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  #31 (permalink)  
Old 11-14-2007, 11:53 PM
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I knew I read about this problem recently, the Cannuk knows his stuff, you just have to wind him up.

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Old 10-27-2007, 06:29 PM
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re: Carb tuning issues - 750 speed demon
K-Star you are wrong. The idle circuit of a Holley carb is not isolated from the effect of the power valve. In order for the motor to idle clean, while idling in gear, the power valve must be closed at idle. If the power valve is open at idle the main well gets more fuel which enrichens the main circuit. The idle circuit is feed off the main circuit and will also be enrichened if/when ever the power valve is not closed at idle.
Usually not a problem with a manual trans car but essential on a automatic car with a big cam to get a clean idle while idling in gear. Thats when the available manifold vacuum is lowest.

A carbs secondary metering block's idle circuit (idle feed restriction and idle air bleed) will not be the same calibration on a carb that does not use a sec power valve as compared to one that does use a power valve in the back or even the primary metering block that uses a power valve.
It is calibrated different.

If, in a carb, you eliminate the power valve(s) and up the main jets to compensate (usually 6 to 10 jet sizes) for what ever reason, you must now trim the idle AFR calibration (resize the idle feed restriction) or the idle will now be much richer.

if you don;t believe me, try it for your self. On a motor with a fairly big cam with low manifold vacuum that would normally have say 5" vacuum at idle in gear, first try a 3.5 or 4.5" power valve, then try a 10.5 power valve with no other changes. The 10.5" power valve will be open at idle, making the idle, while in gear ,richer. The 3.5 or 4.5" rated valve will be closed at idle (5" manifold vacuum) and the idle will be leaner and cleaner. If the wrong power valve is used, which is open at idle, the motor will eventually foul up the plugs from an over rich idle AFR.
When the motor has the right power valve that is closed at idle, the throttle blades are in the sweet spot relative to the idle discharge transfer slots and the ignition timing is correct the engine will idle forever while in gear and not load up or foul the plugs.
One of the biggest mistakes that novice tuners do, is eliminate the PCV.
Every carb that has a 3/8" vacuum port on its base plate is calibrated to use a functional PCV. If its eliminated the idle calibration is much richer and the throttles must be opened beyond the sweet spot to get enough idle speed further messing up the idle quality and off idle throttle response.
Do not eliminate the PCV.
When the PCV is used as it was intended and the timing is set correctly at idle (a big overlap rough idle cam requires a lot lot lot of base initial spark advance at idle. Right up to the point of locking out the spark advance in the distributor) it is near never ever required that you need to drill holes in the throttle plates to get a good clean idle.
The PCV will give you that extra airflow at idle. If you need more airflow at idle reduce the restriction orifice in the PCV valve or select a PCV valve with a larger airflow restriction orifice. They are not all the same.
Last edited by F-BIRD'88 : 10-27-2007 at 06:36 PM.

Old 10-27-2007, 07:35 PM
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re: Carb tuning issues - 750 speed demon
turning the idle mixture screws out a little bit will not compensate for the lack of a PCV. You're missing the point. When you remove the PCV you're reducing the total airflow at idle that enters the motor. now you must open the throttles more than the designed amount to compensate and maintain the same idle speed. the throttles are now out of the sweet spot. They are open too far at idle. now the idle is wrong and you get a off idle flat spot.
adding to the idle mixture screws adjsutment will not compensate.
this further agraivated on a motr with reduced manifold vacuum at idle.

DO NOT ELIMINATE THE PCV. If you don;t have a PCV. (racing carb) and a big cam and need more airflow at idle for correct throttle opening, do not drill the throttle blades. Just hook up a PCV to the intake manifold plenum.
The slight air bleed of a PCV system will allow you the extra airlfow needed at idle for a clean idle with a big camshaft.
Make sure the opposing valve cover is vented. A PCV does not vacuum the crank case. it jsut vents the crank case of blowby at idle. Use it. there is no down side to using a PCV on anything that gets street driven.
Its an easy effective method of adjusting the airflow and throttle opening at idle as well as triming the idle AFR without digging into the carb idle fuel calibration or drilling holes on the throttle blades.

