# Rocker arms and bolts



## PisnNapalm (Aug 28, 2010)

So... I bought the car back in September. Three days after purchasing it a rocker arm bolt broke. I figured it was bad luck and while unusual, it did not seem impossible on a 43 year old car... I had it fixed and it's run well since.

Well today it broke another one. Obviously, there's a major problem. This is no coincidence. 

Here's the engine specs to the best of what I know.

Pontiac 400 bored to 30 over. (I think that means 0.030 larger diameter pistons)
Ram Air III cam
Crank was "ground 20 on the mains and rods"
Moly rings
had a valve job and new guides.
I think it has 670 heads on it.


So.... What are some possible causes for breaking these bolts?

I'm attaching pictures to show as best I can what happened.







































































It looks to me like there's some damage to the rocker arm in the fourth picture. The left edge of the hole looks chewed up.

As always... Thank you for your time and help.


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## freethinker (Nov 14, 2009)

did the same bolt break? only two options. your valve train is hitting something or you are over thghtening that bolt.

you say its a fresh rebuild. a ra3 cam does not have enough lift to cause the valves to hit the pistons so its something else. i see several valve spring shims check for coil bind put a thin feeler gauge in the spring and turn the engin until max lift. you should be able to pull out the feeler gauge. did they put in new valve guides. check for spring retainer hitting the top of the valve guide if they didnt machine it correctly. with that valve at max lift try to compress the spring further with a tool. there should be more room to compress at max lift.

it looks like the bolt is breaking right at the shoulder. those nuts are not tourqed very tight. are you over tightening? the nuts on the other valves look upside down?


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## PisnNapalm (Aug 28, 2010)

All the work was done before I bought the car.

It was a different bolt this time. The first one was on the passenger side and this one is one the driver side.

I also don't know how "fresh" the last rebuild was. It was bored and new pistons and a cam were put in, but beyond that... I don't know. I'm gonna give the mechanic a call and see if he remembers anything else about that build.

EDIT:: Is there any way to tell if it has the proper rocker arms for this cam?


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## freethinker (Nov 14, 2009)

PisnNapalm said:


> All the work was done before I bought the car.
> 
> It was a different bolt this time. The first one was on the passenger side and this one is one the driver side.
> 
> ...


pontiac rockers were pretty much interchangeable unless you had the rare ra4.
i dont see a problem there they look right. what about those nuts upside down? something looks wrong with the top of the rocker pivot ball. it shouldnt be worn like that from normal wear.


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## jetstang (Nov 5, 2008)

I think freethinker hit on something. The rockers are torqued to 20 Ft lbs. I think. If they overtorqued the bolts it could stress the bolt and then snap off. Loosen and Retorque all the rockers. If this is a coil bind issue or a valve is hitting the piston, then the pushrod usually takes the damage. The studs could be worn out and snapping, but I've never heard of that. You could install all new studs and press on. The rocker looks fine, no issues from what I see. Just replace the broke stud, this isn't a big deal.


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## geeteeohguy (Feb 2, 2008)

These are easy to replace, screw in studs. Be sure to adjust the valve proerly when you're putting it back together. It looks like metal fatigue...never seen that, tho'.


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## PisnNapalm (Aug 28, 2010)

Thanks for all the input folks.

I checked the pushrod. It's straight with no signs of damage. I doubt the valve is hitting the piston. My guess is it may be a combination of things. Worn out studs as well as over torqued nuts.

Question... Any advantage to using roller rockers in this engine? I plan on replacing all of the rocker arm studs and figured now would be a good time to replace the rocker arms as well if needed. I looked at these from OPG http://www.opgi.com/product.asp?cat...d=50&grpcode=4983&ProdCode=G201130&yearrange=

If so... what ratio rocker arm? 1.5 or 1.65? My research so far says to stick with the stock 1.5, but figured I'd ask.


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## Rukee (Feb 8, 2007)

I have a set of roller tipped 1.7 ratio and they force the push rod into the head with it's relocated pivot point, so I'd say stay with the 1.5s.


Someone in the past prolly overtightened the rockers with an impact or something. I would replace them all.


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## PisnNapalm (Aug 28, 2010)

Rukee said:


> Someone in the past prolly overtightened the rockers with an impact or something. I would replace them all.


Replace all of the rocker arms and studs or just the studs?


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## jetstang (Nov 5, 2008)

Just the studs, unless the rockers show wear.


