Ford 351W (AQ240) overhaul questions

[cb950]

Hi all,
I am rebuilding my engine after getting a block full of water due to either the crack in cylinder#1, or possibly the timing chain seal by the water passages. I have a few questions for anyone who knows the answers.
1. My boat is raw water cooled, and has been running without a thermostat. I bought a thermostat for the engine (140 deg. F) and noticed that the temp would jump up to around 200F, and smoke (steam) out the exhaust, then go back down to 140 or so, and constantly bounce up and down. I didn't like how hot it was getting, or the tons of smoke out the exhaust, so I ran it without the thermostat. Temp stayed pretty consistent at 120ish (on the guage). I don't expect it's possible to get a consistent temp with raw water cooling since the water is always cold. Should I continue to run the rebuild with no thermostat?

2. There was an oil cooler installed on the boat for engine oil, but no water was running through it. Should I replace this, or would it make the engine run too cold? (assuming thermostat gets left out)

3. What Parts should I get specific for marine use besides head gaskets, and brass freeze plugs? any recommendation on piston metal type/ring metal type, oil pump, etc?
Thanks!

 

[lonemust]

Re: Ford 351W (AQ240) overhaul questions

Well if you replace the cam, be sure it is a marine cam or a truck/rv cam. First thing you should do after tear down is have a machine shop "hot tank" everything metal.Valvecovers, block, heads, timing cover, and oil pan. Have them install the new cam bearing and brass freeze plugs.

With a 160 thermastat it should not hit 200. That sounds like either one of the water pumps isn't working or block has alot of scale build up in the block's water jackets. To do the rebuild right have the mach shop redo the heads also. A cracked head could cause water in the oil too. Have seen it happen more times then I careto think about. Now after it is all back together put a 140 stat in and see if you have the same problem with temp. You should not run it without the stat in. Be sure to replace the raw and block water pumps when you rebuild it. that way you know both pumps are good.

 

[cb950]

Re: Ford 351W (AQ240) overhaul questions

I know the raw water pump/impeller is good, but I will replace the block water circulating pump. what about the engine oil cooler? is it necessary? Anyone have recommendations for piston type/ring type? Thanks for the reply!

 

[haulnazz15]

Re: Ford 351W (AQ240) overhaul questions

Well first off, you need to strip down the engine/heads and take it to a machine shop to be cleaned and magnafluxed so you know if what you have is even rebuildable.

As far as the piston type goes, cast pistons are fine, but you can use hypereutic if you want to step up a bit without hurting the pocketbook too much. No real reason to use forged pistons in this application.

I would make sure to have a thermostat in the housing or else you'll be getting worse fuel efficiency. I would pressure test the manifolds and to ensure there isn't any blockage. Use new water hoses too as well as a new marine water pump on the engine.

It has an external oil cooler? Seems odd since there isn't a radiator or any airflow to cool the fins. That might be an add-on from the previous owner who didn't know what he was doing.

 

[cb950]

Re: Ford 351W (AQ240) overhaul questions

It has been rebuilt, and the oil cooler may have been from a previous build. It may have even been fresh cooled at one time. It's pretty frankensteined now. (Raw water is pulled through a thru-hull fitting/exhaust is ported directly out through the transom instead of the outdrive also, etc.) The block has a visible crack in cyl#1, and I will have to have the heads inspected. The oil cooler cools with water. It looks like this: http://www.marineexhaustmanifolds.com/oil-coolers.htm
but I don't trust the one that I have. I will buy a new one, and install it correctly with the rebuild if someone gives me the impression that it's necessary.
Thanks for the info.