Tripower 2nd vacuum can test ?
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Tripower 2nd vacuum can test ?
Hello
Is there a way to test the tripower secondary vacuum cans for torn or leaking bellow ?
The vacuum hose on the right hand ( pax ) side that comes from ea of the 3 carbs and Ts together does not work on this. ( sucking air through the hoses is free flow ).
Rgds Günther
Is there a way to test the tripower secondary vacuum cans for torn or leaking bellow ?
The vacuum hose on the right hand ( pax ) side that comes from ea of the 3 carbs and Ts together does not work on this. ( sucking air through the hoses is free flow ).
Rgds Günther
Race Director
Joined: May 2006
Posts: 18,737
Likes: 2,583
the typical method is to put a paper clip on the rod below the housing, drive the car aggressively to force open the diaphragm and then check the paperclip. If it didn't move the throttle did not open up.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
Yes, I did that, but it doesn't really tell if both cans are OK as 1 ea will also open the carbs, won't it ?
And disconnecting the 2ndary linkage and driving the car to individually check both cans for opening during driving might not be a good idea as forced closing by the gas pedal via the linkage is missing.
Any thoughts except for opening the cans up for visually inspecting the bellows ?
Rgds Günther
Yes, I did that, but it doesn't really tell if both cans are OK as 1 ea will also open the carbs, won't it ?
And disconnecting the 2ndary linkage and driving the car to individually check both cans for opening during driving might not be a good idea as forced closing by the gas pedal via the linkage is missing.
Any thoughts except for opening the cans up for visually inspecting the bellows ?
Rgds Günther
Race Director
Joined: May 2006
Posts: 18,737
Likes: 2,583
where would you hook up an external vacuum source such as a mityvac? Isnt the vacuum source port built into the main body casting? You would have to remove the complete housing from the main body.
Last edited by MelWff; Feb 23, 2018 at 12:33 PM.
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
I'm assuming the OP's question is how to check the secondary carb diaphragms for leakage. If so, unplug the hose from the vacuum can and use the mityvac to see if each can holds vacuum and the throttle shaft rotates.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
There is no hose to the vacuum can. It is internally in the carb.
That's why testing it is so difficult.
I am still struggling to understand what the right side vacuum hoses that connect
all 3 carbs together , do.
Rgds Günther
There is no hose to the vacuum can. It is internally in the carb.
That's why testing it is so difficult.
I am still struggling to understand what the right side vacuum hoses that connect
all 3 carbs together , do.
Rgds Günther
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
You do have Holley 2300 two barrel carbs? Mine has a vacuum hose to each end carb.
Last edited by 3X2; Feb 25, 2018 at 01:32 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
The center carb generates vacuum that is applied to the hose on that carb. Through a tee, the vacuum is transferred to the other (two) hoses on the outboard carbs. The outboard carb hose nipples are connected internally to the outboard diaphragms. There is also a gasket between the diaphragms and the carb body. If you apply a vacuum on the outboard carb nipple (5/32 vac hose), it should apply the diaphragm against the internal return spring. The pod should activate and hold vacuum. If not, the diaphragm and/or the gasket is leaking either because it is loose, or it is faulty.
Last edited by Tom454; Feb 24, 2018 at 10:48 AM.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
So, you mean I disconnect the hoses from the T and apply vacuum to he outbd carb hoses and the pods should activate ?
Both of mine don't. Fells like free flow when doing that by mouth vacuum pulling or blowing.
Guess I need to open up a pod to check whats happening.
Rgds Günther
So, you mean I disconnect the hoses from the T and apply vacuum to he outbd carb hoses and the pods should activate ?
Both of mine don't. Fells like free flow when doing that by mouth vacuum pulling or blowing.
Guess I need to open up a pod to check whats happening.
Rgds Günther
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Hi
So, you mean I disconnect the hoses from the T and apply vacuum to he outbd carb hoses and the pods should activate ?
Both of mine don't. Fells like free flow when doing that by mouth vacuum pulling or blowing.
Guess I need to open up a pod to check whats happening.
