tuning help needed

moper said
I think it's just a mismatch. The intake is more than likely similar to a factory iron, but with the holley flange. The cam is too large, the static ratio too low. the advance curve too slow, the headers too large. I understand the ideas Bobby's given you on the carb. I wouldnt do a damn thing to it except male sure it's been rebuilt fairly recently is it's not new. You do not want to remove the check ball as this is what makes the vacuum secondary work properly. Without it, you've created a manual secondary carb with no secondary accelerator pump and without steep gearing and a loose convertor, it's a disfunctional mess. I would change to a jet plate metering block, but it's not imperative for that combo. I've never seen any issue with the cork gasket except installation error. They are not subjected to enough suction to pull the gasket out if it's installed in the right spot. In any event, take a cylinder pressure reading. What vacuum does it pull in gear, and at what rpm is it idling at?

I don't understand your reasoning here that the carb would be a disfunctional mess. Most holley 750 VS carbs don't even start to bring the secondaries on till well past 3,000 rpm's with the check ball in place, and may never have them fully open. The reason I say this is the amount of vacuum that the carb would see with the tiny hole in the bushing that might be all of .015 isn't sufficeint enough to operate the diaphram, or the restriction of the check ball. Further more almost every 750 VS carb that I've seen in the last few years that weren't gone into before had the gasket problem on the secondary vacuum port to operate the diaphram. Some even had a paper gasket that totally blocked the port altogether which doesn't allow the secondaries to operate any.

As for the carb becomming a manual secondary carb without the pump shot couldn't be further from the truth. Everyone that I've done has operated as it should. I've done these same modifications with the 750 VS on my truck and on others and never had a dissatisfied customer. And none of the vehicles had steep gears or high stall converters. The secondaries don't come on immediately but start to open at 1800 rpm's and aren't fully open until 5,500 rpm's or more depending on the spring that is used. The secondaries don't come on til the engine vacuum falls far enough to pull the diaphram open. So to say that it becomes a manual secondary carb isn't true. But this does allow the engine to get up in the rpm range before the secondaries start to open, making a crisper or sharper throttle response.

Also to you have to have your foot on the floor for the carb to operate this way. Needless to say that most of the time it won't be on the floor, and the carb will operate like a normal 2 bbl. until the vacuum falls enough to open the back 2 bbls.. By removing the check ball or bushing will bring the sec. on quicker when the engine really wants it or needs it.

You can do to it anything that you want, but if it isn't working right now what do you have to lose. Or better yet if you have a DP carb put it on first and see if it doesn't pick it up or make the engine respond better. If it does then the secondaries aren't comming on fast enough. If not and you don't want to do anything more to it or take the chance that it may work, then you or who every owns the car will have to be satisfied with the way that it is.

Moper, You and I have had disagreements before and we may have to differ here too. But hey were still buddies, and anytime you get a group of people together you'll always have differences of opinions. It's just human nature.