Hi guys, just went to load my freshly rebuilt engine into the trailer so it can go off to get fitted in my boat and figured it would be a good idea to drop the oil and put some fresh in.

Problem! When I dropped it, it came out emulsified!
I had recently had a manifold leak and got water in the bores but thought I had got away with it and simply fitted new manifolds and risers.

Do you think I have cracked a head? On compression tests all came out at 140 psi except No. 7 which read 135. Could this be the culprit? Is this common?

TIA

Freshly rebuilt? No this time out right?

I would perform a leakdown check, if you have a crack or a leak it may not show on a just a compression check. the compression tester just records the highest point reached, leakdown will try to hold that pressure.

Could be a headgasket, bad install of new intake, crack in head, leak in cooler, bad install of new risers, old mositure from previous problem.

How long have you ran the engine after repairs?

How many oil changes after repairs?

Why is the engine out of the boat again?

When you say freshly rebuilt, how long ago? And was the entire engine rebuilt?

Tried a leakdown but seemed inconclusive may have to do it again.

I had ruled out the intake as there is no oil to water seperation going on in there so should be no chance of transfer.

Could be gasket, could be cooler??!!

After changing the manifolds I flushed out all the emulsified oil and changed it and the filter. The engine has run for approximately 45 mins since then on a test stand.

The engine is out because I bought the boat as a wreck to restore. The engine had suffered some frost damage to the thermostat housing and inlet manifold but nothing else evident during the rebuild.

I stripped the engine down to the block with the crank and cam left in situ. Everything else has been restored or replaced for new, which in the UK is not cheap!! This was all carried out very recently.

Frost damage? Was the block checked to make sure it wasn't cracked before you rebuilt it? I know that's pretty obvious, but I have seen it done.

Pressure test, my guess its a cracked block.

I guess i should have asked what engine, if you have a GM based small block or big block yes water runs though the intake and will dump in the lifter galley, and into your oil if there is a leak.

A leaking head gasket or cracked head can cause water in the oil, but most likely you will misfire enough to know you have a problem.

Yes, a leak inside an oil cooler will casue water to enter the oil system, or worse oil to exit. If this engine was not winterized the cooler can be split by the ice and cause a breach.

I agree that if you had frost damage (freezing) the leak could be anywhere. A crack that is not obvious during a rebuild will grow when heat and pressure is applied.

If you are confident the valves are seating properly I would perform another leak down check.

Intake is the first thing I would check. While there check the lifter valley for cracks.

I have noticed a small misfire occuring so am leaning towards head or head gasket. I have to take the inlet to get to that so that will be my first job.

Engine is a 454 Mag Alpha, though I am running an aluminium inlet manifold.

If the boat was in salt, check the intake first. Also, square port heads are notorious for cracking. You should see some indication whan you look at the plugs.

motor will run terrible with a cracked head. I had one that I could hardly keep running. The higher the rpms the worse it ran.