Failing to bother to hook up and use a PCV on a street driven car, just makes tuning and drivability a lot more harder than it needs to be.

Not sure what dial plane manifolds youve been messing with but generally a dual plane manifold with a split plenum has more airvelocity at idle and low rpm. A better signal to the carb and is easier to set up in terms of idle quality and much better off idle and low speed throttle response. most dual plane manifolds have liquid fuel management areas (grids, channels fuel direction dams etc etc) in the floor of the plenum under the carb as well as plenum heat to aid fuel vapourization at idle and low speed to improve things during engine warm up. Many single plane racing manifolds do not have this, (some do)
Reguardless of the camshaft, dual plane manifolds as a rule are easier to set up and have much nicer idle and low end throttle response. They tend to cruise at P/T a lot nicer overall. A edelbrock Performer RPM is more flexable overall than say a Vic JR even thou a vic JR is a a very good manifold.
Some of the older single plane manifolds (especialy the more racey designs) are not that good on a street driven car that has to idle and cruise at low rpm.
Last edited by F-BIRD'88 : 10-27-2007 at 07:49 PM.

Hope this helps.

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  #32 (permalink)  
Old 11-15-2007, 12:12 AM
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Good one. He does know his stuff.
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  #33 (permalink)  
Old 11-15-2007, 06:21 AM
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Hmmmm, I have fabricated aluminum valve covers with
-10 male bungs welded in and -10 AN 90's running to -10 line to the header evac. If I drill a hole in my v-c's and put a PCV to the back of the carb and it doesnt work I can honestly say I will be angry, lol.... Not saying it wont or this guy doesnt know his stuff but can we be sure this will fix my problem before I trash $200 v-c's? Also, anything on the super suction holley830hp? lol..... Nobody knows anything about why it sounds like a hoover is inside my manifold under the carb???????????? If nobody has seen this or knows what It is it's obviously a/the problem...

I "CAN" drill a 1" hole in the back of the v-c and put the correct bushing and pcv and then if it doesnt work just use a bushing plug and use it as a fill hole, lol....


Come on guys search the world and your vast knowlage... whats this sucking sound??? May the cam just be drawing so much air it's starving for air at idle?? Causing this sucking sound??
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Old 11-15-2007, 06:30 AM
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Here's the picture... But 1st this carb made this sound and had the same idle problem with plugs with the last manifold Vic Jr. and same 1" HVC spacer... So intake gaskets are starting to look less and less likely... It's gotta be something that was swaped over from old setup ie: Carb, spacer, heads, cam, shortblock.....

#461 Double hump heads, no port, 3 angle, 1.6/2.02 valves big spring seats, screw in studs and guide plates

Super vic manifod, 1205 or 1206 Felpro gaskets can't remeber

1" billit HVC spacer, 4 hole top tappered to open w/ cnc porting

1" NX gemini quad nitrous plate (all fittings tight no leaks anywhere on carb/spacer/nitrous plate bases)

Holley 830hp carb 70/71 jets, 2.5" pv's front and back, idle screws turned 1.5 off bottom, idle at 900-1100rpms, pulls 6-4" at idle in Park.. I will get idle in 1st/2nd tonight

roughy 9.1:1 pistons w/ 20cc dish w/ 74cc heads? So I have 64cc heads so maybe 10:1/10.5:1 compression

cam spec's are 260/271 @ .050 and 589/592 lift 110lsa valves at 24 lash

4k stall in a powerglide 4.88 gears 32" tire 3300# s10

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Old 11-15-2007, 06:33 AM
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Side shots with different v/c's but same setup....



