No Compression No. 8 /cyl.
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No Compression No. 8 /cyl.
I have a 93 F150 with 173,000 miles. A couple of months ago I was pulling a trailer when the engine started cutting out and blowing out white smoke.
Last weekend I did a compression test. All cylinders had between 150-155 PSI except for the #8 which had zero. I pulled the head off and found that water had been getting into the cylinder. The head looks okay but the piston does not look very good. I had already had the head shaved so I bolted it back on to check compression. Still almost none.
Can I get away with just changing the one piston? And if so can this be done with the engine still in the truck? I normally don't shortcut maintenance, but this is an extra vehicle and I don't want to spend a lot of money on it.
Also the head gasket looked okay. I could not tell where the water was getting in. I did not see any cracks.
If I were to look for a used engine would any year 302 work?
Any advice would be appreciated.
Last weekend I did a compression test. All cylinders had between 150-155 PSI except for the #8 which had zero. I pulled the head off and found that water had been getting into the cylinder. The head looks okay but the piston does not look very good. I had already had the head shaved so I bolted it back on to check compression. Still almost none.
Can I get away with just changing the one piston? And if so can this be done with the engine still in the truck? I normally don't shortcut maintenance, but this is an extra vehicle and I don't want to spend a lot of money on it.
Also the head gasket looked okay. I could not tell where the water was getting in. I did not see any cracks.
If I were to look for a used engine would any year 302 work?
Any advice would be appreciated.
Last edited by thinglenn40; Nov 12, 2005 at 03:51 PM.
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Did you have the head checked for cracks? They like to crack in that #8 cylinder because of the pcv system, and that crack can leak water. Also at least have the valves and seats redone on that cylinder, along with replacing the piston.
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Joined: May 2004
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From: The hills of No. Calif.
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You should be able to change out that one piston with the engine still in place, although it can be a PITA to get the pan off. You'll most likely have to undo the motor mounts and lift the engine a bit.
Bearings only come in sets, so you might as well replace all the rod bearings while you're in there. I'd take a really close look at that head for cracks, especially right between the valves. Chances are you'll be looking for a replacement head. The water wouldn't likely be getting in through the cylinder unless it's cracked, so I'd take a close look at that as well.
If you decide to go for a used engine, I'd stick with a later (late '80s-early 90's) truck engine so that you don't wind up with something you have to open up and change cams in. Early 80's motors are low compression smog motors as a rule, so you don't really want to go there either. Avoid anything earlier than '81 so that you don't run into balance problems.
If you get a complete motor (Intake to oil pan) you could swap in a 351W. Some people feel the 351W is the only way to go in a truck, some people feel the 302 is plenty...you're choice, just throwing that out there as an option in case you stumble across a good deal on a 351W.
https://www.ford-trucks.com/guidelines.html
You should be able to change out that one piston with the engine still in place, although it can be a PITA to get the pan off. You'll most likely have to undo the motor mounts and lift the engine a bit.
Bearings only come in sets, so you might as well replace all the rod bearings while you're in there. I'd take a really close look at that head for cracks, especially right between the valves. Chances are you'll be looking for a replacement head. The water wouldn't likely be getting in through the cylinder unless it's cracked, so I'd take a close look at that as well.
If you decide to go for a used engine, I'd stick with a later (late '80s-early 90's) truck engine so that you don't wind up with something you have to open up and change cams in. Early 80's motors are low compression smog motors as a rule, so you don't really want to go there either. Avoid anything earlier than '81 so that you don't run into balance problems.
If you get a complete motor (Intake to oil pan) you could swap in a 351W. Some people feel the 351W is the only way to go in a truck, some people feel the 302 is plenty...you're choice, just throwing that out there as an option in case you stumble across a good deal on a 351W.
