I can't think of any situation where head/block decking would change the relationship/relative timing of a pair of DOHC cams. On vee engines where the timing belt (or chain) returns to the block before going to the 2nd head (Audi V6), any change in cam timing to the 1st head caused by decking/milling would be doubled in the second head.
(Any boxer setups I'm familiar with use seperate belt for each bank which cause no such problem)
The change in cam timing caused by removal of material to reach legal C/R limits is negligible. In the rare case of OHC vee engines, even the 2nd head is very close and splitting the difference via crankshaft key adj would bring the timing marks into apparent positions. (the Audi V6 has infinitely adjustable timing sprockets so a non-issue there) Opening the rules in any way that allows non-original adjustment of the phasing ("lobe displacement angle") of DOHC camshaft pairs is defenitelty a slippery slope given the extremely limited ability of tech to measure or determine the legality of these parameters (in practical terms, change "extremely limited" to "nonexistant" with no prejudice towards tech). Changing lobe displacement angles causes HUGE HP gains.
The argument that IT rules shouldn't reflect how hard an illegal change is to perform/OR/how hard it is to detect is a stupid one. Arguing that adjustable sprockets or offset keys at the cam sprockets should be legal because they make it easier to do is even dumber! It is much better to be pragmatic about such rules. I'm sure the intent of only allowing non factory adjustments to be done at the crank is to make it VERY difficult for someone to run modified cam timing without going to the trouble of manufacturing an original looking cam(s) with different lobe centerlines, or making timing gears with relocated key positions. I promise you that the small amount of offset in the crank key won't render it a failure item.
PS: there's no way that the phasing of in/ex cams changes, no matter how the head is milled, etc because the belt or chain remains in the same relationship where it pulls across the 2 sprockets.
PS2: If there is any need to change the rules, it only applies to vee engines with no provision for cam timing adjustment. Anyone needing this rule? If it ain't broke, don't fix it. Hoping pragmatism saves our class as well as country!
(Any boxer setups I'm familiar with use seperate belt for each bank which cause no such problem)
The change in cam timing caused by removal of material to reach legal C/R limits is negligible. In the rare case of OHC vee engines, even the 2nd head is very close and splitting the difference via crankshaft key adj would bring the timing marks into apparent positions. (the Audi V6 has infinitely adjustable timing sprockets so a non-issue there) Opening the rules in any way that allows non-original adjustment of the phasing ("lobe displacement angle") of DOHC camshaft pairs is defenitelty a slippery slope given the extremely limited ability of tech to measure or determine the legality of these parameters (in practical terms, change "extremely limited" to "nonexistant" with no prejudice towards tech). Changing lobe displacement angles causes HUGE HP gains.
The argument that IT rules shouldn't reflect how hard an illegal change is to perform/OR/how hard it is to detect is a stupid one. Arguing that adjustable sprockets or offset keys at the cam sprockets should be legal because they make it easier to do is even dumber! It is much better to be pragmatic about such rules. I'm sure the intent of only allowing non factory adjustments to be done at the crank is to make it VERY difficult for someone to run modified cam timing without going to the trouble of manufacturing an original looking cam(s) with different lobe centerlines, or making timing gears with relocated key positions. I promise you that the small amount of offset in the crank key won't render it a failure item.
PS: there's no way that the phasing of in/ex cams changes, no matter how the head is milled, etc because the belt or chain remains in the same relationship where it pulls across the 2 sprockets.
PS2: If there is any need to change the rules, it only applies to vee engines with no provision for cam timing adjustment. Anyone needing this rule? If it ain't broke, don't fix it. Hoping pragmatism saves our class as well as country!
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