Thanks guys,
I understand that there must be flow in order for the venture effect to work. I just see engines with 3X2 and 2X4 setups and they seem to be “over carbureted” but seem to run OK.
Holley says:
How To Calculate CFM:
Engine size (CID) x maximum RPM / 3456 = CFM
CFM @ 100% volumetric efficiency
SO, 235 CID X 4000 RPM / 3456 = 271.99 CFM
390 CFM CARB / 2 = 195 CFM
Using the above, I think that maybe something is not quit right with my set up. It’s got plenty of go, but if there is something else I can do I would like to do it. My 235 has a 272 In/Ext duration cam, headers free flow exhaust and stacked paper element air filters no serious head work and I think I would be able to get a bit better flow than stock.
Tony,
I do have the vac gauge and will try it. I just didn’t know how much vacuum should be there before a larger carb could be installed.
I found this at Holley. It gives a simple way to check and see how far the secondaries are opening. I am going to try this also.
QUESTION I can rev the engine when it is in park and the secondaries will not open. Why is this?
ANSWER The secondaries will not open by free revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening or not you can take a normal paperclip and clip it onto the secondary diaphram rod. You will then push it up against the bottom of the secondary diaphram housing, now you will need to go out and drive the vehicle. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod then you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring.
