Thread: 305H cam degree help

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Hey guys, this is my first post, and i really need some help, I have a 350 .30 over. swapped the cam to a 305h and sounds like valves are hitting the psitons. We checked by hand and didnt seem like they were hitting but i started motor and it had a really bad clatter.

My buddy said he degreed the cam but i didnt see it happen. Last i saw it the marks were dot to dot.

Could this cause valves to tap pistons? im pretty sure yes but dont want to rip motor apart and be wrong.

heads are 462624 for a 350 with 1.94 ,1.5 and pistons are flat top

If I read the cam specs right it has a .540 lift. And with what little info given, I am guessing the heads are an iron head. They ussually only have a .510 valve spring hieght limit. And maybe the cam is too tall for your valve springs causing them to bind.

Cam is .525 lift heads are from 79-85 350, stock. Anyone have any ideas?

What pistons are in the engine and what was the deck height set at??? In any case, it's time to get a head or two off and see what's happening.... What was your valve to piston clearnce when you assembled the engine???????

It was less than a professional build. ripped heads off thew new cam in turned engine by hand and seemed okay. put all back together.

pistons are .30 flat top fly cut.

What was the guy saying about the springs not going over .510 lift?

just has loud tick from every cylinder. Anything i can check before i rip heads back off?

You could check the springs for coil bind....too much lift for the spring installed height, will bend pushrods and break springs, retainers, rocker arms, and or all of the above....

Were the pistons fly cut, or are you just referring to the stock valve reliefs???? Sounds like waaaaaay too much cam for the rest of your engine anyway.... With that much lift, should have checked piston to valve clearance with some clay on top of the pistons and crank the engine over by hand.....

A click is hard to define on here without hearing it, could be improver valve adjustment, valves hitting the piston, or other things..... Have the heads been milled???

took motor apart, you were right on. bent push rods and can see where valves were tapping pistons. time to start over wanting a 12 to 1, 383 with a nasty sounding idle.

They are flat top pistons and have valve reliefs on one side and lil half moon in the middle of piston, my buddy called them fly cut maybe hes wrong about this too.


Sorry guy im new to high perf and trying to learn, but everyone around here drives hondas and imports, and everyone else obviously donst know what they are doing

Well, now you know what's wrong, time to put it together correctly.... Just don't think you're the only one that's ever made that type of mistake.....and don't ask me how I know that!!!!!!!

Originally Posted by FL_Smokin_PSD

It was less than a professional build.

What was the guy saying about the springs not going over .510 lift?
?

What I was saying about spring height is probably what caused the problem you just found out about. Before you put new push rods back into the motor. You need to have the valve springs changed out to match the higher lift cam. the current springs are probably a .510 maybe even lower. A .510 spring is a Z28 spring, maybe even lower from a passenger car or truck. The cam is shoving the valve open and the current springs only can travel at most .510. And the cam wants to go .525 causing the valve springs to bind, causing the push rods to bend.

you need to check the valve spring height were you are at before you just throw springs in thinking there going to work ? on a race engine for head work this take some time were some think just throw the springs on and go. if the heigth is not there you can stack your new springs to .or like i said someone shims the right spring if down on pressure by added shim will take way from the set up height .height can be added by + valve locks deferent +retainers longer valve s and spot facing the spring pockets you do not want to spot face the spring pockets much if any and you need to check you valve guides to the inside of the retainer if off you at the lest will smash your valve seals .500 lift cams can hit but you have to look at more then just cam lift lobe sep and cam dur and over lap add to this as for the stock valve reliefs if you have bigger then oem valve dia can hit the pistons to .if you do not know much about engines you need to get up to speed or you will be back were you are now with just more money spent watch out for friends that know every thing that learn what not to do next time on your wallet

Yeah, I usually let the know-it-alls show me how smart they are on THEIR OWN engines!!!!!!

I see you are in Palm Bay. Call Frank at Space Coast Automotive repair on State Road 3 in Merritt Island. He knows all about sbc chevys and can repair it for you. Tell him Scott Brown sent you.

if the pistons hit the valves, they bend. then you loose compression, THEN the engine stops running. check for spring bind. Pull the rocker cover, and turn the engine over by hand. Pick any rocker arm, and watch it, slowly turning the engine over till the rocker arm is fully deperssed. Take a feeler guage, and see how much play is left between the coils. I bet you find zero.