HELP with SBC rocker / pushrod problem

I'm the guy who backfired the SBC and broke something inside (see my previous thread for some good advice and a few good laughs!). When I pulled the cover, I see two rockers sideways. The exaust pushrod is bent, I can get a new one. But the intake pushrod is straight. Even if I tighten the intake rocker all the way down, it is loose. And the intake rocker stud is 1/4" longer than the exaust stud. Is this normal or did I pull this stud up 1/4"?? Or is the lifter collasped causing the loose rocker?? Any help with this is appreciated, it's finally nice here and I need to be driving this coupe!

 

bummer! you can get screw-in studs but can be a pain in the ass doing on the car. probably allmost as easy swapping it out if you have another head.

 

If the stud is taller than the rest you have pulled it out. Try driving it back down even with the rest. Oversize OD studs are made or tap the hole for a thread in one if it pulls out again.

 

i would get a screw in stud, if taller than other stud, i think guys would pin studs in the old days,

 

If those heads have had the guides replaced make sure that they are installed properly. If the guide is to high the retainer for the valve will hit it and cause the bent pushrod problem. Would also cause the pulled stud I would imagine. Another one of those things that you don't forget when it has happen to you. Been about forty years ago now. Dennis D

 

Thanks for the help. I'll try tapping the stud down with a BFH, hope it goes back down and stays down. What's on that rocker stud, splines like a wheel stud?

 

Bad idea. Once it's pulled it's pulled. It may stay for a short period of time, but it will pull again and could cause a real disaster. They are knurled and you MAY be able to pin it, but you are way better off installing screw in studs.

 

Is it an exhaust and intake on the same cylinder? If so, it sounds like something hit the valves on the overlap between exhaust and intake stroke. The exhaust push rod bent but the intake stud slipped before the intake push rod bent. The question would be, what hit the valves? Did something get into the cylinder, did the rod stretch or a rod bearing fail. Could the valves have been improperly adjusted? Did you just change anything on the engine, like valve springs?

Check the valve stem height to see if either of the valves is sticking down because it's bent. You could put an air hold in and see if any air comes out the intake or exhaust. If you have access to a bore scope it would be good to take a look at the top of the piston.

 

I wouldn't trust just knocking it back down, that's asking for trouble! Like engine man says, something funny is going on here for both of those valves to be fubar'd...

 

Thanks Engine Man, the engine has 10,000 miles on it. Ran good before it backfired, after swapping intake manifolds. So valves were adjusted OK. I should have set the timing, but thought I was close enough to start it. Didn't hear a rod knocking, no smoke out the back, just lifter noise and a miss before I removed the valve cover.

 

pull the head and know for sure. there dime a dozen and gaskets are cheap.

 

I pinned a few heads way back when. I'd rather use screw in studs. That knurled stud will pull right back out.

 

Hydraulic the cylinder? How long did it run before the backfire or did it do it while cranking? Dennis D

 

Dennis D, it Backfired hard while cranking over the first time with the new intake.

 

The stock studs are NOT knurled !! Straight smooth shank.

 

Is it possible that something fell in or came out of the intake manifold? I'd pull the head and check the piston and valves.

 

hi just a quick note , make sure your valve isnt froze. ray

 

Don't pin the studs ... you can never get them apart and if you break a stud you throw the head away. pull the heads and have them machined for screw in studs ... you wont regret it.

 

Nope no knurl on studs what are you smoking?

Tig

 

hydrolock,

 

Probably wipe the lobe on the cam out pull the lifter out and check the lobe and lifter.I have bent push rods and broke rocker arms and recovered.Wound a BB chevy to tight one time and floated the valves and push rod peaned the lifter and wiped the cam out.Need to look at the lifter for sure

 

Why did it backfire after the intake swap, did you have a plug wire out of sequence. I agree install screw in studs.

 

Bummer, sounds like your going to have to pull the head and take whatever fell in the intake out. I hope the pistons not hurt to bad. Like 41fred207 said gaskets are cheap.
Good Luck

 

Ran into the exact same situation way back in the 70's on my buddies car.
He calls me up and says his car runs like crap... I pull the valve cover and see both rockers on one cyl off to the side with one bent pushrod and one stud higher than the rest. I pulled the plug and couldnt find anything wrong and since we were poor punk kids I pounded the stud back down and replaced the pushrods and rockers with some good used ones and it ran fine.
Never gave him any more trouble.. I remember this pretty well because I spent a lot of time trying to figure out what had caused the problem with no luck

 

I had some crappy aftermarket Chinese rockers once and one of them seized at the fulcrum which in turn bent a pushrod and wiped out my cam. I'll never do that again. I had screw in studs or it would have pulled it out. Its worth inspecting the rockers and the balls if you haven't done that. It's a long shot but so is something falling in the cylinder and stopping both valves. If the motor was fresh and the rockers didn't have a liberal douche of assembly lube they can seize up pretty quick also.

 

If you drill all the way through the boss when you pin the stud it can still be removed later. This would probably get you back on the road.

All this talk about screw in studs sounds quite expensive because the bosses have to be machined down to make room for factory type studs, however; the circle track guys use some "cheater" studs that have threads but no hex for a wrench. One of these could be put in with the motor still assembled if you contain the shavings properly. Just don't forget the Loc-Tite!

 

My.02.

The intake stud was pulled out BEFORE the intake swap. The result of that problem is the back fire that occured on the exhaust stroke with the valve open thus bending the pushrod.

 

Here is a pic of a tool used to keep the tap straight while threading for a rocker stud. Also included (I hope) is a pic of the non-hex type rocker stud.

I do not remember stock rocker studs being knurled.

 

Let's try those pics again





These should allow you to install screw-in studs at home. If I remember correctly, you also need to use a "bottoming tap". Cast iron actually threads quite nicely. I would not try to thread the existing stud hole "free hand" ... the tap guide is very important.

 

Time to pull the head and check the piston top. If you don't see any damage I would have to believe it had to hydraulic lock on you. A friend of mine ran a 57 fuel inj. unit off of a Corvette on his 283. When it would set for a few days the number one cyl. would fill with gas because of no check valve in the fuel spider. His car would bend the rod when he cranked it. While you have the head off, check the piston travel on that cyl. Good luck, Dennis D