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One more question: I've seen replacement metering blocks that supposedly can convert a 4160 into a 4150-style carb with jets and everything. Worth a try?
For your existing carb? I wouldn't mess with trying to swap out parts on that platypus. There's very little information on those, to fully understand it. And since you've had it worked on a couple times previously, who knows what's been changed/modified as far as the components already.

You could convert one of those refurbished factory offerings and make it a 4150, but less expensive to buy it already setup that way. The 4160 models were just the budget version of the 4150 (with the exception of your rare oddball reverse idle emissions variant).
 

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One more question: I've seen replacement metering blocks that supposedly can convert a 4160 into a 4150-style carb with jets and everything. Worth a try?
Hi Ken. I was impressed with the 4160 #80457 street warrior. But if you want to use the factory Holley dual inlet lines yes you need a 4150. I have 2 warrior 80457 4160s heavily modified to 4150s, center hung float bowls, modified primary throttle shafts, chokes removed, QFT vs adjustable actuators, light yellow vs spring, special secondary float bowls that Holley never provided a part number for and say they werent intended for sale as a piece part and a number of other things. But I only did this to build my cross ram project. My only other option was spending 3k-5k a piece for two very unique factory carbs. So I found another way.

You can buy a refurbished 4160 and convert to 4150 with Holley kit 34-13, but this only gives you half of what you need.
If you really want a 4150 just buy it as a 4150. You know its right out of the box.

My project has not been fun and its not done yet. Car was meant to be driven and enjoyed not sit in a garage for 2 years. Instead I study engineering data and search for parts that dont exist, are simply not what vendor says they are, (heart who?), or never assigned a part number so cant be sold.

Spring for a refurbished 600 or 650 4150 you will not be sorry.
 

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Discussion Starter · #63 ·
For your existing carb? I wouldn't mess with trying to swap out parts on that platypus. There's very little information on those, to fully understand it. And since you've had it worked on a couple times previously, who knows what's been changed/modified as far as the components already.

You could convert one of those refurbished factory offerings and make it a 4150, but less expensive to buy it already setup that way. The 4160 models were just the budget version of the 4150 (with the exception of your rare oddball reverse idle emissions variant).
Thanks! The more I looked into it the more I was/am leaning toward that approach. The reason I was even thinking of the custom alteration of my, or another, 4160 into a 4150 is because the refurbed 4150's are not very available on the Holley or Summit sites...and I don't trust the eBay offerings. I really appreciate all your help.
 

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Thanks! The more I looked into it the more I was/am leaning toward just getting a refurbed 4150. The reason I was even thinking of the custom alteration of my, or another, 4160 into a 4150 is because the refurbed 4150's are not very available on the Holley or Summit sites...and I don't trust the eBay offerings. When I saw that there was such thing as a 4160 to 4150 kit, I thought I'd see if anyone on here had done so—I got two opposite opinions. LOL. I appreciate your kind remarks and all your help.
Holley updates their refurbished carbs site regularly, so dont get discouraged, just keep checking for the carb you want.
 

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Discussion Starter · #65 · (Edited)
Holley updates their refurbished carbs site regularly, so dont get discouraged, just keep checking for the carb you want.
HA. Another mystery. Here is what I found when I started looking at converting my 4160 to a 4150-ish carb. THIS is the metering block I found that has the exact same number #7482 and also stamped 6619-1 for a reverse idle carb like that which is on my current carb. We thought mine had a "metering plate," but, unlike what we were thinking, this DOES have changeable jets and and power valve. I either need to take mine apart just for fun or find a 4150, which is looking like the best option right about now. smh.
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HA. Another mystery. Here is what I found when I started looking at converting my 4160 to a 4150-ish carb. THIS is the metering block I found that has the exact same number #7482 and also stamped 6619-1 for a reverse idle carb like that which is on my current carb. We thought mine had a "metering plate," but, unlike what we were thinking, this DOES have changeable jets and and power valve. I either need to take mine apart just for fun or find a 4150, which is looking like the best option right about now. smh. View attachment 290558
Ken the 4160 uses a metering plate on the secondary. 4160 secondary has no metering block that just has the float bowl attached directly to the main body. If you take the float bowl off the secondary side you will find the metering plate and since thete is no metering block there is no provision for a PV. Snap a shot of the metering plate when you find it and maybe I can find the listing for what jets it is equivalent to. 👍
 

