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  #16 (permalink)  
Old 05-19-2013, 11:20 PM
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I often find a 750 holley likes 70 pri and 80 sec jetting.
It is well within what I find to be normal jetting for that carb..

The slight lean stumble is that on the primary throttle tip in or when getting into the secondaries from cruise? Or from rugging it from a stop?

If it is a primary offidle tip in response issue the throttles may be out of position at idle. (T slot exposure) can be eithe thte primary or the secondary throttle position that is the one causing the flat spot ...or both LOL.

It also indicates the the idle circuit fuel curve trim (idle air bleed size) is not quite right and may need fine tuning. It is slightly too big.

Look at the origional stock carb body. Look at the size of the primary and secondary idle air bleeds on it.
I bet they are smaller than the 75's you got in the new carb body.

It could be a air leak too.

When i did my upgrade using the Proform HP carb body I had to tune it a bit too.
Once you get it dialed in, it is very sharp and smooth.
The afr meter/gauge really lets you fine tune the idle air bleeds so that the throttle tip in transition is nice and smooth right from idle thru to when the main jets starts to flow fuel, as you get further into the throttle..
The 75's they give you are just a rough base line. idle air bleed.

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Old 05-20-2013, 09:00 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
I often find a 750 holley likes 70 pri and 80 sec jetting.
It is well within what I find to be normal jetting for that carb..

The slight lean stumble is that on the primary throttle tip in or when getting into the secondaries from cruise? Or from rugging it from a stop?

If it is a primary offidle tip in response issue the throttles may be out of position at idle. (T slot exposure) can be eithe thte primary or the secondary throttle position that is the one causing the flat spot ...or both LOL.

It also indicates the the idle circuit fuel curve trim (idle air bleed size) is not quite right and may need fine tuning. It is slightly too big.

Look at the origional stock carb body. Look at the size of the primary and secondary idle air bleeds on it.
I bet they are smaller than the 75's you got in the new carb body.

It could be a air leak too.

When i did my upgrade using the Proform HP carb body I had to tune it a bit too.
Once you get it dialed in, it is very sharp and smooth.
The afr meter/gauge really lets you fine tune the idle air bleeds so that the throttle tip in transition is nice and smooth right from idle thru to when the main jets starts to flow fuel, as you get further into the throttle..
The 75's they give you are just a rough base line. idle air bleed.
I ended up back at 72/80 actually, the bog is all over the place really, if I rug it out of the hole its fine, nothing weird at all. But any kind of cruising speed and you tip in it stumbles/bogs noticably. I do have a box of blank bleeds but without an afr meter I'm hesitant to make any changes. I looked for air leaks and couldn't find any. I hate admitting this because it just sounds so stupid, but this thing makes a god awful sucking noise anytime you lean on it at all. I have had holleys on everything and not once heard one that sounds like this does. Picture a qjet when the secondaries open only much much louder....this is why I have kept looking for some place that it could be pulling air in. Doesn't do it until you lean into a bit. It also did the same noise with the old main body as well. And yes....I know its a Carb, and air does get pulled in lol....its just real loud. The only other thing i thought might be causing the noise is the little bit of epoxy on the throttle blades from when i filled the holes the original owner drilled. They aernt perfectly smooth so maybe that's my sound.....I dunno.
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Old 05-20-2013, 10:55 AM
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"Bogs every where from cruise"

I would take two of the blank air bleeds and drill with a 1/16th .062" drill bit.
Install in place of the primary 75 IAB and try it. Increase the primary jet from 70 to 72 and try it.
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Old 05-20-2013, 11:02 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
"Bogs every where from cruise"

I would take two of the blank air bleeds and drill with a 1/16th .062" drill bit.
Install in place of the primary 75 IAB and try it. Increase the primary jet from 70 to 72 and try it.
Going bigger on the iab's leans and smaller richens correct?
The proform body comes with,and I bought for the Holley, an extra set of 36's for the secondary outers when used with 2 corner idle like mine. I was concerned that these would richen the idle up way too much and never actually drove it I don't think when i had them in there. I just stayed with the 75 outers on the primary and secondary, and 36's on the inners. It takes about three seconds to swap them over tho so maybe I will try that this afternoon. My blanks are at work and were closed today so can't do much else for now.

Last edited by bygddy; 05-20-2013 at 11:13 AM.
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Old 05-25-2013, 12:10 PM
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OK, so small update. Switched the secondary iab's to 36's. So front are 75 for the high speeds and 36 for the idle, rears are all 36. That didn't change much, this morning set the floats again, and I guess I wasn't setting them with it warmed up enough. Once up to temp the rear would be more then a trickle out of the sights. So I lowered it a bunch, now giving the car a good nudge some will dribble out. This has cured a few things.
1: it no longer bogs anywhere, even cruising in OD at 1600rpm it will pull clean.
2: it no longer stumbles when turning and accelerating.
3: it doesn't stall when i pound on the brakes.
4: when it got hot, it would idle high, 1100 in park, 800 in gear. Now it was too low, but no longer effected by temp. In had to increase it to get back to 900 in park, 600rpm in gear. Much more stable as well.
Still chasing a very rich condition. Driving around town and any moderate and up throtlle input brings black smoke from the exhaust.

