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 Idle and transfer slot improvements 
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Joined: Mon May 15, 2017 4:04 pm
Posts: 81
Don't get me wrong Str8Jacket, I love Holley's Rochesters and Carters but, mostly Holley's.

You can get a $10.00 600VS Holley 1850 and a $20 low buck rebuild and run most any engine from 200 to 500 cubic inch's, and if you have a problem change it with the spare in the trunk in five minutes with a handful of tools on the side of the road if need be. EFI have fun with that. 8)


Sun Jun 18, 2017 5:34 pm
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Joined: Sun Jun 23, 2013 1:41 pm
Posts: 378
Location: Phila. Penn.
Completely agree about manufacturing costs. With the 2100/4150/60 Holley design the transfer slot is the restrictor. A series of holes would have to be larger and jetted or very precise, uh or at least as precise as the trasfer slots. :LOL: My point was only that IF there were significant gains in getting the fuel into the air (improved quality) with additional surface area, it is doable, and might have been worth the expense. I'm sure the Webers are not the only ones with holes instead of slots.

I wouldn't worry about the trash or carbon that high up. Every time I've had trash its stuck in the idle passage or port. Well let me take back the comment about carbon. If reversions that bad then that's a point I was trying to make. Probably the biggest improvements in the idle fuel mixture will come from better combustion. Timing and exhaust velocity are two places to tweak without getting into major changes to the engine.

As far as FI goes, closed loop feed back is nice when it works. For OEM's balancing emmissions and efficiency it could provide far more control and precision than preset analog. For hot rodding and racing the beauty of the carburetor is it provides what the engine calls for. The main system is, or can be, incredibly responsive to the engine demands. That's pretty cool. 8) Its also fun just seeing what can be done with physics and mechanics.


Sun Jun 18, 2017 5:49 pm
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Joined: Mon May 15, 2017 4:04 pm
Posts: 81
Mattax wrote:
Completely agree about manufacturing costs. With the 2100/4150/60 Holley design the transfer slot is the restrictor. A series of holes would have to be larger and jetted or very precise, uh or at least as precise as the trasfer slots. :LOL: My point was only that IF there were significant gains in getting the fuel into the air (improved quality) with additional surface area, it is doable, and might have been worth the expense. I'm sure the Webers are not the only ones with holes instead of slots.

I wouldn't worry about the trash or carbon that high up. Every time I've had trash its stuck in the idle passage or port. Well let me take back the comment about carbon. If reversions that bad then that's a point I was trying to make. Probably the biggest improvements in the idle fuel mixture will come from better combustion. Timing and exhaust velocity are two places to tweak without getting into major changes to the engine.

As far as FI goes, closed loop feed back is nice when it works. For OEM's balancing emmissions and efficiency it could provide far more control and precision than preset analog. For hot rodding and racing the beauty of the carburetor is it provides what the engine calls for. The main system is, or can be, incredibly responsive to the engine demands. That's pretty cool. 8) Its also fun just seeing what can be done with physics and mechanics.


I get what your saying about the carbon and it being high up. I was thinking more of the .020" or so dribble holes on the secondary side of 2 corner idle Holley's. Quite a few of the cores I get in have a lot of carbon in and around those holes is why I mentioned it. It just seems to me for some reason a slot would be more self cleaning. I guess it's because I could see trash building up in that pocket somehow.

If you could get a base plate without the slots cut to experiment with it would be much easier then welding up an old base plate and re-machining it.

Did anyone tell Troy about this, I think he likes to Webberize Holley's? B| Just Kidding.


Sun Jun 18, 2017 6:12 pm
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Joined: Sun Jun 23, 2013 1:41 pm
Posts: 378
Location: Phila. Penn.
That's hilareous. :O

Back to the more serious, you raise good points. What are those dark streaks below the discharge holes? I'm going to guess portions of the fuel that become varnish. I'd be curious if carbs that run only race fuel or alcohol have similar deposits?


Sun Jun 18, 2017 8:14 pm
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Joined: Mon May 15, 2017 4:04 pm
Posts: 81
I kind of doubt race fuel or a race carburetor is going to see the miles the old streeter's saw running everyday with who knows what for fuel along the way. Most people likely don't put a 10th of the road time on carburetors like they used to when we daily drove them, so there's that to consider also. On a side note I got a couple of the new Holley's with the billet anodized base plates and they sure clean up a lot easier. They were not very old though and did not have many miles on them but, they don't seem to hold the crud like the old ones do.

You will have to get a conclusive answer from Mark or Tunner on the Race/Alky deal and the streaks. I have not run race gas in years and it was usually mixed with pump, and I did not pay much attention to it.


Sun Jun 18, 2017 9:47 pm
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Joined: Mon May 15, 2017 4:04 pm
Posts: 81
Interesting development tonight.

Working on a Holley 750 VS Marine Holley for a 460 Ford specific application. I noticed the primary venturi's right above the transition slot, each have a hole intersecting the transition slot channel that pinned out at .055". It's about a 1/4" above the base plate mounting surface.

I had forget all about these when we were discussing the topic earlier and then I had to get one ready to go out.

I checked my other three List Number 7128 main bodies which are also 460 marine specific and they have the same holes also, so I am sure they came that way.

This one it a List Number 50470.

Another difference that caught my eye That I don't recall seeing before on other Holley's, and almost had me getting the drill out for a second until I found a smaller probe, LoL, was the secondary transition slot feeds. The hole goes all the way from the bottom of the main body from the transition slots to the IAB with a hole feeding at the top from the metering plate into the IFR pocket. On the body of the main body there are dimples partially drilled where most Holley's have the transition feed hole drilled through at the back bottom.


Mon Jun 19, 2017 4:14 am
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