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4 Corner Idle Conversion - Holley 4150

28K views 22 replies 3 participants last post by  ericnova72 
#1 ·
Hello Gents (ericnova72 if you are on here please give me your thoughts),

Bought this annular booster 9380 off fleabay. Supposed to be factory 4 corner idle right? Well I start tearing it down and low and behold, the throttle plate DOES NOT look like a 4 corner idle base plate to me, primarily because it is missing the block off on the passages that run front to back. So, I am going to convert it, but what has me stumped, is it seems as though all the other mods / passages to the base plate have been made already.

I will describe in the pics below:

The FIRST pic is obviously that of the bottom of the main body. All of the green arrows connect to all of the respective blue arrows on the face of each side of the main body.

In the SECOND pic, all of the holes marked with yellow arrows, match up with a corresponding hole in each bore marked by a yellow arrow in the THIRD pic. Additionally, the areas in red in the SECOND pic is where I plan on filling with JB weld to seclude the front from the rear.

In the FOURTH pic, I had a question about what these two holes that are marked in yellow are used for. They connect with one another and they are only located on the passenger side of the vehicle / primary side of the base plate (it also mates up with one hole on the main body bottom).

So in the end, to make this a true 4 corner idle set up, all that is left to do is to block off the passages in red in the SECOND pic correct? And yes my front and rear metering block already have idle mixture screws for all 4 corners.

Thanks in advance guys.

P.S. I used this link as a guide for my problem solving. Just an FYI. http://racingfuelsystems.myfunforum.org/4_Corner_Idle_Modification_about364.html
 

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#2 · (Edited)
I have included 4 photos from my super tuning holley carburetors book and one thing you will have to check on your tower is the first photo you posted you will have to check that the two holes on each side of the rear of the tower will go clear through from the horizontal and vertical passages. On many two corner idle carbs they have the holes but are not drilled to meet up with the bottom ones and you will have to drill the holes more and have it just like the front ones are. You have to be very careful not to go to far or your tower will be junk. I will post some more info of what my book says.
 

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#3 ·
That last photo that you posted that is the timed vacuum port that connects to the vacuum port on the side of the primary metering block. Also after you get your base plate and tower done you will need to check the air bleeds of what size they are in the front and they will have to be squared to match in the rear. For example if it has .070 idle air bleeds and .028 high air bleeds then they will have to be the same in the rear and also you will want your idle feed restrictors to be the same as the primary metering block. It will be a little sensitive to tune as just a 1/8 inch adjustment on the idle mixture screws will make a big difference but it nice once you got it dialed in.
 
#4 ·
OK, let's see if I can get this all understandably explained ;)

Carb is already 4-corner idle, you don't need to do anything to it.....here's why:

Pic #1, 2, and 3 - green and blue arrows are the idle mixture feed circuit and transition slot circuit feeder passages....note that one set of green arrows points to a hole very near each end of transfer track in casting/gasket imprint, but does not break into it....this has automatically made the transfer track inoperable, it is just an un-used left-over in the baseplate casting. The holes right near each end of the tracks are providing the idle fuel mixture to the idle discharge hole(which are visible in Pic's #2 and #3, yellow arrows, just outboard of transfer slot location discharging into throttle bore lower than the transfer slot).

So, no need to plug track at your red circles like you would when converting a 2-corner carb. ;)

Pic #4 - this hole, circled in yellow, is the vacuum feed to the ported vacuum nipple on the front primary metering block, drivers side, above the idle mixture needle. Note it is above the closed throttle blade at idle, so it is not exposed to manifold vacuum, but immediately starts to come into play above idle as throttle is opened. :)

All you need to do is clean it up and r-gasket /rebuild it....unless you want to take the time now to dis-assemble the shafts/blades, thin the shafts in each bore, and install button head allen screws in place of the stock bulky brass screws....increasing total cfm about 35cfm. :thumbup:
 
#6 · (Edited)
You are the bomb Eric as usual. So the "transfer track" was just cast into the base plate as a matter of practice even though its not needed here?

