VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1928 piston scoring

Just picked up a 1928 4 cyl motor for parts, and when dismantled I noticed that all the piston's had major score mark's on the one side of the piston, (just below the piston pin and the base of the piston).
I have seen this on several of these motor's.
What is the major cause for this, and what can be done to prevent this???

Is this a common problem with these motor's???
Any info would be great.


Keeping vintage Chevy alive.

Just a few things I know of that score pistons. running very hot for a long time, No oil on piston when assembled, Dirt or grit in bore when assembled, no or very little honing after boring, no air cleaner used, dirt or metallic debris in oil, piston pin too tight when fitted, pistons fitted too tight in the bores possibly piston fitted too loose might cause it to rock in the bore and do that. There may be more someone else can think of. I am assuming it has alum pistons.

If it was still a runner, it would have to be down on compression would you think???

Thank's Bob
These score's seem to be confined to the front side of the piston, (facing towards the front of the motor),like they all been tipped to the one side.
I checked the piston pin's and all seem to be within there limits.
Put a dial indicator on the crank and is running true.( with in it's limit,+ crank bearings are worn evenly).
Do you think out of round piston well's may of caused this??
I don't know what to think.


Keeping vintage Chevy alive.

Scoring like that is not common at all. Is it possible that the pistons were not cam ground (take off 0.002" or so on pin sides)? If not then when hot the pistons tend to expand more in the pin direction causing them to stick against the bore. If not that I would check to see if the cylinders were bored correctly (90 deg. to crankshaft). Could be rods bent (highly unlikely more than one). Scoring from tight pins and other pistons rocking, etc. is most always on piston sides and not inline with pins.

Thank's Chipper
I am thinking they weren't cam groung + I noticed that all the piston ring gaps where all inline with each other, where they should of been offset, look's like someone tried to do a back alley rebuild and did a bad job of it.
Oh well, I didn't need the pistons anyway's, I thought I would just put the bug out there to see if this was a common problem with these motor's,and if I needed to watch out for any hidden problems when I finish my rebuild, Thank's for all your help.


Keeping vintage Chevy alive.

Since your pistons scoring is at the front and not the thrust face and because it is on all pistons I would suggest your crank has too much end play or an incorrect thrust bearing. If the piston is tilting like that you should also see contact on the opposite side ring lands and the contact marks on the thrust surface should be on an angle.

I should have added to the above:
When you press on the clutch pedal the pressure on a crank with too much end play moves forward and you will get wear as you indicated.

My Dad was a Chevy four cylinder owner and drove a 1926 from 1926 till 1930 when he bought a new leftover 1929 six, he always cautioned us to not "ride the clutch" and to shift out of 3rd as you coasted to a stop at a stop sign, then when it was clear shift into first and go! He said it was hard on the crankshaft and pistons(from his 4 cylinder days) and caused short clutch life. He also told us that when we got summer jobs driving trucks that a truck had to be greased every day. We each had a grease gun that we carried to work along with our lunch bucket and our little 3 gallon Gott galvanized water cans with a dimes worth of ice and water. We didn't spend a lot of time on breaks, time was money!

According to old blokes that I've spoken to over the years they told me that Chev 4 con rods were prone to bending, one even gave me a rod staightener that he made. This could be the problem here.
Chris