klleetrucking

The car in question
Hope it's OK I moved my engine issues here from the newbie thread.
For those that may have not seen my intro here's what's happening. I got my '70 350 hot a couple summers ago (my fault) and since then the engine has pushed coolant out the overflow. When the engine is cold and running I can see a small stream of bubbles in the coolant. The cooling system will stabilize but maybe be 4" down from the filler neck. 16# cap, btw. Plugs look good. 100k on the engine (original). The car runs fine and drives great but I believe I compromised a head gasket.

Today, I got everything in place and took a compression test. Results: LB, 166,165,166,160. RB, 176,169,150,155. Leads me to believe blown head gasket in #5/6 cylinder area.
Current plan is to pull the top end, get the heads pressure checked for cracks and go from there. Anyone see anything I'm missing?
Thanks for looking.

76olds

What caused it to overheat a couple years ago ? What parts have you replaced ? So with the cap off, you run the car and see a stream of bubbles in the coolant then it clears up after it starts to flow really well through the tubes? Does the rad have good flow through the tubes once the car warms up and t-stat opens or does it throw up out of the filler neck ?
We need more info here.

Eric

coppercutlass

Have you done the coolant test to see if there is any contamination from exhaust gasses in it ?

oldcutlass

You probably have a blown head gasket between 6 and 8 if the RB is on the passenger side.

klleetrucking

Not sure how to do the Multi Quote so I'll try to address the reply's in order.
The engine lost coolant because yours truly put the reducer bushing in the lower radiator hose incorrectly (fits all type radiator). No leaks in the shop but somehow lost coolant later that day when driving. I totally deserve all blame and subsequent issues.

The thermostat does open and the coolant flows well but after it reaches operating temp and you open the cap/release pressure and then it "throws up". Water pump has been replaced.

I have not done an exhaust gas test at the filler neck.

Yes, RB (right bank) is the passenger side.

I only drive the car around town and it runs fine and doesn't overheat BUT, I just don't feel good about it.
I've got the car on jackstands now and drained the coolant and am proceeding to pull the accessories in prep for pulling the head/heads. It's an A/C car and I'm actually considering pulling the A/C box and system, #1 to have an excuse to install Vintage Air, #2 to gain some room to work. It's a 2 bbl. 350 so no great expectations, just want to get the engine reliable and happy for some stress free cruising this summer.
That being said, the engine has never been apart. I'm soaking all the bolts with Kroil right now and realize I'm going to snap off a few. Any quirks should be aware of?

And yes, I will be way more diligent in all aspects of disassembly/assembly. Thanks everyone.

FWIW, replaced the timing chain and gears about 2k ago.

classicmuscle442

Why are you removing radiator cap when engine is hot?

joe_padavano

I would run a leakdown test before taking anything apart, but I suspect you are correct about the head gasket. Frankly, at 100K miles, I'd pull the heads and do the valves anyway. This is also the time to replace the timing chain and gears if you haven't previously done that.

76olds

X2

The coolant will spew out the filler neck since its under pressure at that point. That's a good sign actually, its holding pressure. How much ? That needs to be determined.
I agree with others here, I wouldn't take anything apart until you have done a few more tests.
I myself would start with this,
Fill the rad to the top of the trans cooler, no further. Leave the rad cap off, fire up the engine, let it run until you see some bubbles, a little flow. Turn the heat on to defrost at this point, keep the heat on at max . Add coolant as the level drops keep it topped up to 2 inches below the filler neck at this point. Once you get full flow, rev the engine to 1500RPM or so, top the rad off to 1 inch below the filler neck. Put the cap on, return back to idle
If it continues to spew out the filler neck into the overflow with the heat on, cap on, for 10 minutes or so, then you have a head gasket problem.

Fun71

I guess I'm X3 on this one.

klleetrucking

Thanks everyone for the advice.
Unfortunately, I don't have access to leak down test equipment.
This little project has been put on hold temporarily, had to go back to work.