My car developed a miss and a valvetrain noise awhile ago. I parked the car because I didn't have time to look at it. I drove the car a little bit today and under light throttle the car drove and pulled great but under heavy throttle there was a lot of popping and skipping so I knew there was a problem that amounted to more than "needs a tune up".

I pulled the valve cover and noticed the number 7 exhaust valve rocker arm wasn't moving hardly at all, so I removed it. I then saw the retainer had broken and was kind of cockeyed on/in the spring. The pushrod isn't bent.

Its an LT4 retainer so I'm going to go to my dealer today and order one. I really HOPE that I can replace the retainer and call it good. What do you think the chances are I could have a broke spring or bent valve?

If I have a bent valve do you think I can get away with just rebuilding that one head since I dont have a ton of miles on the motor?

 

Little better picture of the valve stem...it doesn't look worn on the edges at all, only on the center


The rocker arm body got a little beat up by the spring but the rest of it looks fine. The spring *looks* fine but I'll check it better when I remove it.

 

You are so lucky you didnt drop a valve. when i first got my car i got it with a blown motor becuase the guy that had it before me was driving it and one of the rocker arms broke on the part that that pushes on the valve. it was just a stamped steel one though. but the valve was not there anymore and a couple holes in the piston and a ruined head.

 

You need to figure out why that happened first. It could have been defective, but I dunno about that. I'd be checking for coil bind.

Hard to see but... is there a wear mark on the shoulder of that rocker arm bolt? Thats the radiused part at the bottom.

 

There is no abnormal wear on any of the parts except the body of the rocker arm where it hit the spring. I think it broke due to over revving honestly.

 

looks like valve float, valve float is like a jackhammer on the valvetrain.

 

the #7 exhaust valve wont open all the way, as shown by the rocker arm movement, and the popping in the exhaust/hesitation of the motor. Also, at a certain RPM there is a fluttering noise when you rev the motor a little.

I dont see any metal in the oil that would lead me to think the cam went bad. I did switch from synthetic to dino oil after I resealed the intake, and I hadn't got around to putting synthetic back in, even though the car wasn't driven much.

Could I bad lifter cause the retainer to break like that?

 

Remove the rocker and measure the lobe lift at the pushrod to see if the cam is wiped. Also try and open the valve manually to see if it is sticking/bent/whatever.

 

its confirmed that the valve is not bent. Whats a good way to measure the lobe lift? Sorry if this is a "newbie" question, I've just never had to do it

 

If you have a dial indicator and a stand, you can set it on the pushrod, zero it out when the cam is on the base circle, and then spin the engine by hand and record the max lift.

If not, you can set a tape measure on the pushrod guideplate, measure the tip of the pushrod with the cam on the base circle, and then spin the motor by hand and measure the pushrod at the highest point.

The lobe lift should be on your cam card. If not, divide max lift by rocker ratio. I.E. if you have a 450 lift cam and 1.5 rockers the lobe lift would be 300 (3/10 of an inch).

 

so the caliper will be on the pushrod itself, and measure how high the pushrod goes? I had someone to tell me something similar, but they said put the caliper on the lifter itself.

I think I found a craftsman caliper on the sears website. I'll see if I can buy one tomorrow. Thanks for the heads up!

Yes, I got your PM. I hope I dont need to replace the cam, but im pretty sure I do.

 

He said dial indicator, but if you use it correctly, calipers would do the job as well.

Pushrod, lifter -doesn't matter. They'll both move the same amount.

 

well a compression check last night shows all cylinders between 195-200 psi. Makes me think that the head/valves are good. Looks like im definitely looking at a cam/lifter problem. I'll pull the car out in the spring and measure the cam before I tear into it.

 

 

Ouch.

Looks like you might have more than one broken retainer or some other issues going on with other valves.

 

yeah, engine is getting rebuilt and all new cam/heads/rockers etc are going on.

 

That's pretty impressive.

 

that's impressive if it's a roller cam