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> Subject: Re: [T3] Question on Perfect 65 notch > > > Jason wrote: > >>So my question is how did VW lower the compression on the 1500S. > Were they domed-dished, flat or flat-dished 83.5mm pistions?<< > > Dave Hall tells me that he has a parts book that indicates flat top > pistons for the M240 lower compression 1500S as opposed to > domed pistons > for the standard 1500S or recessed pistons for the M240 low > compression > 1500N (thanks Dave). > > The engine numbers section on Dave's site says that an engine number > including the letter N indicates a low compression 1500S > (M240), so I'm > sure that's the engine I have. I'm still a little confused, though, > because my parts book definitely calls this M249 and the metal tag > bolted to my case reads M-249 90-oktan. > There is only one way to know for sure what engine/compression ratio you have. That is to pull the heads. In the over 30 years since the car was built, the engine has no doubt been apart before, unless it is very low milage. These engines were notorious for being chenged when the engine was apart. Sometimes it was because the orinal parts were not available, and sometimes it was the owner wanted to get away from the need for the high octane fuel. Most were converted to the flat top pistons if they were the domed, The low compression were converted to the flat top to get a couple more horse power. A lot were upgraded to the 85.5 flat tops to get a "free 100cc", if the pistons needed replaced. If you can come up with an inspection scope, you might be able to tell by looking into the cylinder through a spark plug hole. This will tell whether you have, flat, dome, or recessed pistons, but not tell you the bore. Russ Wolfe russ_wolfe@MAHLEParr.com Mahle Parr Filter Systems 505 E. Madison Winterset, IA 50273 ------------------------------------------------------------------- Search old messages on the Web! Visit http://www.vwtype3.org/list/