78 280zcar Posted March 16, 2006 Share Posted March 16, 2006 OK, I originally had an N47 head on my 78, but it was in bad shape. I came across a P79 head for 125.00 rebuilt from a machine shop, so I bought it. What kind of compression changes am I looking at and does this type head really need flat tops to run normal compression. Thanks Quote Link to comment Share on other sites More sharing options...
78 280zcar Posted March 16, 2006 Author Share Posted March 16, 2006 I forgot to mention that I have an N42 block and stock domed pistons Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2006 Share Posted March 16, 2006 Dished pistons. Get the Lengine.exe utility and figure it out yourself. That's how I found the compression ratio that I gave you on classiczcars.com when you asked there. It's in the Download section here. Quote Link to comment Share on other sites More sharing options...
78 280zcar Posted March 16, 2006 Author Share Posted March 16, 2006 So I pretty much F--ked up when I bought this head:( . I dont want to have to buy flat top pistons because of this head, any other cheaper way I can bring compression back up with the P79 head? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2006 Share Posted March 16, 2006 Mill the crap out of it and put cam tower shims in. You probably didn't want to hear that answer though... Quote Link to comment Share on other sites More sharing options...
78 280zcar Posted March 16, 2006 Author Share Posted March 16, 2006 I already have a set of cam tower shims coming that will be here tomorrow at .015in. How much would have to be milled, what if I just shaved it .015 and put the shims on would that work? Or how about I just beat on it like that guy. LOL Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2006 Share Posted March 16, 2006 I don't know exactly, but this ought to give you an idea: http://www.geocities.com/zgarage2001/head.html Quote Link to comment Share on other sites More sharing options...
78 280zcar Posted March 16, 2006 Author Share Posted March 16, 2006 I was just wondering that wouldnt the D shaped recesses in the P79 make up for the change in compression, because the N47 has round recesses? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 16, 2006 Share Posted March 16, 2006 No, because the chamber is deeper. Download the Lengine utility and it shows you the volume of the chamber. That's the important part, not the shape. Quote Link to comment Share on other sites More sharing options...
cobraz240z Posted March 16, 2006 Share Posted March 16, 2006 Ok I have good news and bad news. Good news is that your ready for a turbo and or could run on 70octane hahaha:icon45: The bad news is for just a replacement its not that good you will get 7:52 with a felpro non shaved if you shave the Funk out of it you might get 8:1 I would get a N47 head from a maxima put the big valves shave it a bit and you will get about 9.5:1 I think some where around there give or take a little Quote Link to comment Share on other sites More sharing options...
78 280zcar Posted March 16, 2006 Author Share Posted March 16, 2006 I was thinking about doing that mod he has on this page http://geocities.com/zgarage2001/head.html I already have three heads for the valve spring shims and the longer valves from the N47, all I need is more tower shims and to shave the head .080. It says with dished pistons it will bring my compression to low 9's. I know it is little change but it would only cost me about $60.00 to do. Anyone ever done this mod? Quote Link to comment Share on other sites More sharing options...
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