST faster than hand working a set of heads. The characteristic circular swoops you see in the surface of the head are from the grinding operating - the same can be seen in a resurfaced flywheel. Basically - any modern thing that is machined to a flat surface and has to be flat to within say one thou is ground anymore. Grinding can easily produce both the best suface finish and the highest accuracy - most of the flat surfaces found in a machine shop are ground to within .0001" and I've seen granite sufaces certified to within .00001" Other ways including running the head against a belt sander (sounds bad I know but there's a method for doing this), or surfacing them by hand with a lapping plate and either grinding compound or wet-dry paper (yes - I have done this and it is very effective albiet time consuming ) Flycutters, but comparison, have the tendancy to "trench" if the milling head isn't properly trammed to the table and work surface. The larger the cutter, the harder it is to properly setup and the more sensitive it will be to the head tram. I would be more likely to bolt the head to a lathe faceplate and face it off if I had to choose between that and a flycutter. GD Link to comment Share on other sites More sharing options...
Fuzpile Posted July 22, 2010 Share Posted July 22, 2010 The "flycutter" in this case is a multicutter type of insert to a vertical mill. Since you know what "tram" is you know where I'm going about removal of surface. I just thought that abrasives get lodged in the aluminum. Since the person didn't take down the head to bare i didn't think the Blanchard process ever happened. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 22, 2010 Share Posted July 22, 2010 (edited) I just thought that abrasives get lodged in the aluminum. More like the Aluminium gets lodged in the abrasive....... You have to use the right type of abrasive for sure. Just as you use Silicon Carbide for sharpening carbide tools but you use Aluminium Oxide for grinding HSS..... If I had to guess I would say it's probably done with a diamond impregnated wheel. Aluminium is very soft and will easily clog most conventional grinding stones. With the right lubricant and grinding medium though it is defintely possible. When I have hand-lapped Subaru heads I have used conventional Aluminium Oxide wet/dry paper and WD40 as a lubricant. You have to clean the paper (with WD40) every half dozen passes or it clogs badly. But it does produce a fine finish and so we can say that undoubtely there are methods that allow abrasive resurfacing of aluminium cylinder heads. The shop I take mine to does not care if they are still assembled or not. I leave the valves in but remove everything else. It's just easier that way. I haven't had a problem yet and they clean them very well before giving them back to me. GD Edited July 22, 2010 by GeneralDisorder Link to comment Share on other sites More sharing options...
Fuzpile Posted July 23, 2010 Share Posted July 23, 2010 Last thing I want is to get into some match with you or anyone who has spent more sweat than me with these vehicles. Just my .02 and it's sorta over. I haven't been with and supported the newer members like you guys did. There were just fundamental things which i too have learned and wanted to share. It becomes "what works for ..is okay" Possibly a fresh look is okay also. Link to comment Share on other sites More sharing options...
johnceggleston Posted July 23, 2010 Share Posted July 23, 2010 so, what questions should i ask when looking for a shop to work on my 98 obw heads?? the belt broke so i'm looking at valves, actually it was the passenger intake cam sprocket that broke. i have donor heads that have been over heated, would they be a better choice?? does it matter? i have never dealt with a machine shop so i'm going to be at their mercy, sort of. thanks, Link to comment Share on other sites More sharing options...
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