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Leon has done more, and better, data taking than anyone else I know. This is really useful stuff to know. I wonder if the combustion chamber volumes are all the same on these heads. That would change the compression ratio and make a big difference, and might explain some of his observations. On 14 Mar 2003 at 11:24, Martinez, Leon wrote: > - German VW head (good) 370 degrees goes higher as road grade goes up, > top temp seen 400 degrees at 70 mph , good hwy grade, (heads cracked > after doing this daily. > > - Spanish AMC head (junk) 370 degrees temp goes higher as road grade > goes up, top temp seen 450 degrees at 70 mph, good HWY grade, (the > valve seats on this head melted into the head after this daily use, > seen other melted examples of this brand at my local machine shop). > > - Brazilian Autolinea (Empi, Bugpack, CB and most Aftermarket > performance heads) (1/2 reach is junk) 400 degrees temp goes higher as > road grade goes up, top temp seen 450 degrees at 70 mph, good HWY > grade, (the heads cracked around the sparkplug area with 1/2 reach > after this daily use, some other heads found to be machined crooked at > the plug area and this aggravates the problem). I have bought 6 heads > in 2 years , pile decorates the corner of my garage. > > - American Mofoco (Machining is crap, at least what they gave me after > I returned it). 325 degrees temp (cooler) but goes WAY higher as road > grade goes up, top temp seen 550 degrees at 70 mph, good HWY grade, > (one head dropped both valve seats in one cylinder after this daily > use), the head seemed to have been machined very badly , this was > visible from external inspection. 2 heads bought one head still in use > on cyl #1 and #2 . Suspect that higher temps at high speed is due to > exhaust valve area cooling is limited because the lack of flowthrough > of the casting design. > > - Mexican Genuine VW head bought at Mexican Dealership (are available > in USA from different suppliers). 250 degrees temp (MUCH cooler) and > stays cooler at higher speeds than the others. Temps stays 25 degrees > below the meter's midpoint of 350 degrees even at 90 mph for 15 minutes > on varied grades. Never seen any reading above 350. Cooler temps seem > to be due to the metal alloy and the flowthrough design of the air > around the exhaust valves and thicker valve stem areas. -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------------------------- List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org