Holley: What does "100% wet tested" mean? - Team Camaro Tech
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post #1 of 8 (permalink) Old Dec 19th, 08, 07:13 AM Thread Starter
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Holley: What does "100% wet tested" mean?

I have "wet tested" some perfectly good underwear before but I'm wondering what that means when it comes to carbs.

Does that mean they have been on some kind of dyno motor or just had fluid put in them to make sure they don'e leak? Thanks!


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post #2 of 8 (permalink) Old Dec 19th, 08, 07:59 AM
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Re: Holley: What does "100% wet tested" mean?

Wet testing refers to flow testing the carb. You can dry flow which is done with air pressure and done on test equipment called a flow bench. Taking it up a notch you can add a wet flow adapter to a flow bench that allows you to semi-suspend liquid within the air flow and measure it.

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post #3 of 8 (permalink) Old Dec 19th, 08, 09:04 AM Thread Starter
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Re: Holley: What does "100% wet tested" mean?

Always coming up with the answers.....aren't you Mr. Dennis! Funny how I know a lot about Holleys and you have probably forgotten more than I ever knew!


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post #4 of 8 (permalink) Old Dec 19th, 08, 05:27 PM
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Re: Holley: What does "100% wet tested" mean?

I have toured the Holley plant twice. Every carb is flowed and tested with the best I remember to be mineral spirits before it is shipped. The circuits are calibrated and the carb is tested for leaks.

The carb is assembled with gaskets that "stick" to the surfaces so that if it is taken apart they will be destroyed. I think that poster "Doug F" is employed in research and development at Holley. I am sure he can do a better job answering this question than I have.
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post #5 of 8 (permalink) Old Dec 20th, 08, 08:50 PM
 
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Re: Holley: What does "100% wet tested" mean?

Wet tested means the carburetor is tested with air and fuel flowing to simulate actual engine operation. The test stand is comprised of a large vacuum pump and fuel supply. A fuel line is connected to the carburetor using mineral spirits at 6 psi (typical). The test stand is instrumented to measure fuel flow and air flow. The vacuum pump is turned on, and air and fuel will flow through the carburetor in the same way as on the engine. From this the A/F ratio can be calculated. The idle airflow and fuel flow is adjusted to spec, then the A/F ratios at different throttle positions representing off-idle part throttle and full throttle are measured. If the flows do not meet specification, the carburetor will be inspected and parts replaced as necessary to make sure it is correct.
By the way, I was carburetor engineer at Holley for many years.
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post #6 of 8 (permalink) Old Dec 20th, 08, 10:02 PM
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Re: Holley: What does "100% wet tested" mean?

[quote=Bob Telep;1123
By the way, I was carburetor engineer at Holley for many years.[/quote]

Fantastic..care to share how your Holleys respond to vacuum created by a roots blower vs a naturally aspiratred set up?Yep..we are all in tune to the pv boost referance.lets go further.Is the supercharger drying up the idle/transition ckt at idle and leading to Detroit roll?Iwould like your thoughts on a open power valve at idle,not a failed pv.I have not come across anyone that can explain this in full.I always get the Yes..the engine will idle rich with an open pv.Why?.How do the ifr,s that drink from the main well flow more fuel with an open pv?is it fuel weight atop the ifr?

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post #7 of 8 (permalink) Old Dec 22nd, 08, 07:33 PM
 
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Re: Holley: What does "100% wet tested" mean?

Quote:
Originally Posted by fatblock View Post
Fantastic..care to share how your Holleys respond to vacuum created by a roots blower vs a naturally aspiratred set up?Yep..we are all in tune to the pv boost referance.lets go further.Is the supercharger drying up the idle/transition ckt at idle and leading to Detroit roll?Iwould like your thoughts on a open power valve at idle,not a failed pv.I have not come across anyone that can explain this in full.I always get the Yes..the engine will idle rich with an open pv.Why?.How do the ifr,s that drink from the main well flow more fuel with an open pv?is it fuel weight atop the ifr?
You've just about hit the nail on the head. Because the ifr is connected to the main well, fuel flow through it will be affected by the fuel level in the well. Think of it as the idle and main systems playing tug of war. At idle, the idle system draws fuel from the main well. Since the main jet offers some restriction, the fuel level in the main well drops. This results in a lower head of fuel (height of the fuel above the ifr). If the pv is opened, itís just like opening up the main jet. This lower restriction raises main well fuel level and the idle becomes richer.

It is by design that the idle circuit feeds from the main well. With the idle system pulling the main well level down, a higher airflow is required to get the main system started. This helps prevent the main nozzle (boost venturi) from dripping or starting prematurely. As the throttle is opened, the venturi signal increases, and the idle signal eventually decreases, so there is a smooth transition to the main system. When the throttle is opened suddenly, the idle system drops out because it is sensitive to vacuum, not airflow. This raises the fuel level in the main well and the main system will now start faster to compensate for the weaker idle signal.

You can observe this effect - with the vehicle in neutral, open the throttle with the idle speed screw slowly until you see fuel flow just beginning to discharge from the booster. Holding the throttle at this position, open the mixture screw and the nozzle should stop.

I've not heard of a Detroit roll. Is that like getting mugged downtown at night? lol
I haven't experience with Roots blower applications, but as long as the vacuum under the carburetor at idle is about 16 in. Hg or higher, the air flow and fuel flow will remain constant. It doesn't matter if there's a blower or not, the carburetor will not know the difference. This is because the carb has reached what is called critical flow - you could increase the vacuum to 24 in. Hg and the carb will meter exactly the same as at 16 in. Hg. Let's look at this possibility - assume the carb idle is adjusted too rich initially and the engine develops less than 16 in. at idle. The engine is started and the vacuum under the carb is less than 16. So, the engine speed drops due to the rich mixture, the vacuum drops, the fuel flow drops, and the mixture now becomes correct. The engine speed and vacuum increase, and the cycle repeats itself as the engine rolling condition. This could also possibly happen with a too-lean idle mixture and the power valve opens when the vacuum drops. Another cause for the roll could be the vacuum advance or the centrifugal advance changing timing under these conditions.

I hope this is helpful and not too long winded.
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post #8 of 8 (permalink) Old Dec 22nd, 08, 09:15 PM
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Re: Holley: What does "100% wet tested" mean?

Bob..thank you for taking the time to explain how open pv,s will affect the fuel flow thru the ifr,s.
What got me started months back, is a post about removing primary jets completely and seeing no differance in the idle a/f ratio.I struggled with this concept..kinda blew the wrong pv opening point at curb idle speed a mute point from there on.I think the poster was refering to the fact that the ifr is a fixed orifice so there can be no change.
There was some talk about raw fuel..but imo,the ifr,s yank on an emulsified mix in the main well.With no change to the lsab but increasing the level of fuel would change the ratio of air to fuel that the ifr would sip on...hence the need to adjust the idle mixture(volume) screws to compensate.
lol.Detroit roll..blower surge/hunt etc.I guess you could get rolled in Detroit by a mugger..that would be getting off easy.
I understand that a carb is a passive device and responds to what is above and below it only.I have 12 hg under the dual 850,s and 6hg in the manifold at 900 rpm in gear.I have a lean tip in off idle and upped the nozzles from .031 to .045.It helped and goes beserk when the boosters flow.Should i up the ifr size to buy me some time during transition?I am also thinking these dual double pumps may transition better with more vacuum created by turning the rotors in the blower faster with a pulley swap.I will adjust the tune up accordingly with boost retarded ign timing.

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