Ok, one more question on the Holley jetting.

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TrailBeast

TrailBeast

AKA Mopars4us on Youtube
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I swapped out my main jets (#72) for a pair of 68's
Then put the 72's in place of the 75 secondaries.
Everything looks, feels and runs great except for one thing.

The transition slots are a couple of numbers rich.
I say this because idle AFR is perfect, but as soon as I start into the throttle at normal driving around town speeds the AF ratio drops to 10 or so until I get up around 40-45mph.
Then when the main jets take over the AFR goes back into the 14-15 range where I want it.
I do a lot of driving between idle and 45 at light throttle, so it would be nice to lean those down a bit.

I know for sure I am still in the transition slots when the AFR is in the 10's
This where the transition air bleeds come into play, correct?

Thanks
 
Are you looking at an O2 sensor? You might be over-tuning. Look at the plugs instead. You could watch the vacuum gauge and see if/how long the PV is open. I believe that's what Dana might have meant.
 
The way I read it was, you are cruising, then step down on the pedal and it goes rich for quite a while. Is that right?
 
Dana said:
The way I read it was, you are cruising, then step down on the pedal and it goes rich for quite a while. Is that right?
Click to expand...

Correct, but only as I'm in the transition slots.
Idle and anything over the transitions and it's about perfect.
Just super light throttle is about the only way I can explain it.
I know it isn't the pump shot doing it as I can hold it in that first 1/8 or so of the throttle for any length of time and it says in the 10's on the AFR.

Probably most people would say screw it, that's close enough.:D
 
You can add transfer slot restrictors in the main body. If it is not the PV.
 
My inclination would be to install smaller idle feed restrictions - primary side.*
it would be good to know how much transition slot is showing at idle.
This is an Avenger 770?
Could be slot is too wide or too long.
Even if it is, I'd still start with with primary idle feed restricitons.
You didn't mess with the secondary idle position. right?

*It's easier to install threaded IFR than to press in new ones.
Before you do, might as well map out the various holes and restrictions.
It is possible the Idle Air bleed or a passage has something goofy going on. Shavings - a hole not drilled - you never know.

If the engine idles with less than 12 or 14"hg, its going to flow noticible more fuel as the engine gets more vacuum - up to around 14" when flow through the restriction will max out and things will act normal from there up.
This why I'd head toward IFR based on what you have written.

You'll need a pin vise and small drill bits to measure the holes (use the shank) and to bore a hole in the a brass set screw.
Hold the screw in the jaws of the drill. Go slow.
Also a tap set with bottoming tap.
Lots of info here
Relocating the Holley Idle Jet

How Are You Drilling Your Set Screws?
 
Dana said:
What PV is in it?
Click to expand...

Dana said:
You can add transfer slot restrictors in the main body. If it is not the PV.
Click to expand...

That's the answer I needed, thanks.
I was thinking it needed larger air bleeds, but you are referencing limiting the fuel to the TS's, correct?
It has a 6.5 PV (new) and I have right at 14 manifold vacuum at idle.

I don't understand what the PV has to do with idle or just off idle.
Unless it was blown or leaking, what would it have to do with it?

Sorry, I know Edelbrock but not Holley.
 
At 40-45 mph around town you are most likely into the main circuit. When you are in the main circuit the PV is a factor if your vacuum drops low enough for enrichment. Cruising with a vacuum guage inside helps add a afr guage and your really cookin.
 
Mattax said:
My inclination would be to install smaller idle feed restrictions - primary side.*
it would be good to know how much transition slot is showing at idle.
This is an Avenger 770?
Could be slot is too wide or too long.
Even if it is, I'd still start with with primary idle feed restricitons.
You didn't mess with the secondary idle position. right?

*It's easier to install threaded IFR than to press in new ones.
Before you do, might as well map out the various holes and restrictions.
It is possible the Idle Air bleed or a passage has something goofy going on. Shavings - a hole not drilled - you never know.

