jhall Posted January 18, 2005 Report Share Posted January 18, 2005 Bbobynski, I've pulled down the heads on a N* from a '97 Deville. A close look at the valves indicated stem seal leakage based on the oily carbon built up on some of the valve stems. The exhaust valves are covered with some seriously hard deposits. Some of the exhaust valves and seats have slight pitting. Some exhaust valves also have slight grooving at the face (a machine shop, and possibly some new valves, appear to be in my future) During the teardown and inspection, I noticed that the upper spring retainers (where the keepers are installed) have what appear to be stress cracks in the metal. See photo. Have you seen this before? I assume I'll need to buy new ones. Most retainers (intake and exhaust) have some level of cracking just like this, but I'm not sure if this is a typical or something that needs to be replaced. My engineering background tells me this is material fatigue and they will fail. Any comments appreciated. Link to comment Share on other sites More sharing options...
jhall Posted January 18, 2005 Author Report Share Posted January 18, 2005 Bbobynski, Whew! What a relief! Glad I don't have to replace the retainers. One of the retainers has a crack up to the edge of the center hole at the top. This looks like it's from the forging process, so I'll reuse it. I don't see any encroachment into the taper. I greatly appreciate your insight on the seals and the use of RTV & Loctite. I plan on replacing the stem seals since I damaged one on removal. Anyway, I'll feel better since I'm not sure if the valve stem retiner lands cut into the seal lips as I removed the valves. I'll send a couple of pictures of the valve face and seat to give an idea of the pitting / grooves. I am checking on some machine shops - just in case, but like you mentioned, I am wary of a "regular" shop so it might take a while to find a good one. I'm not adverse to spending a few dollars to get it right. I'll kick myself if I have on-going problems inside the engine for not spending a few bucks on the necessary replacement parts. I don't plan on doing this again - at least on this car. Link to comment Share on other sites More sharing options...
Scotty Posted January 18, 2005 Report Share Posted January 18, 2005 I can't wait to see your results! Keep up the good work Link to comment Share on other sites More sharing options...
jhall Posted January 19, 2005 Author Report Share Posted January 19, 2005 Bobbynski, See attached photos of one of the exhaust valves and a valve seat I cleaned up on my N*. The dark spots are pitts or etching in the valve seat and valve face. This appears to be limited to the exhaust valves. The file attachment limit of 64k on the forum does not allow a high quality view, but there is a slight groove one one side of the valve face. Look at the lower portion of the valve picture and you can make out the ridge on the groove. The groove is probably not more than 1 - 2 millimeters in depth. Based on what I'm seeing on the other exhaust seats, it looks like slight seat cutting and resurfacing of the valve faces would be in order, or do I just use some fine grinding compound and let it go?? Timesert kit came in today for the head bolts. Looks like progress will be made this weekend! Comments appreciated. Link to comment Share on other sites More sharing options...
jhall Posted January 19, 2005 Author Report Share Posted January 19, 2005 bbobynski, Thanks for the quick prognosis. I'll clean 'em up and use some fine compound. I like the stick for lapping the valves better than the drill - easier to control. Next big step is the Timesert installation for the headbolts. If I can get past this without wrecking anything I think I'll be on the way to getting the car back on the road. I'll keep everyone posted. Link to comment Share on other sites More sharing options...
Barry94 Posted January 19, 2005 Report Share Posted January 19, 2005 bbobynski, Thanks for the quick prognosis. I'll clean 'em up and use some fine compound. I like the stick for lapping the valves better than the drill - easier to control. Next big step is the Timesert installation for the headbolts. If I can get past this without wrecking anything I think I'll be on the way to getting the car back on the road. I'll keep everyone posted. Just some words of encouragement. Several years ago I had to remove a head due to a burned exhaust valve. I purchased the car this way. It was 1,000 miles off warranty and GM would not fix it. So I picked it up at a bargain price. I replaced both exhaust valves in that cyl and lapped them with rubbing compound with the stick/cup. I just wanted to see the pattern and be satisfied that the new valves were seated properly. The fine valve compound I had seemed too harsh, so I didn't use it. That was 50,000 miles ago. Still working great. (Well, except I had to remove the head a couple years later because I didn't know anything about Timeserts). The Timesert process is actually quite simple. You must follow the instructions. Once you do one hole, then it's just labor after that. Keep up the good work. Barry 2008 STS V82016 Colorado Z711970 Corvette LT-1 Coupe Link to comment Share on other sites More sharing options...
Scotty Posted January 19, 2005 Report Share Posted January 19, 2005 jhall what symptoms were you getting before this rebuild? Do you think that carbon could have created seating/sealing problems? Mike Link to comment Share on other sites More sharing options...
Scotty Posted January 19, 2005 Report Share Posted January 19, 2005 The valve seats in the picture would have caused no driveability problems from what I can see. That is a perfectly normal seat. The only reason for cleaning them up with the lapping compound is to visualize the actual valve seat as they clean up. It will only take a few swipes of the valve to clean up the way they look. After a few thousand miles the seats will look just like they look now anyway so the lapping is basically just an inspection process to make sure the seats are uniform and clean. Oh good! Link to comment Share on other sites More sharing options...
jhall Posted January 20, 2005 Author Report Share Posted January 20, 2005 Scotty, I've been tied up for a couple of days thanks to a North Carolina snow storm and most people not knowing how to drive in ice. Imaging this - 5 hours to go 15 miles to get the kids from school.......what a mess. Anyway, I pulled the engine because of a head gasket failure (130K miles - not too bad in my view). I wanted to check the valves as this had been beat into me in my previous job as an industrial engine mechanic. There were no real symtoms other than a few puffs at start-up in the morning. bbobnyski is correct that the valves will look "dirty" in a few weeks, but I wanted to make sure the heads were in good shape before a reinstallation. Link to comment Share on other sites More sharing options...
jhall Posted January 21, 2005 Author Report Share Posted January 21, 2005 bbobynski, you said: Since the heads are completely apart just clean them up good and use a wicking grade of Loctite to seal the OD of the guides for insurance. Just apply the wicking locktite to the interface of the valve guides and the cylinder head material on both ends. OK, I'm a little confused. I can get the red Loctite that's good to 400 degrees, but the instructions (like all Loctite) say to add Loctite to the parts and assemble. I'm not sure what viscosity is good, so can you elaborate on the "wicking" type that you reference? Thanks again for the help! Jeff Link to comment Share on other sites More sharing options...
jhall Posted January 21, 2005 Author Report Share Posted January 21, 2005 Sweet! I know the type you're talking about. Thanks very much! Link to comment Share on other sites More sharing options...
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