"Blown" Ford 351

Wondering if you can use an air compressor and the block drain fitting to make air come out the cracks. Maybe stick a soapy rag up the rear exhausts and take thre hull intake off and put a rag or wood plug to block flow. Remember to drop your regulator down to 15lbs.
If you can suck up soapy water first, you might be able to blow bubbles through all cracks.

Pressurizing the block is a good test to verify no leaks but remember there is always the chance you have a crack in the head or block that opens up when hot.
I did a cold test on a 460 Ford last year using 35 PSI of air pressure. You do not want to use more than that because it can blow out good gaskets if you go higher.
I put a gauge on my 460 closed the ball check valve to seal it and left it 24 hours to make sure it held pressure. That work saved me pulling the heads.   Turned out in my case we found a leak in the exhaust risors gaskets was putting water in the oil. The 460 was fine with an oil change. It ran all summer this year. My Nephews boat.   It is pretty easy to plug all the water exit holes and plumb in a connection to your air lines. I used a ball check valve and hooked it to one heater hose. Brought pressure slowly up to 35 psi then got out the soap and water spray and started checking for leaks.   I found 3 leaks at my hose clamp connections with the soap and water before getting a good test.   It will tell you quickly if you have an internal leak letting water flow into the oil.
One thing I learned the hard way, when you bleed down the air pressure after the test do it slowly. I popped off my air hose with the valve open and the water in the block under 35 PSI sprayed out, soaked a lot of stuff within 10 feet of the boat. I did not think of that when I disconnected.

Juts need to block off everywhere the water goes in & out of engine. Just get an air hose, quick disconnects, & tire chuck. Use your spare tire for pressure source. When you disconnect it will let you know if there still is pressure in the circuit.

Personally, I think this is a waste of time, as you aready know there are serous cracks.

Better to spend the time disassembling, imo.

This is a picture of a coolant test on my BMW X5 4.8L. It must be pressure checked before final assembly or you may waste a 1/2 day of labor.
My tool is homemade using parts in the garage and a trip to the local hardware.
Not shown but off to the right side of the brass T in the picture is a Ball Check valve to allow me to shut it off when needed and on the end of the ball check valve is the connection for my air compressor hose.
I just turn the compressor regulator down to 35 PSI before this test to make sure I don't blow out the gaskets in the engine.

It worked well on the 460 and on the wifes X5.

If its freeze damage. It is the block that is bad. As already pointed out if water is going into the oil the likely crack is in the lifter valley. Start looking for a block.
Overheats will damage heads and cause head gaskets to blow.

If you have a 1 piece seal block you just need a 1 piece reverse rotation seal
I think Ken in the past had located another cheaper sourse

I like that but it has 2 flaws:
1) My wife would kill me.. again.
2) I'd stub my toe on it in the middle of the night and be crippled for life.

I think you are emotionally attached to your engine Block like a dying pet or loved one. Ya got to let it go.

Yee of little faith. The fat lady is still eating.

Well that Monty Python was freakin hilarious. I AM that Black Knight! Good call tryathelete. Alas, I took the intake manifold off and found the lovely big crack and it look like to continues under the starboard head, so, I give up. Although I'm tempted to patch it too, I'd be on edge every time I take the boat out with Frankenstein engine patches all over.        Also, from the pic can someone tell me if I have the one piece seal block or two? I'm at sea on this at the moment. Would a difference enable me to use a standard 351 block? Not sure if I'm even asking a coherent question.

I would swap your parts into a new block.

Time for the funeral

You have a 2 piece rear main seal in a 78 engine, that was mentioned way back.

If all your other parts are good and you want to transfer stuff to another block you'd need an early block with the 2 pc rear main seal because your reverse rotation crank has wick lines, helix lines or whatever somebody may call them for oil at the back of the crank for oil control reasons. You also have a rotation specific camshaft distributor (just the gear on the distributor is rotation specific) and starter

You can buy a long block reverse rotation engine from numerous rebuilders, transfer your marine parts and be good to go. Of course it will cost more than transferring parts to another block, but in the long run, it may be worth it for you.

You could get a junkyard 351W from a truck that rotates the opposite way, transfer parts and reindex the transmission to work for you. You'd have to buy a normal rotation prop so that when you put the boat in forward, it will go forward. And you'd need a normal rotation marine starter and distributor (gear).

People will tell you that the boat will handle differently and lean much more to the right with a normal rotation engine To the CC purist types this is absolutely sacrilegious

I'd spend the next week or 3 of your life going through old threads here on CCF about 351W engines, read other people's experience, listen to recommendations, then make up your own mind based on your budget, engine assembly experience and
tools available to you etc

There are west coast people who will come along that could tell you what places they used for things like a long block

Oh yeah, ask questions first instead of after buying parts to make sure you get things right.

More importantly is why,meaning you would not need to. You could machine it for a 1 and put a speedi sleeve on the crank. If my Mustang engine ever comes out,which I doubt,I'll have it done.
google link

Gary S wrote: More importantly is why,meaning you would not need to. google link

My point exactly

We're just saying the same thing differently

This is why I enjoy this site. Good luck on your project. I’ll be following and hoping to learn a lot. Please update as you go.