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Old 11-15-2007, 08:27 AM
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Too much carb?
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Old 11-15-2007, 11:06 AM
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Okay Josh, try this read, same thread and same F-Bird comments:


Old 10-30-2007, 10:53 PM
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re: Carb tuning issues - 750 speed demon
Black exhaust smoke at idle indicates a large amount of unburned fuel. its getting in the motor somehow.
i would look for a weak ignition (ground, coil whatever) usually a spark box either works or it doesn't, but a coil and or magnetic pickup coil can be weak and intermident. Eventually the plugs get fouled and ya get black smoke.

I would also look for an internal leak in th carb allowing extra fuel (a lot of extra fuel) to get in the manifold. power valve diaphram leaking, PV gasket seal, metering block gasket seal, main jets loose. BLOCKED AIR BLEED OR EMULSION HOLE in the metering block will really throw ya off.

Having the power valve open at idle and the throttles open too far at idle and no using a PCV all will very much contribute to the problem as well.

Fix this stuff and try another known good running carb. Remember carb problems are often often really ignition problems. just for grins run a ground wire from the engine to the body of the car. Don;t ask .....
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And you can add this quote too,

Old 11-01-2007, 05:12 AM
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re: Carb tuning issues - 750 speed demon
Quote:
Originally Posted by k-star
I have tried it, more then once and changing the PV has never fixed a rich idle. I have a custom built carb that i built for my test stand. It has no PV at all in the front, I have ran that carb with and with-out PV and it makes zero difference in how the carb idles...

Show me in the holley and BG books about the power valve being closed to make sure the idle is correct. I have 2 or 3 books on the holley carb and not one of them mention that.

You are partially corect about the main wells, but no-matter how you slice it you can only get X amount of fuel through that orfice. dosen't matter if it's mixed with air or not. So if your theory is correct, then by adding more fuel to the bowls the jets will flow more fuel.....It just doesn't work that way.

Keith


I'm more than partially correct on the fuel in the main main wells. It is a mixture of air and fuel. not 100% just fuel. Makes a big difference.

Well actually it does. More fuel in the bowls gives a bigger "head" to push the fuel thru the jet. How much stuff flows thru a orifice is a function of its size and how much you push on the stuff ( pressure and how much you're pushing back on the other side. (pressure differential). and its density
You're missing the point. if the mixture is richer ( more% of fuel making up the total volume) overall in the main well because the power valve is open, then the fuel flowing thru the idle feed restriction will be richer also. it is more dense because of the higher %of fuel to air in the main well.
It also by the fact that the power valve is open adding the PVCR size to the jet hole size, increases the "head" acting on the fuel in the well.
This increase the overall pressure differential across the idle feed restriction.
A higher pressure differential increases the amount of flow thru the idle feed restriction.l

if on your test carb you didn't notice the motor become rich without a power valve and bumped up jetting on your custom carb, ts vey likely the idle calibration overall was richer than nessessary to start with. If the idle calibration is off a good bit to start with then the effect of the power valve being closed did not bring the AFR back far enough so you did not "notice" a change. The throttles must be in the sweet spot relative to the idle discharge slot, reguardless of the idle speed required.
Its is hard to distinguish between "too rich" and a little less too rich"
when the idle is to fat or even too lean to start with.

A direct quote from the BG carb manual re the power valve
The power valve, located between the two main
jets, offers a boost in available fuel to the engine
in high load conditions without creating an
over-rich idle or part throttle. Power valves are
marked with a vacuum rating. This rating is the
point at which the valve will open. The lower
the number, the more the vacuum has to drop
for the valve to open. When the engine is under
a big load, it produces decreased manifold
vacuum along with an increased demand for
fuel. When the manifold depression is less than
the rating on the power valve, it opens and
allows extra fuel to enter the main circuit of the
metering block. It is a good idea to have a
power valve rating that is lower in number than
the vacuum produced by the engine at idle

