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Old 10-19-2013, 02:24 PM
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toomanytoys2 toomanytoys2 is offline
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Join Date: Sep 2012
Location: Lefty California
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As Johnny 5 mentioned, if you go with a big bore kit, you want to go with one with a thick cylinder liner. I am an old school VW guy and have been working on air cooled VWs for about 35 years. In an air cooled engine, most of the cooling actually takes place at the head, with a much smaller percentage of cooling occurring at the cylinder. The problem with running a thin cylinder is when they get hot, the cylinder itself will expand. when this occurs the rings can no longer form a good sealing contact with the cylinder and you end up with blow by and a lost of compression. This doesn't do any damage to the engine, but you actually lose power when the engine is hot. Also the combustion squish is more critical in an air cooled engine. Since the head is where most of the cooling is done, keeping you squish numbers low is a big determining factor in engine temperature. If you have a high squish number, more of the combustion will take place in the cylinder and will raise your engine temperature. Also, an oil cooler is always a good idea for a hopped up air cooled engine. Since air is not a good medium for the transfer of heat compared to water, adding an oil cooler will cool the oil and the cooler oil will help to cool the head. I can't tell you what direction will give you the most bang for the buck since I installed my A12 cam and the big bore kit at the same time. At the same time I P&P the head, did the redneck intake and opened up the exhaust. However, I can tell you that unless you make the intake and exhaust more free flowing, you will not see huge results in what ever mod you end up going with.
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2005 Hammerhead 150
170cc BBK, PnP Big valve Head, A12 Cam, Uni Filter, Custom Exhaust, 10G rollers, 1500 Contra Spring, 2000 Clutch Springs

Just added - 2007 Joyner 250 SV - Let the fun begin

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