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## Jerry64 (Apr 20, 2010)

If hose are stock rocker nuts,it looks like some are upside down.The crown should be up and the flat side of the nut should be against the pivot ball.Looking at the pivot ball.it looks like the crown of the nut was down and cut into the pivot ball..........JB.


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## Topkat (Sep 9, 2010)

The nuts are upside down.
Here's a pic of the heads on my '67, exactly as they were removed. The nuts are rounded at the tops


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## PisnNapalm (Aug 28, 2010)

They are a different kind of nut. I think these are the exact ones that are on the car.

Mr. Gasket 920G Mr. Gasket Sure-Lock Rocker Arm Nuts


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## Rukee (Feb 8, 2007)

PisnNapalm said:


> They are a different kind of nut. I think these are the exact ones that are on the car.
> 
> Mr. Gasket 920G Mr. Gasket Sure-Lock Rocker Arm Nuts


I like your nuts!! 
No, those are not original, but they are a great rocker nut, nun the less!! :cheers


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## PisnNapalm (Aug 28, 2010)

So... are they on the stud properly?? Seems to me that the "bolt head" end ought to down tight against the rocker arm ball nut.


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## Jerry64 (Apr 20, 2010)

Never used them kind of nuts before.Mine are stock.......JB.


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## PisnNapalm (Aug 28, 2010)

Just got done ordering stuff. 

New valve covers and gaskets, rocker arm studs, those Magnum roller tip rockers, and a few other goodies.... Oddly enough my wife talked me into spending more money than I intended. *scratches head*


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## jetstang (Nov 5, 2008)

That is a good price on the posi locks, but if you have a torque to spec valvetrain you don't need adjustable rocker nuts. Are you replacing all the studs, that is whats breaking..


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## PisnNapalm (Aug 28, 2010)

Yes. I'm replacing all of the studs and the rocker arms. I'll decide after some research whether or not I'll reuse the posi-lock nuts on the rocker arms. I have a suspicion that they may have contributed to the breaking studs.


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## geeteeohguy (Feb 2, 2008)

Posi locks won't break studs. Overtightening any nut will. Posi locks are great because they are adjustable. They work well with any engine that has had any machine work done or parts replaced, because as heads are milled, blocks surfaced over the years, etc, the deck height changes and the standard _"torque to 25 pounds" can result in a valve that is too tight. If you do use the standard nuts, use new ones, and use them once. They tend to back off and blow out pushrods if re-used. I always run poly locks on a bottleneck studded engine. Napalm, what you are seeing on the "upside down" nut is the allen screw in the middle....


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## PisnNapalm (Aug 28, 2010)

Question.... What is the stock size for the rocker arm studs on a Pontiac 400 engine?

I thought it was 3/8ths on the bottom part that screws into the engine and 7/16ths on the top that you bolt the rocker arm to.

The bolts currently on the engine at 5/16ths on top. Could this be why it's breaking the bolts?

My new set of rocker arm studs arrived today and I was hoping to get the Mutt fired up again, but no... Those adjustable rocker arm nuts fit the 5/16ths studs. So.... I'm still SOL for now.

Anyway... just wanted to vent a little. Looks like I'll either be buying a new set of adjustable nuts or use the ones that comes with the new rocker arms and torque them to spec. What is the spec for those nuts? 20lbs?


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## jetstang (Nov 5, 2008)

I was checking summit and they say they are 3/8" nuts. Which are the same as used on Chevy and small ford. 5/16s is real small, but that is whats on my old heads for my 4.3 Chevy motor.


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## PisnNapalm (Aug 28, 2010)

I bought the new studs from Ames. Part number N508B
https://secure.amesperf.com/qilan/Detail_Web?part_num=N508B

EDIT:: I did test fit one of the new studs into the engine. It screwed in tight. The top is a bit bigger is all.

Will I be able to use this thicker bolt with the "stock" rocker arms that are currently in the car?

I ordered the new arms from OPGI along with my other goodies. However, the confirmation email said that all.... yes ALL... of the parts are on backorder. Fark that... There was no indication on any of the part webpages that they weren't in stock. I'm too damn impatient to be waiting weeks for the new parts.


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## jetstang (Nov 5, 2008)

You could use your old nuts without issue, but if the new studs are bigger than you had in the car, then all the parts need to be the larger size?
I would get my motor parts through summit or Jegs. I use The Parts Place and nothing has been on backorder through 3 orders! And they ship fast.


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## PisnNapalm (Aug 28, 2010)

I don't have any old nuts. I've only had the car for a month and a half. 

EDIT:: ok that sounded weird when I read it back to myself.


