What Rob said... Either piston/bore clearance is too large, or in some cases where a low silicon piston (CP, ACL for example) is used the motor will be slappy when cold to allow for expansion.
Ah okay, so it's not likely to happen with stock pistons? Reason I'm asking is that a mechanic has informed me that my car has piston slap...
He's actually a very well know zed mechanic (warren at dontex) so he does know zeds quite well. Maybe it was just his terminology
I've been fed bullshit by "good mechanics" before. Ask him to explain exactly what he means by piston slap, because a stock engine doesn't develop that kind of thing over time.
Here is a reasonable definition of piston slap - Piston slap is nothing new to piston driven internal combustion engines and compressors. It is the secondary (sideways or perpendicular) movement of a piston against the side of a cylinder bore where the primary movement of a piston is intended to be parallel (up and down) to the cylinder bore. All piston driven internal combustion engines and compressors have a certain amount of piston slap. Excessive piston slap occurs when the clearance between the piston and the cylinder bore is too great. The piston to cylinder bore clearance becomes too great either through wear, mismatched pistons and cylinder bores at manufacturing or, a combination of both. The audible noise associated with excessive piston slap is due to the perpendicular impact of the piston against the wall of the cylinder bore. Audible piston slap is typically loudest when the engine is first started up. The pistons then expand with heat reducing the piston to cylinder bore clearance thus, reducing the perpendicular impact of the piston against the cylinder wall and its resulting noise. At some time on this forum we have all seen a post where someone is chasing a single used piston or a complete set. Any engine assembled with used pistons would be a prime candidate for excessive piston slap.
Thats not good Depends on the tolerances - its not likely that a hone will suffice with piston slap because the tolerances are most likely to be to excessive. Unfortunately most require a rebuild due to an oval shape that is present in some or all parts of the bore. Piston Slap can occur in a stock motor but is less common than when using ceramic piston components and used motors that have had previous re-ringing/ honing without boring. In very simple terms it is generally where either the piston or bore develop an oval shape so the piston can slap around anywhere inside the bore under operation. A common scenario for piston slap (on a stock motor) is whereby an "old" engine is/has/was previously re-honed and/ or re-ringed without a rebore once (or even several times) thus allowing the bore to become more oval with wear over time as opposed to re-boring (resetting that bore circle from top to bottom) Chances in the engine being within specs after "piston slap" is detected in a stock motor (Rough Guide only) < 5-10% Re-bore - Re-Hone - Re-ring (rare - e.g. where water has hardened the rings and distorted them into an oval shape but the bore is still circular) 20% Re-bore / Re-hone / Re-Ring and new pistons 25% As above with new bearings/ gudgeon pins etc 50% Fully Motor reconditioned (crank bearing / new pistons/ heads etc.) As you can see from the above - its still a bit of a flip a coin - but once you start its gets very expensive quickly - so tread carefully. You cannot expect a mechanic to give you a "piston slap report" Unfortunately - the engine bores must be examined before any specs can be taken, only then can the true costs be considered. (Bring the motor back to within tolerances complete) A compression leak test can give a rough guide of costs in the interim by the numbers present, but this is still not definitive until the bore examination is completed and bearings are inspected. Sorry - I don't trust mechanics with rebuilding engines -- I trust only well known head and engine specialists! (it's a bit like getting heart surgery with your G.P !) I advise you to see a specialist in engines rather than Z's ! :agree: Based on your stock motor having piston slap - be prepared for a complete rebuild given the engine is most likely to be old in age, old in wear and therefore old in specs. Sorry I am not Santa Claus! - hope this still helped somewhat JC :zlove:
