piston to wall clearance

[sdwarf36]

The stock spec is .001--boy that sounds tight. Anyone have suggestions if this is ok-or what spec you used? I work in a high performance machine shop--so the block will be bored with a torque plate + honed on a Sunnen cylinder king-so I'll be able to hold any number quite accurate.

[Rabbit on Roids]

if the book says its .001, then you should bore it .001. diesels are super tight clearance engines.

[Vincent Waldon]

In fact... this is a good test for your machinist.  If he takes the factory spec in stride it's a good sign.  If he tries to convince you that it's too tight... find another machinist!!

[Rabbit on Roids]

you could bore it a little looser, but you are basically building a new engine that is already worn. (it thinks it is atleast.)

[rabbitman]

if the book says its .001, then you should bore it .001. diesels are super tight clearance engines.

I always thought the gassers has more clearance too but I checked in the bentley mk1 gasser manual and the new and wear limits are both the same .

[sdwarf36]

In fact... this is a good test for your machinist.  If he takes the factory spec in stride it's a good sign.  If he tries to convince you that it's too tight... find another machinist!!

Vincent- I"M the machinist.  Been at it 25 years. Any decision  made i'll be the one living with it. I seen every kind of failure imaginable over the years. I've seen scuffed pistons from insufficiant clearance. If the pistons were factory VW or a set of Mahles, I'de have more faith in the spec.-but I have a set from Topline (engine kit company -all the parts are reboxed in their packaging.) The piston looks ok-but origin unknown. They are equal in weight + size-thats a good sign. It looks like the notch for the oiler was machined after the piston was completed-and they made real sure the piston wouldnt get too close to the oiler!    If everything is working correctly-all is well. But the day I pop a radiator hose + have to get off the hiway with the gauge pinned-or the cold day i boost it a bit too soon-thats when the poop hit the fan.
 But if you guys with experience say "i built my motor with .001 + it works fine"-I'll cross my fingers + run with it.

[Vincent Waldon]

In fact... this is a good test for your machinist.  If he takes the factory spec in stride it's a good sign.  If he tries to convince you that it's too tight... find another machinist!!

Vincent- I"M the machinist. 

Ha ha... we need more like you around!!  You sound like a guy who will do things right... just what these fine machines deserve !!

[rabbitman]

If the pistons were factory VW or a set of Mahles, I'de have more faith in the spec.-but I have a set from Topline (engine kit company -all the parts are reboxed in their packaging.) The piston looks ok-but origin unknown. They are equal in weight + size-thats a good sign.

I think topline makes all their own parts, I have a head from them and it says "Topline" right on it. It's been good for 53,000 miles. I've heard all bad stuff about their rings though.

[maxfax]

Topline used to make all their own stuff, but I've gotten several reports from my machinist and others that they are farming some of their manufacturing out now days..  Nothing definite though..   I would suspect that maybe this pertians to some of the older, less demanded parts..  Such as oh I dunno VW 1.6 diesel pistons...

I've had several sets of their rings that were crap..  I've installed them on freshly bored engines, and on re-ring jobs..  The result was always the same, unacceptable oil consumption.. I think it was Zukigod that had less than happy results with a set of their pistons, but that could be an isolated incident as well (everyone makes a dud once in a while)...

[smutts]

one thousandth!!!!!!!
...........I can dream can't I?