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## Eric Animal (Oct 28, 2007)

I just saw a set of factory rocker arms on e-bay a little while ago.......


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## PisnNapalm (Aug 28, 2010)

In every catalog I have there are rocker arms for 3/8ths and 7/16ths sized studs, but none for 5/16ths.

This is pissing me off.... I believe that someone previously used the incorrect studs.










Also... another question... How would I go about turning the engine manually so I can redo the rocker arms? I know I need to remove the spark plugs. Every video I've seen the engine has been out of the car and on an engine stand without a pulley on it. They used breaker bars to turn it.

How do I do this while it's in the car with everything still attached?


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## jetstang (Nov 5, 2008)

I just rechecked the link of the studs that you bought, and they take a 7/16 rocker nut, as they aren't tapered at all. The originals are 3/8s. Install the new studs and get a 7/16 nut set and you should be good. Nice studs, ARP are great and will never break.

To turn the engine get a socket and small extension to fit the center bolt in the lower pulley, then turn it clockwise so you don't loosen the crank bolt. You can remove the fan to give easier access or do it from the bottom of the car.
Hope this helps.


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## PisnNapalm (Aug 28, 2010)

jetstang said:


> I just rechecked the link of the studs that you bought, and they take a 7/16 rocker nut, as they aren't tapered at all. The originals are 3/8s. Install the new studs and get a 7/16 nut set and you should be good. Nice studs, ARP are great and will never break.
> 
> To turn the engine get a socket and small extension to fit the center bolt in the lower pulley, then turn it clockwise so you don't loosen the crank bolt. You can remove the fan to give easier access or do it from the bottom of the car.
> Hope this helps.


Ok.. Thanks. That means pulling the radiator out as well. Yea!! :willy: Well I did buy the car to get my hands dirty, so to speak.


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## jetstang (Nov 5, 2008)

PisnNapalm said:


> Ok.. Thanks. That means pulling the radiator out as well. Yea!! :willy: Well I did buy the car to get my hands dirty, so to speak.


No need to pull the radiator, just get a long 1/2 drive ratchet, or torque wrench as it's longer, short extension to get in the pulley and turn bolt. *Or just bump the engine over with the starter!*


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## freethinker (Nov 14, 2009)

PisnNapalm said:


> Ok.. Thanks. That means pulling the radiator out as well. Yea!! :willy: Well I did buy the car to get my hands dirty, so to speak.


no need to pull the radiator. do it from underneath the car.


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## PisnNapalm (Aug 28, 2010)

Bugger bugger bugger.... My order from OPGI, the entire order, is backordered. Some of the parts are 4 to 6 weeks. So... I canceled it and ordered from Summit. Same price and it should ship today. Of course I don't get free shipping, but it'll be here Monday or Tuesday instead of December or January.









I'm also gonna need to buy... MORE TOOLS! Woohoo!! I don't have a socket large enough to fit the nut/bolt head on the main pulley. So... Off to Sears for some more tools. 

Anyway...


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## 66tempestGT (Nov 28, 2009)

sorry i didnt read this sooner. i have broken several studs in the past by improperly tightening those locking nuts. the correct way is to adjust the rocker perfectly then tighten the allen screw. well, i was getting the rocker almost adjusted then snugging the allen screw. then turning them both together till it was adjusted right. usually about 1/8 turn but sometimes more. got them super tight but puts some crazy pressure on the end of the stud for no reason. they didnt break right away, but after some driving. i was breaking 3/8 studs this way so its no suprise the 5/16 are breaking. im sure if you replace the stud and properly adjust the rest you would have no more problems.


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## freethinker (Nov 14, 2009)

PisnNapalm said:


> Bugger bugger bugger.... My order from OPGI, the entire order, is backordered. Some of the parts are 4 to 6 weeks. So... I canceled it and ordered from Summit. Same price and it should ship today. Of course I don't get free shipping, but it'll be here Monday or Tuesday instead of December or January.
> 
> 
> 
> ...


its a 15/16 socket


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## PisnNapalm (Aug 28, 2010)

freethinker said:


> its a 15/16 socket


Thanks! Of course the largest I have is 7/8ths. I don't mind buying tools though.


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## PisnNapalm (Aug 28, 2010)

66tempestGT said:


> sorry i didnt read this sooner. i have broken several studs in the past by improperly tightening those locking nuts. the correct way is to adjust the rocker perfectly then tighten the allen screw. well, i was getting the rocker almost adjusted then snugging the allen screw. then turning them both together till it was adjusted right. usually about 1/8 turn but sometimes more. got them super tight but puts some crazy pressure on the end of the stud for no reason. they didnt break right away, but after some driving. i was breaking 3/8 studs this way so its no suprise the 5/16 are breaking. im sure if you replace the stud and properly adjust the rest you would have no more problems.


