1975 K-10 Project

[BBM3]

Okay finally a confirmation of my guess regarding the vent pictured above.

From another forum:
"Some trucks (over a certain GVW) came from the factory without vapor canisters and on those trucks GM simply installed a vent cap (like the ones used on transmissions/rearends) onto the vapor line fitting of the sending unit."

Time to drop the right hand tank and figure out why it is disconnected from the selector valve, fix whatever is wrong, and pick up two vent caps.

Wow! It has taken more internet searching time trying to figure out what is going on and why my truck has no sign of ever having an evap. system than actual wrenching time.

[enaberif]

These old trucks are funny. We sometimes forget that they can be over 40 years old and never know how many previous hands have touched the truck in its lifetime.

So when we start working on them and doing a small job it turns into a medium job then a massive job because we want to do things right and fix it properly.

[BBM3]

Exactly!!!!

[BBM3]

I forgot Plan 'C'
Another vented tank solution.
The "Rolling Molotov".
I remember seeing this solution often when I was much younger.




Edit: Spelling

[enaberif]

LOL. That is perhaps if you got extremely annoyed with the truck and want to burn it down.

[LTZ C20]

Nope not just you! Plus they match my engine, same paint.

[BBM3]

Not a great day. 
I finished installing my dual exhaust system today started the truck and the left side is blowing blue smoke.
I let it warm up to make sure it wasn't just valve guide seals but it still smoked.
I guess the truck was burning oil all along but it was being diluted by the right bank with the old single exhaust system.

Looks like I'll be pulling the motor and giving it a refresh.
I really hoped I was going to be able to avoid an engine rebuild.

[enaberif]

Not a great day. 
I finished installing my dual exhaust system today started the truck and the left side is blowing blue smoke.
I let it warm up to make sure it wasn't just valve guide seals but it still smoked.
I guess the truck was burning oil all along but it was being diluted by the right bank with the old single exhaust system.

Looks like I'll be pulling the motor and giving it a refresh.
I really hoped I was going to be able to avoid an engine rebuild.

Do a compression test before you do anything to get an idea of the motors condition.

[BBM3]

Yep picked up a compression tester yesterday.
I'll also look at the plugs.

[BBM3]

Finally did the compression test today.

All 8 spark plugs were dry and black, not black and oily. I am sure the carb is running rich.
All 8 cylinders were 90 PSI +/- 2 PSI.
Corrected for altitude (8000 feet) that would be about 115 PSI. Not great but not disastrous?
I ran the test with all of the spark plugs removed, disconnected the "Batt" terminal from the distributer, and held the throttle and choke wide open while cranking.
One thing I did wrong was I did not bring the engine up to operating temperature. It was 70F in my garage.
I put a couple tablespoons of oil in one cylinder just to see what would happen and I noted an increase of about 5 PSI.

Other than running the test again with the engine warm I'm not sure where to go next.

[enaberif]

115 psi is pretty low for a sbc but as long as the numbers are within 10% of each other then its ok.

I would prefer to see numbers in the 130-140 range for a healthy engine.

[BBM3]

I agree.
For sure this motor is well worn. But no knocks, starts instantly, idles smoothly, and runs fine under load.

So I just put the old plugs back in and started it.
No more blue smoke!
What the heck is / was going on?
A piston ring that somehow became stuck after I installed the new exhaust and suddenly fixed itself after I did the compression test?

[enaberif]

I agree.
For sure this motor is well worn. But no knocks, starts instantly, idles smoothly, and runs fine under load.

So I just put the old plugs back in and started it.
No more blue smoke!
What the heck is / was going on?
A piston ring that somehow became stuck after I installed the new exhaust and suddenly fixed itself after I did the compression test?

You put oil into the cylinders. That could have helped.

[BBM3]

I did but only cylinder number 3 as a test which I chose because it was easily accessible.
Maybe by chance that cleared things up (no pun intended). If so I need to buy a lottery ticket tomorrow.

[MannyDantyla]

Have you checked compression?

There's oil additives that help with compression and oil consumption. I think they work by adding zinc to the mix which bonds to the cylinder walls and helps the compression rings seal a little better. A product called Engine Restore has really good reviews, look it up on Amazon.