Holley Street Avenger 770 - stall issues - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-01-2012, 07:06 AM
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Holley Street Avenger 770 - stall issues

Hey guys,
Before I get going bear with me as I am a self proclaimed novice at this and am doing my best. Bought this truck a little while ago. Already have had some help on this forum that was appreciated.

First the low down on the engine.
402 BBC (from what evidence I have gathered)
781 heads
Performer RPM intake
Headers
3" stainless exhaust
MSD HEI distributor
It has an aftermarket cam but I do not know what it is. Pretty rumpy though.

The trcuk had (from what evidence I gathered) a small Holley Marine carbuerator on it. List #50418

Just bought a new Holley 770 Street Avenger carb. Put it on last night. Hooked all of the ports and such up to the required items as called out in the instructions. (Does the full manifold port go directly to the intake?)

After all was hooked up I tried to start the motor and it just cranked and cranked. Nothing. So I advanced the timing slightly and away it went. Lots of fuel came out the back of the pipes. I am guessing this was due to the time I was cranking and not getting spark at the right time??

And the engine did backfire through the carb one time with a gray mist type offering that I am guessing was all the excess fuel built up.

Before you ask I did not recheck my timing yet.

I let the engine idle until it came up to operating temp. At one time the fumes were string enough to make my eyes water. (Sounds like more and more fun as I go doesn't it?)

Finally when the engine was at full temp and running quite smooth actually I took it out for a ride.

I idled out my driveway and started easing down the street when I decided to give it a little goose to see what it was going to do. and..... blah!!!

I stalled out. I cranked it a couple times and it started back up but I bascially had to idle it back to the garage.

When I got back jsut for kicks I took out the front sight screw and fuel just came raining out.

Obviously I need to adjust this float. But can this cause the stall?

Also please note that the prior arb that was on the vehicle had all of the vacuum lines connected to the manifold. (Was there more vacuum for the vac advance on the distributor?)

Any feedback would be appreciated.

Getting a new timing light today too.

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Old 08-01-2012, 07:44 AM
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sounds like you need to set the air fuel and sync the squirters these are never acurately set on the out of the box holleys however they are usually close you still need to jet and change the squirters according to application if your timing is set correctly you should be able to run without the vac. adv. I set my base at 8-10 deg and full adv. I degree in at 28 for a full swing before 2500 rpms at 36-38 deg. I do not run vac pod after I do this for the simple reason it advances the timing even higher and takes it even farther out of the power curb. however people will argue about timing this is how I do it .Until you get your timing straight you will not be able to correctly adjust any carb. Holley carbs are very tempermental when it comes to fine tuning in this aspect if the timing valve adjustment plug heatrange are not correct it will effect the carb.
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Old 08-01-2012, 08:05 AM
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It just hit me.

I have a vacuum line attached from the front of the carb at the port labeled "full manifold" to the intake manifold.

This should be attached to my tranny or something.

So if the intake manifold has more vacuum it may be sucking fuel directly into the intake or maybe acting like a vacuum leak.

Told ya I was a novice.

Does this make any sense??
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Old 08-01-2012, 09:34 PM
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float adjustment

Yes an overflowing bowl is something that will stall the engine and flood it. Get both of them set ASAP - the fuel flooding will fight you every way you go.

Plug all of the vacuum ports, get the engine idling and set the primary mixture screws with a vacuum guage - tuning for the best rpm / best vacuum.

Set the inital advance where you know its run before. Must have worked with the old carb?