If the engine idles with less than 12 or 14"hg, its going to flow noticible more fuel as the engine gets more vacuum - up to around 14" when flow through the restriction will max out and things will act normal from there up.
This why I'd head toward IFR based on what you have written.

You'll need a pin vise and small drill bits to measure the holes (use the shank) and to bore a hole in the a brass set screw.
Hold the screw in the jaws of the drill. Go slow.
Also a tap set with bottoming tap.
Lots of info here
Relocating the Holley Idle Jet

How Are You Drilling Your Set Screws?
Click to expand...

Yes, Street Avenger 770.

Now you are speaking the things I have been reading and asking about.
The transitions show near a perfect square and I have not changed the secondary idle position.

I have been reading and watching video's about all this as much as I can, so I know exactly what you are describing.
I wanted to check in with you guys before doing anything with the T slot feeds, even though we can believe everything we see on the net, right?:D
I have a pin vise as well as bit sets down to a couple of thousands, so no problem there.
I'll study up more and pick up some brass set screws of the correct size.
I watched a video of a guy doing exactly this earlier, so what you say and what I saw matches. :D


Thanks for verifying this for me.
 
Dana said:
At 40-45 mph around town you are most likely into the main circuit. When you are in the main circuit the PV is a factor if your vacuum drops low enough for enrichment. Cruising with a vacuum guage inside helps add a afr guage and your really cookin.
Click to expand...

I thought that was possible as well, but I really don't think I am where the AFR shows 10's.
I also have a ,67 to one overdrive, so take that into account.
In 3rd I would agree at 40-45 I would probably be in the mains.

PV is a 6.5 if I didn't answer that yet
Manifold vacuum at 800 idle is 14.
I can get a vacuum hose for my gauge to reach my wiper arm.:D

Probably over it for tonight, but thank you.

Ah crap I forgot to mention I'm normally in OD at 40-45 with 3.55 gears so it takes very little throttle. (I'm the dumbass this time) :D
I'd bet I could put a round toothpick under my idle screw and do 40-45 in OD.
 
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What elevation are you at? If your at high elevation the IFRs are to big. Most OOTB carbs are setup for sea level.
Are the IFRs at the top or bottom? Move to the bottom.
Are the air bleeds tune-able. If not drill and tap for 8/32 brass set screws.
Treat the idle/transition circuit as a mini carb. With an OD trans driving around town you are definitely on the idle circuit.
Drop the IFRs in .001 increments and readjust the idle mixture. You will also find a smaller MAB will allow you to control the idle circuit curve. With the OD trans you are cruising around in low throttle high load conditions when the OD gears come in.
I run a GVOD and find the smaller IFR/IAB lets you get control of the carb in the 0-45 mph range. Getting the idle screws in the 1 turn out range has worked for me to get an acceptable idle in neutral/drive and off idle transition.
Transition slot restriction is another option but I have had success without them at sea level.
Don't get wrap around the axle with the AFR gauge in the idle circuit range. Low throttle high load needs a richer mixture for driveability. Read the plugs, clean but not white for today's fuel.
 
mbaird said:
Its easy enough to throw a 7.5 pv in and record any change .
Click to expand...
If the PV was the issue, a 7.5 would be going the wrong direction. But I don’t think the PV is the issue after all the good info Trailbeast has given. In the beginning, I was expecting to hear he was running around a 10.5.
 
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Dana said:
If the PV was the issue, a 7.5 would be going the wrong direction. But I don’t think the PV is the issue after all the good info Trailbeast has given. In the beginning, I was expecting to hear he was running around a 10.5.
Click to expand...

Yes but it would provide some iinsight .
And a combo of higher pv and lower mains might work . Might...
 
The PV comes into play every time you accelerate when cruising. The Accelerator pump works off idle and a little at low cruising speeds. But it the PV that gives you the boost in fuel when your cruising (say at 30mph or 60 mph) and "punch it".
 
Dana said:
If the PV was the issue, a 7.5 would be going the wrong direction. But I don’t think the PV is the issue after all the good info Trailbeast has given. In the beginning, I was expecting to hear he was running around a 10.5.
Click to expand...


