What is piston slap and is it a normal characteristic of the F20C?
 

Please refer here to a previous post

Thanks,
John

John,
Piston slap occurs when the piston is a bit smaller than the bore it's moving in. Look here for an engine visual. Metals contract when they are cold, including your pistons. This, combined with a bore that might be on the large side of their specification tolerance, leads to a little "play" in the bore. The actual "slap" is the skirt of the piston hitting the cylinder walls, as the piston is free to rotate slightly around the wrist pin.

Woodwork is a Honda guy who knows what he's talking about, so I wouldn't worry too much about your engine. After having been run for a minute or so, your pistons should be warmed up and expand, eliminating the slap noise. I haven't heard of it before on an F20C, but there aren't many folks driving their cars in very cold climes.

Other thoughts are to maybe check valve your adjustments, and if your engine is fully broken in, to start using synthetic oil.

Jzr,

My engine has 10,500 and before I put the car in storage I switched to Mobil 1 synthetic. Didn't make any noticeable difference in cold start sound. It sounds like a loose bolt rolling around in a can. Cold or warm weather doesn't really matter. The noise happens for a minute or so for the first start up of the day or when the car has not been run for a while. I would probably never notice the sound if I didn't park in a garage where every little sound can be heard.

My dealer thought it was valve noise which is normal and would be willing to adjust the valves to make me happy. This Spring I may have him adjust the valves. The problem is the engine runs fine when warm. I sure would rather have it as valve noise than as piston slap. The piston skirt hitting the bore does not sound like a "normal" thing but I am no expert like Woodwork who has much more experience with Hondas. I do value his opinion.

Thanks,
John