Only once, but it was weird, it would want to just shut off. Pulling to light, it would just want to shut off. Had to 2 foot it to keep it running. The fuel level was very low, less then an 8th of a tank, so maybe it suffers a pressure drop at that point? I got gas and it didn't do it again.....yet.
And all in all it actually feels stronger, which I have no idea why an improper float level would effect, but it does....with 327 gears and an OD it an absolute animal on the highway....I have buried the speedo in a heartbeat out on the country highway where I live....and it still keeps pulling. Kinda neat
The stock 750 bleeds were actually richer based on size then the current ones. So I have 10 blanks now, I'm going to use what I'm running as a starting point and start opening them up a bit at a time and see if I can eliminate the smoke and rich condition. Im not sure if i should open the high speeds up, or just the idle bleeds. Or all of them in small steps. Indomt believe its a jet issue, I'm running 70/80's in it now and any less in the primary and it develops a lean surge condition.
So that's my novel, I'm sure nobody has time to read it all and add input....but I need to write stuff down to get a grasp of things so this is my way to do that.
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  #21 (permalink)  
Old 05-25-2013, 12:55 PM
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Do not use a 75 as a high speed air bleed. Use a 36.

What is the size of the primary and secondary idle air bleeds in the stock carb body?
Guestimate using a1/16th and 1/32 drill bit. or a straight pin that you can mic ,,etc.
This is your start point.

The final pri and sec IAB sizes will be very close the IAB sizes in the stock body.

Ya the float level matters.
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Old 05-25-2013, 01:19 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Do not use a 75 as a high speed air bleed. Use a 36.

What is the size of the primary and secondary idle air bleeds in the stock carb body?
Guestimate using a1/16th and 1/32 drill bit. or a straight pin that you can mic ,,etc.
This is your start point.

The final pri and sec IAB sizes will be very close the IAB sizes in the stock body.

Ya the float level matters.
The stock bleeds are
70 idle, 31 main on the primary,
28 idle and 25 main in the secondary.

But these bleed sizes will be richer across the board compared to what I'm currently running.
Right now I'm 75 idle, 36 main and
36 idle and main on the secondary
Bigger is leaner correct?
I was shocked to see the difference float level made.
I was going to start with opening up the fronts to 80 and 40
Secondaries to 42 on both primary and secondary
This should lean it out a bit for idle and high speed bleeds.
I have read to try and get it to a point where it has a lean surge while cruising, then go back a bit in bleed size.
What do you think?
Or should I try and take some jet out of it first? With the floats wrong I wasnt getting an accurate test before so I could go back and try 68/76 again and see how it feels and how the plugs look.
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  #23 (permalink)  
Old 05-25-2013, 02:04 PM
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FORGET the I read this that and other.
Start with a 70 primary idle air bleed.. drill 2 blanks with a 1/16th " drill bit .062" and hone to size.
WHY are you making this harder than required.

The 36 pri and sec high speed air bleeds are fine.

The 36 sec idle air bleed is fine. If it needs to be smaller than 36 solder it up and redrill with a 1/32" .031" drill bit.
now its smaller.

Just get the pri IAB right. start @ .062 (1/16th drill bit") this is not that hard.

forget the lean it down till it surges BS. The jetting will be between 70 and 74 primary and 80-84sec.
It is just that simple. The black smoke is a ignition issue.

I don't know why you bothered getting all these blank air bleeds when you are going to have to custom size tune them anyway.

The final primary IAB size wil be +/- .003 of what is in the stock carb body. start at .062" not that hard.

.075 is too big.

Stop trying to tune by feel and voodoo.

I don;t know who told you how to set a holley carb float level. It is just to the bottom of the bowl sight screw hole.
There should be no fuel dribbling out at all unless you bounce the car. EVER...anything higher is too high.

Stop the voodoo BS.... The jetting will be 70-74 pri and 80-84sec.

Last edited by F-BIRD'88; 05-25-2013 at 02:16 PM.
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Old 05-25-2013, 02:20 PM
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A high speed air bleed of between .031 and .036 is fine.
get a 1/32" drill bit and a 1/16th " drill bit .. It is just that easy.

If you want to know the numbered drill bit equivelent of a given drill bit diameter in incheds or MM's
good search drill bit size chart and download the PDF.

The most you will need is a few numbered drill bits like a #72 (.025")

or a #51 (.067") you do not need all the air bleed sizes or all the numbered drill bit sizes.
final hone by hand as required.

You cannot tune high speed air bleeds by feel, smell or plug appearance or any other voodoo.
requires having the correct main jets first. requires dyno or extensive accurate track testing using a WB AFR meter
and accurate main jetting and timing, first. You can burn up a motor by getting it wrong.
on my car the .036" high speed air bleeds work just fine. .031" to .036" will be fine.
when the correct jets are used too (70-74 pri 80-84sec)
and the air cleaner installed (ya it matters)

You can do this whole job with what you got and a 1/16" and 1/32" drill bit and a simple NB heated afr meter/gauge/Voltmeter

Last edited by F-BIRD'88; 05-25-2013 at 02:48 PM.
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Old 05-25-2013, 03:29 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
A high speed air bleed of between .031 and .036 is fine.
get a 1/32" drill bit and a 1/16th " drill bit .. It is just that easy.

