exhaust valves hit pistons but intake valves did not ?

[oldnelly87]

i have a 355 dart heads 14:5.1 compression been winning with it my exhast valves hit my pistons their 1.6 but my 2.08 intakes did not and my cam is straight acrost .640 and my valve lash is .020 straight acrossed and i have .100 clearance when i built it heads where built to match spring pressure of cam and all . wondering if anybody has ran into this and what happen so i can fix it ?

[andy16]

valves

it is actually most common in engines i have been around that the exhaust usually will hit the piston before the intake. its pretty common. the piston will chase the exhaust valve up as valve is closing piston is coming to tdc. if you over rev or your springs are weak or there wasn .125 clearance you will see the kiss mark of the echaust valve on the piston. i recomend checking your exhaust valve clearance at -5 degrees before tdc thats where the clearances will be the closest on most sbc and check springs. if there just kissing the piston your lucky and should try and get it fixed soon this will cause premature ex guide wear in the head too. try flycuting piston less ex lift or duration or lower rocker ratio however you can get more clearance. hope this helps

[stockcar5]

if you have enough clearance on the intake you can advance your cam to gain ex clearance.