&%^%$&...O for 3 Part 2... And the winner is

[midnight sun]

Another push rod poked a hole in the rocker arm.  Last time it was the #5 intake, this time the #6 exhaust.  

Easy to fix but there has to be a reason this keeps happening.  Rockers are 1.5 ratio, standard valve springs, standard push rods, 327 camel hump heads.  I guess I can carry 3 or four sets of rockers and pushrods with me all the time!!!!

Im stumped.

Later

[enjenjo]

I may have mentioned this before, but Crane, and a couple of the other cam manufacturers make a plastic jig for checking rocker geometry. My guess is the geometry is off, and you may need shorter pushrods. The cause could be a decked block, milled heads, more cam lift, valve stem length, how deep the valve seats are set, or any combination of these.

[slocrow]

I think big Frank's got it surrounded. You are getting sufficient oil up there, aren't you?

[midnight sun]

I think big Frank's got it surrounded. You are getting sufficient oil up there, aren't you?

Yeah, plenty o' oil.  Im gonna check with Crane and Comp cams tomorrow for one of their length checking pushrod setups.  In checking my spec sheet when I had the machine shop prep the engine, it does show that the block was decked so that could make a difference.  Everything else seems to check out.  Shorter pushrods sounds like the answer but Im gonna make sure before I jump too far too fast.

Thanks for your input.

Later

[Bruce Dorsi]

Shorter pushrods sounds like the answer but Im gonna make sure before I jump too far too fast.

-------------------------------

One possibility is that the slot in the rocker arm is too short, and the rocker is hitting the stud before the valve is at full lift.

If my memory serves me, a paper-clip is the approriate instrument to measure for adequate clearance.   ....With the engine rotated so the valve is at maximum lift, the paper-clip should fit between the rocker arm and the stud.  

I believe most aftermarket rockers have elongated slots to provide the needed clearance.  .....If you are using old OEM Chevy rockers, they may have the "short" slots.

[midnight sun]

One possibility is that the slot in the rocker arm is too short, and the rocker is hitting the stud before the valve is at full lift.

If my memory serves me, a paper-clip is the approriate instrument to measure for adequate clearance.   ....With the engine rotated so the valve is at maximum lift, the paper-clip should fit between the rocker arm and the stud.  

I believe most aftermarket rockers have elongated slots to provide the needed clearance.  .....If you are using old OEM Chevy rockers, they may have the "short" slots.

Thanks Bruce, Ill check that out.

Later

[river1]

as i posted in another thread

adversity builds character    

you're becoming quite a character  >


later jim

[Bruce Dorsi]

Two more thoughts, Jack:

Is it possible the valve springs are compressing completely, and becoming a solid mass?  
.....There should be clearance between the coils when the valve is at full lift.  
.....I think .010"-.015", checked between the coils with a feeler gauge is correct, but I don't trust my memory.  Maybe someone else will chime in.  

Another possibility is that the valve spring retainer is hitting the top of the valve guide.  ....This too, can cause the problem you experienced, since the valve can not open further but the cam has not yet reached maximum lift.  
....With the valve fully open, there must be some clearance beteen the valve spring retainer and the top of the valve guide.  

Hopefully, your problem is something easily corrected!

[Crosley.In.AZ]

as posted check geometery and push rod length.

I had an engine long block i bought years ago for a customer.  It had .100 long push rods ( by mistake) in the 350 chev motor.

this caused many troubles with rockers and studs on a near stock engine

[kb426]

Rule of thumb is: .050" clearance on all valve gear. Coil bind on springs, pushrods in slots, retainer to guide, rocker to stud,anywhere there is a chance for interference.

[midnight sun]

Another push rod poked a hole in the rocker arm.  Last time it was the #5 intake, this time the #6 exhaust.  

Jus a quick update.  I checked the spring pressure and its 105-110 lbs.  There is no coil bind and the rockers are not hitting the studs.  All clearances seem to be in tolerance and the push rods are not too long either.  Everything points to the rockers being bad.  Im replacing them with OEM chevy small block rockers.  (The ones with the little Triangle stamped into them.  Guess time will tell.  

Thanks for all of your ideas

Later

[kb426]

Years ago I had a 38 Chevy with a 283 bored to 4". I had the same problem. I don't know how many miles it takes to wear out rockers but I was there.

[midnight sun]

Years ago I had a 38 Chevy with a 283 bored to 4". I had the same problem. I don't know how many miles it takes to wear out rockers but I was there.

I replaced them with roller rockers and have no problems since.  Go figure!!

[EMSjunkie]

Years ago I had a 38 Chevy with a 283 bored to 4". I had the same problem. I don't know how many miles it takes to wear out rockers but I was there.

I replaced them with roller rockers and have no problems since.  Go figure!!

I was gonna suggest the stock replacement ones from
Summit, the ones with the grooved pivot balls.

Had the same problem with a sprint car motor.
OEM ones just didn't cut the mustard, so the speak.

never had anymore problems after replacing the OEM with the ones
from Summit.

just my 2 cents worth.


Vance

[moose]

Another thing to look at is the rocker studs. If they are the original press in style make sure they are not pulling out of the head. I had some pull out slightly and this throws off the clearance as well....

Tim