#$%@! 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]

Sealed Power Vintage Parts:

[wcstory]

Parts are all in.

I started tearing down the top end. Those darn heads weigh almost as much as my 14 year old daughter.

From what I can see it looks like none of the valves got smacked by the pistons.

I took a bunch of pictures for reference during re-assembly.

Did find something odd. On the exhaust manifold bolt retainer for cylinder #2 there was a metal tag attached with wire. Stamped on the tag is "060" or "090" . Any idea what this is? The truck has less than 13,000 miles so I doubt it is a rebuild over bore tag.

[Jurassic-1]

How long has the engine sat since the rebuild? I have seen many bent pushrods due to low mileage engines sitting without being run for awhile. Tight valves combined with old gas does this a lot. We ran into one recently that broke 2 pushrods and we pulled them out and I aired up the cylinder and pulled the valve spring to get to the valve and cleaned it with carb spray then worked wd40 into the guide until it moved free. We then ran the engine at idle for a bit using sea foam to loosen the varnish. We ran the engine gently for a bit and it cleaned up nice and ran great. Just make sure the old gas has been removed and put clean fuel back in. You already have it apart and I wondered what you found inside.

[wcstory]

Originally Posted by Jurassic-1

How long has the engine sat since the rebuild? I have seen many bent pushrods due to low mileage engines sitting without being run for awhile. Tight valves combined with old gas does this a lot. We ran into one recently that broke 2 pushrods and we pulled them out and I aired up the cylinder and pulled the valve spring to get to the valve and cleaned it with carb spray then worked wd40 into the guide until it moved free. We then ran the engine at idle for a bit using sea foam to loosen the varnish. We ran the engine gently for a bit and it cleaned up nice and ran great. Just make sure the old gas has been removed and put clean fuel back in. You already have it apart and I wondered what you found inside.

That's 13,000 since manufacture. She was a fire support truck.

Prior to me getting her I'm guessing the PO bought it non running. It must of sat for a couple years. The old carb was frozen, the gas tank rusted out and fuel lines clogged. I found the old carb in a body compartment. There was a brand new tank in it, but not hooked up. It ran on a boat fuel tank and 10' of fuel line to the pump.

He must of put the new carb on it, a good blast of starting spray and fired it up without checking to see if it turned free. The push rods were the weak point and gave (luckily).

It was running rough when I got it. I hooked up the new tank and found the fuel line 100% plugged. Bought a new fuel line from Inline Tube

I've got both heads off and on the bench. When I open the valve covers I found #1 intake didn't want to compress with a bar, #3 exhaust was sticky/slow. Tomorrow I'm going to see which valves are stuck/sticky. Hoping to be able to pop the springs and tap out the stuck valves.

[Jurassic-1]

Sounds like it was a case of it sitting too long. It will be a nice rig once you get it back together. What year is it? A friend of mine had a 1965 Fire truck in Ark. about 10 years ago he was selling it also had about 18,000 actual miles and was sure a cool truck. Post some pictures of the truck if you get a chance.Good luck.

[wcstory]

A couple photos.

The utility body was built like a brick ****house and weighed every bit as much. I recently pulled it off and have it for sale.

My plans are to keep mostly original aside from adding power steering and power brakes. I had hoped to keep the paint, but the truck was repainted at some point and it is not holding up well.

[1971 GMC SHORTY]

Be careful I once was Pulling a Big Block Chevy With Maifold and Popped My Rotorculf Uggg Fought my work for 2 Years to Fix It

[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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