-
piston projection too high on one cylinder
by
paolomarks
on 09 May, 2011 06:27
-
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
-
#1
by
arb
on 09 May, 2011 08:43
-
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.
-
#2
by
RabbitJockey
on 09 May, 2011 08:47
-
i'm sure u did but id be double checking hard core that everything was perfectly clean, whats the history of the rods
-
#3
by
745 turbogreasel
on 09 May, 2011 12:39
-
3 pistons with valve marks?
-
#4
by
paolomarks
on 09 May, 2011 13:31
-
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
-
#5
by
R.O.R-2.0
on 09 May, 2011 13:37
-
get the piston crown shaved .003...
-
#6
by
paolomarks
on 09 May, 2011 14:01
-
They are coated pistons. Hate to shave them.
-
#7
by
RabbitJockey
on 09 May, 2011 14:06
-
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.
-
#8
by
paolomarks
on 09 May, 2011 15:16
-
I guess I'll have to get some new conn rod bolts.? Allready did these the extra quarter turn. Paolo
-
#9
by
nathan_b
on 09 May, 2011 16:23
-
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?
-
#10
by
Toby
on 10 May, 2011 00:31
-
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.