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914World.com _ 914World Garage _ Calculating compression ratio...

Posted by: BMXerror Apr 13 2008, 09:14 PM

Anyone know the CCs of 1.7 heads and the bump on the Euro pistons? I am coming down to the wire on my build and need to know if the deck height needs to be changed at all. This info or any related info would be great. Thanks guys.
Mark D.

Posted by: Joe Sharp Apr 14 2008, 09:03 AM

Mark, how many times have the heads been milled? I just had to do this on a T-1. I weighed 50cc's of water 3 times on a tripple beam and came out with an avarge weight of 54.2 gr. My heads on the type 1 are 51 cc's.
Remember that for every shim you add to the base you need to add that volume to the combustion chamber. That drops your C/R fast.

Posted by: Dave_Darling Apr 14 2008, 09:39 AM

Small changes to the head CCs or the dome/dish CCs result in relatively large changes to the overall compression ratio. That's why there's no substitute for actually measuring the parts yourself.

--DD

Posted by: Mark Henry Apr 14 2008, 09:58 AM

What Dave said....

To figure out the dome use modeling clay, make an impression and measure.

Posted by: toon1 Apr 14 2008, 10:01 AM

I have the same combo.

If memory serves, the heads where 56cc, DH was .038, compression was 8.2:1

The bump on the piston is 3cc

basically this is a euro spec motor,

the US engine( 3cc dish) was 7.1

euro spec( raised to pistons) 8.1

What cam are you using?


BTW- you will notice a big difference with the higher comp. pistons

Keith

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