nightmare90gt

so i had to take my engine out of my car to do all gaskets so i ordered a cam and took off heads to inspect the pistons and noticed one of my pistons had a lot of little dimples in it from what might be something was jumping around in it at one point in time so i took my piston out and i noticed that the rod bearing on the rod side has copper showing through it on all pistons the cap bearing has normal wear and the main caps have normal wear any ideas

mjr46

the bearing side on the rod cup to have more wear then the cap side is normal, think about it, where is all the force placed on the piston to move it down the bore......exactly the downward force from combustion to rotate the crank places the stress on the underside, meaning the piston is pushing not pulling

nightmare90gt

but is it suppose to have alot more wear and the wear is just in the middle of the bearing and the cap bearing almost looks new

67mustang302

You've had detonation possibly. The dimples in the pistons are from peppering where the piston material is vaporized during detonation. It also has a tendency to beat rod bearings out because of the extremely violent forces involved...even when you don't feel it.

Either that or something was in the chamber. Do you have pics of the pistons? And were the worn rod bearings on all rods or just the 1?

And bearings like what are used in a car should almost never wear as long as everything is running right and lubed properly. The only time the crank and bearings should have any form of contact is during cranking when starting and you're running off the oil film. Once running the bearings should never touch the crank.

Theoretically with a system to prime the oiling before engine start; rod, crank and cam bearings should have an infinite life if everything is running properly.

mjr46

post a pic of it

nightmare90gt

the piston is the only one like that and all the rod bearings are like that.

67mustang302

Can you post a close up of the piston damage? Looks like prolly detonation though, since mechanical damage would be all over and highly uneven in shape.

What kinda tune/fuel was it running and what compression?

uedlose

take a look at the sides of the piston also like at the top of the piston from the top ring to the top of the piston does it look like it has been sandblasted? That is also a sign of detonation. but looking at the pics. and the rod bearing it also looks like detonation to me also. you need to look at your tune.

nightmare90gt

the piston skirts are fine no problems with them just the top and sorry cant get a closer pic not to good of a camera

and this has to be from the po cause i havent herd any detonation and for a tune none yet was going to get it done when the motor gets put back together

thinking of building a big bore 347 with the big bore boss block

67mustang302

There ya go, a reason to build a 363 =)