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Author Topic: pistons  (Read 2291 times)

Offline woody02

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pistons
« on: May 27, 2010, 04:03:04 pm »
Should my pistons have indentations like this?  im guessing not...??  all 4 have the same indents, same shape and size. The cambelt had'nt snapped and all the valves are straight. I have another set that i bought because one of mine has melted. The pistons ive bought are the same size and have the same part numbers ( although there is a small no. and symbol that are different, batch number?) but they dont have the big indentations in them? Just want to know if the pistons that came out of my engine are useable or not?  bit confused lol,  cheers.
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Offline hayesey

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Re: pistons
« Reply #1 on: May 27, 2010, 04:10:36 pm »
no they shouldn't have those indentations in them, that's were valves have hit at some point in the engine's history.  Who did you buy those off?
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Offline woody02

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Re: pistons
« Reply #2 on: May 27, 2010, 04:47:03 pm »
That is one of the pistons that has come out of my engine, the other pistons aren't as bad but they do have some marks and dents in them. Really don't wanna buy new pistons... Gonna cost a fortune!
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Offline hayesey

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Re: pistons
« Reply #3 on: May 27, 2010, 05:10:52 pm »
you say in your post you've already bought another set of pistons without dents in them? cant you use those?
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Offline woody02

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Re: pistons
« Reply #4 on: May 27, 2010, 05:21:57 pm »
I have yeah, il give them a good clean up and make sure there's no bad dents like the one in the pictures, there are definately some dents . obviously is best to have perfect pistons but are they still useable with slight dints? I know it's not ideal..  Got a receipt for an engine rebuild not so long ago so the pistons must have been like that when it was rebuilt.
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Offline Yoof

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Re: pistons
« Reply #5 on: May 27, 2010, 06:14:30 pm »
Valves can't be straight- either that or they've been replaced previously...

You can use these pistons, I'd take a file and carefully remove any sharp points and chamfer edges that can lead to hot spots in cylinders and promote det.

Ideally use the good ones you have, but these will work.
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Offline hayesey

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Re: pistons
« Reply #6 on: May 28, 2010, 10:05:47 am »
yeah I'd choose the best four out of the lot.  They'll still work but as yoof says, points of thinner metal around the dents can heat up excessively and cause hot-spots leading to det.  Also you can get excessive carbon build up in the dents too.  Smoothing them out to some extent will help both.  You'll also have lost the coating that the piston crowns have on them where the dents are.
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Offline woody02

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Re: pistons
« Reply #7 on: May 29, 2010, 09:35:20 am »
Thanks lads, much appreciated  :)
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Offline g40dabbsy

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Re: pistons
« Reply #8 on: June 07, 2010, 05:08:41 pm »
yeah I'd choose the best four out of the lot.  They'll still work but as yoof says, points of thinner metal around the dents can heat up excessively and cause hot-spots leading to det.  Also you can get excessive carbon build up in the dents too.  Smoothing them out to some extent will help both.  You'll also have lost the coating that the piston crowns have on them where the dents are.

as said i wouldent realy want to use pistons with dents in them were the exhaust valve hit looks like your cam belt may have snaped 1ce or mayb some 1 fitted the wrong cam
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