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Discussion Starter #1 (Edited)
Hello all i am still working with a new to me 1970 nova with an unknown 350 in it. It has 041 heads and for the most part seems very stock. The engine seems very low miles but has defiantly sat for a long time, as when i first got the car the valve covers were full of milkshake sludge but there is no coolant leak, just to give an idea of the condition...

One of the first things i did when i got this motor was run around and check the lash on all the rockers, i was looking for a different sound and needed to eliminate valve lash tapping. All the valves seemed to have the recommended loose 0 setting, and nothing was crazy off.

I was in the process of finishing a tune when it developed a valve tick, i pulled the cover to find that the number 2 intake rocker had rotated off the valve. I found that that pushrod is slightly bent, and had marks from rubbing the head. I pulled the other covers and have now found that 3-4 other pushrods are rubbing in a similar fashion. I only ran the car tapping the side of valve for a few minutes before looking, and only at low rpm.


Who ever had been running the car before me had the timing set at something like 22-30 degrees btdc INITIAL timing, but other than that the car was running just fine, and when i put it back to 12 it was happy as a clam.

So my first question is this a chicken or the egg problem, could the super detonation timing have caused some of my pushrods to bend? or likely something else?

The second question is now that some pushrod holes in my heads have been rounded out weirdly to the sides do i stand a chance of this not happening again? I don't want to have to pull the heads and install pushrod guides on a mostly stock motor...
Thanks


Just looked at the rocker stud and it is pretty well chewed...
 

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those are really good GM heads. can easily make 400 hp with 1.94/1.50 valves too...

the push rod guide slot is rectangle with radiused ends. or some call it a double D slot. this guides the pushrod. check to see if it has worn a groove. if its really worn and the pushrod cannot be guided by it any longer because it became rounded or worn then an easy fix may be self aligning rocker arms. they stay aligned by the valve tip. just try one first and make sure that the pushrod doesn't bind in the head anywhere while the self aligning rocker is mounted....then do the rest...
 

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I doubt if they wore the heads any. The pushrods should be 5/16". If you were to add guide plates you would probably have to open up the push rod holes either by drilling them or milling them open.

Any closeup picture of the head slots?
 

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Discussion Starter #4
Here is the damage, I am in the process of deciding how much i want to put into these when i would rather have a set of vortecs... not a big fan of the high compression.

You can see chewed rocker stud and the hole. This is the most damaged valve, which is intake on cylinder 2. From just a quick glance around with a flashlight there are 2 others that are showing signs of going this direction. 1 intake and 1 exhaust on cylinders 4 and 7.
 

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something is not right there, prob want to pull the intake and check that your lifters aren't stuck,pull out of their bores look at cam, sure the lifters were pumped up before valve adj? milkshake could just be moisture from sitting. maybe pushrods were already bent?
 

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Discussion Starter #6
The engine ran well and didn't have any lifter tick. My guess is someone starting it on old gas or the timing being so far off for a while might have bent the pushrods. Ill pull the intake today and check it out.
 

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I doubt if they wore the heads any. The pushrods should be 5/16". If you were to add guide plates you would probably have to open up the push rod holes either by drilling them or milling them open.

Any closeup picture of the head slots?
Yes, I ended up doing both for my EQ heads. Very tight clearance. 2 piece guides were a must in my case.
 

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Discussion Starter #8 (Edited)
Would i have to open the pushrod guide holes to run self aligning rockers?

I realize it would be a kludge, but i already have several that rub, i dont think i would lose much.

Or if i put straight pushrods back in whats the likelyhood that it is just going to start rubbing/bend again.
 

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Discussion Starter #9
Just ripped the intake off, and pulled all the rockers that are exhibiting the rubbing behavior, all the lifters came right out and look brand new. Like i said i think there are very few miles on the motor.
 

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You can see chewed rocker stud and the hole. This is the most damaged valve, which is intake on cylinder 2. From just a quick glance around with a flashlight there are 2 others that are showing signs of going this direction. 1 intake and 1 exhaust on cylinders 4 and 7.
Is that antiseize from the build I see in and around the stud and pushrod opening?
 

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Discussion Starter #12
I think tomorrow i might run to the local yard and see if i can grab a set of self aligning rockers just to get me running again. Thoughts, comments concerns?
 

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hi, like I mentioned, self aligning rocker arms are your best bet in your case and cheaper to buy and fix. the yard may have a good used set. just mock them up first to make sure they are not pinning the pushrods against the slot in the head. sometimes you get a good set of arms that do not cause the pushrod to rub anywhere at all. you just have to check it. also you may need new pushrods. that wear that you have could be from a bent pushrod. which is very common. so go get that particular pushrod that the head and roll it on a slightly tilted glass table and let me know if it wobbles or not. also all SBC pushrods are hardended. and if you buy new pushrods you will have to roll them on a glass table to check if there straight first. sometimes you have to check 5-6 sets of pushrods to make 1 good straight set. also take some bounty paper towel dipped in some solvent and then wrap it around a small magnet too and wipe that area clean....
 

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Discussion Starter #14 (Edited)
Put rockers in, with new pushrods. My luck goes from bad to worse, a bunch of the rocker studs have chewed damage, and a few have stripped threads. At this point i just wanted to hear the engine run again.

I got the car running again and it is only pulling 16 in lb vacuum no matter what i do. It was pulling 18 in lb before.
 

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Put rockers in, with new pushrods. My luck goes from bad to worse, a bunch of the rocker studs have chewed damage, and a few have stripped threads. At this point i just wanted to hear the engine run again.

I got the car running again and it is only pulling 16 in lb vacuum no matter what i do. It was pulling 18 in lb before.
if the rocker studs are chewed at the bottom from the rocker just leave it . once you put straight pushrods and good rockers it wont be a problem. as far as the rocker stud treads you can run a die on them. if not there easy to replace. also mr gasket makes a replacement stud that will screw in if you tap the head boss they press into....
 

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Discussion Starter #16
Ive been looking into the screw in studs, i think it might be time for some junkyard vortecs.

I'll run it as it is for a while and just pay attention to if it is moving. I figure ill hear it when it starts to let go and hopefully wont be too far from home. I am still working on other aspects of the car so just having an engine that runs is a huge help.

Thanks for the replies!
 
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