Guest christo Posted January 7, 2004 Share Posted January 7, 2004 Hi, Hopefully you guys can help me out. I just rebuilt block L 28 block attached new aftermarket flattops. They seem to protrude twenty thou. I have a milled E31 with all the mods including larger valves This head I believe has now been slightly milled twice. The head width according to the machinist is 4.235 The question will I have clearence, do they have to be fly cut. Thanks, Brain itch Quote Link to comment Share on other sites More sharing options...
Guest Joe17 Posted January 7, 2004 Share Posted January 7, 2004 how radical is your cam? how far down do your valves go? what is the gap between the valves and the deck when the valves are open? Quote Link to comment Share on other sites More sharing options...
Guest BigWhyteDude Posted January 7, 2004 Share Posted January 7, 2004 Isn't this a candidate for the play-doe test? Andrew Quote Link to comment Share on other sites More sharing options...
Guest christo Posted January 7, 2004 Share Posted January 7, 2004 Is the flatop sticking out normal? Quote Link to comment Share on other sites More sharing options...
Guest Zachb55 Posted January 7, 2004 Share Posted January 7, 2004 i think it is liveable if your valves wont hit it and your head sits on the block without any interference. like they said, play dough test. -Zach Quote Link to comment Share on other sites More sharing options...
Guest christo Posted January 7, 2004 Share Posted January 7, 2004 I think the other prob might be to high a compression for the cast pistons. Quote Link to comment Share on other sites More sharing options...
Guest Joe17 Posted January 7, 2004 Share Posted January 7, 2004 i was thinking about that.. and yes that might be a problem. throw the head on and crank the engine over by hand..... if your good.... then go form there. Quote Link to comment Share on other sites More sharing options...
katman Posted January 7, 2004 Share Posted January 7, 2004 That figures to be around a 10.9:1 compression ratio depending on the combustion chamber mods. The piston sticking out 0.020 ain't too big a deal (on the 1973 L24 that's how much the stock pistons were "positive deck") since the gasket is usually about 0.052 thick, but as previously mentioned valve clearance could be a problem depending on the cam. Play Doh, fer sure. Quote Link to comment Share on other sites More sharing options...
Guest christo Posted January 7, 2004 Share Posted January 7, 2004 After consulting with ten different people the outcome is I can't make it work with the E 31 I have. Unless I want to see what a valve stuck in a flattop looks like. I do have a stock N 42 which I'm going to mildly work over. I'll have to put the E 31 away for a serious setup or maybe sell it on ebay. I already have a full race GT 2 engine ready to go. I'm building this one for the three novice races I have to do this season. After that I'm going to swap engines. Thanks, Chris Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted January 7, 2004 Share Posted January 7, 2004 Why not just run the 2mm thick HKS headgasket? Quote Link to comment Share on other sites More sharing options...
Guest christo Posted January 7, 2004 Share Posted January 7, 2004 I was thinking of that also. Since the head has been milled twice I think its getting kind of dicey. Piston to head might only be .035" Maybe I'll try the 2mm and do the putty test. Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 7, 2004 Share Posted January 7, 2004 The flattops will stick up a little past the deck. I built one last winter, and I'm building another this winter. I used an N47 head on the one I did last year (I had it, and it was rebuilt). Engine runs strong. No interference problems what so ever, but then again, I used the stock cam. I'd take some measurements before you bolt the head on to be sure. Pete Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted January 7, 2004 Share Posted January 7, 2004 well we ran a 500 lift cam on a P79 milled 110 thousandths on a flat top 280ZX engine with no issue's, so I wouldn't be scared unless the cam is way bigger then that. Quote Link to comment Share on other sites More sharing options...
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