I’ve heard that but I’ve never seen any evidence of it. I’ve also asked on a couple of other websites about any testing done with a GD verses a BD verses a TC set up and only one guy posted some testing done.
The problem with that paper was (IIRC the testing was done by Rousch-Yates but my memory…can be in question some times) was the GD was a Pete Jackson style dual idler. Not a 3 gear, fixed idler type of GD.
It has been my theory for years now that the crankshaft produces far more harmonics than the cam train ever will. And my thinking is that the gear drive MAY transfer crank harmonics to the cam train IF the crank damper isn’t capable of doing its job.
I forget what year the NHRA and ASScar passed the rule that you had to run an SFI damper but I think it was the early 1980’s. At that time most everyone was using an elastomer style damper that has a very narrow tuning range. Now some 30 plus years later even the elastomer dampers have gotten so much better that what we used back then can’t compare to what we have today.
Thats just my opinions on the harmonics issues. I bought my first GD in 1984 and in all those years and in using as many GD’s as I could convince people to use I have never seen an issue that I could trace back to a harmonics issue.
What I have seen is a flexing pushrod will do more damage and and cause the most weird issues you‘ll ever see. Like adjusters backing off, rocker shafts coming loose and bending and/or breaking…but the most insane one I ever saw was a SBC.
That thing would break the cast aluminum oil filter adapter right off the block. It would fall ofr and make a massive mess. At the time we thought it was breaking them because they were just cast.
So we bought a remote filter set up and that cured that issue. Then it started losing valve lash. Every run. At that time, BRC made a very expensive shaft rocker set up, so we bought that thing and it stopped losing lash. And then it started crapping out the pushrods.
Once we updated the pushrods all that went away. One thing we noticed when it first cracked off on the dyno was how noisy the valve train was at idle and how much more quiet it was under load, making a pull.
The pushrod was bending so much it was quieting some of the lash noise. Under load making a pull the bending pushrods made a big racket and the bigger diameter, thicker wall pushrods didn’t make any more noise than it did at idle.
There are so many things going on inside of a running engine that it’s mind boggling.
