Milky oil after 1984 K10 305 top end rebuild.

[AlexK10]

Hi everyone, About 8-10 months ago I tore down the top end (removed intake and heads) to fix a head gasket leak in cyl #8. This cylinder had water when I pulled the spark plug to do basic maintenance and led me to remove the heads etc.

Anyways after getting valves reseated (new stem seals) and flattening the heads at the machine shop, I got new gaskets and reinstalled the heads and continued with all the extra work involved

Details of what I did and used:
Head surface and valve job
Fel pro 8510 pt head gaskets
Visually checked the block surface and cleaned with solvent rag
Used thread sealer on all head bolts
Torqued in 3 step process following the correct sequence
Fel pro 90314-1 intake gaskets with black Permatex on front and back china and around water ports
Thread sealer on all intake bolts although 4 don't go into water or oil passages.

On initial startup I noticed bubbling between the intake and the head surface. So I timed the engine at 12BTDC tuned the carb (over several days). Noticed condensation on the oil cap and lots of water droplets on the dipstick.

Removed the intake and used:
Mr. Gasket 8520 intake seals that have a silicone ring around each port
Used the right stuff around all ports (not only water ports) and also on front and back.
Thread sealer on all intake bolts although 4 don't go into water or oil passages.

All start ups have been great, meaning No bubbling between intake and heads as before and no droplets on the dipstick.

To flush the water that had leaked into the oil from the original intake leak... Did two oil changes to flush out any water or condensation. The first one with a diesel flush (added a quart of diesel to the oil in the crank, ran for 5 minutes and drained). Added new oil and filter, ran for 10 minutes and drained. Then added new oil and filter and that's what it has now.

However, my oil is slowly getting milkier and oil cap always has condensation. Which leads me to believe I still have a leak, and coolant is also slowly dropping.

Extra info:
No oil in coolant
No visible bubbling in radiator
Engine temp between 180 and 200
Timing at 12BTDC
Starts and shuts down without issue
New PCV valve connected to lower vacuum port on quadrajet and new breather filter on the other valve cover.
Stock 305 other that bored cylinders. Not a performance or high HP engine.

When I removed the heads the first time I noticed either a .30 or .40 stamped on the top of the pistons. Will check photos to confirm.

Getting ready to remove the heads again and have them checked at the machine shop for flatness.

The question:
If my block was bored to .30 or .40, what head gasket is best? Any part number recommended?

Was thinking of using the Fel pro 17020 head gasket (instead of the 8510 pt) but not sure if it would seal correctly with oversized cylinders.

Any other ideas?

 

[AlexK10]

Just found out that the following:
Fel pro 505SD
Bore 3.90

Fel pro 8510 pt
Bore 3.855

Fel pro 17020
Bore 3.84

If stock bore is 3.736 and it was bored .03 or .04 or .06 over

Actual bore is either 3.766, 3.776, 3.796

Am I calculating this correctly?

 

[1987 GMC Jimmy]

Yes, it’s factory bore plus 0.0X0.

 

[AlexK10]

Thank you for confirming the measurements.

Now I'm thinking it may be another intake manifold seal leak and not a head gasket.

Since heads where cut flat and a Fel pro 8510 pt / 3.855" was used and all bolt threads were sealed. Torqued to spec and sequence in three steps.

Is there anyway to find out before I tear the engine apart again?

Any indications to look for that may point towards an intake or head gasket problem?

 

[PrairieDrifter]

Don't forget that chevy heads are notorious for cracking on the chamber surface of the heads and from water jackets to water jackets. Especially in the later years

 

[AlexK10]

Thank you Prairie,

In this case it would be advisable to remove the heads and check them anyways to be sure?

Are these cracks visible to the naked eye or do I need a penetrant dye marker?

 

[bucket]

How about the intake mounting surface? Has it been checked for flatness and pitting? When I first started reading, I was thinking there could be a crack in the #8 cylinder, but the fact that you changed the intake gaskets again with a significant decrease in coolant consumption makes me think it's an intake sealing issue.

Don't forget that chevy heads are notorious for cracking on the chamber surface of the heads and from water jackets to water jackets. Especially in the later years

But 'normally' a crack in the combustion chamber will cause a minor compression leak into the cooling system and no coolant will find it's way to the oil. Again, that's 'normally' the case.

 

[Snoots]

When you decked your heads that caused them to sit lower on the block.
In turn that changed the angle between the heads and intake manifold.
You either have to machine the intake to match or the cheap and easy way out would be to use 2 intake gaskets.

 

[bucket]

When you decked your heads that caused them to sit lower on the block.
In turn that changed the angle between the heads and intake manifold.
You either have to machine the intake to match or the cheap and easy way out would be to use 2 intake gaskets.

Good point.

The test for that would be to dry fit the intake with no gaskets. If it bottoms on the China wall before it mates with the heads, then the intake needs the ends shaved.

In no way do I recommend it, but...
Those two areas of the intake can be "machined" with a careful eye, a steady hand and a flap disc on an angle grinder.

 

[AlexK10]

Thank you bucket and Snooks,

Yes there was a significant decrease in water being mixed with the oil when I changed the intake gasket the second time.

The first time around it was very obvious water was getting into the oil in about 30 minutes of running I noticed something fishy with "condensation" and the dipstick droplets.

After the second intake gasket install... the oil stayed clean for about two weeks of weekend startups and tuning (about 4 hours total run time) then slowly started getting cloudy and whitish.

Initially I had used a felpro 90314-1 and the second time I used the Mr Gasket 8520 which seems to be "better". Also used the right stuff lightly on all the ports and a thick bead in china. On the china it did squeeze out ok/uniform.

Even though the cast iron or steel (not alum) manifold surface was always super cleaned with a razor, wire wheel and solvent. I never checked for flatness with any pression straight edge or the matting surface angle.

What's next?

Remove the intake and check surface condition and angle in relation to heads before removing heads?

 

[bucket]

What's next?

Remove the intake and check surface condition and angle in relation to heads before removing heads?

Yes, that would be my next move.

 

[Snoots]

There ain't no way on God's green earth that Mr. Gasket is better than Fel-Pro.

 

[AlexK10]

Hey Snoots,

There ain't no way on God's green earth that Mr. Gasket is better than Fel-Pro.

That made me laugh!

Just said that because I was perhaps fooled by Mrs Gasket's silicone rings around the ports, and by the fact that I used Permatex " the right stuff" on all the ports and have reduced the original leak I had with felpro 90314-1.

But I do get what you mean. I'm not a mechanic, just a weekend warrior which is trying to slowly fix up a beat up truck the best way I can, first mechanically then the cosmetics.

 

[BBCfan]

I forget what type of exhaust gas they look for but I had it done to my plow truck...warped head. There's a special cap they put on to detect small traces of exhaust gas in your cooling system in place of the radiator cap. Sorry for the loss of memory....getting old.

 

[78C10BigTen]

Good point.

The test for that would be to dry fit the intake with no gaskets. If it bottoms on the China wall before it mates with the heads, then the intake needs the ends shaved.

In no way do I recommend it, but...
Those two areas of the intake can be "machined" with a careful eye, a steady hand and a flap disc on an angle grinder.

Educate the dumb here.... whats the china wall?