Guest butlersZ Posted September 30, 2003 Share Posted September 30, 2003 Out of the E88, N47, and the P79, which is the best head to use on an NA L28 F54 with flat top pistons and '72 SU's? I have 3 heads sitting on my coffee table and there is a noticable difference in the combustion chamber design. The E88 is like a standard chamber with a crappy quench area, the N47 has a heart shaped design with some sharp edges and the squish area near the plug sucks, and the P79 has a heart shaped combustion chamber with smooth edges, a nice high quench design, but has the biggest chamber and lowest compression of them all. Now the P79 was shaved and I have the shims but am not sure of what the compression ratio would be. Currently the E88 was on the motor with a 268 reground cam and now that the head is off I can see that the valves were hitting pistons! little notches are on them now. Not too serious damage, any suggestions? Oh and the pistons do come above the deck on the block about 1/32". Thier P79 pistons. I want the high compression of the E88 but are the other heads any better due to combustion chamber design? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 30, 2003 Share Posted September 30, 2003 Someone out there has a web page that discusses using a P79 or a P90 (same chamber) and milling it for compression and using the shims to get the timing chain back to normal. I haven't been able to locate that page lately. Hopefully someone will know where it is. I think that's your best bet. The E88 came in 2 or 3 variations, sounds like you have the boat anchor version with no quench whatsoever (I've got the same head sitting in my garage). I wonder if the valves actually hit the pistons. Even if they just barely touched you would have had some driveability issues at the very least. It may be previous damage, but I seriously doubt that valves and pistons came in contact and you kept on driving the car without realizing it. Are you sure that those aren't flycut pistons? Jon Quote Link to comment Share on other sites More sharing options...
Guest butlersZ Posted September 30, 2003 Share Posted September 30, 2003 Yes, I'm sure the pistons are not fly cut. They are well were actually hitting the pistons. The weird thing is that #1,2,3,4,6 all have marks of different depth from the valves hitting them and the #5 has none! Crazy. I was just looking at the head with the valves still in it and you can see where the valves were hitting. Perhaps my cam timing was off by a few degrees. I know that while I was driving there was no strange sounds but at idle there was a ringing sound and now I know what it was. Any preferences on choice anyone??? Quote Link to comment Share on other sites More sharing options...
texasz Posted October 1, 2003 Share Posted October 1, 2003 For the easiest cheapest best compression you can get with the F54 block and flat-top pistons you need to locate an N42 head. This is a bolt on improvement! There is no milling, shaving or other work to be done and you will come out with about a 10:1 compression ratio. On the other hand you could get a P90 (NOT a P90a) and do some additional work such as milling to get you to about the same place as the N42. Here is the site that jmortensen was talking about: http://www.geocities.com/zgarage2001/z.html You will also want to check this out: http://www.geocities.com/row4navy/ Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 1, 2003 Share Posted October 1, 2003 That's the page I was talking about! Thanks texasz. I'll bookmark that one. Jon Quote Link to comment Share on other sites More sharing options...
texasz Posted October 2, 2003 Share Posted October 2, 2003 I also have an engine calculator that I want to attach but I just can not figure out how to attach a file, maybe this board does not allow that. Any how, if you want it I will gladly email it to you. I got it from a member on another Z car forum and do not know personally about how accurate it is but the members of the other forum say that it is pretty accurate. Quote Link to comment Share on other sites More sharing options...
Guest angryAJmonotone Posted October 7, 2003 Share Posted October 7, 2003 this should lead to a thread with an engine calculator on it: http://www.classiczcars.com/forums/showthread.php?s=&threadid=1292 Quote Link to comment Share on other sites More sharing options...
texasz Posted October 7, 2003 Share Posted October 7, 2003 Thanx angryAJmonotone, that was the one I was talking about! Where in TX are you located? Quote Link to comment Share on other sites More sharing options...
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