Also, the vacuum feed hole in the 4th pic is actually on the front passenger side. Is that where it is supposed to be? You indicated front drivers side.

Finally, in the picture I have attached to this post, the track actually goes through to that hole. Is that ok / normal, or do I need to do something about that?

Thanks again, I was about to email the seller on fleabay and chew his *** out lol. :D
 

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#8 ·
Yes, I meant passenger side on the ported vac, sorry about that, just was thinking faster than I can two finger peck type and messed up, then proof read right over it.

Yep, transfer track was cast into every older baseplate I think.

No worry about the track hitting the hole on the one end, it is inoperable from the other end anyway, it isn't machined into the idle hole at the other end.

You can just clean and re-assemble. :thumbup:
 
#9 ·
Ok thank you again sir. Already disassembled and dipping it in Chem Dip. A previous owner decided to paint the entire carb black for some reason. :spank:

Going to throw a complete rebuild kit in it, shave off the horn, and complete the Hangar 18 mods for a blow through set up on my big block. :thumbup:

Thanks again!
 
#10 ·
Ericnova72,

Just discovered that the outside air bleeds on the primary side of the carb are missing. Can I get press in ones for it or am I going to have to tap and screw in some of the removable ones? Any way to gauge the set on the secondary side to I can determine how big / small they need to be on the primary side? See pic below.

Thanks,

Brent
 

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#11 · (Edited)
Looking at your tower even though its hard to see with all the black on it if it was already a 4 corner idle carb from holley itself then the rear air bleeds will be the same as the front ones for idle and high speed at least that is how all the 4 corner idle carbs I have seen is they are equaled front and back. I honestly would at this point just drill the old ones out and tap it for screw in air bleeds. As far as I know you can't buy ones to press in.

Quick fuel on there 850 annular booster carbs has .070 for the idle air bleeds and .033 for the high speed air bleeds. That would be just a starting point.

If you have a drill bit set of #61-80 that will have your size for doing the high speed air bleeds and a # 1-60 drill bit set will have the size you need for doing the idle air bleeds. Just pop in a drill bit at a time for sizing up the high air bleeds since there still in the tower.

I got one of the sets below and for just basic carb stuff they are more then good enough since you would not be using them everyday all the time like in a shop.

115 Piece High Speed Drill Bit Set w/ Drill Index
 
#14 · (Edited)
You will probably need to go with a smaller tap size for the bleed than the newer 10-32 size bleeds used on the newer HP type carb bodies, older Holley bodies typically just don't have enough material around the hole for the 10-32 thread to reliably prevent breaking the casting. 10-32 is #21 drill at .1590", 5/32" at .1562" can be used in a pinch, but go careful with the tap at this tighter dimension.

Tap size is 6-32,Drill size is #36 at .1065", (7/64" can be used in a pinch at .1094", or #37 at .1040") it is the same size used for screw in emulsion bleeds, idle restrictors, PCVR orifices, metering block bleeds. Make sure to tap shallow, so you get a wedging affect on the bleed without sinking the bleed too far.

You'll just have to check to see which your main body is going to a better fit with, but I don't think it looks like your main body will handle the 10-32 bleeds thread size.

Bleed size should be the same for front and back, or at least quite close to the same.

I know QuickFuel sells the smaller ones in blanks that you drill yourself and premade, I did my own just buying boxes of 50 brass 1/8" long allen socket head set screws from MSC Industrial, those and the small drill bits are a whole, whole lot cheaper than buying the pre-made restrictors.
 
#15 ·
Eric,

Thanks for the info, but just so I am clear, are you saying I should use a 6-32 tap size then or? I am guessing I would like to use whatever will stay in there and not risk breaking the air bleed castings. I will drill out whatever blank you think I should use. If you have a link to the exact part that would be great. Thanks.
 
#17 ·
Thanks for that extra info ericnova72. I did read some more reading and that on some of the holley castings like you said they don't have enough area on the tower without risk of breaking the casting. From what I info I read on someone who did this mod you can use the 6/32 to tap for the high speed air bleeds and a 8/32 for the idle air bleeds using the allen head set brass screws but I am not sure how much material would be left still as I did not get to see any photos.