You do not set power valve opening by idle vacuum. You set it by cruise vacuum. If TB has 14 inches at idle he’s probably 22 inches at cruise.

I’d drop a 10.5 PV in there and start over.
 
yellow rose said:
You do not set power valve opening by idle vacuum. You set it by cruise vacuum. If TB has 14 inches at idle he’s probably 22 inches at cruise.

I’d drop a 10.5 PV in there and start over.
Click to expand...
I agree 100% we’ve been over this idle vacuum bs over and over here.
There is no room for “probably “ though.
 
mderoy340 said:
What elevation are you at? If your at high elevation the IFRs are to big. Most OOTB carbs are setup for sea level.
Are the IFRs at the top or bottom? Move to the bottom.
Are the air bleeds tune-able. If not drill and tap for 8/32 brass set screws.
Treat the idle/transition circuit as a mini carb. With an OD trans driving around town you are definitely on the idle circuit.
Drop the IFRs in .001 increments and readjust the idle mixture. You will also find a smaller MAB will allow you to control the idle circuit curve. With the OD trans you are cruising around in low throttle high load conditions when the OD gears come in.
I run a GVOD and find the smaller IFR/IAB lets you get control of the carb in the 0-45 mph range. Getting the idle screws in the 1 turn out range has worked for me to get an acceptable idle in neutral/drive and off idle transition.
Transition slot restriction is another option but I have had success without them at sea level.
Don't get wrap around the axle with the AFR gauge in the idle circuit range. Low throttle high load needs a richer mixture for driveability. Read the plugs, clean but not white for today's fuel.
Click to expand...

I'm at 5k feet and when I first put the carb on it was in the 10's everywhere in the throttle except WOT, and that was in the 9's.
No tuneable air bleeds unfortunately.
The air bleed for the idle circuit is where I was going with it because I have everything in range now save for that just off idle cruise.
I am about 1 turn out on the idle mixture.
I'm thinking the idle air bleed restriction will still leave plenty on the mixture adjustment.

I can try the larger PV and see what happens before I do anything else though.


yellow rose said:
You do not set power valve opening by idle vacuum. You set it by cruise vacuum. If TB has 14 inches at idle he’s probably 22 inches at cruise.

I’d drop a 10.5 PV in there and start over.
Click to expand...

This would be better than jumping into modding the carb right off.
I'll recheck the vacuum at cruise and see, as I may be not be remembering it right.
I might not get to it right away though, as like I said, everything seems perfect except for that one small spot.
Now the weather is turning back cold again for a few days.

I'll tell ya, if I had a decent shop or garage I'd probably live in it.:D

Thanks guys.
 
If you spend enough time in the garage your wife might just start naming your cars like mine did .

"Those Bitches in the Garage"
 
TrailBeast said:
I'm at 5k feet and when I first put the carb on it was in the 10's everywhere in the throttle except WOT, and that was in the 9's.
No tuneable air bleeds unfortunately.
The air bleed for the idle circuit is where I was going with it because I have everything in range now save for that just off idle cruise.
I am about 1 turn out on the idle mixture.
I'm thinking the idle air bleed restriction will still leave plenty on the mixture adjustment.

I can try the larger PV and see what happens before I do anything else though.




This would be better than jumping into modding the carb right off.
I'll recheck the vacuum at cruise and see, as I may be not be remembering it right.
I might not get to it right away though, as like I said, everything seems perfect except for that one small spot.
Now the weather is turning back cold again for a few days.

I'll tell ya, if I had a decent shop or garage I'd probably live in it.:D

Thanks guys.
Click to expand...
Power valve is not going to fix 0-45 mph normal driving, unless the one you are running is blown.
At 5K feet you went down 4 jet sizes to get the primary cruise where you want it, the IFRs will be no different. Again you need to think of the idle/transition circuit as the circuit in your carb that operates in the 0-45 mph range driving like grandma. Drill, tap, and tune the circuit.
 
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