The painting the rad was one of the thing I put in my list to do when I first saw the pics from the seller last year. As it turned out, the motor wasn't in the condition I was led to believe. So I've got it totally redone now, and get to start working on a rather long list of nits.
Art,
I'm kind of old school. For 50 years or so, we've been drilling holes in the front butterflies on Holleys, or some choose to buy the blades from Holley with the holes already in them. If this was a 4 corner Holley it probably wouldn't be nesessary as the back barrels would have an idle circuit. My thinking is that idle is already poor with the air and fuel mixing in the same vicinity. The idle that puts such a huge grin on our faces, is lean misfire. So why would I want to be introducing air several inches away from where the fuel is? In the manifold, under the primaries you would find a rich mixture, and under the secondaries there would be a very lean mixture. We staggerjet carbs to cure cylinder to cylinder mixture distribution differences that are occurring under full throttle and the highest velocities through the carb. However, perhaps we could maintain or enhance all the idle nastiness, while closing up the primary so that the idle transition circuit would come in properly. I'll have to consider that one.
In the '60s, I'll admit that all my carb work was around getting the highest mph at the track, and it was done by changing jets. If it would start and move to the line, and go fast down track, all was good. Gas was cheap, and I left my "give a $hit" about economy over there somewhere. All about "go fast." However, I spent some time with a real Holley Guru, and he went about things differently than I had. Idle circuits were about idle. Idle transition circuits were there for the tip in off idle. There are fuel and air bleeds to modify the fuel curve if nesessary. The jets in the primary are there for cruise mixture. Yes, we can short cut and use them just like the secondary jets for full throttle only, but that's not how the carb was built to work. the PV system is there for enrichment under full throttle. They are found in the secondary side of mechanical carbs because the secondary's may be partially open under circumstances that don't require full rich. Most people just jet the secondary for full throttle mixture as they weren't intended to operate under cruise conditions. PVs are seldom found in the secondaries on vacumm opened secondaries, but that is not an absolute. Your friend, who went back to the 6.5" PV was in all probability using it to mask a problem with the idle transition circuit not right, or the accelerator pump circuit cam or shooters not properly chosen. Full throttle air/fuel mixture should be about 12.5-1, idle @ 13.5 to 14-1, and cruise 14.5 or a tad higher. The idle transition circuit is not there to fatten the mixture, but to prevent a lean out, and carry until fuel starts out of the boosters. NThe accelerator circuit likewise is there to prevent leanout, not enrich. Old school, as well as Holley, says to choose a PV# 1/2 the idle vacumm. As mine was idling @ 10" in neutral, the 4.5" PV seemed appropriate. I havent got my dizzy on the machine yet, my total timing is 38*. Comp recommends 18 initial.
Sorry for the long winded reply. Us old guys can just go on and on, so I'm told.
Mike
