Bent Pushrods

[Harry Dawg]

Alright y'all.

So I was getting some chatter in the engine area, so I pulled the rocker cover off to inspect.

Pushrods were definitely bent, so I pulled the rocker shaft to find this. All the rods were bent, but this one was the most severe.

For background, this motor jumped time by about 15 degrees I'd say (fairly recently) and I reset it, but not before the damage was done it seems.

So I'm going to change the cam gear and timing chain, as well as the pushrods but what about other components?

I know the right answer is to pull the heads and check valves, replace if bent. Pull cam and inspect to make sure a lobe didn't get wiped out etc.

However, given my limited space and time - is there any harm in just replacing the essentials and firing it up to see what happens?

I'm worried I may have a bent valve, but I've read threads on the Mopar forums of guys just doing a timing set and pushrods and the motor runs like a tap.

As an aside, I got a steel Melling cam gear of Rock Auto. Should hold up better than the factory nylon gear I've heard horror stories about.

In fact, they have all the top end components for the 327 which I was surprised by. At least I have a source for parts if needed.

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[seventynine]

Subscribed. I don’t know the answer but I want to know too ;~>

[Yeller]

I’d be willing to try just replacing the parts.

Bent valves are easy enough to check for. Using a piece of wood as a drift and a hammer, hit the top of each of the offending valves to make sure they move up and down, if they do, reassemble with new parts. If they do not dig deeper. Then run a compression test before installing the valve covers to confirm they are working, one of those cylinders is making no or very little compression there is a larger issue. This will at least let you know there are deeper issues before you ruin the new parts. Betting probably not any issues but never know for sure without investigating.

[Harry Dawg]

@seventynine - I think some of your bad luck rubbed off on me.
Not 3 days after replying to your post on valve issues I find this! LOL.

I kind of figured this would be the case though, so I'm not too hard up about it.
It has been sitting like this for a month or so now, so I am finally un-aggrivated enough to dive into it.

Noted on the wood and hammer technique. I'll give this a shot while the rocker shaft is off and see what happens.
As far as a compression test, what difference would it make if the rocker cover is on or off?
I should just be able to insert the gauge into the spark plug hole and turn it over, right?

[Yeller]

Yes you are correct about the valve cover. For me it’s a “put the valve cover back on and guarantee it has to come back off” lol.

Yes insert the gauge, open the throttle and spin the engine over with the coil disconnected. The throttle open is an important step that many over look, allows the cylinder to draw air and make more pressure.

[Harry Dawg]

Sorry. Sometimes you gotta spell it out for me lol.

Didn't think about the throttle technique. Will definitely make sure to do this.

Shopping for a compression gauge now.

Everything looks to have metric threads. I figured this truck would use standard threads. The kit comes with rubber end pieces, so I guess worse case I use those.

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[seventynine]

@Harry Dog…sorry for the bad luck. Keep us posted.

If you at least rest the valve cover on you’ll avoid excessive oil squirting all over the place when you run the starter. Although you’ll be able see if it’s oiling properly.

[Harry Dawg]

Update on the wild goose chase.

Replaced the pushrods.

That went pretty smoothly, except I heard a mysterious ping noise when tightening down the rocker shaft. Hopefully it was just a rod settling into the lifter cup...sounded spring like.

Rotated the motor over by hand and all of the valves are moving.

Pulled the front cover off expecting to find a worn out timing set, but it's actually pretty decent.

However, the camshaft gear does not appear to be nylon which leads me to believe it has been done before.

It 100% has a new water pump, as it has reman markings on it.

Chain has about .30" deflection, but I doubt it jumped time. Gear teeth are grabbing fine.

So that is good, but uninformative news.

The only thing I can think now is I messed up the timing while I was setting dwell, replacing points and didn't realize it. Dizzy hold down seemed tight when I reset the timing.

It is possible that a misfire caused the bent pushrod, but still doesn't explain the timing issue.

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[Harry Dawg]

I had to pull the oil pan to get the front cover off.

While I was in there, I inspected the oil pickup tube and low and behold, there were the infamous nylon teeth.

Makes me wonder what kind of shape this motor is actually in. (It has 34K on the odometer, but it's looking more like 134K at this point.)

Anything I should check on the bottom end as far as bearing play or clearances?

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[tgreese]

How can the engine jump time with an intact timing set? Even so, that should not result in bent pushrods unless this is an interference engine.

Bent pushrods can result from over-revving too. BTDT (on a VW long ago). Lots of history with a 55 yo engine.

Have you measured the oil pressure? Suggest a dedicated mechanical gauge. I use this one: https://www.summitracing.com/parts/sum-g2934 If the oil pressure is good, and no noises, I'd leave the bottom end alone.

34K miles is 618 miles per year. Seems unlikely.

