shaving the head down - Toyota Yaris Forums

06silveryaris · 04-08-2009, 09:43 PM

I have shaved many cylinder heads since I worked at a machine shop. Most heads have small markers indicating the limit before timing is affected. They are usually small circles on the intake end and on the exhaust end. They are usually not close to the chambers more like on the outer sides. You will see minimal gains by doing this, the only way to get a significant increase in compresion is by shaving a lot off but then it affects timing. Here it is very comon for people to shave .040 and is claimed to make good gain, which were noticable in the buttdyno. I shaved .160 on a hyundai excel that I owned, the thing revved like a sportbike but I had heating issues. Worked with the timing and all fixed out the increase was OK but not great. IMO got with higher comp pistons that is were there a real gain. The risk of clearance is not my major concern just damaging a perfectly good head is when the gain is so little.

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04-08-2009, 09:43 PM	#13
06silveryaris Drives: 2006 yaris Join Date: Oct 2008 Location: Puerto Rico Posts: 536	I have shaved many cylinder heads since I worked at a machine shop. Most heads have small markers indicating the limit before timing is affected. They are usually small circles on the intake end and on the exhaust end. They are usually not close to the chambers more like on the outer sides. You will see minimal gains by doing this, the only way to get a significant increase in compresion is by shaving a lot off but then it affects timing. Here it is very comon for people to shave .040 and is claimed to make good gain, which were noticable in the buttdyno. I shaved .160 on a hyundai excel that I owned, the thing revved like a sportbike but I had heating issues. Worked with the timing and all fixed out the increase was OK but not great. IMO got with higher comp pistons that is were there a real gain. The risk of clearance is not my major concern just damaging a perfectly good head is when the gain is so little.