A direct quote re the emulsion holes in the main well

There are six (6) emulsion bleeds per metering
block, three (3) for each main well. These orifices
play a part to control the density of the fuel
in the block by metering the amount of air that
is introduced into the fuel in the main well.
This, in conjunction with the air bleeds in the
main body, help to control the shape of the fuel
curve. The emulsion circuitry of your Mighty
Demon has been engineered through extensive
wet flow, dyno and street & track testing.
A note of caution: tuning of emulsion bleeds
should be performed only by those with a deep
knowledge of carburetors, otherwise, a poorrunning
engine or damaging internal engine
parts could be the result.
Last edited by F-BIRD'88 : 11-01-2007 at 05:31 AM.
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Old 11-01-2007, 06:14 AM
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re: Carb tuning issues - 750 speed demon
You're taking it in way too simple terms and ignoring the fact that the main wells are not full of fuel. You are ignoring the difference in fuel density that the fuel inthe main well is when the poer valve is open or closed.

I've been tuning and setting up carbed motors for more than 30years.
The poer valve opening point has a big effect on the idle,
A motor always runs over rich and eventually loads up the plugs unless the power valve remains closed at idle. * especialy a automatic car while idleing in gear) When you examine the real way the power valve and main jet affect the idle air fuel ratio and accept that the fuel in the the main well is not just fuel but is in fact an air fuel mix and understand the difference that density of a liquid has on the flow thru a orifice. You can see how this all comes together. If you ignore and overlook basic physics and fluid dynamics laws and only read what you want to read you come to the conclusion, that you have.
I suggest like you choose to overlook and ignore what really goes on inside a carb and
ignore a clear statement in the instructions, you have overlooked and or ignored some other factor that made your custom carb not work as you wanted it to.

"It is a good idea to have a
power valve rating that is lower in number than
the vacuum produced by the engine at idle"

Why? because when the power valve opens at idle, the idle AFR gets richer. A good bit richer. Especially while idleing in gear. Understanding this is key to getting a clean stable idle, on a motor with a big racey cam. If you choose to ignore this, you'll always have a car that seems just too racey for daily use as the thing will always load up. Spark plug life will be short. You'll always be fiddling with the carb to "keep it in tune". You'll always want to "two foot it" when idling at a stop light. Or need to put it in neutral at a extended stop and "clean 'er out". caue its loading up on you from a over rich idle.

Further reading about power valves and idleing from Holley
Last edited by F-BIRD'88 : 11-01-2007 at 07:56 AM.

Hey Josh, try reading the whole thread for yourself:

https://www.hotrodders.com/forum/carb...on-126870.html

If this helps you out, elect FBird for Prez! Good luck and post back your sucess.
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Old 11-15-2007, 05:49 PM
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I still don't understand the powervalve issue... It can't be the powervalves being open causing a ritch idle... If so then Im screwed cause I have the lowest powervalve made, lol... I will put a block off in the front and let it idle and if it still smokes then it cant be the powervalve correct? It's smoked and shot liquid drops threw the pipes with a 3.5" and a 2.5" powervalve... I think we have come to realize it's not the powervalve

It HAS to be something else, internal or external but NOT jets or powervalves.....
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Old 11-15-2007, 06:51 PM
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Quote:
Originally Posted by Joshua Lee
I still don't understand the powervalve issue... It can't be the powervalves being open causing a ritch idle... If so then Im screwed cause I have the lowest powervalve made, lol... I will put a block off in the front and let it idle and if it still smokes then it cant be the powervalve correct? It's smoked and shot liquid drops threw the pipes with a 3.5" and a 2.5" powervalve... I think we have come to realize it's not the powervalve

It HAS to be something else, internal or external but NOT jets or powervalves.....
The lowest power valve Holley makes opens at one inch of vacuum. The power valve can leak from a backfire even with a protection device in the carb. There's other sources of leaks, I'll get to that.