I plan on doing this as a mod to my double pumper next year. 31fordcoupe I hope you get it all worked out. Post some photos when you get it done as I am highly interested how your carb comes out.
 
#18 ·
This is probably going to sound really backwoods but I have read where guys have pressed in lead shot into the bleed hole and then drilled it out to the desired size. Hmmmmmmmm?

I guess my big concern now is fracturing the casting while tapping it. I called Holley on it and they want, get ready for it......$90 to press in the old style air bleeds. WTF!?!?! Oh and they won't send me any of them so I can do it myself. Go figure.

So today I am going to my machine shop with main body in hand and I am going to get this figured out one way or another. Results to be posted soon.
 
#20 ·
Yes, that will work just as well. I would suggest sticking to brass screws. Socket head allens are much easier to drill because you just don't have to drill through very much material due to the hex already being 1/2 way through the blank.
Set Screws | MSCDirect.com

Stainless screws will prove very hard to drill such a small hole through them, without breaking or completely dulling that small a drill.
 
#21 ·
Ok guys, the 4150 saga continues. I ordered another used main body and base plate off of fleabay to have as a spare and in case my original doesn't end up working for some reason. This is what I discovered upon receiving it.

It is also a 9380 but with a different 4 digit suffix (see pic #1 below).

It is also MISSING the primary outside air bleeds? This can't be a coincidence. Is it possible that Holley did not install any from the factory on the primary side in the 9380? The air bleed holes are a little smaller than the ones I just had tapped (see below), but not by much. They are significantly larger than the secondary openings, just like with my original 9380 (see pic #2 and #3 below).

Also, the carb I just got came with a baseplate. How "flat" does the bottom of the base plate need to be that mounts to the intake? I ran a straight edge six different ways on the bottom and I am getting between 1/16" and 1/32" of light between the base plate and the straight edge. Double up a gasket??

Also one of the accelerator pump arm stands has a crack / missing part of the base plate around it. Do you guys think that will hold (see pic in next posting)?

Finally, some moron decided to "crimp" one of the vacuum stubs on the base plate. Probably just going to cut it off right behind the crimp (see pic #5 below).

So in summary, is it possible the primary outside air bleeds on the 9380 came as shown without fittings inserted as air bleeds? Will my base plate work with that much / little warpage? And do you guys think that area that has broken off will hold the accelerator arm. I guess I could just jb weld he crap out of it. I paid $141 shipped to my door for the base plate, the main body and one metering block. Figured it wasn't too bad for an annular booster main body with a base plate that is already set up for four corner idle. It came as a parts carb but I was told nothing was broken. Anyway, if you guys could give me your opinions I would appreciate it.

Attached a pic of my original main body after tapping it for 8-32. Ordering brass allen head cap bolts for it this week (see pic #4 below).
 

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#23 ·
I guess it could be possible that the idle bleeds on the primary side could have come that way, maybe the small step part way down the bleed hole in the casting is an actual drilled bleed size, drilled right into the cast boss?? Maybe pressing in a bleed blank and drilling it that large would have left too little of the brass bleed remaining so they don't use them there?? I just have no experience with that particular carb model, other than the basic's of how to identify it at a swap meet.

I would say call Holley tech but be prepared for them to not be a real big help, or possibly no help at all.

Is the baseplate warped around the throttle blade portion, basically the area that the opposite side sits against the main body, which means that it would impact sealing there also?? Or is it just warped out on the mounting ear areas from a yahoo over-torquing the hold down studs?? If it is just the ears, mill or file or sand them flat, if it is all across the baseplate you will need to mill both sides....sounds like too much for just gaskets to seal as it is.

The broken pivot stud area looks to large to reliably hold the stud to me, but it could be easily TIG welded, redrilled (use an end mill rather than a drill, so you don't hurt threads on the other side of the hole), you won't even need to disassemble just remove the pump cam (plastic :pain:) I don't know if JB weld could be a good fix or not, probably could if you can get the area clean, and paste wax the stud so it doesn't stick permanently.
 
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