1978 5.7l pre-alpha with alpha gen 1 drive over heating

[Searay205]

I love the empty miller lite can in the bilge. At lease somebody had a good time.

 

[matt0107]

I love the empty miller lite can in the bilge. At lease somebody had a good time.

Must have missed one. I already cleared out the cans once before. I’m sure there will be a couple more after I pull the heads. Lol.

 

[nola mike]

The rest of your compression numbers aren't so hot either

 

[matt0107]

The rest of your compression numbers aren't so hot either

It’s a cheap Amazon one tester. Lost my good tester. It always reads low. Like 20 psi ish. So basically I was more looking for cylinder balance.

 

[Rick Stephens]

Once you disassemble your motor it is too late to "pressure test your heads". That is crap. Always do cooling system pressure test before teardown. Screwing yourself on ever knowing for sure if there are any cracks until you get it back together.

After cooling system pressure test do a leak down which tells you where your issues are.

Between the two you can target your repairs. Otherwise all is a guess until fully assembled again.

 

[Lou C]

Chevy small blocks are easy to take apart & repair but you have to know what you’re starting with. Might want to line up a machine shop to check out the heads if you do wind up taking it apart based on testing

 

[matt0107]

Once you disassemble your motor it is too late to "pressure test your heads". That is crap. Always do cooling system pressure test before teardown. Screwing yourself on ever knowing for sure if there are any cracks until you get it back together.

After cooling system pressure test do a leak down which tells you where your issues are.

Between the two you can target your repairs. Otherwise all is a guess until fully assembled again.

I just figured either way it’s getting water in the pistons 4 and 6. From the washed plugs. It’s also gurgling when I shut it down so I’m assuming it’s pushing Water into those cylinders. And the exhaust starts getting steamy after it warms up. By pressure I meant pressure the coolant journals on the heads and check for leaks with water around the valves. They plug all the water passages in a jig. They have the tools to do that. That’s how they check for cracks anyway. Might even have the valves done. Worst case I have a spare set of heads. Or multiple sets. Lol. I just figured either way this thing is coming apart. Does that seam logical?

 

[Rick Stephens]

I just figured either way it’s getting water in the pistons 4 and 6. From the washed plugs. It’s also gurgling when I shut it down so I’m assuming it’s pushing Water into those cylinders. And the exhaust starts getting steamy after it warms up. By pressure I meant pressure the coolant journals on the heads and check for leaks with water around the valves. They plug all the water passages in a jig. They have the tools to do that. That’s how they check for cracks anyway. Might even have the valves done. Worst case I have a spare set of heads. Or multiple sets. Lol. I just figured either way this thing is coming apart. Does that seam logical?

Suit yourself, it's your motor and your money. You won't know whether the block has a crack until you reassemble.

 

[matt0107]

Suit yourself, it's your motor and your money. You won't know whether the block has a crack until you reassemble.

I appreciate your input. But if it is a blown head gasket and I pressurize the coolant system. Wouldn’t I not it leak just the same as a cracked head? Always open to ideas anyhow. Just want to know the logic.

 

[nola mike]

I appreciate your input. But if it is a blown head gasket and I pressurize the coolant system. Wouldn’t I not it leak just the same as a cracked head? Always open to ideas anyhow. Just want to know the logic.

Not necessarily, and that's what a leak down test would show. Combustion gases are under a lot higher pressure than what you'll be pressurizing the block to.

 

[matt0107]

Not necessarily, and that's what a leak down test would show. Combustion gases are under a lot higher pressure than what you'll be pressurizing the block to.

Ok I will grab the gauges. Guess the higher compression could lift the head and push the gasses through gasket to the coolant passage. Where a cracked head would leak easier and even easier when it warms up. Wish I could save time. Just want to get this thing in the water. Thanks for all the replies.

 

[matt0107]

Not necessarily, and that's what a leak down test would show. Combustion gases are under a lot higher pressure than what you'll be pressurizing the block to.

Ok I got ya. Wasn’t thinking about cracked block. Just worried about the heads. Thanks.

 

[Scott06]

I appreciate your input. But if it is a blown head gasket and I pressurize the coolant system. Wouldn’t I not it leak just the same as a cracked head? Always open to ideas anyhow. Just want to know the logic.

A blown head gasket between those two low cylinders i would expect air pressure to come into combustion chamber and out sparkplug holes if you back the rockers to close the valves.
cracked block that pressure will end up in crank case.
if over head you could also have cracked heads not just gasket

 

[matt0107]

A blown head gasket between those two low cylinders i would expect air pressure to come into combustion chamber and out sparkplug holes if you back the rockers to close the valves.
cracked block that pressure will end up in crank case.
if over head you could also have cracked heads not just gasket

Yeah since I don’t have milky oil I’m leaning more against cracked head/ blown head gasket.