Broken Rocker Arms

[bucket]

This has to do with my '70 Impala, but it's no different than most any other Chevy small block. Since getting the car, I have broken two rocker arms, over the course of about 900 miles. First one was the #8 exhaust rocker, I kept driving the car to get home and in the process, I broke the intake pushrod for the # 8 hole. I replaced both rockers and pushrods for #8 just to be safe. A few hundred miles later, I broke the #4 exhaust rocker. I was able to repair that one before doing any more harm.

#4 on top, #8 on the bottom.

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Now a little history. The long block is 42 years old now and it's original, the previous owner had JUST installed a mild Summit cam before I bought the car. He was aware of the proper break-in procedure. The valve springs do not bind. When I bought the car, there was some amount of clatter under the valve cover, at the right rear of the engine. After a short amount of time, #8 failed. I pulled a lot of stuff apart on the motor to check the PO's work and found some other unrelated issues. All other rockers, pushrods, and pivots were in good shape. Put it all back together and later on #4 failed without any warning at all. It just broke.

Is there something else I should be looking for? I can't find anything wrong at all. I'm going to chock it up to 42 year old rockers that are seeing more movement and pressure than they did before with the stock cam. The best thing to do is put on a set of full roller rockers, but in the mean time I will carry a couple extra rockers at all times in case one breaks again.

 

[RetroC10Sport]

My Blazer has done this twice...

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[bucket]

My Blazer has done this twice...

Huh. No abnormal wear on the pushrod?

 

[RetroC10Sport]

Nope...Both times on the #1 intake.

 

[HotRodPC]

How mild is this cam? What do the rocker arm studs look like? What this looks like to me, is to much lift. You might need long slot rocker arms to run that cam is going to my guess.

http://www.summitracing.com/parts/MAN-43141-8/?rtype=10

 

[Tyger13us]

How mild is this cam? What do the rocker arm studs look like? What this looks like to me, is to much lift. You might need long slot rocker arms to run that cam is going to my guess.

http://www.summitracing.com/parts/MAN-43141-8/?rtype=10

X2

long slot rockers or short,, i need info?!?!

what the oil pressure,, burned and galled,,what rpms?

groved balls wont help and rollers? wont run dry..... im running a full set of rollers.

but dude i need info,,, my other Bf,sbc has done the same..

coil bind?,, over revs,, adjusted to tight

i recommend most valve adjustment 1/2 down,, i run 0... 1/4 is good...?

bad oil pressure? old motor? bad cam bearings?

i have a 500 hp sbc motor,,many miles on it cam bearings are old,, new Groved balls,, ball tiped pushrods,, yep punched most of um,, but if your Burnin balls? No oil to the top end..........or? hahahaha To much oil pressure.. it wont drizle into the rocker,, it will shoot clean over the fended and never make to the ball...........

fire it up,, pull the cover,, and see where the oil goes,, if it pissin streem clean out and over,, ya have to high of oil pressure gettin to the top end..

all ya want is a lil dribble................

 

[Tyger13us]

How mild is this cam? What do the rocker arm studs look like? What this looks like to me, is to much lift. You might need long slot rocker arms to run that cam is going to my guess.

http://www.summitracing.com/parts/MAN-43141-8/?rtype=10

I dont know what cam he has,, no specs,, but? ya really dont need long slots..
.500 lift,, eh,,, but like my post,, and im sure every one will chime in on this..
and yes Ladies and germs im dislectic and cant spell worth a ****,, but bear with me.....Growl..........

 

[Tyger13us]

This has to do with my '70 Impala, but it's no different than most any other Chevy small block. Since getting the car, I have broken two rocker arms, over the course of about 900 miles. First one was the #8 exhaust rocker, I kept driving the car to get home and in the process, I broke the intake pushrod for the # 8 hole. I replaced both rockers and pushrods for #8 just to be safe. A few hundred miles later, I broke the #4 exhaust rocker. I was able to repair that one before doing any more harm.

#4 on top, #8 on the bottom.

You must be registered for see images attach

Now a little history. The long block is 42 years old now and it's original, the previous owner had JUST installed a mild Summit cam before I bought the car. He was aware of the proper break-in procedure. The valve springs do not bind. When I bought the car, there was some amount of clatter under the valve cover, at the right rear of the engine. After a short amount of time, #8 failed. I pulled a lot of stuff apart on the motor to check the PO's work and found some other unrelated issues. All other rockers, pushrods, and pivots were in good shape. Put it all back together and later on #4 failed without any warning at all. It just broke.

Is there something else I should be looking for? I can't find anything wrong at all. I'm going to chock it up to 42 year old rockers that are seeing more movement and pressure than they did before with the stock cam. The best thing to do is put on a set of full roller rockers, but in the mean time I will carry a couple extra rockers at all times in case one breaks again.

