#$%@! Bent Push Rods

[wcstory]

Been too busy to spend much time tinkering with the 1966 GMC 2503 I bought last winter. I decided to have my mechanic see why she was running so rough. Figured it has to be the points. After all it only has a 305 v6 with only 13,000 miles.

A few days later I call asking if they have the motor out as a joke. He gives priority to peoples daily get to work vehicles over weekend toys (as he should)

A couple days later he calls to tell me the motor may have to come out. The started with a compression test, cylinders 2 & 3 are flat zero and #1 is at 50 pounds. NOT what I wanted to hear. He stopped right there till he could talk to me.

I was going to have him pull the valve covers and check for problems with the heads. I decided to not have him do that, I figured put that money toward a used engine or repairs.

I brought my '66 home in abject defeat. I decided to pull the valve covers and look for a bent valve or other obvious damage.

The push rod in #1 was a "S" and 3# was tweaked. Time to pull the heads.

[TJ's Chevy]

Good cleaning and a basic valve grind and lap should work nicely. Have the heads surfaced and the block to while yer at it. My 305 has a slightly bent rod as well. Not THAT crazy but enough to make it out. lol

[wcstory]

Ordered a Fel-Pro gasket set from Amazon and Sealed Power RP-3099 push rods (12) from Rock Auto.

Hopefully I can pull the heads, remove the stuck valves, clean the heads and polish the valves and surfaces.

Any issues to look out for?
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[TJ's Chevy]

You'll need new manifold gaskets for sure. And those heads are STINKIN heavy. lol I lifted one out by hand and lucky I didn't get a cracked rib or two outta it. lol

[wcstory]

I just ordered the "GMC TRUCK MAINTENANCE MANUAL, MODELS 1000 THRU 5000" before I found out I need it now. Damn slow media mail

Can anyone post some pages covering the top end replacement.

[TJ's Chevy]

What do you need to know? Or do you just mainly need pictures?

[wcstory]

I was looking for the torque pattern on the heads and other re assembly specs.

I've done heads on Chevy 350s, but that was 25+ years ago. If I messed up a head or part on a 350 there were parts available everywhere.

[TJ's Chevy]

I made my own torque pattern for my v6 because I didn't have one and they have "two sets" of head bolts. If you subscribe on Jolly's GMC site I'm sure some of the guys there can give you some advice. I did my pattern similar to a 6 cylinder's. Seems to have worked fine since these heads don't get seriously torqued down. They're just like a V8 only bigger. lol

[wcstory]

Without a proper pattern I was going to follow the SBC cross hatch pattern.

Torque the head bolts in three stages (snug, 55ft lbs and 68ft lbs).

After 25 miles pull the valve covers, re-lash, re-torque to 68ft lbs and I'll change the oil'

Looking at the meat on those heads I'd bet they weigh close to that of my 454s heads. I found a fantastic 305e head rebuild thread where the member used a shop crane on the heads.

http://67-72chevytrucks.com/vboard/s...d.php?t=575596

Rufton's thread has to set the standard for "How to rebuild heads"

[TJ's Chevy]

I torqued mine to 70 pounds in three stages using the 6 cylinder pattern. There's so many head bolts you don't have to worry about getting them torque super tight like a cylinder. Stock torque specs for the 292 was 90 pounds each bolt. lol 70 is alot nicer. You'll have fun lifting them out though as it takes some groaning and growling because they're so stikin heavy.

[wcstory]

For reference:

Fel Pro Gasket part numbers

[wcstory]

I hear ya!

I'm planning on an extra set of hands putting them back in.

Anyone have a torque spec on the rocker arm bar bolts?
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[chevybuldr]

Sounds Jurassic-1 got it. The fuel has turned bad. It gets on the valves and just does bad things. Valve job time. Your this far its not worth the time to put it back on and do it again if it does not work out. Oh and drain the tank and put in some fresh fuel and then ad some fuel stabilizer. I work at a machine shop and we see this a lot on vehicles that sit. We have seen the fuel go bad in 60days.

[wcstory]

Had I gotten her from a long sit I would of drained and flushed fuel tank, lines and carb. Oiled cylinders, pulled valve cover, oiled the top end and rotated the engine manually before firing.