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Discussion Starter · #67 · (Edited)
Ken the 4160 uses a metering plate on the secondary. 4160 secondary has no metering block that just has the float bowl attached directly to the main body. If you take the float bowl off the secondary side you will find the metering plate and since thete is no metering block there is no provision for a PV. Snap a shot of the metering plate when you find it and maybe I can find the listing for what jets it is equivalent to. 👍
Well, duh, my mistake. All this time I was thinking there were no blocks, just plates on both sides. Obviously misread a post a while back. Thanks again, sensai.
 

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Discussion Starter · #69 ·
Thanks. I'm looking for a 4150. That's a 4160. They have a refurbed 670 cfm 4150 on there today. I'm thinking I might pull the trigger. (Or in your opinion is that too big?) Do you know if all 4150s require the dual fuel inlet line? My 4160 (600 cfm) has only one inlet with a tube running to the secondary side.
 

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Discussion Starter · #70 ·
Ken the 4160 uses a metering plate on the secondary. 4160 secondary has no metering block that just has the float bowl attached directly to the main body. If you take the float bowl off the secondary side you will find the metering plate and since thete is no metering block there is no provision for a PV. Snap a shot of the metering plate when you find it and maybe I can find the listing for what jets it is equivalent to. 👍
I found a refurbed 4150 (670cfm) on the Holley site. (Electric choke, VS, quick change secondary spring thing) It's only $335 or something. (Do you think that would be too big?) Since it runs a little rich right now—there's also a 570cfm for $314. (Too small?) I'm still tempted to experiment with the one I got, though, just for fun. I've read that Holley usually jets the primaries too large, the PV too low, and the secondary spring too stiff. However right now it runs best when the idle is adjusted almost as rich as it can be. So I'm wondering if a couple sizes smaller primary jets and it might not run at all. But I'm thinking adding a little higher number PV and a less-stiff VS spring just to see if it might run a little peppier? (Purple or orange?) That'd be cheaper than $335.
 

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I found a refurbed 4150 (670cfm) on the Holley site. (Electric choke, VS, quick change secondary spring thing) It's only $335 or something. (Do you think that would be too big?) Since it runs a little rich right now—there's also a 570cfm for $314. (Too small?) I'm still tempted to experiment with the one I got, though, just for fun. I've read that Holley usually jets the primaries too large, the PV too low, and the secondary spring too stiff. However right now it runs best when the idle is adjusted almost as rich as it can be. So I'm wondering if a couple sizes smaller primary jets and it might not run at all. But I'm thinking adding a little higher number PV and a less-stiff VS spring just to see if it might run a little peppier? (Purple or orange?) That'd be cheaper than $335.
I would think that 670 would be a good carb for your 350. Throttle bores are the same as the 600 warrior and it worked great for me. Plus it has quick change VS spring cover, 4 corner idle mixture screws, electric choke which I really miss (simple hook up to your fuse block). Dont know what trans you currently have but if it is an auto 700R you could need another $70 worth of hardware to hook up the linkage according to Holley, which they have. No its not too big, ventury bores being 600 venturis, the purple VS spring installed will not fully open secondaries until 6950 rpm, which I dont think you are going to see. The yellow or yellow short spring will both fully open around 5700 if you so choose to try later. Plus Holley says you get the kit of VS optional springs with this carb if I read that correctly.

CFM estimated
Engine CID x max rpm/3456 x Ve = cfm potential

Ve is volumetric efficency. Holley considers most hi perf engine = 85%, full modified racing engines 95%, smog motor low perf 75%.