[Harry Dawg]

How can the engine jump time with an intact timing set? Even so, that should not result in bent pushrods unless this is an interference engine.

That is what I am trying to figure out.
Initial research research indicated that this is not an interference engine.

The only thing I can think of now is that the distributor hold downs were loose, and I moved the whole assembly when replacing the cap, setting dwell or running a new lead to the coil. Something of that nature.

I did have a couple of bad misfires just due to incorrect carb tuning and bad ignition system, so it is possible that this bent a pushrod.

There were only 2 that were severely bent like the picture. The rest ranged from barely bent to straight.

[Harry Dawg]

As far as oil pressure, I haven't measured it yet.

The factory assembly is just an idiot light and doesn't tell you actual pressure.

I have been looking into a gauge set, but am being picky about which one I want.

Off topic, but I would really like a Stewart Warner gauge set, but the price tag is out of my budget.

I think the Smiths is a good compromise of classic look and affordability,
https://www.amazon.com/Smiths-Replica-g ... B08HPMKBHN

At this point I just need to get something so I'm not flying blind.

[tgreese]

To me, 'jump time' means that the cam is no longer in sync with the crank. Then timing marks no longer align with #1 TDC. How is the distributor driven in these engines? I'd expect it's driven off the back of the cam, since that turns at the required half-speed of the crank. Not much can go wrong, unless a distributor drive gear slipped, either on the cam or the distributor. Or maybe the rotor turned on the distributor shaft. Have you removed the distributor for inspection? Kinda suspect your 'jump time' problem is not related to the pushrods.

Might be worthwhile to survey the AMC forum posts regarding these engines. I understood these engines were considered smooth, reliable and durable in their day; no obvious weaknesses. If the oil pressure and compression were good, I'd close it up and attribute your issues to abuse by the previous owners.

The Summit gauge is cheap (was even cheaper when I bought it, ca $20), has a big face, full sweep, and seems accurate. Something to keep in your toolbox and use to evaluate engines - not suggesting you install it in the truck.

I've used the S-W mechanical OP gauges, and they were good. Reacted fast. I have an Autometer mechanical gauge in my CJ-6, which matches the factory voltmeter with a black face and red pointer. I liked the S-W better, since it reacted faster. May be the nylon installation kit I used with the S-W allows for faster action... dunno.

[1978J10REDWHITE]

Need to figure the Root cause of Bent PR.
Yes verify compression in ALL cyls,
Possibly stuck vlv in guide on one cyl.
You said "Pushrods, as in 5-6 or all of them on one bank or the whole engine?
Verify the one bad PR vlv spring good or broke.
Many bent PRs seems like an overrun issue. One bad cyl shouldn't affect the whole engine PRs like this.

[67GMC]

I agree with Redwhite-Could be a stuck valve. I had a 89 YJ with the straight-6 4.2L. The pushrod on one cylinder kept coming out from under the rocker arm and it ran horrible. It happened a few times when trying to get on the highway. I thought it was from over-revving (it was a 5-spd) or it was more a stuck valve. Took the rocker arm off and it was worn enough that the push rod could pop out. Changed the arm and all was fine. I don't know if the rod would have bent if I drove it not under the rocker arm for a long period of time or not.

[Harry Dawg]

Got the new crank gear and timing chain installed.

It actually has just as much deflection as the old chain right out of the box. Don't know what's up with that, but it makes me think it didn't need to be replaced.

Oh well. Now I have a spare for when these parts become unobtainable.

Back to the pushrods, do y'all think section E-91 applies to my current repairs? Not sure how you can uncharge a lifter for initial startup without replacing them.

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[letank]

Is there an issue with the oil hole alignment with the 350 as there is with the 360 when using new parts?

viewtopic.php?t=12192&start=20

I need to put those missing picts back (the one below was during a camshaft swap)

OldOilingHole.jpg

[Harry Dawg]

@letank This is an AMC 327, so I'm not sure about the Buick 350. I didn't see any obvious issues with oil galleys not lining up.

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[Harry Dawg]

Got the front cover and water pump back together.

If nothing else, the front cover was leaking so I fixed that lol.

I ordered a dial indicator so I can check the cam lift and operational range of the lifters. If everything checks out I'll put it back together and do a compression test.

Also ordered a gauge set so I'll have temp, oil pressure and amp readout in the cab.

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[Harry Dawg]

Just finished picking the remnants of the old timing gear out of the oil pickup.

Definitely enough to cause low oil pressure, and that might not even be all of it.

I'm also wondering if this might lead to premature failure of the pump gears or other parts. If microplastics are circulating through oil galleys and such.

Maybe the pushrod got bent 40 years ago when the first timing set went out. Still waiting on my dial indicator to confirm the top end clearances.

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