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On 18 Jan 99, at 10:33, Keith Park wrote: > Oh yes theT3 do too!! most dont anymore as nearly all engines have had a > valve job by now and the heads machined. without this the CR will be too > high (MUCH too high) and they will run hot and detonate. Ive been through > this with the aftermarket heads and it is why I reccomend ONLY new heads at > rebuild. > In fact.. the 72 motors came with dished pistons in a last ditch attempt to > keep the CR down and running cooler with all the smog crap on them. I THINK that while beetles got the raised lip in 71, the 71 type 3 heads do not have the lip. The 68-71 FI "U" engines all have a compression ratio of 7.7:1. The 72-3 type 3 heads (the ones with the extra valve box ventilation ports) for both U5 and X engines have the step, which in combination with the dished pistons in these engines, gives them a CR of 7.3:1. Keith is absolutely right in noting that most all of these have been worked over by now, so most of these engines have been changed in some way or another. Figuring out what stupid, but expedient changes were made is much of the battle in getting your engine to run properly. Such =as getting all 4 combustion chambers to have about the same volume, and hence the same CR is important, but it will not happen automatically; it requires personal intervention. Just another detail to pay attention to. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- Search old messages on the Web! Visit http://www.vwtype3.org/list/