piston projection too high on one cylinder

[paolomarks]

my no. 4 piston projection  on the AAZ I'm rebuilding with new pistons and bearings is .043. The other pistons are between .035 and .037.  Bentley spec for a 3 notch gasket is between .0358 and .0402.  Will I have any troubles?  Thanks, Paolo

[arb]

New clean pistons ? Where did they come from ?  You double checked the measurement and to be sure the rod bearing was clean and installed correctly ? Sounds odd. I would not try to run 2.8 thousands over limit.

[RabbitJockey]

i'm sure u did but id be double checking hard core that everything was perfectly clean, whats the history of the rods

[745 turbogreasel]

3 pistons with valve marks?

[paolomarks]

Here's a bit more info.  Engine came out of a running 96  golf AAZ I picked up in Canada. Engine had close to 200,000 miles so I tore everything apart and found it to be in quite good shape. Bores were just out of spec so I bought some brand new .020 over SM pistons from German Ebay. Had my machinest install new piston pin bushings in the conn rods and polish the crankshaft which is still in spec for standard bearings which I installed. (Glyco)  Cleaned everything very well and put it all back together and torqued to spec.  Checked the projection with my dial indicator several times and that # 4 piston is proud by almost .003 . (.043.  THere was no sign of valve contact on the old pistons so I don't think I have 3 bent rods.  I'm just wondering whether I'll be allright. someone correct me if I'm wrong but I don't think .003 high will be enough to touch the valves as long as the timing is right. Compression would theoretically be higher in that clinder but can't imagine by much?  Any thoughts would be appreciated. thanks, Paolo

[R.O.R-2.0]

get the piston crown shaved .003...

[paolomarks]

They are coated pistons. Hate to shave them.

[RabbitJockey]

you could have the rod resized, perhaps, i'd talk to a machinest, but at the same time its hard to tell if that little bit will matter enough to go through that trouble.

[paolomarks]

I guess I'll have to get some new conn rod bolts.?   Allready did these the extra quarter turn.  Paolo

[nathan_b]

headgaskets blown bends rods too. Tore down a motor last friday that blew the head gasket and was supposed to have 1 bent rod. well, it had 1 straight rod. lol. sometimes they only bend a tiny tiny bit, making them stick out a too little. Probably wouldn't lessen the life of the motor too badly, but far from ideal. A new motor should have all pistons in the same range. I like the idea of swapping rods around, didn't put them to final torque yet did ya?

[Toby]

I suspect that you have a small end bushing that is not concentric OD to ID. Try swapping rods, but not pistons and see if the "proud" piston follows the rod. If so, poke the bushing out and measure the wall thickness all the way around.

I would generate a .003" offset bushing rather than resize the rod if it turns out not to be a bad bushing.