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scicala · 02-09-2020, 01:41 PM

Original carbs made to work with Loadomatic distributors supply a blend of vacuum between the venturi suction and ported manifold vacuum. The max the distributor diaphragm will see is maybe 4" hg. With the 390 Holley 4 barrel, as soon as the throttle opens slightly, there will be manifold vacuum to the dist. diaphragm, and wil be a lot more than 4" hg. Therefore, it will more than likely over advance the spark and cause issues. With vacuum to the dist. blocked off, you will only have the base timing setting in all engine modes with extremely hot exhaust temps, not to mention a severe lack of power.

Sal

02-09-2020, 01:41 PM	#36
scicala Senior Member Join Date: Jun 2010 Location: Detroit suburb, MI Posts: 3,703	Re: Distributor to 1951 255 8BA Original carbs made to work with Loadomatic distributors supply a blend of vacuum between the venturi suction and ported manifold vacuum. The max the distributor diaphragm will see is maybe 4" hg. With the 390 Holley 4 barrel, as soon as the throttle opens slightly, there will be manifold vacuum to the dist. diaphragm, and wil be a lot more than 4" hg. Therefore, it will more than likely over advance the spark and cause issues. With vacuum to the dist. blocked off, you will only have the base timing setting in all engine modes with extremely hot exhaust temps, not to mention a severe lack of power. Sal