<VV> Bizzare piston slap memories

Jay Maechtlen jaysplace at laserpubs.com
Sat Nov 2 03:28:43 EDT 2019

Over the years, a couple of motors I've overhauled have had piston slap.
These were quick 'rings & inserts' jobs, with my un-patented back yard 
valve jobs.
(Support a valve in a piece of tubing, let the face spin at an angle to 
the side of a fine grit bench grinder, adjust angle to regulate spin 
rate. Cleans them up ok. Then lap the fresh valve onto the seat, cleans 
the seat and knocks the grinding marks off the valve face)
The motors would chuckle or 'talk' a bit at idle, but they ran fine.
One was a 383 Merc (MEL motor) and one was the Ford 240 cid six.
Of course, the 'slap' from a piston .020 or .030 too small would 
probably be pretty awful, and might not quiet down much under load...

On 11/1/2019 5:17 PM, N2VZD TIM via VirtualVairs wrote:
> I had a crazy issue a few years ago with brand new pistons . They were supposed to be .060 (factory marked !) but were actually .030 measured . This was after going nuts with the sounds. The compression was "OK" but the noise was almost like lifter noise or oil pressure problem , but gauge showed good pressure. I will never buy parts like that from anywhere but my trusted source. These were new parts in the boxes from a private vendor at the Sturbridge .He probably had no idea , because they were NOS not  properly marked in correct boxes  (they said .060 on top but measured .030 at the shop.   Very strange noise!  I never had to check measurements before !Regards, Tim Colson
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Jay Maechtlen
'61 2-dr modified w/fiberglass skin,
transverse 3.8 Buick V6 TH440T4 trans

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