We're assuming your wet plugs are fuel not oil or water, knowing this is most important. You can see, smell, and taste the plugs we can't. Black liquid out the exhaust doesn't tell us much. It could be raw fuel, a match ought to id that or not. It could be oil, in which case it will feel smooth and slick between you fingers and will probably not ignite with the match test. It might be dirty water. That and CO2 are the principle products of combustion so there's plenty of the stuff though it usually comes out the pipes in vapor form but it can condense and drip out. Plus it could be leaking coolant into a cylinder and pumping that out the exhaust.

Certainly if the problem is oil or water then chasing the carb isn't the solution, so you gotta check this out and report back.

The carb you have has 4 corner idle, that should be plenty to distribute the idle air and fuel requirement around to where none of the transition circuits are exposed. Nor should it be pulling any fuel out the boost venturis. If it's doing the latter the reasons are as follows:

1) The power valve has failed and is leaking or the vacuum is so low it's turned on. All the carb's circuits feed from the main well. The well is fed by the main jets and the power valve. If the power valve is leaking (one can consider a bad gasket or a crack in the metering block or main body to also be a contributor to this) there will be so much fuel in the main well that changes in main jet size will prove to have no effect upon mixture ratio.

2) If the amount of fuel in the mainwell is excessive, the air correction jets will loose control of the emulsion process and can result in dripping boosters at idle. Same for way too high of a fuel level in the bowels.

3) If the secondary idle is not set properly the primary throttle plates can be too far open allowing the transition circuit to be exposed.
a) In that case the idle and transition circuit will feed fuel making a rich mixture. The rich mixture causes you to open more throttle since the idle mixture screw is becoming ineffective.
b) The excessive amount of air flowing thru the primary side can cause the mains to turn on and drizzle fuel. What now happens to many tuners who find themselves faced with too much fuel, they close the idle mixture screws, or nearly so and open more throttle. You just get into this vicious cycle where you end up idling the engine too fast to try and burn too much fuel which is running out the boosters because of so much air going thru the venturis.

Any of this sound familiar?

You're running what for fuel, gasoline or alcohol? If alky, ethanol or methanol?

Was this carb set up for alcohol and is now running gasoline? Talk about being rich!

You've got nitrous, does that system leak fuel when it should be off? Is it jetted properly?

You sure that stack of spacers is really air tight? Holley's are pretty easy to bend on a stack like that such that the throttle plate is bowed in the middle and not making a seal.

Bogie
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  #40 (permalink)  
Old 11-15-2007, 08:21 PM
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Quote:
Originally Posted by Joshua Lee

#461 Double hump heads, no port, 3 angle, 1.6/2.02 valves big spring seats, screw in studs and guide plates

Super vic manifod, 1205 or 1206 Felpro gaskets can't remeber

1" billit HVC spacer, 4 hole top tappered to open w/ cnc porting

1" NX gemini quad nitrous plate (all fittings tight no leaks anywhere on carb/spacer/nitrous plate bases)

Holley 830hp carb 70/71 jets, 2.5" pv's front and back, idle screws turned 1.5 off bottom, idle at 900-1100rpms, pulls 6-4" at idle in Park.. I will get idle in 1st/2nd tonight

roughy 9.1:1 pistons w/ 20cc dish w/ 74cc heads? So I have 64cc heads so maybe 10:1/10.5:1 compression

cam spec's are 260/271 @ .050 and 589/592 lift 110lsa valves at 24 lash

4k stall in a powerglide 4.88 gears 32" tire 3300# s10

I'm not being antagonistic or trying to bust your chops but, you do not have enough compression for that camshaft unless that small block is near 500 cubic inches. No amount of tuning will likely result in the truck being any quicker than it already is.

On top of that the heads are choking it up at about 5500-6000 rpm, the plenum volume is too large, and yes 70/71 jets may very well be too rich for your engine. There is no set-in-stone rule concerning jetting. The engine wants what it wants.

Now with that said, you probably don't have nearly enough cylinder pressure at any rpm, or enough timing, to have a complete burn cycle and the rich mixture is slowing the combustion process even further.

If your plugs are black after a full throttle pass, it is rich. Whatever the reason may be, it is rich. Period.

