Friday I brought home a 1957 Corvette engine. When I took it apart, the right bank of pistons were all stuck. One of the worst ones had a pile of white and yellow crystalized corrosion filling the cylinder. It reminded me of a severely corroded battery terminal. I decided to test the PB Blaster and Kroil on the motor to find out which one actually worked the best.
For the sake of clarity I will number the cylinders 1-2-3-4.
The two outside cylinders (1 and 4) had the most corrosion, and I assumed they would be the toughest pistons to remove. The two center cylinders were stuck and not quite as bad.
Cylinders 1 and 4 seemed to be the worse of the four, and I decided that since the Kroil was the most expensive I would give it the task of the worse cylinder (#1). I also chose to use kroil in the number 2 cylinder. PB Blaster was used in 3 and 4, with 4 being the worse of those two.
First I took a 2" wire wheel on my die grinder and removed as much rust and corrosion from the tops of the pistons and I cleaned the tops of the cylinders too. I then propped the block so the right bank of pistons were level.
I then sprayed Kroil into cylinders 1 and 2 until the top of the piston was covered, then the same to 3 and 4 with the PB Blaster. I noticed the PB Blaster was bubbling a little around the edges of the piston. It reminded me of carbonated beverage when you pour it in a glass. I let them both sit for about 18 hours. All the cylinders looked like they had the same amounts of penetrant on top of the pistons when I returned.
First I took a wood 2 x 2 and hammered the two center pistons (2 and 3) down into the bore. Both came loose relatively easy. I pounded them from the bottom and they both came out of the cylinders fairly easy and with reletively equal force.
I pounded on the tops of the 1 and 4 pistons to see if they would loosen up. The number 1 cylinder with Kroil started to move so I continued to work on it. I got it far enough down the cylinder to see where the rings has set against the cylinders. I took my wire wheel and cleaned up the cylinder again and then pounded the piston from the bottom and it came out of the cylinder.
I then turned my attention to #4 with the PB Blaster. I pounded and pounded on the top and bottom of the piston and it would not move. I sprayed some more PB Blaster on top of the piston and waited about 15 minutes and pounded again. The piston did not move.
I decided that I had better prop the motor up again and let it soak another day. I was already leaning towards the Kroil as being the better of the two, and I sprayed some Kroil in the #4 cylinder.
After 10 minutes I took the 2 x 2 and hit it with the hammer. The piston moved on the first hit. After moving the piston down far enough, I again cleaned the cylinder with the wire brush. I pounded from the bottom and got the piston out.
Now you could say that all the pounding on the #4 PB Blaster piston helped loosen it up before switching to the Kroil, but I really believe that the Kroil did a better job of penetrating and loosening up the pistons. I also looked at the cylinders afterwards too. The PB blaster cylinder showed deeper scores in the cylinder walls from the hard deposits left behind.
I also noticed the lubrication of the kroil was much higher. The PB Blaster seemed dryer and less oil like.
My test finds Kroil superior to PB Blaster.
