GD71240z Posted February 25, 2007 Share Posted February 25, 2007 Just got my n42 head back from the machine shop last week and thought I should post a couple pics. After I had finished porting it and unshrowding the valves I had the machine shop shave it .060, do a valve job and shave the intake/exhaust side to clean it up. With the .060 shave and unshrowding the valves chambers are now 41cc. This should give me a compresion ratio of 10.5:1 using a standard nissan head gasket on my f54 block with flat top pistons. The quench is much better now too. This is the first head I have ported so any comments/advise are apreciated. Greg Quote Link to comment Share on other sites More sharing options...
rwdawg2 Posted February 25, 2007 Share Posted February 25, 2007 That looks really good. Everything turned out very nice. hope everything turns out ok with results Power wise. Quote Link to comment Share on other sites More sharing options...
ecp48 Posted February 26, 2007 Share Posted February 26, 2007 I think you have a problem. It is my understanding that the N42 head will provide 9.8 to 10.5, depending on the head and head gasket (without cutting the head). The P90 needed to be cut .080 to reach 10.5. You may have a very high compression for the street. CC the head and do the math. You also might want to private message Pete Paraska (sp??) on this board. Check the L Series engine calculator as well. Quote Link to comment Share on other sites More sharing options...
GD71240z Posted February 26, 2007 Author Share Posted February 26, 2007 I have calcutated the compression ratio several times now and according to the lengine calculator a stock n42 head with a standard nissan head gasket on a l28 with flat tops gives a 9.82:1 c/r. My n42 head has 41cc chambers (stock is 44.6cc) and using the lengine calculator this gives me a c/r of 10.48:1. I have run the numbers on a couple different programs and I keep on getting the same result. Is there something that I am missing? Can someone double check my numbers for me? Thanks Quote Link to comment Share on other sites More sharing options...
Mack Posted February 26, 2007 Share Posted February 26, 2007 yeah, there is something you are missing..... the L engine calculator is kind of fubar-ed. running your numbers, I get a compression ratio of 10.8. get a cam with more duration or it will probably ping. Im running a MN47 with 39cc combustion chambers and MUCH better quench than even a shaved N42. It pinged, with a 256* cam and the stock fuel system. I went megasquirt and I havent looked back. Quote Link to comment Share on other sites More sharing options...
GD71240z Posted February 28, 2007 Author Share Posted February 28, 2007 Mack Thanks for running the c/r number for me. I was unawear that the lengine calculator was not accurate. The cam I have is a .460 lift 270 Int/280 Exh. duration. For now I was going to run S.U.'s with SM needles until I can aford megasquirt. The maximum octane available here at the pumps is 94, with the correct ignition timing I was HOPPING it would be ping free. After reading through posts for 3-4 weeks (before I decided to use my n42 head) I knew there was a good chance I may have problems with pinging. On the other hand there are a few people on this site that have had good results using the n42 head. I'll have to wait untill it warms up and some of the snow melts so I can swap engines and post the results. Quote Link to comment Share on other sites More sharing options...
DATZ Posted October 9, 2022 Share Posted October 9, 2022 On 2/24/2007 at 6:10 PM, GD71240z said: Just got my n42 head back from the machine shop last week and thought I should post a couple pics. After I had finished porting it and unshrowding the valves I had the machine shop shave it .060, do a valve job and shave the intake/exhaust side to clean it up. With the .060 shave and unshrowding the valves chambers are now 41cc. This should give me a compresion ratio of 10.5:1 using a standard nissan head gasket on my f54 block with flat top pistons. The quench is much better now too. This is the first head I have ported so any comments/advise are apreciated. Greg http://album.hybridz.org/data/705/IMG_0017.jpg http://album.hybridz.org/data/705/IMG_0020.jpg http://album.hybridz.org/data/705/IMG_0016.jpg It’s an open chamber cylinder head. There is no quench. Quote Link to comment Share on other sites More sharing options...
calZ Posted October 10, 2022 Share Posted October 10, 2022 You're replying to threads from 15+ years ago Quote Link to comment Share on other sites More sharing options...
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