Geonovast Posted August 20, 2010 Share Posted August 20, 2010 My 91 2.5 has running problems, which I've blamed on the 50 psi compression reading in the #1 cylinder. It also goes through a lot of oil. I'm hoping it's not rings. If the rings are fine, I'm going to change the head gasket(obviously), and most likely the valve guides. Few questions: 1. Is it ok to change the valve guides without an actual full valve job? 2. Anything else I'd need to change in order to change them? 3. I've heard head bolts can be pricey, would I be ok with these? : http://cgi.ebay.com/ebaymotors/ws/eBayI ... 0356942460 4. Will this have everything I need? http://www.rockauto.com/catalog/moreinfo.php?pk=124547 Link to comment Share on other sites More sharing options...
Eagle Posted August 20, 2010 Share Posted August 20, 2010 Does the 2.5L have replaceable guides? Or do you mean "seals"? Link to comment Share on other sites More sharing options...
Geonovast Posted August 20, 2010 Author Share Posted August 20, 2010 Must be seals, I remembered reading that the 4.0 didn't have seals, just deflectors. I'll pop the valve cover off tomorrow and see. Are the seals something somewhat easily replaced, or am I over my head on this one? Link to comment Share on other sites More sharing options...
jimoshel Posted August 20, 2010 Share Posted August 20, 2010 A simple test. Find the steepest hill you can. Go up the hill working the engine. Don't lug it. Just make it work. If you burn oil, blue smoke out the tailpipe, it's rings. Turn around and go back down the hill riding compression. Now if it smokes it's valves, seals. You can change valve guides without doing a complete valve job. I would suggest you lap them tho, to insure they're concentric. The 2.5 uses the umbrella deflector on the valve stems. From what I've gathered about your capabilities from your postings, you can do it. Link to comment Share on other sites More sharing options...
bigd44889 Posted August 20, 2010 Share Posted August 20, 2010 first thing i would do is take the head and have it checked thay have a habit of cracking i went thru 3 used ones never did find one that was not cracked have it decked and yes seal can be changed no not hard just get the tool to compress valve springs Link to comment Share on other sites More sharing options...
Geonovast Posted August 20, 2010 Author Share Posted August 20, 2010 Sounds like a good test Jim, really nowhere around here I could do it, and knowing my luck, I'd get pulled over for having expired out of state tags. bigd, where were those heads cracked? I've never head of a common head cracking on the 2.5 before. Also, were yours Renix heads? I'm 99.9% sure the 91+ 2.5 heads are a different casting. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted August 20, 2010 Share Posted August 20, 2010 Bad valve seals, and bad valve guides can cause oil usage, but if you do replace the valve guides, you WILL need to have the seats reground to be concentric with the guides, otherwise your valves may not seat properly and leave you with no compression. If you are pulling the head, and only replacing the seals, get some lapping compound and lap all the valves just to see that they are all sealing well. If you don't know what lapping it, you have the valve loose in the guide without the spring, you put a light grit compound on the valve seat, you put the other end of the valve into a drill chuck, and you start the drill and grind the valve seat and valve together with the compound and see if it is making a complete seal. This also ensures a proper seal by cleaning any imperfections at the sealing surface. Good luck. Link to comment Share on other sites More sharing options...
bigd44889 Posted August 20, 2010 Share Posted August 20, 2010 were the valve stem comes thru the head up th the rocker mount if i get time to da i will take a pic of were i'm talking about Link to comment Share on other sites More sharing options...
Geonovast Posted August 20, 2010 Author Share Posted August 20, 2010 Thanks guys, I'd heard of valve lapping before, never knew what it was, figured it was a machine shop thing. Did a bit of googling last night, and it seems pretty straightforward, so I'll definitely be doing that. What about the bolts I posted? Think those are good, or should I be looking for something a bit more pricey? Link to comment Share on other sites More sharing options...
Geonovast Posted August 23, 2010 Author Share Posted August 23, 2010 Another thought... If I were to pull one of the pistons to inspect the rings and full cylinder, is it alright to re-install the piston with the original rings, or does that require a hone/new rings? Link to comment Share on other sites More sharing options...
jimoshel Posted August 23, 2010 Share Posted August 23, 2010 Just clean everything up, remove any carbon, crud, and put it back. Make sure to offset the rings. You could use a hone, very fine and very little and break the glaze on the cylinder wall. As long as you have the piston out would be a good time to check for wear. Or maybe not. Might find a little wear and end up rebuilding the engine. LOL. Link to comment Share on other sites More sharing options...
Geonovast Posted August 23, 2010 Author Share Posted August 23, 2010 While I'm certainly not opposed to yanking the motor, boring it out, and slapping a bigger cam in it, it would be best avoided at this time. I'm currently not able to pull the motor. I have no flat, hard surface to work on, and my cherry picker is still at my brother's place in Wisconsin. When I get a decent day, and fight with the hood enough to get it open, I'll pull everything apart, take some pics, and see what you guys think. Link to comment Share on other sites More sharing options...
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