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Technical
Engine assembly: 87 mm barrels with EMPI heads
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<blockquote data-quote="Malc" data-source="post: 626889" data-attributes="member: 13535"><p>I have a technical question about engine configuration, parts compatibility and compression ratio... </p><p>I've bought a set of 87 mm barrels and pistons from VW heritage, along with some EMPI GTV2 heads (40 mm inlet 35.5 exhaust). My crankcase is a stock rebuild I think, crank stroke is 69 mm. Deck height at TDC appears to be about 3 to 3.5 mm, and cylinder head combustion chamber is 55 cc. Based on that, I calculate my compression ratio to be 6.6 to 1. However, my original 85.5 mm pistons had a clearly bigger deck height, around 8 mm. The old heads have (I think) a combustion chamber volume of 47 cc (043 series heads) and I calculate this to have a compression ratio of about 5.5 to 1. Both of these seem really low, and the Haynes manual says the original compression ratio was 7.5 to 1. Any thoughts? Don't understand... Any wisdom greatly appreciated!</p></blockquote><p></p>
[QUOTE="Malc, post: 626889, member: 13535"] I have a technical question about engine configuration, parts compatibility and compression ratio... I've bought a set of 87 mm barrels and pistons from VW heritage, along with some EMPI GTV2 heads (40 mm inlet 35.5 exhaust). My crankcase is a stock rebuild I think, crank stroke is 69 mm. Deck height at TDC appears to be about 3 to 3.5 mm, and cylinder head combustion chamber is 55 cc. Based on that, I calculate my compression ratio to be 6.6 to 1. However, my original 85.5 mm pistons had a clearly bigger deck height, around 8 mm. The old heads have (I think) a combustion chamber volume of 47 cc (043 series heads) and I calculate this to have a compression ratio of about 5.5 to 1. Both of these seem really low, and the Haynes manual says the original compression ratio was 7.5 to 1. Any thoughts? Don't understand... Any wisdom greatly appreciated! [/QUOTE]
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Technical
Engine assembly: 87 mm barrels with EMPI heads
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