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Old 02-28-2005, 08:53 PM
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Bad advice

Here is a good example of bad advice. First, this guy says you should run a powervalve 1 to 1.5 inches below your vacuum at idle in gear. The way you are really supposed to do it is to take your idle vacuum in gear divide by 2 and add .5. His 8" formula would require a 4.5 powervalve.

Then, he says to use 25 to 30 degrees initial timing as a starting point. ***? Is he going to buy the people that believe this new pistons, head gaskets, or rings?

http://www.omniracing.net/html/4_corner_idle.html

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Old 02-28-2005, 08:53 PM
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What do you think? Should we send him some hate mail?

You will have to copy the link and paste it. It looks like the links aren't working today.
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Old 02-28-2005, 09:07 PM
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I am confused by what he wrote on that site. After saying to use 25 initial he then says Caution do not do this or you'll have 50 total timing and burn out the motor.

Then after that he says to use 25 initial again due to the idle circuit on the carb.

I hope no one is going off this site for info just based on the fact that its damn confusing. But I also hope no one follows the advice on the note that its wrong lol.
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Old 02-28-2005, 09:13 PM
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Quote:
When you go to the distributor shop and tell him you want 25 initial and 38 max at 2200 he's going to look at you funny…he’s just used to Holley's and Edelbrock's and there insensitive idle circuit and transition technology.
I think what he says has merit. I bet the Demon is a rich biatch and a bunch of timing will help. If my car will start I'm going to run it locked this time around
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Old 02-28-2005, 09:34 PM
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Quote:
Originally Posted by Siggy_Freud
I am confused by what he wrote on that site. After saying to use 25 initial he then says Caution do not do this or you'll have 50 total timing and burn out the motor.

Then after that he says to use 25 initial again due to the idle circuit on the carb.

I hope no one is going off this site for info just based on the fact that its damn confusing. But I also hope no one follows the advice on the note that its wrong lol.
He is talking about limiting the distributor advance or else you will end up with a lot of initial + the normal distributor advance.
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Old 02-28-2005, 10:02 PM
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power valves

Holley recommends one half the vacuum.
Haynes recommends 1.5 below vacuum.

Holley recommends adj the secondary plates to 1/4 turn.
Haynes recommends one full turn.

I found Holleys specs work far better.
Plus they built the thing.
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Old 02-28-2005, 10:05 PM
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Here is the procedure off of Holley's website on how to size a powervalve.


CARBURETOR PARTS &ACCESSORIES
POWER VALVES

The power valve is a key component of the power enrichment system of Holley
performance carburetors. The power enrichment system supplies additional
fuel to the main system during heavy load or full power situations. Holley
utilizes a vacuum operated power enrichment system and a selection of power
valves is available to "time" this system's operation to your
specific requirements.


Each Holley power valve is stamped with a number to indicate its vacuum
opening point. For example, the number "65" indicates that the power valve
will open when the engine vacuum drops to 6.5" Hg, or below.


An accurate vacuum gauge, such as Holley P/N 26-501, should be used when
determining the correct power valve to use.


A competition or race engine which has installed a long duration, high overlap
cam will have low manifold vacuum at idle speeds. If the vehicle has a
manual transmission, take the vacuum reading with the engine thoroughly
warmed up and at idle. If the vehicle is equipped with an automatic
transmission, take the vacuum reading with the engine thoroughly warmed
up and idling in gear. In either case, the power valve selected should have
a vacuum opening point about 2" Hg below the intake manifold
vacuum reading taken.


A stock engine, or one that is only mildly built for street use, will have high
manifold vacuum (17" to 21" Hg) at idle speeds. To determine the correct
power valve, the vehicle should be driven at various steady speeds and
vacuum readings taken. The power valve selected should have an opening
point about 2" Hg below the lowest steady speed engine vacuum observed.
Holley has a 6.5" Hg power valve, P/N 125-65, which usually works out
well for most driving situations.


Many of the new Holley performance carburetors built today now incorporate
"power valve blow-out protection". With this provision, the power valve
diaphragm is protected from damage due to engine backfire, by a check
valve that is located in the throttle body. This check valve is designed to
be normally open but quickly seals to close off the internal vacuum
passage when a backfire occurs. Once closed, the check valve interrupts
the pressure wave generated by the backfire, thus protecting the
power valve diaphragm.
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Old 02-28-2005, 10:06 PM
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You can tell the 1.5" rule is off the mark by the blue smoke coming out your tailpipes. You can make up for the 1.5" rule by using less accelerator pump. That is one place Holley's circuits overlap. I'd rather use a pump cam with a fuel curve to add what the engine wants in street driving conditions, rather than have a strictly on off switch.
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Old 02-28-2005, 10:09 PM
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So going by the Holley site I should be running a 14.5" powervalve. You got one?
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Old 03-01-2005, 06:32 AM
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Bad Advice

A lot of what he says is on the right track, just a little misguided. Normally as a STARTING POINT we'll cut the vacuum in half at idle, and add .5", or go 1" to 1.5" below the vacuum at a normal cruise. Power Valve sizing is something that needs to be adjusted to the specific application, and usage. Normally once you get to about 20 degrees initial advance there isn't much difference AT IDLE going any higher. There will be differences in how the engine accelerates, and how the distributor needs to be curved.
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Old 03-01-2005, 06:54 PM
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So based on your 20o initial theory what dictates going higher or lower on the powervalve rating? At cruise I am at around 16" in traffic at slow speeds, and on the freeway it can go up to 18" to 20" depending on whether I am going uphill or down. I am running 8.5" valves front and back in a 4010. My initial is at 18o.

Last edited by lluciano77; 03-01-2005 at 07:51 PM.
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Old 03-01-2005, 07:18 PM
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his advice is kind of like 4secondsflat.com

my demon has run rich too.
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Old 03-02-2005, 07:32 AM
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I dont think that the high initial timing is bad advice as long as it is understood that you need to make sure and limit mechanical. My turbo engine is running at 24 right now and it loves it. I jump it to 40 by 3100RPM at low load(cruise), and response is awesome. I am probably going to try about 30 degrees initial when I get fuel sured up. Of course I can do things with my tables you cant do with a distributor

Chris
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Old 03-02-2005, 09:53 AM
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Quote:
Originally Posted by TurboS10
I dont think that the high initial timing is bad advice as long as it is understood that you need to make sure and limit mechanical. My turbo engine is running at 24 right now and it loves it. I jump it to 40 by 3100RPM at low load(cruise), and response is awesome. I am probably going to try about 30 degrees initial when I get fuel sured up. Of course I can do things with my tables you cant do with a distributor

Chris
Jeezus man. Do you have to rub it in.

Larry
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Old 03-02-2005, 10:53 AM
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Ah the benefits of FI and being able to tell the engine WHAT you want it to do instead of the other way around.
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