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TR4/4A Well this isn't good...

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ghawk16

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Good news is, my engine is timed! Bad news, and I can't believe I did this...but I tightened the screw on top of the piston while trying to torque the camshaft sprocket. I completely blanked and should have known better. Now I have to rip off the oil pan I JUST put on and take the piston out. Easy, but still very frustrating.Anyone tried to buy ONE 87mm County piston? Guess I will call BPN tomorrow to see what they can do. 20170429_153252.jpg
 
Unsightly - but does it matter?

Original pistons had their size (letter) stamped into the top. Oversized replacements also had the spec stamped on there.
 
Life is WAY too short to bother with changing a piston because of that mark.
Lesson is to not make a practice of doing it again, which would be unskillful.
 
+1. I once had the coil on the end of a glow plug in a diesel boat engine fall off into the combustion chamber. There was very little clearance in there and when I took the head off to see what was making all the noise I found the top of the piston impersonating the surface of the moon. I took out the debris, put in a new plug, ground the valves and planned to rebuild the engine later. That never happened. I put another 2500 hours on it and it ran like a Swiss watch the whole tome.
Tom
 
+1 to the advice and comments above. The witness mark on the top of the piston does not justify replacing it.
 
Wait a minute. If you're going for Concours Judging, if you get to the end and you're tied for first, and they do an engine tear-down and find that mark, you'll end up in second place.































:wink-new:
 
Thank you all for responding. Obviously I don't care about the looks. I'm just wondering how it will affect the performance of that cylinder. Perhaps I should have waited to pull off the oil pan (which means I need a new gasket, ugh) before seeing the responses here. I've always thought that marks like that would be an issue. It is quite a bit deeper than the numbers imprinted on the top of the piston. Maybe I'll try and smooth out the edges where the bolt dug in and go from there. Thanks!
 
Brinkerhoff said:
I might have a new piston in my TR3 spare parts storage trailer. I'll check tomorrow.
Click to expand...

These are 87mm upsized pistons, not stock. So not sure if you have one of those. If so...shoot me a PM.
 
This is what they make dremel tools for, smooth it out put it together and drive it.
 
number6 said:
This is what they make dremel tools for, smooth it out put it together and drive it.
Click to expand...

That was my initial thoughts. Well...guess I should have posted on here first before I jumped the gun and removed it. It's too bad I can't get an oil pan gasket at a local auto parts store. Now I have to pay crazy shipping from one of the big 3 to send me one. Oh well...lesson learned
 
Forget it! I had to beat the daylights out of a frozen #6 piston in a TR6 to get the crank to move. Ultimately it took a 10 foot cheater bar and a sledge hammer to get that crank to move. The piston looked awful. A well seasoned engine rebuilder told me not to even give it a thought. I put 40K on that engine. I was much more worried about snapping the crank than the looks of that piston.
 
IMO you are doing the right thing...it's not just a matter of cosmetics;
there might be a minuscule stress crack that will start spreading and lead to something like this one day.


As far as a gasket, have you considered something like Permatex 'the Right Stuff" ?
 
poolboy said:
IMO you are doing the right thing...it's not just a matter of cosmetics;
there might be a minuscule stress crack that will start spreading and lead to something like this one day.


As far as a gasket, have you considered something like Permatex 'the Right Stuff" ?
Click to expand...

I doubt it's cracked. I barely torqued on it hence why I was surprised it dug in like that. And I used permatex along with a stock seal.
 
Another possibility is that the weight of any piston you install to replace the marked one might not match the three remaining pistons, so you get to re-balance the engine as part of your work - unless you recorded the weights of all engine components ahead of time.

For an oil pan gasket you can just go to FLAPS, buy a sheet of gasket material, and make your own new oil pan gasket for less than the big-3.
 
You did it by hand, I would not worry. I have seen piston tops a lot worse and they ran fine. Put it back together and go. Maybe use some head gasket silver sticky stuff to keep the oil from getting into the water because it looks like the top of the block is eroded in spots. This would not be a blown head gasket or caused by what you did, but a leak. I had a tr motor weep water into the oil once and I believe it was caused by a compromised block surface. The head will seal on the sleeves, but if the sleeves are too high or the block too low, it will not seal in other areas. I might get rebuked for this, but that is my story and I am sticking to it. But then if you got the money buy a set of pistons..
 
If you do grind the mark out a bit, make sure and check the weight as it could be a bit lighter now. May need to balance again.

Perry
 
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