Guest eric_503 Posted October 30, 2009 Share Posted October 30, 2009 I have two engines Both l24's,one is the stock one out of the car. It has an e31 head with flat top pistons. The other l24 has an e88 head and the pistons half valve reliefs,or is it just referred to as dished? Whats not making sence is I see the l28's are dished for the turbo? And the l24's were flat top pistons? I would of thought since the e88 heads had more volume it would not need the dished pistons.I know the ports are notched tho so maybe it was ported for the turbo,and the block was bored? I have to check still. For what I'm thinking,If I put the e88 head on the block with the flat top pistons,the valves will hit the pistons and that will be the end of them. And thats what I need clarifying on since Ive seen in the searchs Ive done that e88 heads and flattop pistons were used,so Im just alittle lost. Quote Link to comment Share on other sites More sharing options...
Xnke Posted October 30, 2009 Share Posted October 30, 2009 Usually, valve reliefs will indicate that you have a higher lift camshaft. Measure the cam lobe across the highest part, and then again across the narrowest part, and subtract the two, then multiply by 1.48. This will give the valve lift. Stock valve lift for the A stamp cam is something close to .394". Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 30, 2009 Share Posted October 30, 2009 Was also thinking that to,its at the shop so I'll get a micrometer on it when Im back there. The cam was a stock cam as far as it looks but could of been reground. So If I use the stock cam from the flat top engine they shouldnt hit in theory right? I guess I could assemble it and turn the cam over on the bench to see if the valves come out below the head. That should tell me if they will hit the pistons or not. Quote Link to comment Share on other sites More sharing options...
Xnke Posted October 30, 2009 Share Posted October 30, 2009 No, it won't tell you that. the piston is moving up and down in the cylinder too. The L series is an interference engine, so the valves, when open, will protrude below the cylinder head surface. The timing between the valves and the piston is what keeps them from hitting, if you increase the duration or lift, then you need to check for clearance, since you have changed the timing of the system. Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 30, 2009 Share Posted October 30, 2009 I owe you a big thank you then. That was my missing link in it all. So...thinking outloud basicly, I can use the e88 head,on the block with the flat top pistons,if i time it so the valves dont hit the pistons. Now I just need to search and try to figure out my timing. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2009 Share Posted October 31, 2009 Actually, the notched pistons tell you someone put notched pistons in it... I have a set of those, NOS, never been in the car, they were a non-us offering and were marketed through the nissan motorsports offices in the USA as a 'performance option' piston. There are more than one E88 as well... Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 31, 2009 Share Posted October 31, 2009 Hmm,so what gain would it be to use them? I could easily rebuild both engines. By the time Im done rings and a rebuild set was close to $300 so it isnt to bad. I know theres 3 or 4 e88's I'll check this one to. So to clarify the way the valves are doesnt matter if its flat top or not? The notched would be just to bring the timing tighter? Just going to put this out there,Im having a slow night and might seem retarded haha. Im just overwelmed in trying to figure this out. Im looking and finding bits and pieces of what I need,but in my notes im writing down its kind of jumbled. e88/e31 head with flat top pistons is the same timing,if i put notched pistons in then I need to change the timing to bring the pistons and valves closer correct? Either way Im using the flat tops,and have to choose a cam,and figure out how to time it.......I just dont understand where my retardation of not understanding is coming from so I must apologize for that. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2009 Share Posted October 31, 2009 The notches are for valves... if you plan to cam the engine with big lift use the notched pistons. If you are sticking with a stock cam forever, then either will work just fine. I had L28 Valves in my E88 on the original L24 in my 240. It had flat tops that had close to 0.040" positive deck height (head gasket accomodation) and no issues with a stock cam. The guy I sold the engine to put in a fairly large cam and still had no clearance issues. You only know when you clay up the assembly. Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 31, 2009 Share Posted October 31, 2009 I wanted to run the bigger cam with the flat top pistons and e31. Keeping the high compression,but also running the bigger cam. Now that I know its just a matter of timing it all,I just have to figure out how,and thats where Im stuck Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2009 Share Posted October 31, 2009 No, it is not a matter of 'timing it all'... If your piston to valve clearance is insufficient they come in contact. There is nothing you can do but add clearance: Loose lift or cut notches in the piston. Define 'bigger cam'... What kind of lift are you talking? 