350 tpi engine, mixing water and oil, coolant appears to still be clean. took the heads off and the gaskets looked ok, so does that mean theres a crack in the engine block somewhere?

 

blown intake manifold gasket.

It will allow coolant down but not up.

 

the intake manifold gaskets looked good though

 

it was also running rough and the timing didnt seem to want to adjust like it wasnt going into closed loop

 

Well my issue is every time I have seen a blown head gasket or a cracked block (my experience is coming from one cracked block and multiple blown head gaskets) their was oil in the coolant. Only time I have experienced it the other way around was when the intake manifold gasket let go.

 

I would agree, GM intake gaskets are notorious for going out, Also while you have the heads off, make sure they are true and straight. warped heads will allow coolant and oil to mix. Do the same with the intake where it meets up with the gasket. If you had a crack in the engine somewhere you would probably notice the milky mix in your coolant as well.

 

i would just do a complete top end renewal and it should fix the problem

 

For the head gaskets, define "looks ok". I'd be more concerned with the block and the heads, there should be a nice and unbroken ring that is completely clean around the cylinder. If there is any point where its not, its leaking there. If you're getting a milkshake, that is probably where its coming from.

 

all the rings on the gaskets are clean and unbroken, intake gaskets appear perfectly intacted, almost new since they're not very old.

Off topic question, are the lower bearings, cam, and timing chain the same in a 350 as a 305? Im asking because if i cant get this issue solved I still have the original 305 sitting that just needs new piston rings and valve seals, figured I would gut the 350 for its brand new parts and put on the 305.

 

Yes those are the same but I would not reuse the bearings.

If you're going to try to fix it and have the heads surfaced, have the block done as well. More often than not, I've found on problem children that the block is not flat.

 

I,m in the same boat too.

(milk choc. in oil and car running like a 5 cylinder when idle hot)

But I did a compresion test. Numbers were:

Cylinders 1, 2, 3, 4 & 6 = 168 psi
Cylinder 5 = 118 psi

Then, I put 5ml oil in cyl. 5 and compresion was incremented in 14 psi only.
Then rings o.k. (the compresion tester was off with a bith water in it)

Put in a bit of compressed air by the spark plug hole and nothing happened.


Took that head gasket off, but it "looks ok" too. Only a bit of white deposits.
(Int man gasket "looks ok". It's 3 years old only).

I'm confused too. Where is the failure?.

What if I replace total top end gasket kit and problem remains the same?


I need the car for work, school transportation, wife's supermarket, children events, etc. etc.

I've headache with a new engine surprise.


Thanks for your ideas and opinnions,


Denis V.

 

Just to add my two cents to the good information already given here, factory heads can crack between the intake and exhaust valve seats. This is hard to see but a pressure test will show it. The pressure test runs about $50-75 at most head shops. Also, there is no oil pressure in the crankcase itself, yet the coolant is at 15 psi. I have seen coolant in the oil and not oil in the coolant due to a cracked block. Generally though, i agree that the intake is the most common cause of coolant in oil.

 

Don't forget the thread sealer on the bolts.
Don't ask why i'm saying that either I never done that I swear

 

Ive often wondered whether the thread sealer is more so that the bolts don't freeze in place than to prevent coolant seepage. Taking a motor apart after 20 years of operation, you'll find the intake manifold & head bolts looking pretty sad. Imagine what they would look like without thread sealer.

 

I actually forgot to put the sealer on once and I got coolant in the oil. took all the crap apart and put the sealer on and tada! no more coolant in the oil.