Maybe at that point you can do something with it to start tuning it up....
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Old 08-02-2012, 07:50 AM
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at full manifold vacuum the distributor pod will advance the timing to full swing so disconnect all the vacuum lines and cap them until you adjust everything too where the motor idles and revs properly from the throttle lever then start connecting the vacuum lines one at a time if you are gonna run the vacuum pod there should be a vacuum port located on your front metering plate located about 1/2 of an inch from the top of the carb this is a metered vacuum port this is where you want to connect the vacuum pod that way the pod will only advance under wide open throttle
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Old 08-02-2012, 08:12 AM
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also there should be "sight" screws on side of the bowls these plus are used to adjust float levels when you take these off the fuel level should be at the bottom thread or barely drip out of the bowl so you need to adjust your floats by screwing in on the needle seats until you get the fuel level corrected and go from there you still may need to change the jets and squirters however but you will not be able too tell until you get the motor to idle properly if the squirters are out of range you will get a bog when you hit the secondaries if they are to close you will get a black puff out of the exhaust or a rich spot where the motor will fall on its power for a few seconds under load when the secondairys open as far as jets once you get your motor idling properly go down the road at 40 - 60 mph turn your ignition of put the car in nuetral and coast to the side of the road pull a spark plug and look at it real good if it is white it is too lean if it is black it is too rich it should have a slight gray tint look to it if every thing is adjusted properly
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Old 08-02-2012, 09:05 AM
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OK. So I revised the vacuum connections and it made a huge difference. I plugged the port on the carb labeled "full manifold" and hooked the tranny directly to the intake for vacuum.
I did hear a knock so I am guessing that atthis point the timing is too far advanced and will be checking that tonoght and getting that corrected per you instructions above.

As far as the timing goes. The guy who I bought the truck from had the distributor advance line hooked to the intake manifold also. I now have it on the metreing block as you would suspect. Is this the reason I needed to advance the timing in order to get the truck to fire up with the new carb on it? Is is bad to have the distributor hooked to the intake? Does the port on the metering block draw enough vacuum immediatley to activate the distributor advance?
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Old 08-02-2012, 09:36 AM
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The vacuum port on the metering block is designed to feed full vacuum under wide open throttle only if the distributor was connected to intake vacuum before and it ran this gives me reason to believe that whom ever had it like this did not have the timing correct either the pod advance on hei distributors are designed to advance the timing under driving conditions for gas mileage emission control it should have no effect on performance other than that if the motor is clattering and knocking without this hooked up or with it hooked up properly then I think you may want to restab your distributor it really sounds to me like it may be off as much as three teeth exspecially since you have too turn the distributor to start it!?! this is a sure sign that your valve timing is out of range.
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Old 08-02-2012, 10:33 AM
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I guess I was under the impression thathe vacuum advance works at idle and then drops off and the mechanical advance takes over.
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Old 08-02-2012, 11:07 AM
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no the vacuum is a secondary for the mechanical it is only supposed to advance the timing when the mechanical needs a extra boost like going up hill or under hard acceleration your vacuum does not drop as rpms go up it increases until max velocity in the cylinders is reached then it levels off and could peak at as much as 55hgs in gas motors
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Old 08-03-2012, 04:50 AM
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OK. So big discovery. As I was looking over my current situation I noticed something odd looking about the "new" vacuum hose I used for the distributor to the carb. The seam of the hose was rough looking. Under extremely close scutiny I discovered that the seam of the hose a a ba-jillion little holes in it. Vacuum leak!!!! Arrrrgggghhh!
Must have been the end of a very long and very old roll of hose that I was sold.

Anyway without hesitation I replaced the hose and waa-laaa. The engine is running with the distributor positioned within reason of where I had initially begun. I had marked the point of the diaphram was pointing to before I had started.

Now my question....
I started with 12 degree intial advance without the vacuum line hooked up. Is that too much?

I did give the idle screw a 1/4 CW turn to maintain my idle also.
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Old 08-03-2012, 06:56 PM
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factory set the "base" at 10 degrees up too + or - 4 degrees won't really do much as far as performance other than maybe cause a hard or easy start problem other than harm the starter until you get into higher rpms the factory chose 10 deg as base for optimal street operation cause it gave a good range of starter life and gave optimal idle and optimal vacuum 2 deg more will make it a little easier to start but you could lose a hg of vacuum which really won't effect much
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Old 08-03-2012, 07:31 PM
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You guys have you ideas of vacuum advance backward. Vacuum is highest at light load and light throttle. You should have no manifold vacuum at WOT. Vacuum advance is for light throttle gas milege and drivability.
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Old 08-03-2012, 07:33 PM
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Ripper you should do your home work before you start giving advise.
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Old 08-04-2012, 12:54 AM
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Check your fuel pressure too... I had all kinds of problems with my holley until I figured out my "o.e spec " replacement fuel pump was generating upwards of 10psi at times...

Holley's like 6psi...no more.. no less.
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