If you want to know the numbered drill bit equivelent of a given drill bit diameter in incheds or MM's
good search drill bit size chart and download the PDF.

The most you will need is a few numbered drill bits like a #72 (.025")

or a #51 (.067") you do not need all the air bleed sizes or all the numbered drill bit sizes.
final hone by hand as required.

You cannot tune high speed air bleeds by feel, smell or plug appearance or any other voodoo.
requires having the correct main jets first. requires dyno or extensive accurate track testing using a WB AFR meter
and accurate main jetting and timing, first. You can burn up a motor by getting it wrong.
on my car the .036" high speed air bleeds work just fine. .031" to .036" will be fine.
when the correct jets are used too (70-74 pri 80-84sec)
and the air cleaner installed (ya it matters)

You can do this whole job with what you got and a 1/16" and 1/32" drill bit and a simple NB heated afr meter/gauge/Voltmeter
The blanks were given to me....so no cost. Jets are still 70/80 and will leave them be for now
Will drill 2 blanks to 0.062 and replace the 75's with them and go from there.

Ignition is stock HEI, but directly from GM...and has less then 2000k on it.
So I'm not sure what ignition issue I would have that is causing a rich condition?
I may still have an old msd 6A kicking around....if so is it worth installing on such a mild motor?
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Old 05-25-2013, 06:55 PM
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Slight wake up call here, remember when I had said it idled to high with the rear transfer slots exposed? Well with the floats set right that isn't the case, I can idle it down to a stall using the idle screw. So currently I have the rear slots closed but now I can actually open them up and get front and rear squared.
Will improper transfer slot exposure effect idle rich condition?
Will improper transfer slots effect things anywhere else? Just wanted to know if this could be my cause of my rich everywhere condition.
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Old 05-25-2013, 06:58 PM
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Adding ignition power to it will not fix a fault.

it is a better than 50-50 chance its the newest most rescently replaced electrical parts
that is the thing that is fubared. Always suspect the new part.

This is the first rule of electronics repair diagnostics. (it is always the most recently replaced part that is fubared)

The black smoke is not a "rich" issue.. it is a misfire issue. (ignition fault)
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Old 05-25-2013, 07:01 PM
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Slight wake up call here, remember when I had said it idled to high with the rear transfer slots exposed? Well with the floats set right that isn't the case, I can idle it down to a stall using the idle screw. So currently I have the rear slots closed but now I can actually open them up and get front and rear squared.
Will improper transfer slot exposure effect idle rich condition?
Will improper transfer slots effect things anywhere else? Just wanted to know if this could be my cause of my rich everywhere condition.
yes it will. the T slot exposure on both pri and sec is critical and so is the float setting.

I guess I assumed you knew how to correctly set the float height on a holley. I thought every one did...

My bad...EH!

but now I bet the plugs are finished (black smoke)

Is the carb still flooding ? ( needle seat fault/dirt in fuel/fuel filter)
inconsistant float level

Last edited by F-BIRD'88; 05-25-2013 at 07:11 PM.
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Old 05-25-2013, 07:15 PM
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I just got thru with another guy on a different forum that has been haveing way too much trouble getting his holley dialed in. Turns out the PCV was staying open at idle, instead of closed.

I must have posted 3 or 4 time for him to check the PCV valve...for the last 3 months.
I guess he finally got around to it....Pretty Billet PCV valve...Wrong vacuum level.

Just shows you its always the little basic stuff.
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Old 05-25-2013, 08:39 PM
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Originally Posted by F-BIRD'88 View Post
I just got thru with another guy on a different forum that has been haveing way too much trouble getting his holley dialed in. Turns out the PCV was staying open at idle, instead of closed.

I must have posted 3 or 4 time for him to check the PCV valve...for the last 3 months.
I guess he finally got around to it....Pretty Billet PCV valve...Wrong vacuum level.

Just shows you its always the little basic stuff.
Smrtass lol....yes, I know how to set a Holley float level.....I have no idea how it wasnt right.....I have set many, and this is the first one I screwed up....regardless....clearly I did!
No, Carb isn't flooding at all, it starts, it shuts off, it doesn't diesel or do anything unusual. Throttle response is now good across the board with no more stumbles or bogs.
Other then once the floats were set right I then had a lower idle.
This will allow me to open the secomdaries up and get front to back even.
Yes, the ignition is new, but its not "brand new" it was on the car last season with no issues. This is only become an issue since I switched over to the Holley.
I'm going to rest the transfer slots tommorow and see what changes. I didn't realize that having the rear closed and front open too far could cause any drivabilty concerns other then at idle.
The baseplate and metering blocks are over 20years old....not much drive time on anything but still old.....so maybe there's more to it then anything I'm doing or not doing.
Will try in the am and see if it helps.
Thanks
Dave
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