cruceno21 Posted April 7, 2010 Share Posted April 7, 2010 I did a search and I found parts list for a complete engine rebuild, or replacing the valve seals. So don't harp on me for not searching... My shop is telling me they think my oil burning is from bad valve seals or valve guides. They recommended a machine shop that does that type of work and I am going to get it over there later this week. As I posted before... I am new to Datsuns... and don't have experience/tools/time to tackle this type of project. That is why it is at a shop for most of the heavier mechanical stuff. I have a 1975 280Z... So assuming they are gonna pull the head, while it is off, what types of things should I do at the same time? What kind of money/time are we looking at here? My wallet isn't a bottomless pit... but I also don't want to miss an opportunity to save on duplicate labor and get stuff done all at the same time. I don't want them to talk me into stuff I don't need, or won't help increase performance or reliability but just something they want to tack on to make more money. Note: I read all about my issue on the forum and I think the diag is correct. She smokes on start up, and its worse the longer she sits. If I drive her daily (or at least start her up) she doesn't start to smoke until I get her warmed up well and then she smokes a little. Checked compression and it was good in all cylinders. Ideas, suggestions, tips? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 7, 2010 Share Posted April 7, 2010 How many miles on the motor/head? Usually bad valve stem seals will smoke more when it's cold than when it's hot. The seals heat up and expand and the rubber becomes more pliable. Valve guides - could be, but that still means the oil is seeping past the valve stem seals. Unfortunately, you can't check the guides unless the head is off the car. You CAN replace valve stem seals with the head on the car though. It's about a 2 hour (4 beer) job. You'd need an overhead valve spring compressor, and a fitting that goes from an air compressor to the spark plug hole(s). I would say that if you're a DIY guy, replace the seals first and go from there. Since you say you're not - no sense paying a shop to do it and then finding out that they weren't the issue. If it was 2 hours out of "your" time - that'd be one thing. 2 hours at $80+/hr. labor - that's another story. Seals are cheap - +/- $15/set. If you/they do yank the head, spend the money and have a 3 angle valve job done. They'll (machine shop) check the guides and replace as needed as part of the process. Not much else you can really do with just the head off. Hoses and injector seals are all on the manifold and easily reachable while it's in the car and all together. There is an "outside" chance your rings could be going bad - as the motor heats up, tolerances change - but without seeing it, or doing a leakdown test to validate, there's no way to tell for certain. Quote Link to comment Share on other sites More sharing options...
cruceno21 Posted April 7, 2010 Author Share Posted April 7, 2010 Doing some research, and I see some vendors who sell rebuilt heads for $400... figure it would be a DIY job for me to swap them right? I also see some heads for like $1000... I know there are different models but once again as a newbe I don't know all the differences between models yet. Still too new to the Z community. I am not sure how many miles are on the motor. I don't think its the original one (the trans for sure was swapped from auto to man). Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 7, 2010 Share Posted April 7, 2010 I assume the car is at the shop? If not -- check where the head meets the block - right underneath the #1 and #2 spark plug, there should be a 3 character designation. If you have the original head, it should say N42. If not - then it's been swapped with something off another year car. A good 3 angle valve job with a light decking (to ensure flatness) shouldn't run over $250 from a competent machine shop. If you have to start replacing guides (replace them ALL if ANY of them are bad) - then you're looking at a little more $$$. If you're contemplating buying a reman head and taking it off and putting it on yourself - there's no reason you can't take the head off yourself - take it to the machine shop, and then put it back on when their piece is done. The $1000 heads you see probably have substantial port/polish work done to them along with an aftermarket cam. No way should anyone pay over $400 for a "stock" reman head. Quote Link to comment Share on other sites More sharing options...
cruceno21 Posted April 7, 2010 Author Share Posted April 7, 2010 Is an aftermarket cam on this motor worth the money? I see the kit from MSA is 800 bucks... for that I would rather put money aside for a motor swap and drive it smokin til she blows... Right now I just want to get it road worthy, autocross her a few times this summer and make plans for more serious work in the future when the money tree finally grows in the backyard. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 7, 2010 Share Posted April 7, 2010 Unless you do port work on the head to take advantage of the cam - along with an aftermarket EFI Management system - TOTAL waste of money. A stock EFI system is not happy with larger cams. I would recommend your shop perform a leakdown test first (maybe they already have to determine for sure where the problem is??) Once the problem is pinpointed, you can go from there. Oil is cheap in the words of TonyD - so what if it smokes? It still starts, runs, and drives. You're not really hurting anything - so drive the piss out of it. Especially if you know you're going to do rebuilding in the future. Nothing is going to "blow" other than oil out the tailpipe - so just keep an eye on your oil level and run with it. Spend your money on suspension (bushings, springs, struts etc.) and brakes first. Get the car mechanically sound, and bite off jobs that won't leave you Z-less for more than a day or so. Since you're new to this - this will give you a chance to drive the car, find it's quirks and flaws (and fix them) and get a better idea of what you really want to do with the car. Kind of gives you time to step back and look at the big picture. Quote Link to comment Share on other sites More sharing options...
yetterben Posted April 7, 2010 Share Posted April 7, 2010 Well put. If yah just got the car drive the piss out of it before you rip it down for long. You gotta get attached to it..... Quote Link to comment Share on other sites More sharing options...
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