Verify that you're not burning oil and fouling the plugs first, then try smaller jets. With those old heads I doubt that the engine is drawing enough air through the venturis to warrant jets that would be considered normal, based on my experience. Try 68s' front and rear.

Good luck to you my man. I hope you get it sorted out and have some fun with it.



Larry

Last edited by coldknock; 11-15-2007 at 08:38 PM.
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Old 11-15-2007, 11:15 PM
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Quote:
Originally Posted by oldbogie
The lowest power valve Holley makes opens at one inch of vacuum. The power valve can leak from a backfire even with a protection device in the carb. There's other sources of leaks, I'll get to that.

The powervalves front and back are new as of yesterday, no way are they leaking or bad just yet

We're assuming your wet plugs are fuel not oil or water, knowing this is most important. You can see, smell, and taste the plugs we can't. Black liquid out the exhaust doesn't tell us much. It could be raw fuel, a match ought to id that or not. It could be oil, in which case it will feel smooth and slick between you fingers and will probably not ignite with the match test. It might be dirty water. That and CO2 are the principle products of combustion so there's plenty of the stuff though it usually comes out the pipes in vapor form but it can condense and drip out. Plus it could be leaking coolant into a cylinder and pumping that out the exhaust.

It's funny you bring up water, cause the evac tubes fogged up while it was leaking the water so the temp outside might have been affecting the air in/out of the engine... I also ran the engine for about 15 minutes trying different stuff to make it idle right and so on... I started to notice that the base plate and spacers along with the manifold runners were starting to be COLD to the touch, not just cool.. COLD... Whats this a sign of?? I run 104 unleaded threw the motor also..

Certainly if the problem is oil or water then chasing the carb isn't the solution, so you gotta check this out and report back.

Im about 10% it's oil blowby, 80% it was water condensation and 20% it's fuel being rich...

The carb you have has 4 corner idle, that should be plenty to distribute the idle air and fuel requirement around to where none of the transition circuits are exposed. Nor should it be pulling any fuel out the boost venturis. If it's doing the latter the reasons are as follows:

It's not dripping fuel..

1) The power valve has failed and is leaking or the vacuum is so low it's turned on. All the carb's circuits feed from the main well. The well is fed by the main jets and the power valve. If the power valve is leaking (one can consider a bad gasket or a crack in the metering block or main body to also be a contributor to this) there will be so much fuel in the main well that changes in main jet size will prove to have no effect upon mixture ratio.

Powervalve isnt leaking unless the 4-6" is still to small for the 2.5" powervalve?

2) If the amount of fuel in the mainwell is excessive, the air correction jets will loose control of the emulsion process and can result in dripping boosters at idle. Same for way too high of a fuel level in the bowels.

I will try lowering the floats and get back with you on that.

3) If the secondary idle is not set properly the primary throttle plates can be too far open allowing the transition circuit to be exposed.

Whats the secondary idle?

a) In that case the idle and transition circuit will feed fuel making a rich mixture. The rich mixture causes you to open more throttle since the idle mixture screw is becoming ineffective.

I noticed that my 4 corner screws all the way in the motor seemed to run better? My old setup with a 750 it wanted to die when you run the screws in all the way??

b) The excessive amount of air flowing thru the primary side can cause the mains to turn on and drizzle fuel. What now happens to many tuners who find themselves faced with too much fuel, they close the idle mixture screws, or nearly so and open more throttle. You just get into this vicious cycle where you end up idling the engine too fast to try and burn too much fuel which is running out the boosters because of so much air going thru the venturis.

Any of this sound familiar?

You're running what for fuel, gasoline or alcohol? If alky, ethanol or methanol?

104 unleaded

Was this carb set up for alcohol and is now running gasoline? Talk about being rich!

No it's a gas carb to my knowlage? It has the small metering plates..

You've got nitrous, does that system leak fuel when it should be off? Is it jetted properly?