Thanks for the advice. I've been watching Youtube "how to" videos. I ought to be able to handle this so long as I can turn the motor manually.


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## 66tempestGT (Nov 28, 2009)

just trying to shed some light on why they can break. you would have to tighten them so tight it could never run with an ordinary nut, but with the sure locs you can do a lot of damage with a 9/16 and an allen wrench.


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## PisnNapalm (Aug 28, 2010)

Does anyone know the torque specs for the rocker arm studs?


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## PisnNapalm (Aug 28, 2010)

Finally found it here: Wallace Racing - Pontiac Bolt Torque Values


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## PisnNapalm (Aug 28, 2010)

Success!! Well... sort of. I do believe that I have the new studs and rocker arms installed correctly. Only problem is one of the arms hits the valve cover slightly. So... I'll be buying new covers sooner rather than later.


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## jetstang (Nov 5, 2008)

Congrats!! How does one rocker hit, do you have the 66 style angled corner covers on there?


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## PisnNapalm (Aug 28, 2010)

jetstang said:


> Congrats!! How does one rocker hit, do you have the 66 style angled corner covers on there?


I have no idea what covers it has. I can take a pic and show you what they look like.


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## PisnNapalm (Aug 28, 2010)

Here's the pics...

This is the inside of the cover. The damage is being done by the forward most rocker arm. You can see the dent in the cover.










This is a profile shot of the cover.


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## 66tempestGT (Nov 28, 2009)

you will love the noise you get from those roller tip rockers.


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## jetstang (Nov 5, 2008)

Nice rockers and congrats for getting it all back together and running? Don't worry the rocker will "clearance" itself, lol.. Now you have a reason to get the trick valve covers, worse things happen!
Did you torque the nuts or adjust them like an adjustable valvetrain, please tell me you adjusted the valves..


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## PisnNapalm (Aug 28, 2010)

jetstang said:


> Nice rockers and congrats for getting it all back together and running? Don't worry the rocker will "clearance" itself, lol.. Now you have a reason to get the trick valve covers, worse things happen!
> Did you torque the nuts or adjust them like an adjustable valvetrain, please tell me you adjusted the valves..



I followed the directions that came with the rocker arms. Specifically see steps 8 and 9. Is this what you meant by adjusting the valves?

http://www.compcams.com/Instructions/Files/250.pdf


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## PisnNapalm (Aug 28, 2010)

66tempestGT said:


> you will love the noise you get from those roller tip rockers.


I was wondering how much noise they are supposed to make. It sounds alot different than the stock rocker arms. It sounds.... more mechanical...? What should it sound like?


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## 66tempestGT (Nov 28, 2009)

thats pretty much it. kind of a chattering sound. sewing machine-ish.


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## PisnNapalm (Aug 28, 2010)

66tempestGT said:


> thats pretty much it. kind of a chattering sound. sewing machine-ish.


That's exactly what it sounded like it. Good! I did something right. 

Question...

Any reason I can't put the old cover on and just run the car? It'll beat the dent a bit deeper, but that should be it right? I don't care if these covers get dented. I'll be ordering new ones. 

I just wanna drive my car.


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## 66tempestGT (Nov 28, 2009)

it will be fine to run the old covers. i would take something and go on and knock the dent out a little farther from the inside just so you dont have to listen to it hitting while you are driving.


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## Jerry64 (Apr 20, 2010)

Rocker may be hitting the oil deflector welded in the cover........JB.


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## PisnNapalm (Aug 28, 2010)

That dent toward the front of the cover is definitely new. I checked the inside for damage before firing the car up. Toward the left side near the lower bolt hole you can see a line. I'm guessing that's damage from the first rocker arm bolt it broke back in Sept.

I'm gonna go hammer the cover a bit and then see how it sounds when I put it back on.

Question... Do you think stock height covers will clear the arms or should I go with taller ones? My only concern is having enough clearance so the cover won't hit the brake dohickey thingy. (Sorry but it's name escapes me right now... brake booster??)


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## PisnNapalm (Aug 28, 2010)

Woohoo!! A few smacks of a hammer and there's no more tapping on the valve covers. It runs great aside from still needing a carb rebuild. It does sound different though but I can get used to that.


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