tri power for a bbc? - Page 18 - Chevelle Tech
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post #256 of 267 (permalink) Old Mar 31st, 10, 6:53 PM
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Tom Terrific II
 
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Re: tri power for a bbc?

the vent tubes just make it harder for gas to slosh out of the bowl during hard stops or bumps. If you're not having problems with slosh killing the engine during hi-G events you don't need the tubes.

If you have the tubes and they're close to the air filter lid it can cause weird fluctuations in the air pressure in the bowl leading to unpredictable mixture changes, usually under heavy load/heavy throttle where there's a lot of air moving across the tops of the tubes.

As said, if you're not having problems then nothing needs "fixed."

Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #257 of 267 (permalink) Old Mar 31st, 10, 8:22 PM
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Re: tri power for a bbc?

Quote:
Originally Posted by Tom Mobley View Post
the vent tubes just make it harder for gas to slosh out of the bowl during hard stops or bumps. If you're not having problems with slosh killing the engine during hi-G events you don't need the tubes.

If you have the tubes and they're close to the air filter lid it can cause weird fluctuations in the air pressure in the bowl leading to unpredictable mixture changes, usually under heavy load/heavy throttle where there's a lot of air moving across the tops of the tubes.

As said, if you're not having problems then nothing needs "fixed."
Tom

Thanks for the response.

Perhaps I have some of the ULTRA rare non vent tube experimental carbs used on the all aluminum DOHC 454 scheduled for the 1972 Corvette? Where are those Vette guys when ya need extra money??

Seriously now. I am not involved in a lot of High G manuvers now that I am gettin older. Good thing cause my pressure suit malfunctioned a few years ago!!!

I suspected that there was no issue...the guy who built my carbs (Jerry Luck) is known for stand up work so I would think he would have fixed the problem if it were a problem. He does everything including machining all mating surfaces on the carbs he does. I cannot believe that he would overlook these pipes if they were critical.
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post #258 of 267 (permalink) Old Mar 31st, 10, 10:01 PM
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Tom Terrific II
 
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Re: tri power for a bbc?

too bad you got those. you could have gotten the ultra-rare TOHC (triple overhead cam) versions. But now I understand those engines were only installed in the uber-rare rear steer Chevelles. Those are the leaf spring cars, worth their weight in gold like everything else being sold by a Vette owner.

Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #259 of 267 (permalink) Old Mar 31st, 10, 11:35 PM
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Chris
 
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Re: tri power for a bbc?

Quote:
Originally Posted by Tom Mobley View Post
too bad you got those. you could have gotten the ultra-rare TOHC (triple overhead cam) versions. But now I understand those engines were only installed in the uber-rare rear steer Chevelles. Those are the leaf spring cars, worth their weight in gold like everything else being sold by a Vette owner.
wasnt that the one with the really rare 8 speed manuel trans. lol
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post #260 of 267 (permalink) Old Apr 1st, 10, 10:07 AM
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Re: tri power for a bbc?

I see that others have some of the same viewpoints on this uber rarity quest some of our friends are always on!!!!
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post #261 of 267 (permalink) Old Apr 1st, 10, 8:05 PM
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Re: tri power for a bbc?

Quote:
Originally Posted by Tom Mobley View Post
the vent tubes just make it harder for gas to slosh out of the bowl during hard stops or bumps. If you're not having problems with slosh killing the engine during hi-G events you don't need the tubes.

If you have the tubes and they're close to the air filter lid it can cause weird fluctuations in the air pressure in the bowl leading to unpredictable mixture changes, usually under heavy load/heavy throttle where there's a lot of air moving across the tops of the tubes.

As said, if you're not having problems then nothing needs "fixed."
So based on your experience and technical know-how, If the air cleaner top is too close to the "vent (tube or not), and if it creates a low pressure area above the vent (as discussed in the noted posts) would the fuel get sucked out (as described in the posts) or not?

What is "too close" to the air cleaner top?
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post #262 of 267 (permalink) Old Apr 1st, 10, 8:11 PM
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Fred
 
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Re: tri power for a bbc?

Quote:
Originally Posted by oman View Post
I see that others have some of the same viewpoints on this uber rarity quest some of our friends are always on!!!!
While there are quite a few "entries" that would substantiate your observations, it seems that there are a nearly equal amount of C**v***e "Enthusiasts" that pay no attention to the "stuffed shirt" attitude of the "if it ain't NCRS correct, It's _______" crowd.

I like those guys LOL

(Not that I have anything against making an authenticated car authentic, it's just not what I want to do)
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post #263 of 267 (permalink) Old Apr 1st, 10, 8:16 PM
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Re: tri power for a bbc?

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Originally Posted by Chicken Coupe View Post
While there are quite a few "entries" that would substantiate your observations, it seems that there are a nearly equal amount of C**v***e "Enthusiasts" that pay no attention to the "stuffed shirt" attitude of the "if it ain't NCRS correct, It's _______" crowd.

I like those guys LOL

(Not that I have anything against making an authenticated car authentic, it's just not what I want to do)

C**v***e enthusiast mantra = "Correctness Uber Alis" roughly translated "Correctness Above All" ...taken from "Deutchland Uber Alis" or "Germany Above All"

No you are not gonna set me off today. Not going there had a good day and I am not gonna ruin it now.
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post #264 of 267 (permalink) Old Apr 2nd, 10, 2:13 AM
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Tom Terrific II
 
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Re: tri power for a bbc?

Fred, it doesn't suck fuel out the tube but even minor variations in the air pressure in the bowl affect the fuel level. if the fuel level rises the mix richens and vice-versa. I *think* the magic number was 3/8". I also think it's been many years since I've seen that doco.

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post #265 of 267 (permalink) Old Apr 2nd, 10, 11:29 AM
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Fred
 
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Re: tri power for a bbc?

I read the first 3 words...thought this post was going far off course

After reading it all, I get the fluctuation concept now and why that could cause major headaches in tuning a set-up, regardless of how many carbs.

Anyone out there have related measurements with different air cleaner elements? (AC filter, aftermarket AC filter, vs. K&N air horn/vent tube to air cleaner top)
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post #266 of 267 (permalink) Old Apr 8th, 10, 10:16 AM
Stephen
 
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Re: tri power for a bbc?

Hey all, found this thread while researching some tri-power info for my Vette. Anyway, the thread over at CF about tripower tuning (link below), had some good info on the air cleaner/vent tube issue. Basically, raising the aircleaner base up 1/2" from the carbs evened out the AFR across the whole operating range.

http://forums.corvetteforum.com/c3-t...496-build.html
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post #267 of 267 (permalink) Old Oct 5th, 10, 5:31 PM
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Fred
 
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Re: tri power for a bbc?

I dug this back up after reading a large number of recent post regarding tri-powers on a number of different sites.

So....

what's news?
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