Rgds Günther
So, you mean I disconnect the hoses from the T and apply vacuum to he outbd carb hoses and the pods should activate ?
Both of mine don't. Fells like free flow when doing that by mouth vacuum pulling or blowing.
Guess I need to open up a pod to check whats happening.
Rgds Günther
First tighten the cover screws and the pod mounting screws to the carb and test for loose screws.
A short piece of 5/32 vac hose and your mouth should do it.
Last edited by Tom454; Feb 24, 2018 at 02:23 PM.
Melting Slicks
Joined: Jan 2000
Posts: 3,326
Likes: 523
From: home
I hate to admit this but, I tried my own suggestion on the end carbs on my engine and a spare set of 3 carbs I have and none hold vacuum using a mityvac. This is going to require some more research. If any of you have tri powers, let us know if your end carbs hold vacuum. The ones on my car were rebuilt 3 years ago.
Intermediate
Joined: Apr 2007
Posts: 27
Likes: 11
You can't test those diaphragms by applying vacuum to the nipple, there's an internal bleed drilled inside the main body that will prevent them from holding vacuum this way.
The only way to test them is to remove the diaphragm assembly from the carb, compress the diaphragm & spring and hold your finger over the vacuum hole on the mounting surface. The diaphragm should remain collapsed until you remove your finger.
FWIW, I've seen brand new diaphragm assemblies leak ever so slightly testing like this. I think it's related to the lid being somewhat flimsy around the perimeter and not staying flat enough when the screws are tightened down to maintain a seal.
The only way to test them is to remove the diaphragm assembly from the carb, compress the diaphragm & spring and hold your finger over the vacuum hole on the mounting surface. The diaphragm should remain collapsed until you remove your finger.
FWIW, I've seen brand new diaphragm assemblies leak ever so slightly testing like this. I think it's related to the lid being somewhat flimsy around the perimeter and not staying flat enough when the screws are tightened down to maintain a seal.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
Thanks so much. This is what I remembered from overhauling the carbs a couple of years ago , but wasn't sure anymore.
Having both carb pods being inop after such short time was nearly out of the question.
Now having all the specialists together, I had the car on a roller test stand and observed the 2ndaries starting to open at 4500 RPM only.
Never opened fully up because the test run couldn't be completed due to speed index of the tires being too low.
Now, is 4500 not too late ? Is there adjustment springs or anything similar available for the pods ? I thought that the 2ndaries could start opening latest at 4000 RPM , may be earlier ?
Rgds Günther
there's an internal bleed drilled inside the main body
Having both carb pods being inop after such short time was nearly out of the question.
Now having all the specialists together, I had the car on a roller test stand and observed the 2ndaries starting to open at 4500 RPM only.
Never opened fully up because the test run couldn't be completed due to speed index of the tires being too low.
Now, is 4500 not too late ? Is there adjustment springs or anything similar available for the pods ? I thought that the 2ndaries could start opening latest at 4000 RPM , may be earlier ?
Rgds Günther
Race Director
Joined: May 2006
Posts: 18,737
Likes: 2,583
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
I hate to admit this but, I tried my own suggestion on the end carbs on my engine and a spare set of 3 carbs I have and none hold vacuum using a mityvac. This is going to require some more research. If any of you have tri powers, let us know if your end carbs hold vacuum. The ones on my car were rebuilt 3 years ago.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Hi
Is it possible to find the bleed hole of the pod inside the carb intake and hold it closed with a finger or is the hole not accessible from there ?
Brgds Günther
Is it possible to find the bleed hole of the pod inside the carb intake and hold it closed with a finger or is the hole not accessible from there ?
Brgds Günther
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
If you look at the carb casting behind the hose nipple you can see a cast in "tube" on the outside of the carb body. This leads to the vac port on the inside of the carb. None of my fingers will fit inside the carb between the booster and the casting. If you really do not want to pull the pod off, maybe you can clean the port area (carb cleaner, brakleen, lacquer thinner) with a cotton swab and coax a piece of scotch tape down in there (with a toothbrush handle?) and cover the hole temporarily for the test. I'd give it a shot.