boxfile
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| posted on 29/6/06 at 09:48 AM |
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Crossflow Piston Valve Pockets
How deep are the valve pockets on a standard +.090 1300 crossflow piston?
I have a set and I know the pockets need to be 2.5mm deeper than stock to suit my 244 cam but I don't know if they've already been done or
not.
Thanks
Lee
I am not a number!
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Fatgadget
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| posted on 29/6/06 at 10:58 AM |
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Id have thought the best way to check if the pockets are deep enough is to trial build the engine with some plasticine or modeling clay stuffed into
the pockets.
This should give you an idea whether your valve - pistion clearance is adequate or not.
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boxfile
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| posted on 29/6/06 at 11:10 AM |
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Yep. thats how I would normally do it but at the moment the heads in pieces aswell and I want to get the pistons done asap if they need doing.
I am not a number!
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lotustwincam
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| posted on 29/6/06 at 07:37 PM |
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Don't know if this helps, but below is a modifed +.060 piston, that I'm using with a 244cam, thought the cutouts would supposedly clear a
266 cam.
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boxfile
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| posted on 29/6/06 at 07:47 PM |
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Thanks that does help a bit looks like they've machined straight across the original pockets and its definatly quite a bit deeper the mine are
now.
I am not a number!
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lotustwincam
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| posted on 29/6/06 at 08:52 PM |
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Don't be misled by the pockets being machined straight across.
I bought this as a modified short engine, and judging by the size of the bowl, I think these are 1100 pistons. The pockets being machined straight
across would help to restore the combustion chamber to a sensible size. Still, I calculated the CR to be approx 11.25:1
AFAIK, the valve pockets are normally just deepened locally. Hopefully the photo will give you some idea of the necessary depth.
HTH
Drew
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