bobt Posted February 25, 2007 Share Posted February 25, 2007 Is it normal for forged pistons to be a little noisey at low revs when cold. Once its been running for a few mins the they quieten down and it disappears. Cheers Rob Link to comment Share on other sites More sharing options...
Rob Walker Posted February 25, 2007 Share Posted February 25, 2007 If your using a full skirt piston and the bores were correctly machined to give the correct clearance then the forged piston should be no noiseier than a standard piston. However if you fitted slipper pistons that have very little skirt to guide them up and down the bores then Iwould expect them to be noiseier than a standard piston ecpecially when cold and clearances are at maximum. In short its not being forged that would make them noisy its the piston design Link to comment Share on other sites More sharing options...
6speedmanual Posted February 25, 2007 Share Posted February 25, 2007 Hi Rob Depends greatly on bore clearance whether pistons "slap" when cold. Many motorsport engines (with or without forged pistons) run looser fit and the clearances are taken up at high operating temperatures. Any particular engine application you are referring to? There's no such thing as too much bhp per ton ! 6SpeedManual Link to comment Share on other sites More sharing options...
oilyhands Posted February 25, 2007 Share Posted February 25, 2007 With utmost respect Rob, that is not entirely true, the coefficient of linear expansion of the material used in forged pistons is higher so they run with cold bore clearances which are higher than with normal cast pistons, hence until they are fully warmed up they may well make a little noise. Symetrical piston pins also allow the piston to exhibit slap since the piston is not forced to the normal thrust side when on light throttle or idleas it would be with an asymetric pins such as used on production cast pistons. Oily Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted February 25, 2007 Share Posted February 25, 2007 My Omega forged pistons in my self build 1800 'K' have been like this from new. It worried me too originally as it sounded like a bag of old nails 'till it warmed up a bit. My mind was put at ease though when I happened to be at Caterham HQ when the very last of the JPE's was being handed over. This was the special one that had the reputed 30k spent on the engine alone at Swindons etc and had the registration mark '600' IIRC. The champagne flowed and then the car was started and sounded................. just like a bag of old nails 'till it warmed up!!!!!! Link to comment Share on other sites More sharing options...
bobt Posted February 25, 2007 Author Share Posted February 25, 2007 Sorry, yes its an 1800K with omega pistons - so I should not worry then Thanks Rob Link to comment Share on other sites More sharing options...
rj Posted February 25, 2007 Share Posted February 25, 2007 My VVC engine without VVC does it, and always has. And yes, I've been worried too. /regin Link to comment Share on other sites More sharing options...
Pelico Posted February 25, 2007 Share Posted February 25, 2007 Another sigh of relief - my Omegas are noisy at first too. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now