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Old 12-14-2017, 08:30 AM
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Tom Vaught Tom Vaught is offline
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Here is a thread from the Turbo Forums with a guy asking about how to convert from a 2-corner idle to a 4 corner idle configuration.
https://www.theturboforums.com/threa...r-idle.340643/

1) Mr Bowtie Guy broke the ear off on his 2-corner idle base plate. So he decided to bolt on a 4-corner idle baseplate. So now he has the mixture screws out 5 turns on the Primary Side
Metering Block to get the thing to barely run.

"Ok.... after 7 hrs of searching the web... I want to convert the carb to a 4 corner idle carb.... but I havent found ANYTHING yet on how to modify the carb body for it......"

"Ok.... I found a diagram showing me the holes I need to drill in the body, here it is:"

(Same picture I posted up in our thread on Carbs showing the different main body drillings.)

"Im a idiot....... For the people who search this thread..... On the secondary side of your carb main body, drill both number 3 holes (in the diagram posted above) to the same length as the primary side holes.... as long as u have a 4 corner idle baseplate, and a secondary metering block that has the idle adjustment screws... this will make it a 4 corner idle carb...
Bowtie Guy"

So in post #7 I replied I am Boost Engineer on the Turbo Forums.

"I was hoping you were going to post up in here Yeah you just described my setup lol. All idle air bleeds are the same size, and its the happiest with the idle screws around 3/4 of a turn out :2thumbs: From a stone cold engine, I can pump the gas twice, hit the key, and it'll run without having to run the throttle I could never get it setup like that with a 2 corner idle setup.... Been tuning it for like 4 months now and it runs just as good as a efi setup would I'm very pleased :cheers: Thanks to all the info on the turboforums of course :bow: Thanks guys :2thumbs:
Bowtie Guy"

So he was a happy guy after searching on the web for hours, and not getting any help otherwise.

So the post today is about part 2 of the 4 corner Idle Conversion Process.

1) He had a 4 Corner Idle Baseplate (like I showed in one of the previous posts so that saved him modifying a stock baseplate. 4-corner idle baseplates can be purchased from Carb Builders like Shaker455. He buys from the same source I do. Now you have a new part and you have not screwed up your stock 2 corner idle baseplate that you could sell to a guy like Bowtie Guy who broke the ear off his.

So now we have a 4 corner Idle base plate and you know the drillings and what they do.

So then we go to this quote:
"Im a idiot....... For the people who search this thread..... On the secondary side of your carb main body, drill both number 3 holes (in the diagram posted above) to the same length as the primary side holes.... as long as u have a 4 corner idle baseplate, and a secondary metering block that has the idle adjustment screws... this will make it a 4 corner idle carb..."

A bit more info here.
There are two drilling in the main body for each idle circuit. One the primary side the two drillings meet each other. A drilling from the Throttle Plate side of the mainbody and a drilling from the Metering Block side.

On the Secondary side of the main body the vertical drilling (from the base plate side upward into the mainbody is ALREADY the correct length. The drilling for the Horizontal drilling on the metering block side is slightly short and does not intersect the vertical drilling.
So Mr Bowtie Guy figured it out that if he measured the horizontal drilling length on the #3 holes on the Primary side and drilled to the same length on the secondary side he would JUST BREAK THRU into the vertical drilling.

If he had tried to guess where the two met he might have drilled right into the booster/throttle
air flow passage and then would have had to somehow plug that screw-up. (Saw a young Holley Engineer do that one time but I helped him fix the deal later.)

So Bowtie Guy already had another 3310 style Primary Metering Block for the secondary side so no mods there.

So now he just needed to make the secondary
Idle Air Bleeds in the Mainbody the same size as the Primary Idle Air Bleeds. And set his Mixture screws to 3/4th turn out.

So he did that and I repost his final statement:

Mr Bowtie Quote: "I was hoping YOU were going to post up in here Yeah YOU just described my setup lol." All idle air bleeds are the same size, and its the happiest with the idle screws around 3/4 of a turn out :2thumbs: From a stone cold engine, I can pump the gas twice, hit the key, and it'll run without having to run the throttle I could never get it setup like that with a 2 corner idle setup.... Been tuning it for like 4 months now and it runs just as good as a efi setup would I'm very pleased :cheers: Thanks to all the info on the turboforums of course :bow: Thanks guys :2thumbs:
Bowtie Guy"

So here you have a real live thread on how to mod a 2 Corner Idle carb for 4 Corner Idle and how happy the guy was later.

Tom V.

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