Doesnt leak cause it's not on, jetted right...

You sure that stack of spacers is really air tight? Holley's are pretty easy to bend on a stack like that such that the throttle plate is bowed in the middle and not making a seal.

Yes, the good old carb cleaner test proved no leak there... I can install the carb strait to the manifold to satisfy this question if need be?

Bogie


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Old 11-15-2007, 11:20 PM
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Originally Posted by coldknock
I'm not being antagonistic or trying to bust your chops but, you do not have enough compression for that camshaft unless that small block is near 500 cubic inches. No amount of tuning will likely result in the truck being any quicker than it already is.

It's a 406 sbc.... It runs 7.2's at 94 mph on motor

On top of that the heads are choking it up at about 5500-6000 rpm, the plenum volume is too large, and yes 70/71 jets may very well be too rich for your engine. There is no set-in-stone rule concerning jetting. The engine wants what it wants.

I know the heads are a weak part of the setup... Cam Motion says the cam isnt TOO big but it's right there.. They made the cam for my setup... I have the jets I can keep going down if need be... On the highway when I pull into the garage the plugs look GREAT and tan... So I know at WOT or part throttle the motor runs GREAT... It's just idle...

Now with that said, you probably don't have nearly enough cylinder pressure at any rpm, or enough timing, to have a complete burn cycle and the rich mixture is slowing the combustion process even further.

36* locked out on the timing

If your plugs are black after a full throttle pass, it is rich. Whatever the reason may be, it is rich. Period.

No, my plugs are bad at idle...

Verify that you're not burning oil and fouling the plugs first, then try smaller jets. With those old heads I doubt that the engine is drawing enough air through the venturis to warrant jets that would be considered normal, based on my experience. Try 68s' front and rear.

I can try anything man, I have nothing but time.... I will try the smaller jets! I know the 71 rears on the highway pulling into the garage and killing it the plugs are a pretty tan... So the WOT is fine, just the idle....

Good luck to you my man. I hope you get it sorted out and have some fun with it.

Im having fun now, lol... This is part of the fun making it go even faster!



Larry

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Old 11-16-2007, 07:39 PM
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Hey Josh not to leave you hanging, I just read your responses. I've got get out of here, will write you on Sat or Sun when I get back on line. Good data thanks.

Bogie
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Old 11-16-2007, 08:43 PM
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Ok now we're getting somewhere.

Driving on the highway doesn't tell the whole story, it's certainly not wide open throttle running, or I hope it isn't.

If you have good color from part throttle cruising, idling at stoplights and meandering about town then it definately not fouling the plugs up from a rich idle/low speed mixture.

The only time the plugs get dirty is at the track under w.o.t. passes right?

If that's the case then your high speed air bleeds could probably use a larger sized "jet". Be careful here and only go up one size at a time. This is where your fuel mixture gets air for emulsification in the main well at upper rpm. Too lean and you could burn a valve or a piston if it's really bad.

Go up one size, make a pass, look at the plugs. Do this until they look just about like they do after a sprint on the highway. Don't go too lean, it will hurt your performance and possibly your engine.

Be careful and keep it slightly rich on the upper end and your engine will be happy.

One more thing, while I'm thinking about it, make sure that the passages for the air bleeds aren't stopped up before you make any changes.


Larry

Last edited by coldknock; 11-16-2007 at 10:04 PM. Reason: Had to add a little note.
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Old 11-17-2007, 04:15 AM
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Well guys... good and bad news

Good news...
I put more jet in the front after my first pass seemed to bog and take off (maybe lean at the hit)

Bad news....
Truck ran great, great throttle response ect.... After the next pass the engine seemed "off" so I go for the next pass and I hit full throttle and "IT" happened.... bent two valves....

I did get some info for you and I will post it up tomorrow... IE: what I changed and what I learned after I tore the top end off..... Yes, I trailored it home and tore it down and it's 4:15 and Im about to go o bed, lol... Hardcore?
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