(The long block is 42 years old now and it's original, the previous owner had JUST installed a mild Summit cam before I bought the car. He was aware of the proper break-in procedure. The valve springs do not bind. When I bought the car, there was some amount of clatter under the valve cover, at the right rear of the engine.)

K,, here is the deal,, came bearing are worn,, high lift cam makes um work more,, a new oil pump,, or spring in the pump= high oil pressure...

the only reason ANY sbc has a major failer to the top end is "ether to much oil pressure?" or none.......

thats just a fact,, to much lift will just cause rocker bind or brokin springs/pull studs,, like HR said,but sbc will pull studs but it wont Punch rocker or stems,,, NO oil,, or to much pressure,, like i said in my previous post..

ive had an OLD motor,, good oil pressure,, wasnt a drop going to the rockers and clattered like a bitch with false teeth,boosted the pump and it just filed the cover with oil,, 1.5 qts-per side..

so ya have an ole motor and someone put a new pump the make it run a while longer,,yea it works,, but no oil to the rockers,or to much?, even though it fill the vale cover full and eventually will handgernaid the motor ,, reason being,, all of the iol "im dis lectic" is in the top end.... 1.5 qt x 2... K ya got 3 qts is the top and 1 in the filter,, so what the pump feedin the rods and mains?

 

[crazy4offroad]

This has to do with my '70 Impala, but it's no different than most any other Chevy small block. Since getting the car, I have broken two rocker arms, over the course of about 900 miles. First one was the #8 exhaust rocker, I kept driving the car to get home and in the process, I broke the intake pushrod for the # 8 hole. I replaced both rockers and pushrods for #8 just to be safe. A few hundred miles later, I broke the #4 exhaust rocker. I was able to repair that one before doing any more harm.

#4 on top, #8 on the bottom.

You must be registered for see images attach

Now a little history. The long block is 42 years old now and it's original, the previous owner had JUST installed a mild Summit cam before I bought the car. He was aware of the proper break-in procedure. The valve springs do not bind. When I bought the car, there was some amount of clatter under the valve cover, at the right rear of the engine. After a short amount of time, #8 failed. I pulled a lot of stuff apart on the motor to check the PO's work and found some other unrelated issues. All other rockers, pushrods, and pivots were in good shape. Put it all back together and later on #4 failed without any warning at all. It just broke.

Is there something else I should be looking for? I can't find anything wrong at all. I'm going to chock it up to 42 year old rockers that are seeing more movement and pressure than they did before with the stock cam. The best thing to do is put on a set of full roller rockers, but in the mean time I will carry a couple extra rockers at all times in case one breaks again.

I would say the rockers were "broke in" (no pun intended. Well, ok, a little punnage) for the stock cam. With the new cam + a little more lift they were working beyond where they were accustomed and ended up being stressed to the point of failure. If I were you I would just get a new set of rockers, pivot balls and nuts and replace them all, it sounds like you're going to continue having this problem and maybe something more severe happening one of those times.

 

[bucket]

Oiling is fine on all rockers and the pivot balls are just fine until a broke rocker ruins the ball. When the rocker breaks it also damages the tip of the pushrod. I don't know what the pressure is, the car only has speed and fuel. Oil, voltage, and temp are all "Don't ask, don't tell".

The cam's spec sheet is in the glove box, but I do know that lift was below .500.

Also, when I had the valve cover off to replace the rocker, an old man I know (retired tool and die maker) took a look at the rocker and thought it was a fault in the manufacturing process of the rocker. That does make sense to me. I've got a work order from the dealer in '71 when a rocker was replaced on my '69 Impala because it had broke. That car was built later in '69 and this car was built earlier in '70, GM could have had a bad batch of rockers at that time.

 

[HotRodPC]

Then I'd replace all of them, with a new set of pushrods, and be sure to inspect the rocker arm studs real good. Just to be sure they rockers haven't started to notch grooves in the studs. If they don't have notches in the rocker arm studs, the problem IS NOT to much lift on the cam. Under .500 should be OK, but be considered the absolute max too. I ran a .510 and a .525 lift cam before and had to use long slots on both.

 

[chevychase]

Check valve springs ,and valves. Think someone may have done a bad valve lash.
Tightened a few to much. Drop a lifter?

 

[bucket]

Studs are fine too. Heads are original and untouched. Also, all valves were adjusted to 1/2 turn past zero lash, like I always do.

 

[HotRodPC]

So then maybe just bad rockers like you suggested. What else is there?

 

[89Suburban]

Holy ****, is this a normal pet peeve for these motors???

I'm already having transmission nightmares as it is.....