The carb cleaner hasn't stopped the tacking, but it is noticeably quieter after a good 60 miles today, so perhaps there is some crud causing the noise.
I can get some of that Marvel stuff locally (interstate) for ~AU$50 a gallon plus post, so I might give it a go. I couldn't find the Forte locally unfortunately.
I like the transmission fluid idea. That's an easy one.
Thanks again everyone.
barnym17 wrote:By going to a 1.9 rocker you have increased the springs pressure on the lifter causing it to bleed off thereby causing your issue.
Yeah, I worked out that there is about an additional 45-50lbs at full lift due to the higher ratio and the shimming (still less than 250lbs open), but also, if these lifters are the same as the LS6, they should easily be able to accommodate the higher pressure. Age and/or accumulated crud is the exception in this case I assume.