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Hi AB, Do you still have my email address? pop me a line if you have. If you go to a wider LSA and a corresponding smaller duration to keep the IVC etc the same you will get much more vacuum and a better mid range pull. But you need the porting to go with it. Port flow and cams have to match. It depends on the transmission etc as to what find works the best for what you need. A lot of the top end problems of carburation come from the tune of the low end. If the combo requires inappropriate corrections it can influence what happens up in the top end of the power. The carbys can only do so much to correct things. See the low speed circuits of a carby work all the time they effect top end .
Fuel with high octane generally has higher distillation temps. Not all fuels follow that rule but 99%do. As the distillation temps are raised it takes more energy to get the fuel components into a gas. That energy is limited by the engine combination. Things like dynamic comp, exhaust gas retention, wall temps, oil temp on the piston, are energy sources, things like vacuum in manifold, carby size droplet size are things that lower the temp necessary to gas the fuel and the time taken to do it. Tuning these areas reduces all this wet flow that everyone keeps talking about now days. Control the wet and it goes harder.
These HP carbys are sold with calibration that doesn't work on the fuel here in Australia thats all I can say. They always run too lean at the top and changing the main jet is not the beat way to fix it. Changing the high speed bleed smaller is the first thing to do then chase the e-bleeds and the low speed circuit to suit the motor. I wouldn't use aftermarket metering blocks, the Holley ones are fine when they are fitted with the correct e-bleed calibration for whatever motor fuel combo. If you havent got the ultra version then you need to thread them. Its just you can spend time on them and then swap in an old 850 and it will beat it. Also power is not everything drivability is a big factor to most people. An Old 850 with a stub stack is hard to beat. Even if you copy the calibration of the oldy they still dont perform the same way. Holleys with a stub stack tuned to the stack work ery well and the HPs are a differnt air horn so its not like a stub stack tune. Some engines love the Hp's some don't, but every engine will go good on an old 850. There a good reference.
Dont bother tuning carbys with a WB you have to use a gas bench to figure this stuff out. A gas bench shows the difference in burns from a modern carby to the oldy.
The problem you face is the other guys are not in sync with your thoughts. While their tuner does it the way he is you wont get what you need. The grooves do something to the combustion there is no doubt but you have to qualify it. Its possible the over rich/over octaned environment is being corrected by the grooves somehow that might not happen the same way if the environment was different. See good racing engines actually burn extremely clean. They even have low emissions at power settings compared to lesser engines. You dont make power from poor combustion and thats what is the source of emissions.
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