Bent pushrod, good compression??

DeCaff2007 · Jul 30, 2022

Yeah, I'm a little stumped, too. I was replacing the valve cover gaskets on my 4.3L and as per the norm, I give the valve train a once over. Well, cylinders 3 and 5 both had REALLY loose rocker arms. They seemed torqued down ok, but the exhaust push rods on those two cylinders were definitely bent :-0

The weird part is, I had just done a compression test the other day and there were no signs of trouble on either of those cylinders. Granted, cyl 3 was a bit low @ 135, but cyl 5 was spot on @ 150!

Now, push rods are definitely cheap enough. So, should I just replace all 12 with brand new, or just go go a yard and rip some good ones out of the first v6 GMT400 I see?

618 Syndicate · Jul 30, 2022

I'd want to know what caused them to be bent before I did anything.

Frank Enstein · Jul 30, 2022

^^^^ What he said!

Pushrods are like a fuse in that they fail first protecting the other valvetrain parts.

If it was fine the other day so the question is what changed?
Over rev? Hydro-lock? Lost a couple lifters?

Peewee0413 · Jul 30, 2022

When was the last time you lashed the rockers?

Peewee0413 · Jul 30, 2022

Frank Enstein said:
^^^^ What he said!

Pushrods are like a fuse in that they fail first protecting the other valvetrain parts.

If it was fine the other day so the question is what changed?
Over rev? Hydro-lock? Lost a couple lifters?

I think Hydro-lock would likely cause more damage than a bent pushrod.

DeCaff2007 · Jul 30, 2022

Peewee0413 said:
When was the last time you lashed the rockers?

Last night was the first time I've ever removed the valve covers on this truck. The purpose was to change the valve cover gaskets.

Dropped88 · Jul 30, 2022

Is this a manual trans truck?

Ron88 · Jul 30, 2022

I dont think exhaust valves not opening would change compression readings much.

DeCaff2007 · Jul 30, 2022

Ok now that I'm not reading and trying to reply on the android version of a flip phone (one day I'll be free of that damned thing), I'll address a few things here.

1. I've never set valve lash on anything, ever. Never had a need to. Even my 76 Rot Box has hydraulic lifters, so no need to set valve lash.

2. It was actually never fine from the day I bought it. I could always here a slight ticking whenever the engine was running. I've only had this truck for a little over a year and haven't put but 3 or 4 miles on it. It's been under the knife ever since. Just last night, however, we found the bent push rod. It wasn't even catastrophically bent. It was just enough that the rocker was loose. Then I rolled it across a table top. The bend was just noticeable.

3. @Dropped88, Yes, it's a manual truck.

Also, it's just now occurred to me that a push rod being bent like that would cause a valve to NOT open all way, as opposed to stay open. I just answered my own question.

Gents, I'm not looking to tear ANY further into this 4.3l than I have to. I was supposed to be going down to pay off the politicians (state inspection lol) today, but then we found this crap last night.

Sorry for the rant, I've been in an incredibly cranky mood as of late and having to deal with society today is NOT helping.

DeCaff2007 · Jul 30, 2022

Ron88 said:
I dont think exhaust valves not opening would change compression readings much.

Yeah you beat me to it. You posted that as I was typing.

Bent pushrod, good compression??

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