titanium Posted February 8, 2006 Share Posted February 8, 2006 I've done about 5 different calculators and they all give me different numbers Heads are 70cc http://www.performancecenter.com/autoparts/edelbrock/edl60739.html Pistons are dished 12cc 4.03" bore 3.75" stroke Standard autozone felpro head gaskets. I'm getting numbers from 10.2 - 8.7 Quote Link to comment Share on other sites More sharing options...
mobythevan Posted February 8, 2006 Share Posted February 8, 2006 I get 9.17 static CR using 4.03 bore 3.75 stroke 70cc head 12cc dish .025 piston to deck .040 head gasket thickness 4.100 head gasket bore Quote Link to comment Share on other sites More sharing options...
jap tin Posted February 8, 2006 Share Posted February 8, 2006 how far are your pistons in the hole? Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted February 8, 2006 Share Posted February 8, 2006 If it hasn't been decked shouldn't it be approx. .015 to .017? Mike Quote Link to comment Share on other sites More sharing options...
mobythevan Posted February 9, 2006 Share Posted February 9, 2006 With aftermarket pistons, the deck clearance may be more, he would really have to give precise measurements for the head gasket thickness, head gasket bore and piston to deck, but 9-9.5 is going to be real close I'd say. Quote Link to comment Share on other sites More sharing options...
titanium Posted February 9, 2006 Author Share Posted February 9, 2006 http://mywebpages.comcast.net/khartnett232402/home.htm This guys got deeper dished pistons 19cc and stock LT1 heads 67cc and hes getting 10.95:1 My friend who I trust has been doing 99% of the work on this car and is also an automotive engineer is calculating mine to be even higher then that motor. Heres a article from Streetrodderweb.com "Prior to our arrival, Hye-Tech had assembled the Eagle SIR 5.7-inch I-beam rods to the Keith Black hypereutectic 197 pistons. With their 12cc dish, they yield a 9:1 compression ratio with our 76cc head chambers--perfect for current low-quality pump gas." So larger chambers and same dish = 9:1 http://www.streetrodderweb.com/tech/0205sr_puller/ http://www.flatlanderracing.com/kbpistons_383.html This says @ 63cc head with 12cc dish you'd get 10.3 and with 76cc you'd get 9.1 http://www.cnc-motorsports.com/product.asp?ProdID=8072 And this says with 64cc 9.5 with 76cc 8.6 No ones numbers match!! GAQhh Quote Link to comment Share on other sites More sharing options...
fastzcars Posted February 9, 2006 Share Posted February 9, 2006 Just because HE said he's getting 10.95-1 doesn't mean he"s getting it. You just can't bend physics. I pluged his numbers in KB pistons website , and I get 8.4. The Lt1 cylinder heads have 58cc. So I pluged that in the calculator and I get 9.8. So I just can't see how He could get almost 11 to 1 compression with the numbers he has on his webpage. Obviuosly there is some misinformation or wrong numbers. NOw if you plug in a -19 cc in the calculator you get 12.7 to 1. But you see by adding the minus sign to piston volume you are actually INCREASING the volume the the piston takes up in the bore. In essence you are putting in a 19 cc DOMED piston NOT a DISHED piston. I think that's where the confussion is coming from. NOw of courese we are taking some measurements from the air,like gasket thickness, gasket bore size, deck clearence. So simply substituting the gasket from a 40 thou to a 15 thou, you can raise compression by almost half a point. Don't worry about someone else's claims, just do your own calcs and match everything together as far as head flow , cam specs and compression ratio. They all got to complement each other. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted February 9, 2006 Share Posted February 9, 2006 This guys got deeper dished pistons 19cc and stock LT1 heads 67cc and hes getting 10.95:1 How is he measuring that? Quote Link to comment Share on other sites More sharing options...
titanium Posted February 9, 2006 Author Share Posted February 9, 2006 My friend did the math again 8.6. I'm in the market for a supercharger and quick Quote Link to comment Share on other sites More sharing options...
Pyro Posted February 9, 2006 Share Posted February 9, 2006 I'll give it a try and show my work. 383 is about 47.875 cid/cylinder or 784.5cc's/cylinder cylinder volume= 784.5cc gasket volume = 8.6cc piston in the hole=4cc cylinder head=70cc piston dish=12cc total volume with piston at bdc= 879.1 cc total volume with piston at tdc = 94.6 cc Compression ratio is 879.1/94.6 = 9.29:1 cr. Assuming the piston is below the deck 0.020". Quote Link to comment Share on other sites More sharing options...
titanium Posted February 10, 2006 Author Share Posted February 10, 2006 Thanks for all your help guys, to save money I've decided to just put in new forged pistons and raise the compressoin up to 10-10.5. The current ones are Hyperutectic so I dont want to risk boost and shatter something. http://www.performanceauto.us/store/product_info.php?cPath=2_18&products_id=475&osCsid=abab7385ac71e83f823b64960d652869 shooting for 500 hp. Quote Link to comment Share on other sites More sharing options...
Pyro Posted February 10, 2006 Share Posted February 10, 2006 15 psi of boost on a 350 goodwrench engine will make 500hp. Your 500 hp, turbo V8 goal should be pretty easy to get. good luck Quote Link to comment Share on other sites More sharing options...
SHAI Posted February 10, 2006 Share Posted February 10, 2006 the price for the heads seems fairly cheap. how well do they perform? should I accept a big increase in power with a mild 230 cam? Quote Link to comment Share on other sites More sharing options...
AdrianZ Posted February 10, 2006 Share Posted February 10, 2006 I'll give it a try and show my work. 383 is about 47.875 cid/cylinder or 784.5cc's/cylinder cylinder volume= 784.5cc gasket volume = 8.6cc piston in the hole=4cc cylinder head=70cc piston dish=12cc total volume with piston at bdc= 879.1 cc total volume with piston at tdc = 94.6 cc Compression ratio is 879.1/94.6 = 9.29:1 cr. Assuming the piston is below the deck 0.020". you win Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 10, 2006 Share Posted February 10, 2006 read thru the links (YEAH ITS WORTH THE EFFORT) http://www.blainetech.net/articles/ http://cochise.uia.net/pkelley2/crc.htm http://members.uia.net/pkelley2/DCR_FAQ.html http://cochise.uia.net/pkelley2/DynamicCR.html http://www.csgnetwork.com/compcalc.html http://kb-silvolite.com/calc.php heres some differant calculators http://www.kb-silvolite.com/calc.php?action=comp2 http://www.wallaceracing.com/dynamic-cr.php http://www.smokemup.com/auto_math/compression_ratio.php http://not2fast.wryday.com/turbo/compression/cranking_pressure.shtml average the results Quote Link to comment Share on other sites More sharing options...
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