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Anonymous
Guest
Just curious, but who much vacuum is needed to activate the secondaries on a 4V carburetor? I'm thinking about a wild modification... 
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Anonymous
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Ha! No electrical pump, just engine vacuum.
I'm still pondering about attaching my 4180 to the log (600 CFM ). I think the primaries would work fine but like Execute stated previously - the 200 doesn't produce enough vacuum to open the secondaries. Plus, I need to overcome the low air intake velocity in order to use more fuel/air mixture. Hmmmm. How about a 3 inch carburetor spacer with grooved walls to create a cyclone effect into the log? Kinda like throttle body spacers.
I'm still pondering about attaching my 4180 to the log (600 CFM
). I think the primaries would work fine but like Execute stated previously - the 200 doesn't produce enough vacuum to open the secondaries. Plus, I need to overcome the low air intake velocity in order to use more fuel/air mixture. Hmmmm. How about a 3 inch carburetor spacer with grooved walls to create a cyclone effect into the log? Kinda like throttle body spacers.
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Anonymous
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I know...I'm crazy. :roll:
Good idea.
The 200 cube engine will not consume any of the extra air-flow or velocity. Its sorta like tying to shove 55 gallons in a 33 gallon drum.
Somewhere it's not going to take the drink. Not unless you get it to rev and cruise at a ratio of 302/200 faster. So instead of 5000 rpm maximum, 7500 rpm. Instead of a 2500 rpm cruise, then 3750 rpm will have to be it. In the end, you use as much fuel as a 302!To answer your first question, the vacuum on a 302 at wide open throttle is actually less than 1.5 inches of Mercury. The flow rate is 630 cfm at that point. But in the 5.0 LX and GT, they never used more than about 410 cfm at maximum revs.
The secondaries crack open very quickly on 5.0's, apparently. This happens in aconditional way. With most mech sec carbs, around 2/3rds throttle, and the secondaries open. With the vac sec its conditional on a number of things.
1. at around the time the throttle is about 60% open.
2. and when the transfer slot between the non-flowing secondary and the primary (at full gale), allows the secondary spring to get over loaded and open things open.
3.The vaccum? Possibly, guessing, about 5" Hg, but it dependes on the weight of the car, and the rate of the throttle stab, and what the road gradient is.
If the car is undercarbed, like a 390 cfm 4-bbl on a 300 six, it'll open often. On a 200 cube car, it possibly would never open at all. The front half of a 4180 is equal to a slightly bigger 350 Holley 2-bbl. There is about 185 hp there if it was jetted for performance, and you shoved a suspension spring-like secondary spring in the carb.
Lots to think on....
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Anonymous
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I know it's useless to dwell on this issue. Sorry guys.
Anyone need a 4180? Very little use! Will sell cheap!
Anyone need a 4180? Very little use! Will sell cheap!
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Anonymous
Guest
I very nearly bought a new Holley 600 double pumber carb for my 250 2V yesterday (too big I know). Changed my mind because I will have more funds latter on and it cost $650 Aust there were no reco 465s availabe and was only about $70 cheaper for a new one.
I really dont care that the DP Mechanical secondary 600 4 brl is too big because I believe it will work anyway and I have more control over when and how it works simply by depresssing the throtte. Was still and am still prepared to take a bit of a risk on it and purchase it latter. Someone else on this forum did try this on their 2502V and alledged that it worked great compared to their previous 465. I think I have seen a 465 Double pumper available (could be wrong)?
I really dont care that the DP Mechanical secondary 600 4 brl is too big because I believe it will work anyway and I have more control over when and how it works simply by depresssing the throtte. Was still and am still prepared to take a bit of a risk on it and purchase it latter. Someone else on this forum did try this on their 2502V and alledged that it worked great compared to their previous 465. I think I have seen a 465 Double pumper available (could be wrong)?
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Anonymous
Guest
Its in Aussie six section today under "how much cfm for a 2V"
