First I'd just like to say I've lurked here for awhile now and enjoy the site very much but haven't really had a reason to post until now.

I have a '70 f100 with a 351w out of a early 70's torino and an automatic overdrive from an 80's f150.

Last night it overheated on me while doing 70 mph down the hwy. I wasn't paying attention to my temp guage at all untill after the fact so I'm not sure if it was gradual or all of the sudden. After noticing a loss of power going up an incline I then saw the needle pegged on the temp guage and quickly pulled over. The radiator had a hole in it and it was HOT.

This morning I put a new radiator in it rather than get the old one repaired, it was in pretty sad shape upon inspection. After getting it in and getting some coolant in it I fired it up. It started right up, idled fine and after a 5 mile test drive all seemed fine.

This afternoon I drove it again and after it warmed up a bit more I got some dreadded white smoke/steam from the tail pipes. I continued on and when I got back up to 55mph or so and it cooled down a little it cleared up. I dont have any water in my oil that I can tell or any oil in my radiator.

So my question is this; Is it a head gasket or a cracked head? My thinking was a bad gasket would have made it smoke on startup.... BUT if it was a cracked head I dont know that it could have cleared up so fast after cooling down a little bit while driving. Are the 351 heads crack prone? Are the headgaskets a weak link?

I will find out soon enough I guess but wanted your opinions.

Thanks... Kurt

 

I wouldn't say that the 351W heads, or really any of the other Ford heads are really crack-prone. Since you ran it hot, lost power, and are seeing white smoke out of the tailpipe, I would be inclined to say that you might have a blown head gasket. You won't necessarily see oil and water mixed, since you can see gaskets compromised in several places. Are you consuming coolant, or are you seeing an excessive amount of pressure in the cooling system? That would be a good indication of blowing a head gasket between a cylinder and a water passage. I really wouldn't worry about a cracked head.

Here are a couple of things to try:
Take off the radiator cap and crank the engine. You'll probably see a little coolant movement, but if it blows coolant out the radiator, think head gasket.
Do a real compression test. That will give you an excellent idea of the condition of the engine.

 

Have a look at the spark plugs as well. Plugs in a cylinder that's using coolant will be nice and clean, almost like you had just replaced them. My Aerostar 3.0L was using coolant thorugh a bad head gasket and I used this method to find out which head to pull. Didn't want to do 2 on that thing!

 

Well I got some new head gaskets installed today. Neither of the old ones looked to too bad but I was definatly getting some coolant in two or three cylenders.

All is not ok though.... I am having a transmission problem all the sudden. It is not shifting out of low gear into 2nd???? It was fine before I pulled the heads s I'm sure it is something I did. It has an aod and I'm thinking somethings not right with the trans cable at the carb but I'm sure its hooked up the same way as before and the linkage looks fine(never touched it though) and it shifts through the gears fine with the shifter. Also the fluid is fine.

Any ideas??????

Thanks

 

Does the AOD have a vaccuum line to it??? If so maybe it isnt connected or is connected in the wrong place.