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Joined: Sep 2009
Posts: 6,689 Likes: 21
ChatMaster - 6,000
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OP
ChatMaster - 6,000
Joined: Sep 2009
Posts: 6,689 Likes: 21 |
No research.
How long does it take for a brand new or rebuilt 216 to develop a piston slap when cold? 10 miles? 500 miles? 1000 miles?
Before any of you say "I've got over 200K miles on mine and not a one of my pistons slaps, let me tell you that it does. Your hearing just ain't what it used to be. Take your grandchild out to the car with that 216 and start it up one cold morning. Ask her/him if they hear a piston slapping? They'll say, "No grandpa." Then when the smile comes on your face and you can't wait to get back inside and post your findings, they will pipe up and say, "No, not one, Grandpa, they're all a-slapping."
Anyone want to hazard a guess to the right answer? Hint, it's less than 10 miles.
Best, Charlie
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
How long does it take to develope when cold????
Normal piston slap will be heard when first starting an engine after it has been standing for a length of time....like 10 hours or so depending on the outside temperature. If you hear a little slap at 50 deg. on a cold start it will be much louder at say 20 deg. For iron or aluminum pistons it should clear up after 15 minutes of driving.
This will not "clear-up" with more driving (putting more miles on the engine). Even the well fit iron pistons can have a faint slap under load with a cold engine.
When Chevrolet went to aluminum pistons in 1953 they had a steel strut in the piston to keep it expanded. They still slapped. In 1954 they made a little improvement. They off-set the wrist pin so it was not centered in the piston. This took care of the problem and when owners with 1953's complained they would put 1954 pistons in them. Prior to that they would slip after market pistons enpanders in the piston. We even had problems with 1951 and 1952 Power Glides with iron pistons. They did the expander trick on those also. The piston noise stood out more with Power Glide becuase the tappet noise wasn't there to cover it up.
If it goes away after a few minutes of driving don't worry about it.
Some modern car engines have a lot of slap when cold. This is due to the short skirt low friction pistons they used.
Gene Schneider
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Joined: Dec 2006
Posts: 837
ChatMaster - 750
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ChatMaster - 750
Joined: Dec 2006
Posts: 837 |
Is there really any way possible to communicate, convey, describe, transmit or just plane get across in print what the sound of "piston slap" would sound like, or "rod knock", or "main bearing clunk". Tappet clatter is pretty easy for most people to describe or to recognize from a description, but I think the other engine sounds in many cases are misinterpreted.
Now next to “How to Hand Form Your Own Fenders” this would probably be one of the biggest selling CD's of all time for the old car enthusiast, just think, "Those Ominous Engine Sounds in Stereo", different tracks for a four, six or eight. Start them all off cold with that crankshaft thump or is that a clunk or thud, and then run them up to a nice warm engine ping.
So all we need is a combination master mechanic/ sound engineer with the entrepreneurial spirit to pick up on this.
Denny (Click & Clack) Graham
Sandwich, IL
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
"Normal" piston slap is just as the word "slap" implies. Not a hard or deep knock but a clap-clap type of noise under load.
If excessive it can be heard at idle speed when engine is cold.
Retarding the timing will lessen it......
Gene Schneider
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