CableSrv Posted April 3, 2004 Share Posted April 3, 2004 Ok guys, I bought my first 240z about a month ago! and Had no idea what was original in it besides a 6-1 header and exhaust. Come to find out it has a l28 block with n42 head with original dual su carbs in a 1972 240z well I did a full fluid change and ran it for a few weeks. One day goign to work having a bit of spirited driving I noticed the car started to get a bit hot almost to the hot side of water temp. I pulled over and let it sit for awhile and it started going back down. I checked the fluid the next day and found I was a little short on water, so I promptly refilled it with more distilled water, then ran it with cap off for awhile to let it warm up. Then I noticed small floating oil spots!!!! Either I blew a head gasket or head got warped due to the heat!. Well I had planned to take the head off this weekend anyway to port it so might as well change gasket, and deck it. Now here comes my question!! I don't have 150 to spend on those hks 1mm gaskets and i'm not doing engine rebuild!! so what gaskets should I get and how much, and how much should I deck the head ? I am porting it so might as well deck it a bit also for more cr. since it's a N42 I would assume it has brass valve seats... but seeing as texas doesn't HAVE leaded gas anymore I would think it has been changed out already to steel ? again assuming. Also any info you could give me on doing the removal of the head and what tools I need or if your local and can lend a hand I'd appreciate it I plan to do this tomorrow and possibly have it reassembled next weekend! giving me all week to port the head! Quote Link to comment Share on other sites More sharing options...
slownrusty Posted April 3, 2004 Share Posted April 3, 2004 First of all. Why don't you do a leak down and or a compression test. That way you'll know for sure if your HG is gone or on its way out. Once the head is off. Check the deck of the block and the bottom of the head once you have PERFECTLY cleaned it and gotten rid of any pieces of stuck HG. To do this you need a good set of feeler gauges and a perfectly straight edge. Inspect the HG for any blow by, damage etc etc as well. On the block you want less than 2thou of variation on the deck. And the head has to be perfect. Pulling the head on a L is a pain in the ass but as you don't have any emissions and EFI junk, it sould be alot faster than the post '75 cars, natually drop your exhaust and pull the headers first. You need some good wobbly extensions and deep sockets. Bank on spending a full morning and a bit of the afternoon to pull the head and having an extra pair of hands really does help as the L head is heavy. Good luck - Yasin Quote Link to comment Share on other sites More sharing options...
akeizm Posted April 3, 2004 Share Posted April 3, 2004 Its not a pain to pull an L series head. Its a pain to put it back on if your torque wrench is stuffed (I know, snapped 1 headbolt, streched 3 and stripped a hole in the block). Quote Link to comment Share on other sites More sharing options...
EvilRufusKay Posted April 3, 2004 Share Posted April 3, 2004 Don't take this the wrong way but have you ever ported a head before? The only reason I as is because you are asking what tools you need just to remove the head . Then you are saying that you are going to deck the head yourself? Some people do port heads themselves but I am sure they have practiced on busted or salvage heads prior to working on their daily driver. Decking is something only a machine shop is capable of because it has to be done on a mill. You cant just grab an angle grinder and deck a head (unless it happens to be on the neck of the guy next to you ) Like I said I am not flaming you, but from the posts of yours I have read it does not seem like you have a whole bunch of expierience in this area of motor modification. I could be completly wrong and if so ...sorry, but if I am right, porting and decking should be left to a qualified machinist. Good luck!! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 3, 2004 Share Posted April 3, 2004 Pulling the head off is a snap on an early Z especially. I've had to do it quite a few times this year so I know from experience! With just lazily getting on about it I can now have it off in about two hours or so, I'd say it took maybe 3 tops the first time I did it, and this is on a fuel injected turbo motor, though I dont think a motor with SU's would be significantly longer or shorter. I had a friend help me put it back together last time and we had it all back together and running in about four hours. To answer your one question about what gasket to use, stock Nissan gasket is great at about $60, but getting harder to get. I've also used Felpro gaskets w/o any problems (thought my one gasket that did blow on me was a felpro but ended up it was a Roc gasket, so I would recommend against Roc), and I know quite a few others have as well, and they are cheaper, I think like $30. If you're not gonna be building a monster motor with really high compression or anything crazy like that especially, then the felpro should work fine and are still easy to get. I agree that you might want to avoid doing any head work if you haven't done this kind of thing before. However there are guys who've had great results doing porting and stuff themselves. About shaving the head for higher CR, keep in mind if you shave the head enough to make any real difference (a common number I hear is .080") you will have to shim the cam towers to compensate and keep your valvetrain geometry correct. Even then I dont think you'd be effecting your CR much, though you WILL effect the shape of the combustion chamber... a few people have touted this as a great way of making the combustion chambers more effective for fuel mixture and avoiding detonation. Norm (the 12 second SU dude) is THE guy to talk to about N42's, I think. Most people who want higher compression find it in the pistons, by switching from dish top to flat top pistons, which with an N42 head will bring your CR up to about 10:1. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted April 3, 2004 Share Posted April 3, 2004 Are you consistently losing coolant? What do the plugs look like? If you're just getting little oil slicks in the coolant, but no coolant in the oil, you might try just retorquing the cylinder head. A few years back I got the same symptoms, and this fixed it, believe it or not. Certainly worth a shot... Quote Link to comment Share on other sites More sharing options...
CableSrv Posted April 3, 2004 Author Share Posted April 3, 2004 whoa whoa I think I came off wrong. I'm not decking the head! I'm taking that to a machine shop to get done. And yes i've ported a head before mainly my focus. Second when I asked for what tools I meant specialty tools for instance what is needed to hold timing chain to keep tensioner tight! sorry if I came off wrong like that. I've pulleds heads off cars before just I'm new to Z's and well you guys know more about what is needed than I do and I'd rather ask first before doing then woops forget a step that might be vital!! no I'm NOT leaking fluid and only reason i'm pulling head is because I originally planned to port it. But since I found oil in my radiator fluid It concerns me as it might have blown a head gasket or warped the head. which is why I came on here to see if you guys know what head gasket to get, and how much can I safly deck the head. Quote Link to comment Share on other sites More sharing options...
CableSrv Posted April 3, 2004 Author Share Posted April 3, 2004 Ok WITH LIGHT, I checked the fluid in my radiator and did a good look and it's not oil it's loose dirt/rust ? floating! So head didn't warp nore did my gasket blow! whew!!! Anyway I still plan to take the head off and do some mild porting. mostly just smoothing out the castings and possibly changing out valve seals to the ford part number SS 72686 which is suppose to be smaller and better sealing than the nissan valve seals. What I'm now asking is what specialty tools are needed to remove the head aka what do I need to keep tensioner from pulling chain down ? and what if any special tool to remove valve springs ? or will a basic valve spring compressor work ? Seeing as it's not a warped head i'm not worried about getting it decked but i'll at least clean up the surface. Quote Link to comment Share on other sites More sharing options...
Guest billyzbear Posted April 6, 2004 Share Posted April 6, 2004 Motorsport sells the tool your talking about or you could use a socket or piece of wood. A N42 head came off a 280z, it has harden seats. Does the block say L28? Mostlikely you have 280z motor. Are the pistons flat or dished? You can pull a spark plug to find out. To help keep cool run a 160 thermostat from a pinto and check fan clutch. Take a piece of cardboard to it and see if she'll still spin. Dealer fan clutch's are best. A 280z rad. is bigger, has more rows than 240 which mite help as well and it bolt's right in just change lower rad hose. Quote Link to comment Share on other sites More sharing options...
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