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Old 06-21-2021, 02:40 PM   #21
pistonbroke
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OK, he Got back to me. He is running 2 Holley 94's on a Fenton intake on a 255 cid with tube headers and the highest compresion heads Offenhouser sold back in the early 80's . The stock loadomatic distributor is hooked up to the front carb only. So that's whole deal, any ideas ?
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Old 06-21-2021, 03:00 PM   #22
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I think that's the key, and as long as you don't go overboard on the rest of the engine (radical cam), it will probably work just fine. There are other folks doing it.
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Old 06-21-2021, 03:22 PM   #23
Ken Henry
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There are two vacuum signals coming from the 94 carb - venturi vacuum related to RPM and manifold vacuum related to load. These are combined through small passages into a common port/vacuum signal going to the distributor. This is the only signal controlling the ignition advance - there are no weights or anything inside to provide a mechanical, RPM-based advance curve.


Adding the second carb changes the nature of these signals, so it will/may no longer function according to how the engineers originally designed it.
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Old 06-22-2021, 09:11 AM   #24
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OK. He got back to me and confirmed he is running a Load a matic with the vacuum signal from just the forward holley 94. This engine is running a stock cam so the manifold vacuum should be normal.
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Old 06-22-2021, 09:30 AM   #25
Ken Henry
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Here's what I'm not sure about: the venturi vacuum signal is related to how much air is flowing through the carburetor. If air flow is split between two carburetors, wouldn't the venturi vacuum signal be less than normal, perhaps by one half? This would result in in less of the RPM-related distributor advance (controlled by the venturi vacuum signal) and hinder performance. The manifold vacuum shouldn't be changed too much, but that would be near zero under heavy loads.
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Old 06-22-2021, 09:50 AM   #26
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I think you hit the nail on the head there. Vacuum would be compromised to my way of thinking.
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Old 06-22-2021, 07:28 PM   #27
tubman
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Yeah, but half a vacuum signal is probably a lot better than none.

From what I am seeing, a lot of guys have decent running cars doing this.
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Old 06-22-2021, 07:51 PM   #28
Ken Henry
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Yeah, the flathead is pretty forgiving before she complains. Extra base timing might help
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Old 06-22-2021, 11:30 PM   #29
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Originally Posted by Zax40 View Post
So heads marked 8BA or 8CM do not flow as well as the EABs. How hard are the EAB heads to find?

Sorry pistonbroke, not trying to hijack your thread but I am in a similar situation and am trying to learn. Have a decent stash of parts, but it's looking like I need to find more.

They aren't falling out of trees but a lot of guys pull the iron heads for aluminum so they aren't rare. Truck heads have low compression. anything can be milled to a point.
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Old 06-22-2021, 11:32 PM   #30
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There are two vacuum signals coming from the 94 carb - venturi vacuum related to RPM and manifold vacuum related to load. These are combined through small passages into a common port/vacuum signal going to the distributor. This is the only signal controlling the ignition advance - there are no weights or anything inside to provide a mechanical, RPM-based advance curve.


Adding the second carb changes the nature of these signals, so it will/may no longer function according to how the engineers originally designed it.

Get a mechanical advance unit from charlieny or bubba and forget about it. PV 3.5 on dual 94s
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Old 06-24-2021, 09:15 AM   #31
Ol' Ron
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There is a book out there that can help all those that want to us a stock flathead with some simple mods that will improve their performance and economy. Written by JWL called "Flathead facts". The information in this book is written for the beginner. and ends up building a Bonneville engine/
Gramps
Mine ain't bad either.
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