Holley 4175 rebuild

maxtwms · Mar 22, 2018

This is my first carburetor rebuild so I figured I share/document. Here's the first night of breaking things down. I'll try to edit where necessary and can post more of a progression "album" if anyone cares to see. Heres a summary of the parts so far..

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74 Shortbed · Mar 22, 2018

Don't forget to remove the floats and needle and seats before cleaning, and the metering block.

maxtwms · Mar 22, 2018

74 Shortbed said:
Don't forget to remove the floats and needle and seats before cleaning, and the metering block.

Thanks. I was cautious about it tonight since it was getting late and the bourbon and beer we're getting in the way. I was running out of room on my rug too. I'm having trouble getting the idle circuit plate off though. Any tips? I've broken a few razor blades trying to pry it open along with a tiny flathead helper. That's how I got the bowls off.

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74 Shortbed · Mar 23, 2018

If you're talking about the plate on the back it's not an idle circuit, it's the secondary jet plate and there's screws that holds it on, they do stick to the gasket, careful prying with a small screw driver will take it off just be patient it's aluminum, metering block can stick too.

maxtwms · Mar 23, 2018

74 Shortbed said:
If you're talking about the plate on the back it's not an idle circuit, it's the secondary jet plate and there's screws that holds it on, they do stick to the gasket, careful prying with a small screw driver will take it off just be patient it's aluminum, metering block can stick too.

I'm talking about the idle circuit plate (bottom of image in kitty litter box). The secondary plate has different screws though... I thought I had seen and had every screw tip there was until I saw this one... What is that?

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maxtwms · Mar 23, 2018

I suppose it could be a flat head but with everything being either AL or brass, I'm hesitant to put too much torque on anything.

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maxtwms · Mar 23, 2018

Now that I'm looking closer at that picture.... Those cracks in the plate can't be good right? Or am I seeing some weird lighting..

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Rusty Nail · Mar 23, 2018

Lol you been smackin on it Bourbon and beer boy?
All you need now is some scotch eh George?

Looks broke to me but i'm no expert!

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74 Shortbed · Mar 23, 2018

maxtwms said:
I'm talking about the idle circuit plate (bottom of image in kitty litter box). The secondary plate has different screws though... I thought I had seen and had every screw tip there was until I saw this one... What is that?
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Ok, you're talking about the primary metering block, it has the jets and PV, they do stick with those old style gaskets, take screw driver and pry it off at the top where the emulsion tubes are, not on the sides it's too easy to damage the gasket surfaces.... The secondary metering plate has "clutch" head screws so you need a clutch head screw driver, and that is stuck on there too, they are a fragile casting, I use a scraper under the gasket and gently work my way around gently prying on it till it breaks loose, be patient it will come loose...

74 Shortbed · Mar 23, 2018

maxtwms said:
Now that I'm looking closer at that picture.... Those cracks in the plate can't be good right? Or am I seeing some weird lighting..

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Those are just casting marks not cracks, probably stuck to the mold a bit, but as I said they are kinda fragile and will bend fairly easy, also there's a metal plate between it and the gasket too.

maxtwms · Mar 23, 2018

74 Shortbed said:
Ok, you're talking about the primary metering block, it has the jets and PV, they do stick with those old style gaskets, take screw driver and pry it off at the top where the emulsion tubes are, not on the sides it's too easy to damage the gasket surfaces.... The secondary metering plate has "clutch" head screws so you need a clutch head screw driver, and that is stuck on there too, they are a fragile casting, I use a scraper under the gasket and gently work my way around gently prying on it till it breaks loose, be patient it will come loose...

Ah. My bad. Im new to all the terms so thats my fault. Yes, metering block. I know theres an idle circuit in there so I just made up a new name and stomped my foot about it. Appreciate that.

maxtwms · Mar 23, 2018

Alright I hope I don't junk up my whole thread but I have a few questions,
1. Is it ok to soak the vacuum choke "bell housing" in carb cleaner? It looks like it doesnt come apart

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2. Does this throttle linkage/plate come off? Ive removed the "2" screw and and the link. I was thinking maybe Id have to remove the butterfly valves and slide the rod out which leads to my third question.

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3. Is it unwise to remove the butterfly valves/screws? I started to remove one but it feels like a small brass screw that is flattened on the backside to prevent backing out.

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4. Is there a torque table for these carbs without buying a book or should I just use the standard best practices. (Although I might need a book with this many questions.)

Thanks guys. I hope Im not blowing up phones everywhere.

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74 Shortbed · Mar 23, 2018

1 No don't soak the pull off, it has a rubber diaphragm in it, just clean the outside, if it works it's good if it don't replace it it's non serviceable.

2-3 Leave the base plate in tact just take it off the mainbody, no need to take the butterflies out unless the shafts are sloppy and need bushings or binding, Brake-Kleen works good to wash it off.

4 If you have a feel for torque that's all you need and common sense, and the theory(a lot of people use) "if in doubt strip it" don't apply, LOL.... But here's a chart if you like..

http://www.junkyardgenius.com/holley/torquespec.html

maxtwms · Mar 23, 2018

74 Shortbed said:
4 If you have a feel for torque that's all you need and common sense, and the theory(a lot of people use) "if in doubt strip it" don't apply, LOL.... But here's a chart if you like..

http://www.junkyardgenius.com/holley/torquespec.html

LOl never heard that.. Im a mechanical engineer and design for a living so it makes me almost cringe to hear. Always worried about stripping helicoils or threaded inserts. But, the real reason I ask is because all of the material used on these feel so soft.

Thanks for the chart. That thing is great

74 Shortbed · Mar 23, 2018

maxtwms said:
LOl never heard that.. Im a mechanical engineer and design for a living so it makes me almost cringe to hear. Always worried about stripping helicoils or threaded inserts. But, the real reason I ask is because all of the material used on these feel so soft.

Thanks for the chart. That thing is great

Well, it is aluminum but still has to be snug though especially the float bowls, just don't tighten till it feels like it's not tightening down anymore, lol.

Holley 4175 rebuild

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