Working on a friends car today.

EG Whiplash Cam
Comp 7455 7.4" Hardened Pushrods
Guideplates *unsure of make*
Crane Gold 1.7 Rockers
Patriot Dual Valve Springs

Car had been running fine for some time. Cruising down the street I'm told that it suddenly started making a bad knocking/rattling racket. I went and troubleshot today. Car started up and I instantly thought broken valve spring. It was a horrible rattling that was RPM related coming from the valvetrain.

Pulled the valve covers......rockers were all tight, no springs broken. I checked every rocker for play with the engine at several positions and couldn't find a single one with any significant play in it.

Ok.....pull the rockers and pushrods. Let's have a look. As I'm pulling the rockers, I notice something troubling on a solid third of them....pic below:



Looks like the actual body is wearing away. The pin is ok and tight, but the rollers have some major play in them. I don't believe this could cause the horrible racket the motor was spitting out though.

As I'm tearing it down, I'm checking the lifters with a good push.....all firm and not giving at all. Ok, probably rules those out.

Start checking the pushrods and I come across a few that are ever so slightly bent. As seen below, this was the worst one.



I don't believe that it's enough to cause the racket I was hearing. I'm kind of troubled by this because I didn't see anything that really says what the issue is though I did find some small issues. If you've ever heard a car with a broken valve spring or a rocker that's completely loose, that's what I was hearing but absolutely not what I found.

Thoughts? My next step is going to be to pull the manifold and see if something ended up in the head rattling around.

 

I hate to be the bearer of bad news, I just had an issue with loud knocking rpm related that I initially thought was torque tube, but turned out to be a broken skirt on #3 piston. Fortunately no pieces got circulated, everything fell to the pan. Obviously yours could be a million other things, hopefully not too bad but let us know what you find!

 

By the looks of that rocker could it be a bent valve stem????????????

 

I would be VERY VERY surprised to find something like that. If it has to go that route, ugh..........

Unlikely, and I say that because the owner hasn't been hard on the car. A bent valve stem would likely cause other issues in the running dept (backfires, idle issues, ect) rather than cause a obnoxious noise like it's got a broken valve spring.

 

Correct me if I am wrong, but those pushrods appear to say "7.400" length. If that is the case, they are wrong. The Cranes use 7.250" pushrods and dollars to donuts the geometry was way off. I would also question the guides, especially if these are aftermarket heads with bronze guides. GM heads "may" be OK due to the harder guides.

 

That's kind of the direction I want going. I was thinking coil binding, or improper PR size, or installation of the rockers being wrong.

 

Too long push rods will cause the valves to hit the piston tops and cause a rattling noise.
This could explain the bent push rods. Continuous running this way could put a hole in a piston and then big trouble.
I would pull the heads to check for piston damage.

 

You said the car has been running fine for some time. I would think if the geometry was that far off to smack pistons it would of done it on the first start up.

 

Spun rod bearing? That'll make a nasty knock/rattle tied to RPM.

 

Exactly. Good thoughts, but the car has seen around 10k miles put on it in this configuration according to the owner.

Not a spun rod bearing. Not the solid deep thump that a rod would make.

I was not aware that Crane Rockers required the use of shorter pushrods, I didn't do the mods that are already on the car. Will DEFINITELY look into that. Word I got is that the pushrods/rockers were bought as a package from the original owners and were fine with each other. Eyeballing it the geometry was close, but I didn't break out the length checker because we were still trying to find what was making the racket.

 

Do a compression test and I'll bet you find a few low cylinders. My guess is that there are a few bent valves due to an over-rev and the pistons hitting the valves. That's a pretty big cam, and the pistons probably should have been fly-cut right from the get-go.
Been there,done that with a big cam when my car was a 346.

Jimbo

 

Start checking the pushrods and I come across a few that are ever so slightly bent. As seen below, this was the worst one.



I don't believe that it's enough to cause the racket I was hearing. I'm kind of troubled by this because I didn't see anything that really says what the issue is though I did find some small issues. If you've ever heard a car with a broken valve spring or a rocker that's completely loose, that's what I was hearing but absolutely not what I found.

Let me guess the bent pushrods came from #5,7, or 8 cyl.
If they did pull the plugs and look for the battered up one when you find it you will know which head to pull to find the broken piston where the top ring land let loose.

 

Number 7 Exhaust was one of them.....I do know that much. Good call......I'd have probably done it already if I didn't come unprepared in teh tool dept.....lol. That won't happen again.

 

Those pushrods won't bottom the springs if they were initially adjusted correctly nor will they cause the valves to hit the pistons. They will however likely ride the outer edge of the valve stem (exhaust side) and that may be why it took time to develop. Look at the top of the valve stem, do you see the contact pattern?

 

I didn't see any marks on the retainers if that's what you're getting it. Contact looked to all be on the top of the valve stems.

 

Wouldn't necessarily hit the retainers, but the rollers would be near the outer edge or possibly over the edge of the stem. You should pull a couple of valve springs and check guide wear while it is apart by just wiggling the valve stem.