So 350 cid x 6000 rpm/ 3456 x .85 Ve = 516 cfm. I assumed 6K redline, 350 hyd flat tappet cam street motor. Remember the purple spring is never going to fully open second secondaries for another 950 rpm beyond that and doesnt start opening until 1915 ish. Assuming the secondary actuation is linear, and I dont know it is or not, at a 6K redline at WOT (wide open throttle) your secondaries will only 80% open. Which would mean in theory to me 20% of cfm capabilty is left on the table, so 670 x .80% = 536 cfm @6K & WOT w/ purple spring.

Maybe some others can chime in here to confirm or correct.

If this is correct 536 cfm is what you can expect to deliver and 516 cfm is what Holley formula feels is required for 350 w/6K redline & .85 Ve. So seems like a good fit.
 

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Discussion Starter · #72 ·
Wow. You know your stuff. You should charge for the "carb school" training I'm getting. With a 100k mile motor, (tho' I have good compression on all) I'll bet my motor is less than 85%, and I'm not going above 5500, (I don't need to blow this thing up at this point) and I'll go with a weaker spring as you suggest…so, if the formula at 6000 and .85 says 516 why not just go with the 570cfm? (The formula at 5500 and .80 ve gets me 445cfm.) I'm not disagreeing with you, just trying to learn. Thanks.
 

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Physics is always present as high pressure is trying to equalize lower pressure.
The engine creates 20 inches of vacuum below the throttle plate(s), and atmospheric pressure, 14.7 PSI, passes through carb to equalize.I
 
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Wow. You know your stuff. You should charge for the "carb school" training I'm getting. With a 100k mile motor, (tho' I have good compression on all) I'll bet my motor is less than 85%, and I'm not going above 5500, (I don't need to blow this thing up at this point) and I'll go with a weaker spring as you suggest…so, if the formula at 6000 and .85 says 516 why not just go with the 570cfm? (The formula at 5500 and .80 ve gets me 445cfm.) I'm not disagreeing with you, just trying to learn. Thanks.
RPM to open for secondary springs are also dependent on the size of the carburetor relative to the maximum potential airflow of the engine (displacement, headflow, camshaft, etc.). If the carburetor is oversized, then yes something like a purple spring may not achieve full open. It's only going to open as far as it needs to supply the maximum amount of air. That's why a 402 with purple spring opens the secondaries quicker and reaches full open sooner than on a 350 for the same size carb. So for the above formula posted, just use rpm, VE, and displacement to calculate minimum carburetor size, and don't worry about the affect of the secondary spring (that's just a tuning device).

A 570cfm-600cfrm would work fine based on your 350/5500rpm. Going back to what I said in a previous post, I'd find a 4150 something with downleg boosters for better signal. The downleg boosters do slightly impact flow compared to straight, so the carbs tend to be rated lower for the same throttle bore size. Both the QFT HR Series and Brawler have downleg boosters from what I see. Interestingly the Brawler states straight leg in the specs, but the pics show downlegs (there's also an online MT article that talks about them having DL boosters). Both also use an adjustment screw for the secondary, so you don't even have to remove the secondary spring. It has a purple spring factory installed, and then the screw just adds/subtracts preload.
 

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Discussion Starter · #75 ·
RPM to open for secondary springs are also dependent on the size of the carburetor relative to the maximum potential airflow of the engine (displacement, headflow, camshaft, etc.). If the carburetor is oversized, then yes something like a purple spring may not achieve full open. It's only going to open as far as it needs to supply the maximum amount of air. That's why a 402 with purple spring opens the secondaries quicker and reaches full open sooner than on a 350 for the same size carb. So for the above formula posted, just use rpm, VE, and displacement to calculate minimum carburetor size, and don't worry about the affect of the secondary spring (that's just a tuning device).

A 570cfm-600cfrm would work fine based on your 350/5500rpm. Going back to what I said in a previous post, I'd find a 4150 something with downleg boosters for better signal. The downleg boosters do slightly impact flow compared to straight, so the carbs tend to be rated lower for the same throttle bore size. Both the QFT HR Series and Brawler have downleg boosters from what I see. Interestingly the Brawler states straight leg in the specs, but the pics show downlegs (there's also an online MT article that talks about them having DL boosters). Both also use an adjustment screw for the secondary, so you don't even have to remove the secondary spring. It has a purple spring factory installed, and then the screw just adds/subtracts preload.
Every time I learn something new it adds another question into my decision-making. Can downleg boosters be bought separately and retro-fitted? Thanks.
 

