tri-power performance
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: tri-power performance (GDaina)
Don't go crazy thinking that you can put the lightest spring in...there is a price to pay....you will be cruising on partially opened secondaries....best bet is to try the purple spring and work to the lightes and see how the car performs.
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: tri-power performance (GDaina)
George and Tom: Holy smokes! You guys have awed me with your info!!!
Okay...let me ask you this, since Ron seems to want "snap open passing gear" type performance from the deuces. Is that type of performance likely with the Vette tripower, or is the system engineered for a more "progressive" openning where the power is delivered, but is not as noticeable? I know he can switch to mechanical linkage, but we all know the downside of that...extreme bogging in most cases. Would a combination of the right spring tension and the right rear gear choice give him the "snap open" he is looking for? I've never ridden in a Vette with tripower, so I don't really know how they run or "feel".
Dep
Okay...let me ask you this, since Ron seems to want "snap open passing gear" type performance from the deuces. Is that type of performance likely with the Vette tripower, or is the system engineered for a more "progressive" openning where the power is delivered, but is not as noticeable? I know he can switch to mechanical linkage, but we all know the downside of that...extreme bogging in most cases. Would a combination of the right spring tension and the right rear gear choice give him the "snap open" he is looking for? I've never ridden in a Vette with tripower, so I don't really know how they run or "feel".
Dep
Crackin' on...
Joined: Jun 2003
Posts: 9,436
Likes: 124
From: Somewhere in Tucson AZ
St. Jude Donor '09
Re: tri-power performance (MNJack)
Man! That one's pricey! I've got a SBC Fenton tripower system I'll sell for half that!
Intake, carbs, linkage, everything!
[Modified by 73sbvert, 9:03 AM 4/10/2004]
Intake, carbs, linkage, everything!
[Modified by 73sbvert, 9:03 AM 4/10/2004]
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: tri-power performance (73sbvert)
Dep... when my trips were set up to "optimize" performance, they did not do the "snap" thing... it was a smooth transition, but noticeable.... a very strong increasing pull that put you back in the seat pretty hard.. but it didn't "snap" as they say.
In my opinion, if the trips are set up to maximize acceleration (i.e.- correct air-fuel ratio by weight), they will just pull extremely strong when opened, but get there without the snap. You can tell wheh they are opening, but not feel an enormous snap.... just a geometric pull.
A lot of people mistake a "bog" and then a "snap" for good performance... IMOP- not the case. The bog is a sign that they are out of adjustment (raises your ET). A well set up tripower system will perform similar to fuel injection.... with a good clean transition. I believe that is the way GM designed it to work. Mine have always worked that way.... no combo bog/snap.... just incredibly hard acceleration....
500 ft lbs worth.
Tom
In my opinion, if the trips are set up to maximize acceleration (i.e.- correct air-fuel ratio by weight), they will just pull extremely strong when opened, but get there without the snap. You can tell wheh they are opening, but not feel an enormous snap.... just a geometric pull.
A lot of people mistake a "bog" and then a "snap" for good performance... IMOP- not the case. The bog is a sign that they are out of adjustment (raises your ET). A well set up tripower system will perform similar to fuel injection.... with a good clean transition. I believe that is the way GM designed it to work. Mine have always worked that way.... no combo bog/snap.... just incredibly hard acceleration....
500 ft lbs worth.
Tom
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: tri-power performance (Tom454)
Tom: I had the "snap" with my Dodge, but I sure wouldn't call it a "bog".
I had vacuum opening front and rear carbs, and when they popped open there was no hesitation. It was more like a "leap" forward. Like when you have a "tight" auto and the passing gear kicks in. It was instantaneous acceleration. I'd cut off my left nad to replicate that acceleration in ANY car I own :D
Dep
I had vacuum opening front and rear carbs, and when they popped open there was no hesitation. It was more like a "leap" forward. Like when you have a "tight" auto and the passing gear kicks in. It was instantaneous acceleration. I'd cut off my left nad to replicate that acceleration in ANY car I own :D
Dep
Racer
Joined: Nov 2002
Posts: 251
Likes: 0
From: Concord Ca.
Re: tri-power performance (DJ Dep)
You guys are comparing the factory setups with a piece meal set of rochesters. The 348s and Pontiacs used a small center carb and two larger outboard carbs (in most cases). The outboard carbs had no idle circuit and everything worked fine. The problem is the Small Block manifolds are only drilled for 3 small carbs so no factory outboard carbs are available. You can setup a progressive linkage but you must be carefull about full throttle unless you have a very big Small Block with a lot of gear.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Update on the springs
I had that lingering doubt about the springs being "generic" since I had handled so many of the GM BB TriPower setups... so I took a diaphram apart this morning.
