tooquick260 Posted December 4, 2012 Share Posted December 4, 2012 Maybe a dead horse but need advice, thoughts or experiences and what do I do now? Have a 74 260z with the DGV webers, sorry i got them with the car and they run great. Have a P90 cylinder head and I want to put on the 260z motor. It Will bolt on, intake manifold fits, exhaust fits. Issue I have been told is the exhaust valve will hit the blocks cylinder hole. I guess an 83mm bore has a problem fitting a 44mm intake and 35mm,(i crammed a 46mm intake and 37.5mm exhaust in a 88mm bore on an air cooled VW) even though that adds up to 79mm leaving the seats to use up the additional 4mm. Reading in the Hotrod Z magazine shows a picture of this where the exhaust valve hit the head and bent them. It also shows they clearanced some of the block to make room obviously not enough. Who has done the clearancing and made it work? Does anyone know the deck height of the piston on a 260z motor, or do I need to check when I remove the head? I was going to flycut the head 80 thousandth, use the 80 thousandth longer valves to get a compression of 9.5 to 1. ( yes I know I need spacers under the towers and spacers under the springs, think I have that handled) Help a back yard grease monkey get his ride a runnin. Or run like the beast that I know is it! Heres the car Heres the head Heres new exhaust sounds awesome Quote Link to comment Share on other sites More sharing options...
kaito Posted December 4, 2012 Share Posted December 4, 2012 I dont know what you are talking about with using longer valves but I just put an n42 head on a l24 that was bored out 1 mm and the valves didnt hit the walls. The best way to check is to put the head on, torque down the head bolts and turn the motor over SLOWLY by hand. It will bind if there is not enough clearance. have fun! Quote Link to comment Share on other sites More sharing options...
brianZortiz Posted December 4, 2012 Share Posted December 4, 2012 You mean valves hitting piston? Weber dual downdraft carbs are great carbs. I had fun with them when I had a set. A lot of people will tell you why not just get an l28. The l26 has domed pistons so slapping a stock p90 will do no good. Shaving 80thou and getting shims involves some work. If you are doing that might as well get the l28 block with flat top pistons. Quote Link to comment Share on other sites More sharing options...
30 ounce Posted December 4, 2012 Share Posted December 4, 2012 The L26 should already be notched. They went with larger exhaust valves that year so it should be notched from the factory. Quote Link to comment Share on other sites More sharing options...
Leon Posted December 4, 2012 Share Posted December 4, 2012 The L26 should already be notched. They went with larger exhaust valves that year so it should be notched from the factory. Not quite... It's the intake valve that has a clearance problem, not the exhaust. No L26 blocks came notched from the factory. Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted December 4, 2012 Share Posted December 4, 2012 And my l26 had flat pistons Quote Link to comment Share on other sites More sharing options...
Leon Posted December 4, 2012 Share Posted December 4, 2012 And my l26 had flat pistons Good point, I forgot to mention that as well. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 4, 2012 Author Share Posted December 4, 2012 Thanks for the input, I have flat top pistons so that should not be a problem. early production 260z motors have lower compression than later. Production of mine is 11/73 What valves come in the N42 head? So the exhaust side of the block is clearanced already for the 35mm valves, I have to check the intakes that are larger for block side wall clearance? I bet with the shaving of the head makes the exhaust go deeper in the piston hole and that would be a possible clearance problem. I will once I get the head back do a bolt on rotation clearance check. Quote Link to comment Share on other sites More sharing options...
Leon Posted December 5, 2012 Share Posted December 5, 2012 So the exhaust side of the block is clearanced already for the 35mm valves... No, re-read my post. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted December 5, 2012 Share Posted December 5, 2012 First off what is wrong with your head/engine that makes you want to change it? I'm assuming E88 in which case yeah the intake an exhasut will bolt up, but you will have a lot of other problems to deal with. The work you are describing with the longer valves and stuff is similar to this mod: SO WHAT ARE YOU ACTUALLY DOING IN THE MOD? - shaving the head .080" - installing '75-78 valves which have .080" longer stems - shimming up the cam towers .080" - shimming up the spring bases by .080" Which is found here: http://datsunzgarage.com/p79/index.htm And finally, why would you do this to an L26. Get an L28 they are about $150 for a longblock. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 6, 2012 Author Share Posted December 6, 2012 Really just to do it! Who has a L28 block for $150? Quote Link to comment Share on other sites More sharing options...
Gollum Posted December 6, 2012 Share Posted December 6, 2012 Really just to do it! Who has a L28 block for $150? I know I'm in CA and there seems to be a lot of datsuns in general, but I see L28 motors on a regular basis for $100-200. I bought my last L28ET as a complete longblock (oil pan to valve cover complete + manifolds & fuel rail, no turbo, no ECU, no AFM) for a whopping $200.... Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted December 7, 2012 Share Posted December 7, 2012 The n42 head would be better. It has the same sizes valves as the P90 but with a smaller combustion chambers. I'd like to trade my n42 for a P90. The P90 has shorter valves because of the raised combustion chamber. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 8, 2012 Author Share Posted December 8, 2012 I am going to make my own shims for the heads. Going to try the head any ways and see what I have to do to make this work. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 9, 2012 Author Share Posted December 9, 2012 (edited) Got the exhaust installed. Went with a twin pipe to the rear with a Dual glass pack muffler, WHat ya think? More to come, wheels coilovers z32 front brakes and of course the P90 head and cam Edited December 9, 2012 by tooquick260 Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 11, 2012 Author Share Posted December 11, 2012 Where should I buy new valves? I want the 77-78 longer valves? Will post pics soon! P90 head is on the bench, cam off going to get reground! Things to come, the z32 front brake adapter is in the mail! have the calipers and master cylinder. Painting the suspension parts, have POR-15 black paint. Quote Link to comment Share on other sites More sharing options...
30 ounce Posted December 20, 2012 Share Posted December 20, 2012 Not quite... It's the intake valve that has a clearance problem, not the exhaust. No L26 blocks came notched from the factory. Mine has notches from the factory ...I'll take pictures when I get home.... Quote Link to comment Share on other sites More sharing options...
Leon Posted December 20, 2012 Share Posted December 20, 2012 Mine has notches from the factory ...I'll take pictures when I get home.... Looks like you might be right, I hadn't heard of that before. Learn something new everyday! However, an L26 would possibly also need to be notched on the intake side when using the larger 280Z valves. Quote Link to comment Share on other sites More sharing options...
tooquick260 Posted December 22, 2012 Author Share Posted December 22, 2012 Changed directions going with turbo conversion stay tuned. Once I get the parts together I will start a new post with the progress. I have coilovers and brakes ready to go on. Just need a day off to do this. Going to Disney World today! Quote Link to comment Share on other sites More sharing options...
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