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Every time I learn something new it adds another question into my decision-making. Can downleg boosters be bought separately and retro-fitted? Thanks.
It's not a bolt-in thing, but it can be done. Requires special tools to remove and properly reinstall. If you're getting a new carburetor anyway, find one with them already installed.


P.S. Summit bought the tooling for Holley's 4010 (old marine series), and sells them now as their house brand. They have horizontally sealed bowls, so you can change jets without spilling fuel all over the place. And they have a number of cool other standard features including annular boosters (one step more responsive than even the downleg), at a budget price. Even comes with the dual feed line. Summit Racing SUM-M08600VS Summit Racing™ M2008 Series Carburetors | Summit Racing
 

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Thanks. I'm looking for a 4150. That's a 4160. They have a refurbed 670 cfm 4150 on there today. I'm thinking I might pull the trigger. (Or in your opinion is that too big?) Do you know if all 4150s require the dual fuel inlet line? My 4160 (600 cfm) has only one inlet with a tube running to the secondary side.
I'm not you, so not sure how you feel about changing your fuel line to the dual feed center hung float, 4150 style.
I just prefer them over the side hung floats on the single feed 4160. I had a Holley 1850 like that when I was a kid, hated that transfer tub and o-ring setup on the fuel bowls.

THIS one, has all the cool stuff.
•All models feature a fully adjustable electric choke for easy starting
Dual metering blocks w/4-corner idle for smooth and efficient idle quality
•Screw-in air bleeds and idle feed restrictions for quick and unsurpassed tuning capability
•Dual inlet fuel bowls with sight glass windows on both fuel bowls for safe and easy float adjustment
•Universal throttle lever with sealed throttle shafts for years of smooth operation
Tunable secondary opening rate
Drop leg boosters...
 

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Discussion Starter · #78 ·
I'm not you, so not sure how you feel about changing your fuel line to the dual feed center hung float, 4150 style.
I just prefer them over the side hung floats on the single feed 4160. I had a Holley 1850 like that when I was a kid, hated that transfer tub and o-ring setup on the fuel bowls.

THIS one, has all the cool stuff.
•All models feature a fully adjustable electric choke for easy starting
Dual metering blocks w/4-corner idle for smooth and efficient idle quality
•Screw-in air bleeds and idle feed restrictions for quick and unsurpassed tuning capability
•Dual inlet fuel bowls with sight glass windows on both fuel bowls for safe and easy float adjustment
•Universal throttle lever with sealed throttle shafts for years of smooth operation
Tunable secondary opening rate
Drop leg boosters...
Thanks, that's cool alright, but that one is also $580. I might go that way, but I was hoping to keep it in the factory-refurb-price range. I was only looking at Holleys, maybe I'll see if they have one of those QFs in the refurb pile. (They sure are proud of their logo aren't they?)
 

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Thanks, that's cool alright, but that one is also $580. I might go that way, but I was hoping to keep it in the factory-refurb-price range. I was only looking at Holleys, maybe I'll see if they have one of those QFs in the refurb pile. (They sure are proud of their logo aren't they?)
 

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Discussion Starter · #80 ·
It's not a bolt-in thing, but it can be done. Requires special tools to remove and properly reinstall. If you're getting a new carburetor anyway, find one with them already installed.


P.S. Summit bought the tooling for Holley's 4010 (old marine series), and sells them now as their house brand. They have horizontally sealed bowls, so you can change jets without spilling fuel all over the place. And they have a number of cool other standard features including annular boosters (one step more responsive than even the downleg), at a budget price. Even comes with the dual feed line. Summit Racing SUM-M08600VS Summit Racing™ M2008 Series Carburetors | Summit Racing
Too many decisions! 🤯
 
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