The factory GM BB spring is 1/4 to 3/8 taller than ANY of the other "generic" Holley springs that I have in my cache. This includes the complete set of "tinkering" springs sold by Holley.
I suspect there will be issues if the springs are switched out because the diaphram and link will not be the correct geometry to interface with the carb throttle shaft. Just a suspicion.
The ends of the springs have the same diameters, but because the factory TriPower springs are taller, there may be a problem using other spings unless you stretch them.
RE: The "snap".... I am referring only to factory GM BB TriPower... specifically to mine and all of the ones I have rebuilt and/or adjusted for customers, not to any other configuration.
My BB Ford (1966 390) with 1962 T'Bird tripower behaved completely differently, as did my 1959 Ford with the Offenhauser manifold and identical 3 carbs.... no oversized end carbs.
There were tripower manifolds available way back in the 60's for 327's. None of this is new ground.
The factory GM BB spring is 1/4 to 3/8 taller than ANY of the other "generic" Holley springs that I have in my cache. This includes the complete set of "tinkering" springs sold by Holley.
I suspect there will be issues if the springs are switched out because the diaphram and link will not be the correct geometry to interface with the carb throttle shaft. Just a suspicion.
The ends of the springs have the same diameters, but because the factory TriPower springs are taller, there may be a problem using other spings unless you stretch them.
RE: The "snap".... I am referring only to factory GM BB TriPower... specifically to mine and all of the ones I have rebuilt and/or adjusted for customers, not to any other configuration.
My BB Ford (1966 390) with 1962 T'Bird tripower behaved completely differently, as did my 1959 Ford with the Offenhauser manifold and identical 3 carbs.... no oversized end carbs.
There were tripower manifolds available way back in the 60's for 327's. None of this is new ground.
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Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: Update on the springs (Tom454)
The factory GM BB spring is 1/4 to 3/8 taller than ANY of the other "generic" Holley springs that I have in my cache. This includes the complete set of "tinkering" springs sold by Holley.
I suspect there will be issues if the springs are switched out because the diaphram and link will not be the correct geometry to interface with the carb throttle shaft. Just a suspicion.
Any case, I'm not concerned about the length, the transition is smooth, and when the R's start to build you can feel the aggressive opening.
Edit: Now this spring issue has me thinking...the only way to tell is to compare performance between the stock and generic spring...I hope I have another spring, I know I have one.
[Modified by GDaina, 11:56 AM 4/11/2004]
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: Update on the springs (GDaina)
George and Tom: Here's something I've been mulling over for some time now...
Would it be possible to run the 500cfm Holley 2bbl as a tripower setup with mechanical linkage for all three carbs? This would give you 1500 CFM, and all three carbs have acceperator pumps, so there shouldn't be a problem of bog. Maybe a chore setting the air/gas for all three, but once it was set, I would think it would be a killer setup for tripower. Not sure if the openning in the tripower mainfold would fit the butterflys on the 500CFM carbs though. Pretty looney huh? :eek: :eek: :eek: :eek:
Dep
Would it be possible to run the 500cfm Holley 2bbl as a tripower setup with mechanical linkage for all three carbs? This would give you 1500 CFM, and all three carbs have acceperator pumps, so there shouldn't be a problem of bog. Maybe a chore setting the air/gas for all three, but once it was set, I would think it would be a killer setup for tripower. Not sure if the openning in the tripower mainfold would fit the butterflys on the 500CFM carbs though. Pretty looney huh? :eek: :eek: :eek: :eek:
Dep
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: Update on the springs (DJ Dep)
To answer your Q, I did run a 500 cfm way back when in the mid 70's, right between the two secondary carbs...had to do some modifications to make it fit, like cut the back of the carb's air cleaner base. I didn't do anything to the intake, and surprisingly the throttle blades opened all the way without hitting the intake. But I realize now that I lost CFM by not matching the intake to the 500 carb's base...oh well...back then I did't know anything. As far as bypassing the vacuum system, no need to fabricate linkeage, just insert a trusty ol' bolt in the primary carb's likeage, and when you mash it down, the bolt will grab the secondary's linkeage and open it up at that very instant.
[Modified by GDaina, 11:07 PM 4/11/2004]
[Modified by GDaina, 11:07 PM 4/11/2004]
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: Update on the springs (GDaina)
As far as bypassing the vacuum system, no need to fabricate linkeage, just insert a trusty ol' bolt in the primary carb's likeage, and when you mash it down, the bolt will grab the secondary's linkeage and open it up at that very instant.
[Modified by GDaina, 11:07 PM 4/11/2004]
[Modified by GDaina, 11:07 PM 4/11/2004]
Dep
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: Update on the springs (DJ Dep)
As far as bypassing the vacuum system, no need to fabricate linkeage, just insert a trusty ol' bolt in the primary carb's likeage, and when you mash it down, the bolt will grab the secondary's linkeage and open it up at that very instant.
