Thread: need help, pisron hits valve

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I'm building my first mild 454 (.060), I was done with the short block assembly yesterday. I installed the Cyl. heads, intake and exhaust pusrods, and rocker arms on one cylinder I turned the crank over and it gets stuck. Exhaust valve hits dome of piston. Is there anything I could do to fix this without changing the rotating assembly or cyl heads. (Could i get a smaller cam) black spots is where the valves hit (pics below). I have spent toooo much money on all these parts and machine work, pls help.
Engine specs
*speed pro hyper. Part # ZH581CP60 Dome height .340" W/two valve relief
*Standard rocker arms 1.72
*stock length pushrods 8.280"/9.250"
*Elgin E930K cam .503"/.528" 292/302 (214/224 @.050) LC 112 w/ matching springs
* stock length stainless steel valves 1.72/2.065
THanks

Originally Posted by sal0327

1. I'm building my first mild 454.........
2. Dome height .340"

Is it just me, or do these statements not seem to go together?

what heads ? wrong heads for piston if hitting hi up on the domes.as for the EX valve hitting.the cam is not big sure your timming marks are lined up right . did you degree in the cam ? intake valve allways hits first allmost 99 of the time

I'm with Pat on this, but why the big dome on the pistons? AND, are you running an open chamber head?

Sounds basic, but I had to ask.

i feel abit much CH for dur 214 @ 050 on a 112 ? what is it going in to ?that piston with a 119 open chamber should be 10.2

Hello, the heads are 049's. Person i spoke to at summit prior to buying pistons told me It should be around 9.5:1 compression. The timing marks are dead on. the engine is going into a 72' nova mostly street driving. I'm starting to see a lot of money down the drain. What should i do? If I buy new set of pistons do I need to rebalance the rotating assembly? thanks

you can always find out how much relief you need and remove pistons take them to machine shop and have the reliefs cut out. Then weigh the pistons for balance.

Originally Posted by sal0327

Hello, the heads are 049's. Person i spoke to at summit prior to buying pistons told me It should be around 9.5:1 compression. The timing marks are dead on. the engine is going into a 72' nova mostly street driving. I'm starting to see a lot of money down the drain. What should i do? If I buy new set of pistons do I need to rebalance the rotating assembly? thanks

no that cam should fit i have put bigger in .i have had the intakes allways hit when bigger valves were put in or over milled did you degree the cam? try retarding the cam 4 degree and see it that helps yes you can get the pistons fly cut there other ways to. i done all of them over the years the ex is the ez side to fix .now the pistons are on the rods it s not so EZ to fly cut them less they are floating pins they have to come off the rods to fly cut them

no the cam was not degree, I know is a silly question, How could i retard the timing if my crank sprocket has only one slot for the woodruff key? when I test fitted the other day, i just had pulled the new lifters out the box ( I didn't sink them in oil first, does it matter I know is critical when you start up the engine) I notice when i adjusted the valves on that cylinder the adjusting nuts went half way down the stud. Thanks for all the input.

I think you over tightened the adjustors forcing the valve part way open before you started rotating it to ck V-P-----or the cam wasn't all the way into the block and you hooked the lifter on another cam lobe

well first off you need to check your piston to valve with a solid lifter and some very ligth test springs . and you can buy a 3 key way timing set or cam bushing or key but not to be mean but you need to know some basic stuff .you should read up on this or fine someone were you are that knows abit about this to help you .that cam is not that big and should fit you are doing some things wrong and if you not going to fined out whats going on first by checking cam timing then ligth set up springs with a solid lifter set at O lash

if you do not get the lifters on the money you will wipe the cam bbc love to eat cams

Hey pat i dont know too much about big block chevys so i plead ignorace but would 4 degrees make that much difference if the exhaust is hitting like it is now? the valve hit pattern doesnt look right on the silly putty or am i looking at it wrong?
Big bumps on those pistons though

I'm certainly no BBC guy, but should the piston be that high out of the block or am just seeing things in your picture????? Looks like the top of the piston is dang near 1/8" above the block?????

Originally Posted by canadianal

Hey pat i dont know too much about big block chevys so i plead ignorace but would 4 degrees make that much difference if the exhaust is hitting like it is now? the valve hit pattern doesnt look right on the silly putty or am i looking at it wrong?
Big bumps on those pistons though

it going to tell that way the cam in the engine but but 4 will give you about 020 or abit more . it may not take much hard to say. if you do not try any thing ??? he said the rocker were crank way down to far?? so they could be hanging open ????hell i do not know what he did .i am not there but you have to start somewere i cut more then one set up pistons and i have moved more then one cam not my first timewere are they hitting ? if the ex was hitting it would make a line cross the dome the clay would be cut .i do not see that .i am thinking he crank the rockers all the way down and there hitting .1 he needs a solid lifter to check the pv so valve timing is rigth and is at O lash .2 ligth test springs would be nice to use but then what do i know