Perry - can you give me a little more insight into why? What do you think is happening here?

 

I did my best to do a compression test. The results are all over the map.

Passenger side (from rear to front):
90
15 (although I'd swear it was 85 the first time)
145
98

Drive side (from rear to front)
80
20
160
85

Both cylinders with low compression are ones that are missing pushrods, but I don't see how that would be related. No pushrod = valve closed.

 

Engine may very well have been hydrolocked at one time. Only other pre-checks for pre-rebuild (I would saw that needs a rebuild) are pull the oil pan and see the condition of the lower end. Sometimes a connecting rod will get bent if the engine gets hydrolocked. Check the axial play on the crankshaft too. I wonder if then engine is timed correctly/ did the valve hit a piston. I actually cant believe it runs.

 

The bent pushrods could be due to stuck valves. The simple way to check this is to remove the rocker arms and tap the valve stem. You will hear the valve open and close. Once you are sure they all operate, retry you compression test. You could easily have a valve stuck slightly open.


Now for my opinion, I would pull the motor and go through it. That is just based on the picture of the heads. They are very rusty in places that shouldn't be. Yes it is an expense, but cheap insurance in the long run.


Good luck and keep the pics coming.

 

That milky substance tells me theres water in the motor. Drain the oil out a take off and drain the.oil filter Maybe its just a hydrauliced motor with a blown head gasket or warped head, either way its not worth spending money on a motor thats been abused like that unless your rebuilding it. Rebuilding it ,its only the top end thats shot some will say. These will be the people that forget that you have bearings and a cam. You have a 351M/ 400 and they are pretty cheap, $500 for nothing special motor upto a gnote or so for one with a cam ,intake and carb mod.

 

Thanks guys. Think I need a beer.

 

Thats probably the best thing to do today Bruce,relax and enjoy the rest of the day. Can start a new game plan tomorrow when its a bit less stresfull

 

So your experience and my beer bring better results. Tapped the valves as you suggested and the 2 low compression cylinders both came up to 90psi. Thanks.

I know the problems probably run deeper but I am going to start by replacing the push rods and see what I have then.

 

Although anyone in Ontario, Quebec or Northern NY who has a running 351M or 400 for sale, I am interested.

 

IIRC your compression shouldnt be below 120lbs, 140 -160 is about normal. May be different for these low compression smog motors but under 140 would have me scratching my head and searching for the specs.

 

If you still have your buddies compression test, tomorrow, hook about 50lbs of air to the low cylinder at TDC and listen to the top of the carburetor, oil cap dipstick opening, exhaust pipe and even radiator cap opening to hear the air escaping.
Carburetor= intake valve leak
Exhaust pipe= exhaust valve leak
Oil cap dipstick opening= broke ring or piston
Radiator cap opening=blown head gasket or warped head
I wish you the best of luck

 

I just did this, first "good used" engine I went to look at was seized. Couldn't find anything without driving for 5+ hours...Gave up and ordered a new long block from Ideal Supply. Turns out the engine was built in Mexico! Only about 5000km in but so far so good. When I called a local machine shop the rebuild price to start was $500 more than the long block. Good luck !

 

Hey Bruce. I have a really nice 460 with 77,000 km out of a 77 Lincoln and all the factory truck 460 motor mounts and truck manifolds. Far better motor then the Modified.

 

Loui- message sent

 

Ah, now we find out why the truck was so cheap!