13 replies to this topic

[liswar2]

Hi all,
Rebuilding the 202 and have got a set of new old stock Pistons they are
RA3300 060 same as I'm running
Bot.0015JE
Looking to work out the piston to bore clearance as they didn't come with any specs or paperwork
Hope some one can shed some light on this ,
Will be getting the new piston heads fitted to the rods next week
Thx wazza
Or if any one has a old spec sheet or can point me in the right direction, all help appreciated ,
And the heads tidy now too.

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[LC-GTR-1969]

Might not be of much help, but with cast pistons 3 to 4 thou should be fine. Forged you want an extra few thou, depending on whether NA or boosted you could go as high as 7 thou with forgies. A rule of thumb is 1 thou per inch of bore. 

 

Disclaimer- I have no idea what the specified clearance for this particular piston is, so obviously if you can find the manufacturer specs this would be better than a rule of thumb guide. 

[koalasprint]

This should help. it seems ACL stamp clearance on the crown. I'm assuming this is piston to cylinder clearance.  Capture.JPG   165.75K   10 downloads

[liswar2]

Bot .0015 bottom clearance ?
Just found this as well ,

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[warrenm]

It's stamped on the top. .0015"

[liswar2]

Thx ,

[EunUCh]

.0015 is 1.5thou  not 15thou , .015 is 15thou. ,  usually a measurement of the skirt is taken at some specified point up from the bottom of the skirt ,take some measurements up the skirt and use the widest or biggest number or biggest diameter of the skirt and finish the bores to  skirt diameter plus clearance, a little

over won't matter as the clearance from new is generally a min. safe number that they specify.

[S pack]

.0015 can also be expressed as fifteen ten thousandths of an inch.

[LC-GTR-1969]

Might not be of much help, but with cast pistons 3 to 4 thou should be fine. Forged you want an extra few thou, depending on whether NA or boosted you could go as high as 7 thou with forgies. A rule of thumb is 1 thou per inch of bore. 

 

Disclaimer- I have no idea what the specified clearance for this particular piston is, so obviously if you can find the manufacturer specs this would be better than a rule of thumb guide. 

 

Hahahaha- if I was building this engine she would be a slapper hahahahaha... wow .0015 is pretty tight but if thats the spec thats the spec. 

[mick_in_oz]

.0015" would be about right if it were a Hypereutectic type piston, they run very tight clearances, but larger top ring gap due to them directing heat into the top ring and over expanding it, rather than the piston expanding as far as a traditional cast piston.

[liswar2]

Thanks all , will keep you up dated with engine rebuild as I progress,

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