OldmanRick
Well-Known Member
I've posted about this here before and some members disagree with me. I disagree with Holley's Power valve recommendations, (PV# 1/2 idle vacuum) when it comes to most street driven carbs, especially when a larger then stock cam is involved. Using your setup as the example, at 12" of idle vacuum with a 6.5PV, it would seem that your just right. The problem arises at cruise rpm when your likely at 14-16"s and throw in the fact that with the manual trans when you decelerate in gear the vac is in the 20-22" range. Now for moderate acceleration, you need alot of throttle opening to get down to the 6.5PV for enrichment, hence the hesitation. Remember earlier i said that installing a bigger squirter is sometimes masking a problem.....well this was it. I believe you need a PV in the 9.5/10.5" range to bring your enrichment in sooner. I know it's not what the books say, but i've experienced this numerous times over the years and this solved the issue.
With all that said, if any timing changes are going to occur, do those first.
With all that said, if any timing changes are going to occur, do those first.