Unfortunately the PO did NONE of this. Now I'm cleaning up his mess.

I do currently have fresh (stabalized) gas in a new tank with all new fuel lines to a new pump and new carb. I need to put a new sender in.


Three valves we're solidly varnished into place. They easily tapped out and cleaned up nicely. No signs of piston contact (woo hoo)

Took the stripped heads to work and scrubbed the hell out of them in the parts washer.

Once reassembled I'll pull the plugs oil the cylinders and rotate the engine a couple cycles to verify no bind. This is not one of those things I want to do twice.
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[61_FL_Apache]

Those old V6's are cool.

[Jurassic-1]

That is a very cool truck. It would be a great stake truck or modify a bed to put on it. My friends truck was a much larger Fire truck. Fire departments take good care of their equipment most of the time.

[TJ's Chevy]

Good looking truck! You'll have that big v6 running like a champ in no time. If not..you can have my 305 so I can get a 478!

[wcstory]

Originally Posted by TJ's Chevy

Good looking truck! You'll have that big v6 running like a champ in no time. If not..you can have my 305 so I can get a 478!

I actually have a rebuilt 454 sitting in the garage that my wife wants me to use rather than spend money on this V6. I just like the uniqueness of the Big Block V6.

What's not to love about a motor that you can put a quart can into the cylinder.
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[wcstory]

Originally Posted by wcstory

What's not to love about a motor that you can put a quart can into the cylinder.

forgot to add picture

[MusicMan70]

Anyone have a torque spec on the rocker arm bar bolts?

My manual says 20-25ftlbs for the rocker arm shaft bracket bolts.

[wcstory]

Originally Posted by MusicMan70

My manual says 20-25ftlbs for the rocker arm shaft bracket bolts.

That is one of the few times I've guessed correctly. I did 25 as a educated guess.

Thank you MM

[1976gmc20]

I don't remember the heads on my 305 v6 being that terrible heavy, but I was a lot younger back then and pretty damn strong (worked in the timber every day!). Also, I had pulled the head on my old 4-cylinder Cat and that thing was really heavy!

Neither do I remember torque specs or order. I suspect that I just guessed back then, and the engine ran fine for years afterward, pulling heavy loads of logs. Those v6 GMC engines are pretty simple and tough, so as long as you don't do anything too stupid then you can't really hurt them. Too much rpm can be bad news, though.

Did you pull the distributor to remove the heads ??? You don't have to, you know I never did.

[wcstory]

Last night I spray bombed the heads.

Made some good progress today.

Clean the head and deck surfaces, cleaned the gasket surfaces, Re-assembled the heads, cleaned & painted the galley cover, installed galley cover, heads in & torqued, rocker bar in & torqued.

That bolt on the firewall side of the passenger side head was a SOB to access with the torque wrench. Had to use the old bend bar torque wrench for that one.

As it got dark I painted the intake and water neck housing.

[wcstory]

Tried to embed video with no luck

[wcstory]

Well after all that work she still wasn't running worth a hoot above idle.

Started re-checking everything. Valves lashed properly, checked the carb for vacuum leaks checked the distributor cap & wires for good connections, checked the spark plug wires twice to make sure they were in the correct spot (I marked them where they came from) - see a flaw in my thinking

Yes folks I didn't check to see if the plug wires were in the RIGHT order before marking. 1 & 2 were flipped. DOH!!! Stupid human tricks again.

She still wouldn't stay running for more than a few seconds. Start tapping the gas tank....hollow, hollow, hollow.... You have to be kidding! Empty 5 gallon mower gas can into tank. WooHoo!! I twisted the distributor till it sounded decent and tightened it down. Hell with the timing light I was going for a ride!

It's amazing how much better they do when you use the factory firing order.

A few laps around the development weren't enough so I got adventurous and grabbed my wallet and cell phone. Drove all the way to the local gas station to put 10 gallons in and then back home....2.5 miles round trip, maybe 3 if you count the neighborhood victory lap, but it still felt good , damn good.

Manual steering, bias ply tires and 4 something gears definitely made her feel like a truck.

Now I'm even more impressed! Cylinders 1, 3 and 4 had stuck valves or popped push rods - 0 compression. Cylinder 2 had the wrong plug wire. So she was running on 2.5 cylinders. That's impressive.