0.575"? 0.620" at the valve? If not, and you are talking 1/2" lift or less...chances are good notching will not be necessary, especially with stock valves. The only way to know is to assemble the works and clay it up. Then work the pistons for clearance. Notched pistons would add more clearance at a slight penalty of compression ratio (less than .1, .2 CR point...) Only run the notches if you NEED to, but you were sounding like you wanted an 'assemble it with the least chance to screw it up' methodology and that would employ the notches. They don't affect CR that much. Anybody using a flat top in an L24 is not building a 'high compression' engine by any means. (Or even a stroked L24 like mine was, using positive deck height!) BIG cams like compression, you will not be making it with flat tops on an L24. It will not like a "BIG" cam...so again, define 'big'... I'm thinking your cam will be 460 lift, and far less duration than you think you need because of the low compression you will have using stock components. Now, running an 05L head, or even the early E31 head and the stroker L26 will boost the compression far more than any E88 flat top... You don't have 'dished' pistons, they are for all intents and purposes identical in terms of compression ratio with the head you use. This is all a stock buildup. Well under 10:1 compression no matter how you slice it, not high compression by any means---meaning again 'no big cams need apply'... Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 31, 2009 Share Posted October 31, 2009 Thank you for clearing that up. By high compression,I mean the 9:13:1 or so that the stock l24 and e31 gives over the l24/e88 thats 8:76:1 (im using the L engine program) The cam may not be huge,I also havent measured it. I figured that if the pistons needed the notchs it would be bigger then stock by abit,but nothing to huge I was hopeing somewhere around .480 http://www.racingheadservice.com/Information/Technical/PistonToValveClearance.asp this is what i have been reading and going by. But Im unsure of how much clearance I should be looking for. (i took note of the .080,and .100 but does that apply for all steel connecting rods and engines?)I know all the information is here,im just to slow to put it all together and probably making it more difficult then it should be,Once agian thank you for the help its greatly appreciated,I know not alot of people would try to help and explain. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2009 Share Posted October 31, 2009 crap, it didn't post... the clearance stated is fine, the only way to know where you're at is to physically assemble it and clay the tops of the pistons and go from there. I'd put in the flat top and check #1 before reassembly, and make the decision on which to reinstall from that check. Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 31, 2009 Share Posted October 31, 2009 Alright,thats what I was thinking to. I passed my retardation moment,forgot about it and came back to it and it seems to make sence now. piston to valve clearance .080 intake,.100 exhaust minimum Running it threw my head. start with the crank tdc(piston 1),and the cam with the mark pointing up(crank and cam keyways up?) then put the timing chain on lining up with the marks(but im not sure which ones theres 3 or 4 i think,looking into this),adjust valve clearance to .007 intake (Cold) and .010 exhaust (cold) Am I missing much/does it sound like jibberish or is it sounding alright? Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 31, 2009 Share Posted October 31, 2009 After you're set like that with #1 cylinder, rotate the crankshaft 720 degrees, then pull it apart to measure the impressions in the thinnest part of the clay on the head of the piston. That is a direct reading of the piston to valve clearance at it's closest point. This assumes camshaft timing is correct according to the cam card...but 4 degrees one way or the other shouldn't appreciably alter the results. And that is all the maximum you should have to move the cam to optimize the setup. Valve clearance is per cam grinder's specifications, you quote numbers, but I don't know your cam. Defer to cam instructions. Quote Link to comment Share on other sites More sharing options...
Guest eric_503 Posted October 31, 2009 Share Posted October 31, 2009 Thanks for the info once agian. I will get the cam specs tommorow and see if that helps more,I believe the .007 and .010 were for the stock cam. The engine the notched pistons are out of is a mystery engine to me,It did come with a 2400 ohc valve cover tho,and the notched pistons,and the heads been ported,so im assuming the cam isnt stock. On the stock timing gear for the cam is there a chart of what the different holes do,I know theres 3 drilled in it. Is that for advancing and etc? Quote Link to comment Share on other sites More sharing options...
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