Based on analysis of a layout drawing I completed today, the Duntov cam's valves cannot be adjusted accurately by indexing the crankshaft at #1 and #6 and adjusting eight valves as specified in the 1963 Corvette Shop Manual.
This procedure will only work for hydraulic lifter cams.
I've revised the paper to eliminate this optional method, and the revision is dated 09-23-2008.
If you google any combination of two words - williams, hinckley, corvette - you will see that this paper is posted on a number of web sites and discussion boards. If you have a copy of this paper or have it posted on your web site, please email me so I can send you the latest revision. Some of these web sites still have the original version. It has now been revised twice.
The changes only affect the first paragraph of page 2 and the new text reads as follows:
Addendum (May 19, 2003)
Lash settings revised 12-14-2005
Optional indexing for Duntov cam revised 09-23-08 (#1, #6 TDC positions will not work for Duntov cam)
This procedure should also be used for the LT-1 cam. The exhaust is “on the ramp” at TDC. The inlet is not, but just barely. With the Duntov cam this indexing procedure may be used, or both valves may be set with the cylinder at TDC of the compression stroke. Adjusting eight specified valves at the #1 and #6 TDC positions as discussed in the 1963 Corvette Shop manual is only valid for hydraulic lifter cams. It will not yield accurate settings with any mechanical lifter cam because not all the specified valve’s lobes at these two positions are on the base circle due to mechanical lifter cams’ long constant velocity clearance ramps.
I also changed the date on the first page to 09-23-2008.
I apologize for the error. If you adjusted a Duntov cam at #1 and #6 at my recommended settings of .010/.016 for 283s or at .008/.016" for 327s, the error is no worse than using traditional methods to adjust them to the OE specified clearances of .012/.018 or .008/.018".
Duke
P. S. I also sent an e-copy of the revised paper to John Hinckley and Barry Kimmelman, so you can request a copy from them, and Barry keeps a downloadable copy on his Web site. Remember, the latest revision is 09-23-08. All previous revisions are obsolete and should be purged.
This procedure will only work for hydraulic lifter cams.
I've revised the paper to eliminate this optional method, and the revision is dated 09-23-2008.
If you google any combination of two words - williams, hinckley, corvette - you will see that this paper is posted on a number of web sites and discussion boards. If you have a copy of this paper or have it posted on your web site, please email me so I can send you the latest revision. Some of these web sites still have the original version. It has now been revised twice.
The changes only affect the first paragraph of page 2 and the new text reads as follows:
Addendum (May 19, 2003)
Lash settings revised 12-14-2005
Optional indexing for Duntov cam revised 09-23-08 (#1, #6 TDC positions will not work for Duntov cam)
This procedure should also be used for the LT-1 cam. The exhaust is “on the ramp” at TDC. The inlet is not, but just barely. With the Duntov cam this indexing procedure may be used, or both valves may be set with the cylinder at TDC of the compression stroke. Adjusting eight specified valves at the #1 and #6 TDC positions as discussed in the 1963 Corvette Shop manual is only valid for hydraulic lifter cams. It will not yield accurate settings with any mechanical lifter cam because not all the specified valve’s lobes at these two positions are on the base circle due to mechanical lifter cams’ long constant velocity clearance ramps.
I also changed the date on the first page to 09-23-2008.
I apologize for the error. If you adjusted a Duntov cam at #1 and #6 at my recommended settings of .010/.016 for 283s or at .008/.016" for 327s, the error is no worse than using traditional methods to adjust them to the OE specified clearances of .012/.018 or .008/.018".
Duke
P. S. I also sent an e-copy of the revised paper to John Hinckley and Barry Kimmelman, so you can request a copy from them, and Barry keeps a downloadable copy on his Web site. Remember, the latest revision is 09-23-08. All previous revisions are obsolete and should be purged.
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