yogib Posted January 30, 2008 Share Posted January 30, 2008 I have a F54 turbo block and a set of new flattop .030 ITM pistons to put in it.Other than surfacing the P90 for flatness I dont want to shave the head and open that can of worms If a thinner head gasket will give me the compression I need.Does anyone here know what compression roughly I will have with the P90-flattops and a thinner head gasket.I would like to do better than the 8.8:1 with normal head gasket.1mm or 2mm? I searched and didnt find anything. Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted January 30, 2008 Share Posted January 30, 2008 down load the L-engine calculator. I think the F-54, flat tops, 20 thous over, p90 head, 2mm head gasket = 8.2:1 CR ... but thats just from memory. Matt- Quote Link to comment Share on other sites More sharing options...
yogib Posted January 30, 2008 Author Share Posted January 30, 2008 I found this site. http://falconperformance.sundog.net/compcalculator.asp And calculated with a 1mm gasket,.030 overbore.3.50in. gasket opening,3.39in. bore,3.11 stroke,didnt know deck heigth so I went with 0 and flattops with no valve reliefs,and 53cc combustion chambers.Couldnt do the stock 53.6cc and came up with 9:1. So adding the .6cc and some more taken out due to unshrouding valves Im probably more like 8.5:1 with the 1mm gasket.I think Im going to be stuck with shaving the head.Bummer.I used the mm to inch chart at www.metric-conversions.org to help. Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 30, 2008 Share Posted January 30, 2008 You can get to 8.8:1 with a Felpro gasket (1mm). Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2008 Share Posted January 30, 2008 I'd shave the head and do the N head valves if you're running it NA. 8.8:1 compression is pretty low, and then if you want a thinner headgasket I'd use the HKS metal gasket. Quote Link to comment Share on other sites More sharing options...
yogib Posted January 30, 2008 Author Share Posted January 30, 2008 Ya I was hoping I wouldnt have to do the "P90 head shave Mod" but I guess I will have to shave it the .100 thou. and run the N42 valves.Any body have some good N42 valves they can part with cheap? That or I will have to buy the stainless from ArizonaZcar.com for around 200 bucks. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 30, 2008 Share Posted January 30, 2008 You can go to any machine shop and they can order you up some generic valves if you don't want to spend the money on the SS ones. I think there was a guy in OR selling SS valves super cheap. A couple guys were going to buy some and test them out, I don't remember ever hearing about them again... Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 30, 2008 Share Posted January 30, 2008 If your compression ratio goal is around 8.8:1, and the head is flat, don't waste your time and money shaving it and replacing the valves. You also need to shim the cam towers BTW. If you are looking for a CR in the 10:1 range (the most I would run on todays pump gas), then you will need to do the shave/N series valves/shims thing. You can run N42 or N47 valves BTW. Quote Link to comment Share on other sites More sharing options...
johnc Posted January 30, 2008 Share Posted January 30, 2008 I think Todd at Wolf Creek Racing has some used SS valves for sale. http://www.wolfcreekracing.com/. Quote Link to comment Share on other sites More sharing options...
yogib Posted January 30, 2008 Author Share Posted January 30, 2008 Whooooa! Thanks Z-ya I didnt realize until further investigating that the N47 has the same valves as the N42.I can just use my N47 valves off my current motor.I checked The Datsun Garage for that. http://www.geocities.com/zgarage2001/z.html Cool. Quote Link to comment Share on other sites More sharing options...
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