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Valve Machine Angles
I'm getting my guides replaced and valves trimmed this weekend. The porsche spec book calls for three angles 30 deg. 45 deg. and 75 deg. The Haynes book references 35 rather than 30. I assume the spec book is the preferred reference.... Right???
The Haynes book also gives a procedure that says to take the 45 cut first followed by the 75 then lastly the 35/30 until the proper seat width is achieved. What is the proper seat width?? Intake 1.3MM / Exhaust 1.5MM plus or minus 0.1MM on each?? Anybody ever had to replace inserts if the machinist went too far?? ------------------ 78 911SC |
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02-14-2001, 02:07 PM
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Yes, the spec book is correct about the 30 degree angle!
There is a tolerance for valve length, 'Dimension c' ... that could be ground down some to put the projection limit 'Dimension A' back into spec if the seat cut is deep and is over by just a few thousandths. The seat widths you cited are correct for an SC engine ... other engines have slightly different specs. ------------------ Warren Hall 1973 911S Targa |
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02-14-2001, 02:46 PM
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Thanks Warren,
I'm hoping we can take the slightest of cuts but its good to know the limits. I appreciate your help. |
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02-14-2001, 02:55 PM
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