mattsny83 Posted March 16, 2012 Report Posted March 16, 2012 Just put a 421 cub togther going to run alky ring gap was .013. Domes are 18 cool head. Sea level around 1300 i only have 150 psi. I know i need more then that what you think could be my problem Quote
sheerider11 Posted March 16, 2012 Report Posted March 16, 2012 Base gasket thickness? What crank you have 4 10? Quote
mattsny83 Posted March 16, 2012 Author Report Posted March 16, 2012 Squich is .06. Crank is hot rod long rod 4 mill crank Quote
vulvafan537240 Posted March 16, 2012 Report Posted March 16, 2012 (edited) What thickness base gasket? .012 is what most 421's run. You didn't use a stock. 030 gasket did you? Also a dumb question. They are cub alky domes right? Edited March 16, 2012 by volfan537240 Quote
mattsny83 Posted March 16, 2012 Author Report Posted March 16, 2012 What thickness base gasket? .012 is what most 421's run. You didn't use a stock. 030 gasket did you? Also a dumb question. They are cub alky domes right? i got the gasket and domes from jhon sand toyz told him what i was doing and he sent me domes and a gasket not sure on gasket thicknest Quote
vulvafan537240 Posted March 16, 2012 Report Posted March 16, 2012 Was it a single gasket or 2 separates? Quote
camatv Posted March 17, 2012 Report Posted March 17, 2012 the alky 350 i have runs about 145 psi kicking. alky 421 cub i do is usually around 155 - 165 but i use custom domes, and run around 14-1 to 16-1 ratio Quote
EvilBanshee Posted March 18, 2012 Report Posted March 18, 2012 Is your engine broken in? YOu ll need 4 hours on it for the rings to seat. Makes a big difference Quote
mattsny83 Posted March 20, 2012 Author Report Posted March 20, 2012 No have not even fired it up yet. How much will it change ???? Quote
RadarRacing Posted March 20, 2012 Report Posted March 20, 2012 If you have .060 squish that is generally more than we run but not bad if its just a play bike. We usually run around .040-50 give or take .005 . If it is cranking 150 without ever being ran then dont worry about it. It would be 10 or 20 more with a warm broken in motor. A 421 usually runs a 12 to 20 thous gasket depending on the builder. Quote
mattsny83 Posted March 20, 2012 Author Report Posted March 20, 2012 It going be drag bike sheer inframes 39 pwk on alky Quote
EvilBanshee Posted March 20, 2012 Report Posted March 20, 2012 My 421 jumped up 25psi after a few days of riding. Roughly 3 hours worth of riding. Also make sure you break it in With lots of throttle movement. Lots of WOT!! Push those rings out!! Quote
RiDeTRIKES250R Posted March 21, 2012 Report Posted March 21, 2012 do 3 heat cycles. start cold, let it run for 4-5 minutes or until it gets to operating temperature. then shut it down, let it cool completely and redo. 3 heat cycles and you should be good. Quote
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