Bent push rods - specs needed
 

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 13,000 miles on a 305 v6.

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 25 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 drivers side valve cover. One of the push rod in #1 was a "S" and 3# was tweaked. Time to pull the heads. I'm hoping there are no bent valves.

I ordered a Fel-Pro Master gasket set and 12 Sealed Power RP-3099 push rods. I'm waiting for the parts to come in before tearing down the heads.

What are the head torque specs? Can someone please post or PM me the torque specs and valve lash. I'll take ALL the info I can get.

Re: Bent push rods - specs needed
 

I found the torque and lash on Jolly's site

http://www.6066gmcguy.com/EngineData.html

Head torque 65-72 ft lbs

Valve lash (hot running) Intake -- 0.012", Exhaust -- 0.018"

Re: Bent push rods - specs needed
 

When I bought my GMC it had not been running for many, many years. After I started tinkering with it, I pulled the valve covers to see what was up. (The PO believed the exhaust valves were fried from non-leaded gas) I found 3 exhaust pushrods just laying loose, not touching the rockers.
Before you pull the heads, I would pull the rocker assemblies and plugs. With the rockers removed all the valve should be closed, squirt some oil in the cylinders and do a compression test.
You would still have to do these steps, but maybe it will give you an idea how bad it is.
I think the valves stick on these engines, especially if they sit for long periods. I try to use the truck to run an errand at least once a week.

Re: Bent push rods - specs needed
 

The intake valve on #1 is stuck, this was the bent rod. The exhaust valve on #3 is very slow. I think because of #1 I'm going to have to pull the head. Any damage to the valves and I will end up going with plan "B"

I have a line on a 1965 305E that came out a month ago to do a SBC swap. The owner's mechanic wants it out of his shop. The price is now at $300. Plan "B" would be to pick up the 305E and swap the motor.

From there I'll decide on rebuilding the original. I have a set of 20 over pistons I traded for.

Re: Bent push rods - specs needed
 

Forgot to update my thread.

Ordered Fel Pro full gasket set FS 7961 SB-1

Once it came in I pulled the valve covers - popped pushrods on 1, 3 & 4. #3 intake valve solid frozen, 1 & 4 super slow.... pull the heads

Set out my metal bench and started disassembling the top end. Took a ton of pictures for reference. They're on my Flickr account feel free to browse https://www.flickr.com/gp/79753808@N07/a67a50

The heads are **** heavy! So much I got out the garage scale to weigh them. Just shy of 70# dressed. I've got a 14 year old daughter that doesn't weigh much more.:ahhhh:

Cylinders look good. :thumbsup:

Pulled the rocker bar off, removed the springs and pulled the valves. Intake #3 had to be tapped out. Varnished in. They all got cleaned and polished with flitz. #3 slid in and out smoothly with no sign of being hit by a piston. No marks on pistons 1, 3 & 4.

Those are some big bores, my quart can of Flitz fits right in cylinder #1

Cleaned all the top end components. Valves got cleaned in diesel at the house. Didn't want to mess up the order, I kept them all where the were. Everything else went to work and into the parts cleaner.

All external parts were degreased, power brushed, degreased and painted.

Re-assembled the heads with springs, valves and retainers in the same positions. New valve seals.

I bought a factory manual for torque specs and torque sequences from a seller on Amazon. Of course I click the address for my niece I buy text books for. Seller promises to fix so I don't have to cancel order. Guess where manual get shipped to....

Several awesome members of the 60-66 GMC Truck Club and 67-72 Chevy Truck Forum helped me with specs. :yourock:

Got her re-assembled, torqued and lashed. Fired her up to less than stellar results. Trouble appears to be timing and or carb. Valves move freely and are hot lashed to factory specs.



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

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! I need a new gas sending unit! Empty 5 gallon (fresh) mower gas can into tank.

WooHoo!!

I twisted the distributor till it sounded decent and tightened it down. **** with the timing light I was going for a ride!

It's amazing how much better they run 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 , **** 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.

https://youtu.be/PBLQRVSzU2U

Re: Bent push rods - specs needed
 

305E head Torque Sequence

Re: Bent push rods - specs needed
 

A while back I mailed a head or two to another member. USPS will take up to 70 pounds. They didn't even try to deliver to him, as I recall, but just delivered the "please pick up at the post office" slip. :)

One of the trucks I bought was running rough. But ran well enough to climb the ramps up onto my carhauler. When I took the heads off, one bank had no gasket at all between two cylinders and the upper passageway (lifter access). The other side had started blowing between two cylinders. So yes, I would second your experience. These trucks will run on 2 cylinders almost as well as on all 6. Almost. :)