[Modified by GDaina, 11:07 PM 4/11/2004]
George: That is OLD SCHOOL!!!! :lol: :lol: :lol: :lol: :lol: :lol:
Dep
[Modified by GDaina, 11:07 PM 4/11/2004]
George: That is OLD SCHOOL!!!! :lol: :lol: :lol: :lol: :lol: :lol:
Dep
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
Re: Update on the springs (DJ Dep)
Dep,
Probably will not fit the Outer carbs with the idle circuits and accelerator pumps on the factory manifold. Not enough space between the mounting flanges for the extra metering block.
:cheers:
Probably will not fit the Outer carbs with the idle circuits and accelerator pumps on the factory manifold. Not enough space between the mounting flanges for the extra metering block.
:cheers:
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Re: Update on the springs (DJ Dep)
Dep, one problem that you would probably run into is a lack of sufficient flow with the stock manifold at 1500 CFM. I'm guessing 1000 - 1100 CFM (which is still a bunch!) is about all you could squeaze out of it with optimized heads, exhaust and cam.
Hans
Hans
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Update on the springs (DJ Dep)
Dep,
The 2 barrel Holley carbs are rated using a stronger 3Hg vacuum to measure the flow while the 4 barrels use 1.5 Hg of Vacuum to measure theirs. This means that a 500 cfm 2 barrel is only equal to a 354 cfm 4 barrel.
It would be nice if there was enough spacing between the rear carb and the center one to run the 500cfm carbs front and back. I've spent more than a few hours trying to figure a way to do it.
Chuck
The 2 barrel Holley carbs are rated using a stronger 3Hg vacuum to measure the flow while the 4 barrels use 1.5 Hg of Vacuum to measure theirs. This means that a 500 cfm 2 barrel is only equal to a 354 cfm 4 barrel.
It would be nice if there was enough spacing between the rear carb and the center one to run the 500cfm carbs front and back. I've spent more than a few hours trying to figure a way to do it.
Chuck
Cruising
Joined: Apr 2004
Posts: 11
Likes: 0
From: Seattle WA
Re: tri-power performance (Tom454)
Tom, Dep,
Holly Crap!!! I take a relaxing 3 day weekend off, come back to work today and I see that you guys have been working overtime. You guys are incredible. I can't thank you enough for all this information. Not sure I understand it all but I'll give it my best. Funny......I sent this same question to the guys at Holley a few weeks ago and have yet to receive a reply. Well, now I know where to turn for advise. Thanks again Tom and Dep and everyone else who replied. I'll let you know how it turns out once I receive the springs I ordered from Summit.
Ron
:thumbs: :thumbs: :thumbs:
Holly Crap!!! I take a relaxing 3 day weekend off, come back to work today and I see that you guys have been working overtime. You guys are incredible. I can't thank you enough for all this information. Not sure I understand it all but I'll give it my best. Funny......I sent this same question to the guys at Holley a few weeks ago and have yet to receive a reply. Well, now I know where to turn for advise. Thanks again Tom and Dep and everyone else who replied. I'll let you know how it turns out once I receive the springs I ordered from Summit.
Ron
:thumbs: :thumbs: :thumbs:
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Re: tri-power performance (Ronbos 69)
Chuck...Forum Member "427tri" had the Ford FE fuel bowl modified setup on his Vette, but you have to give up the center hung floats to do it. I've never tried it myself. I sold my FE trips many years ago. The bowls and metering blocks may still be available though.
http://forums.corvetteforum.com/zerothread?id=230493
Ron... we enjoy this stuff.... what can I say.
Tom
http://forums.corvetteforum.com/zerothread?id=230493
Ron... we enjoy this stuff.... what can I say.
Tom
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Re: tri-power performance (Tom454)
<sigh> I am still fantasizing about 1500 cfm out of three 2bbls :crazy: :crazy:
Yeah...the low rise tripower Vette manifold wouldn't handle it...but what about the earlier high rise version? I bet you could have some kind of baseplate adapters made that would slightly move the two outer carbs away from the center one enough for all three to have clearance. Or maybe one long baseplate adapter that would allow the three 500 CFM carbs to be mounted.
Like the old ram log manifolds. Hell..they had SIX Stromberg 97s mounted on a smallblock manifold!!!
Dep
Yeah...the low rise tripower Vette manifold wouldn't handle it...but what about the earlier high rise version? I bet you could have some kind of baseplate adapters made that would slightly move the two outer carbs away from the center one enough for all three to have clearance. Or maybe one long baseplate adapter that would allow the three 500 CFM carbs to be mounted.
Like the old ram log manifolds. Hell..they had SIX Stromberg 97s mounted on a smallblock manifold!!!
Dep