Bo Knows

In my 1990 330 hp 454 I put Crane cam # 133802 with 529 - 525 lift, new Crane valve springs with closed pressure at 90 lbs & open pressure at 268 lbs, adjusted at zero lash then 1/2 turn, and when it fired up for the first time I bent or broke 8 stock push rods. Stock spring pressure is 85 lbs closed & 240 open. anybody got any ideas why this happened ?

Bo don't know ???

Steve 1

The Cam was a nice selection, But the number “8” does not sound good assuming everything else is ok sounds like stacking of the Intake springs,But when adjusting the valves you would of seen that ! Here is what Crane says about it

) Mechanical interference.
There are many factors that can cause mechanical interference.
(1) Spring coil bind: This is when all of the coils of the spring (outside, inside or flat damper) contact each other before the full lift of the valve. We recommend that the spring you are using be capable of traveling at least .060" more than the valve lift of the cam from its assembled height.
(2) Retainer to seal/ valve guide boss interference. You need at least .060" clearance between the bottom of the retainer and the seal or the top of the valve guide when the valve is at full lift.
(3) Valve to piston interference: this occurs when a change in cam specs. (i.e.; lift, duration or centerline) is enough to cause this mechanical interference. Also: increased valve size, surfacing the block and/or cylinder head may cause this problem. If you have any doubt, piston to valve clearance should be checked. Minimum recommended clearance: .080" intake and .100" exhaust.
(4) Rocker arm slot to stud interference: As you increase valve lift, the rocker arm swings farther on its axis. Therefore the slot in the bottom of the rocker arm may run out of travel, and the end of the slot will contact the stud and stop the movement of the rocker arm. The slot in the rocker arm must be able to travel at least .060" more than the full lift of the valve. Some engine families, like small block Chevrolet, have stamped steel rocker arms available in long and extra long slot versions for this purpose.

Hope everything works out ok! Best Regards

Bo Knows

Update:

After closer examination I discovered all of the bent push rods are intake valve push rods only ??

Bo

tripps

OUCH, sorryto hear that!!!!,i did it once when i put a cam in my 409,wish i still had it,but was the problem was,i put the cam in wrong,very easy to do. at 525 lift i think it should work,but do as the above post says first,but you should yank the heads and make sure there are no bent valves or it could get worse and check your timing marks good luck, tripps

FloridianSon

Never bent the push rods but when I was younger I was working on duel overhead cam and had it out of time and did some valves, From then on I allways turn the motors over by hand one good time before putting the juice to it.Hope you get it fixed. James

GregP

On "new" hydraulic lifters it's real easy to think you found "zero lash" when in fact you have the plunger bottomed (it takes very little resistance to bottom the plungers since their is no oil in them). In this case when you start the motor you can bend the push rods. I've found the only truly reliable way to find "zero lash" is to have the intake off and look for when the plunger "just" starts to depress below the retaining clip.

BBC intake and exhaust push rods are also different lengths. Is it possible you have all one length, or have them backwards? (just asking to all the possibilities).



-Greg

Dave F

Check to make sure the Crane cam doesn't use different length push rods.

Crane sometimes has a larger base circle than stock cams therefore they need shorter pushrods than stock.

just a thought
DAVE

Bulldog

You can check for valve damage by pressurizing the cylinders with compressed air. Loosen all rockers so valves will stay shut. Pressurize each cylinder- I have a snap-on compression tester with a separate hose that can be connected to a quick coupler air fitting. Make sure yor hands, etc are away from belts- the motor will try to spin. Listen and feel for air flow up through the carbs. If an intake is even slightly bent you'll know.

If you can't tell, try to find someone with a leak-down tester. You will get a reading to work with.

Good luck, and hope you only need pushrods.

Bulldog

Bo Knows

Thanks to all that replied,

Pulled off intake to check valve adjustment at zero lash - ok, pulled off timing cover to check timing marks - ok, checked for rocker arm slot clearance - ok, checked for spring bind - ok, took off one intake valve spring & reassembled & adjusted to zero lash, turned engine over while moving valve up & down to check clearance to top of piston, guess what, intake valve kisses piston as its opening & stops hitting piston before lifter reached top of cam lobe. Checked the exhaust & not much clearance there either! I thought I was ordering a rather conservative camshaft so this wouldn't happen ! Motor is stock 1990 330 454 8.0 compression, with notched flat top pistons. anybody got any ideas where I can go from here or why this happened.

Thanks for all your input

Bo

mcollinstn

Always clay-check your setup before buttoning it up. Unless you know sombody running the exact same combo who DID measure with clay, then you have no baseline.

They make a piston cutter you can use with the slugs still in the block. You just replace a valve with the proper size cutter and bolt the head on. Set the depth stop and crank until you hit the stop. Shopvac all the shavings out.

This works well enough in motors turning under 5500rpm. Over that, you should rebalance the rotating assembly.