Metal clanking sounds at idle

Jaycee604

Jaycee604

Member
Hey guys me again back at it with a unique question. Just finished building a new engine, i have noticed that during idle it has a weird metal clanking sound, almost louder than exhaust. It completly goes away at half and full throttle and is very smooth. I put quality work into this engine, a part of me is thinking that it needs to wear in. I can supply details of engine if needed. Thanks for the help guys. And no the piston is not hitting the head. Everything is nicely filed off on the cylinder and piston too.
 
PTCSWC piston to cylinder side wall clearance
.
When the clearance is close or at the maximum specifications some piston slap can be heard

SLAP- The piston skirt slapping the cylinder wall

CLEARANCE- distance between the piston and cylinder wall

Slap usually causes no damage but makes piston music
 
Jaycee604 said:
Hey guys me again back at it with a unique question. Just finished building a new engine, i have noticed that during idle it has a weird metal clanking sound, almost louder than exhaust. It completly goes away at half and full throttle and is very smooth. I put quality work into this engine, a part of me is thinking that it needs to wear in. I can supply details of engine if needed. Thanks for the help guys. And no the piston is not hitting the head. Everything is nicely filed off on the cylinder and piston too.
Click to expand...
If your gas octane rating is too low you can have Knock and Ping
Knock - is some fuel igniting on the compression stroke before ignition
Ping - is the fuel igniting from the spark
Knock and Ping sounds like a metallic clack

Some guys add octane boost to their gas

If you made your cly head high compression burn a higher octane gas 91
But most M/B kits are low compression and can burn 87 octane without having a Knock and Ping
 
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