302 motor

[towtruckerfour]

I have a couple questions for you all. On my 70 F100, I ran a compression test because the truck isn't running right now. It has a 302 and the front 2 cylinders on driver side only have about 50 lbs each where the rest were between 110-125. Reading in my manual, it says it might be a head gasket. I have to wait for the battery to charge to try testing the rings with a shot of oil.

1. When you do a compression test, don't you remove one plug at a time which is what I did?

2. Is there an easy way to tell if it is a head gasket other than teardown?

Oil looks fine but has a little burnt smell to it. Thanks for your help and all opinions.

[fordman]

a wet test is the best way to check the compression. if the head gasket is blown it cna put pressure out 3 places that i can think of. into the water jackets. into the crank case or into the next cylinder. if the engine runs and burns alot of oil and tries to puke oil out of the top of the pcv then it could be blow and goign into the crankcase. if it runs and when it wrams up look into the radiator. if you are getting bubbles or air out of hte water then it would be leaking into the water jackets.
worn rings can also cause low compression. or it could be leaking past the valves. another way to check is to do a leak down test. and i forgot how to tell you to do it. basically you put air pressure into the cylinder and see if and where it leaks out at if at all.

[towtruckerfour]

I checked the radiator and it is low on water. The oil didn't seem to have any water in it. The other day when I took the truck to Boise I didn't know the oil was low until we got into Boise and it was clattering. I put some oil in it ( 2quarts) and it quieted right up. It never got real hot, just stayed in the normal range. I'm just trying to figure out if the top end is bad or the bottom end. Either way means teardown to some point. Would pulling the valve covers reveal anything?

[towtruckerfour]

Ok. I tried doing the wet test and if I did it right the two cylinders only went up by 5 pounds. I also pulled the valve covers and all pushrods are pushing oil. I guessing this is sounding like a head gasket that has blown. My biggest concern is if I do the top end, how do I know if the bottom end is ok without tearing it down? My other thought is to just get another remanufactured motor when I can afford it. That way I know the motor is good. Any thoughts?

[ToughOldFord]

It really depends on your budget and your preference. If it was me, if the bottom end isn't smoking or knocking and has decent compression I don't worry about it. Just don't let it run so low on oil that it starts making noise, that's bad engine Karma.

[towtruckerfour]

Thats the biggest problem is 6 out of 8 have decent compression. I knew it burned oil but didn't realize it got that low. I could kick myself in the ass, I'm normally better on keeping up on it. I guess driving 40 miles at 80 mph and 2 quarts low, something has to give. I can say the truck got us back home from Boise and didn't have problems til 2 days later when the alternator quit working. Budget wise, there isn't one so the truck will sit for now.

[ToughOldFord]

Old Ford are pretty durible/forgiveable, one of the reasons I like them. You could at least pull the heads and inpect the gaskets and valves. If you have any burnt valves replace them and reassemble. If it's just the gaskets then clean and reassemble. More than likely run for a long time after.

My old diesel burns about a quart every 150 miles. I just got in the habit of topping off every fill up.

[towtruckerfour]

Ok. For todays entertainment, I pulled the driver head and was surprised how good of condition the motor was in. I'm guessing the coolant is from pulling the head.

I found this break in the gasket. I believe this should be the reason for low compression in the two cylinders.

The head has a bit of carbon buildup which is not surprising. Since bringing the truck up from California, it only sees around town driving and an occasional run to Boise.


I guess what I might do now is clean things up and put in new head gaskets. Worst case, the truck is in the same condition it was before. Best case, compression comes back and all is good. Doing both sides is the best way to go, right?

[ToughOldFord]

Those cylinders do look good. If you haven't already I'd dry off that coolant before it starts to rust those cylinders.
That gasket should be your problem, you more than likely will have a good runner there. Yes, do both sides, the other gasket is as old as this one and you've got it torn down this far.

[towtruckerfour]

Sounds like a plan for this weekend. Thanks ToughOldFord and everyone else for the help with this one. This is one of those times when I wish my dad was still here for his expertise. I can do most the work on the truck but sometimes guidance is very helpful when you are unsure. You guys have been a great help. I'll let you know how it goes.