Holley Jet size

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Kendog 170

Kendog 170

Let the boy go !
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My buddy says he has a 20 year old Holley 650 double pumper new in the box I can have . I have a bunch of Holley jets and parts.
Any suggestion on what primary and secondary jet size to start off with? 340 20 over, around 10.5 to 1, Eddy heads . 4 spd, 323 gear if it matters? 20 Years old I have to open it up to inspect so it would be nice to start with something close.
 
The Holley 0-4777 650 double pumper would have shipped from the factory with 67 primary and 73 secondary jets. That's what I would start with and tune from there.
 
Best to be a little rich than lean when tuning a new carb with today's fuel.
 
Unless you like buying plugs, start with ootb tune/jets. A slight lean wont hurt anything while sreet test n tuning -driving it easy . Check vacuum at idle and cruise fir power valve tune...Drive it mellow, roll the throttle at first...cruise and set/figure primary jets...then do some short wot.
 
MOPAROFFICIAL said:
Unless you like buying plugs, start with ootb tune/jets. A slight lean wont hurt anything while sreet test n tuning -driving it easy . Check vacuum at idle and cruise fir power valve tune...Drive it mellow, roll the throttle at first...cruise and set/figure primary jets...then do some short wot.
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This exactly. There is a mega difference between just touch lean of MBT and actual lean. What most guys call just right I call pig rich.
 
Thanks for the response Gives me something to to start with. I'm no pro but will will start 1st checking the power valve . 15" vac. #8 valve.Then go from there with jetting. I am now definitely too lean with current carb. which 1st leads me to think I had a vac. leak. But don't think that's the case as 15 is about right with stock ( I think ) cam . If I had $$$ I should have upgraded cam (just replaced lifters). All I did was inspect measure for wear and re-used.Motor sounds sweet with 160 psi Comp. check.
 
Kendog 170 said:
Thanks for the response Gives me something to to start with. I'm no pro but will will start 1st checking the power valve . 15" vac. #8 valve.Then go from there with jetting. I am now definitely too lean with current carb. which 1st leads me to think I had a vac. leak. But don't think that's the case as 15 is about right with stock ( I think ) cam . If I had $$$ I should have upgraded cam (just replaced lifters). All I did was inspect measure for wear and re-used.Motor sounds sweet with 160 psi Comp. check.
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If that's 15 inches at idle it doesn't matter. Don't set PV opening from idle vacuum. Do it from cruise vacuum.

You probably have 18-20 inches at cruise, so the best you can do is 10.5 and that's opening it a bit late.
 
Kendog 170 said:
Thanks for the response Gives me something to to start with. I'm no pro but will will start 1st checking the power valve . 15" vac. #8 valve.Then go from there with jetting. I am now definitely too lean with current carb. which 1st leads me to think I had a vac. leak. But don't think that's the case as 15 is about right with stock ( I think ) cam . If I had $$$ I should have upgraded cam (just replaced lifters). All I did was inspect measure for wear and re-used.Motor sounds sweet with 160 psi Comp. check.
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1. Get the List number from the choke tower (assuming it has one) if not it will be on top. Then you can look up the basic factory specs on Holley's Carb list.
2. Start a logbook or build sheet.
3. Check the floats. This determines the fuel level and is the first thing that has to be checked. If you have a chance, take pics of the metering blocks.
4. Turn the carb upside down and turn the throttle screw until the throttle is closed. Turn it in until it just touches and count how many turns until 0.020" of the transition slots show. Write that number down. Count how many turns of the screw is needed to get .030 and .040 visible. Write those numbers down.
Now you're ready to go try the carb out.
 
Mattax said:
4. Turn the carb upside down and turn the throttle screw until the throttle is closed. Turn it in until it just touches and count how many turns until 0.020" of the transition slots show. Write that number down. Count how many turns of the screw is needed to get .030 and .040 visible. Write those numbers down.
Now you're ready to go try the carb out.
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I am not sure if this is referring to the primary or secondary side, but the secondary side will have a stop screw that sets the 'at rest' secondary throttle opening. You will want to set that stop screw so that the secondary transition slots are showing about as much height as width when the secondaries are fully closed. (I.e.: Slot exposure is 'square'.)

This will get adjusted when you get to the point of testing light off-idle accelerations cruising around at low speeds. It also effects idle vacuum and interacts with the PCV valve idle airflow. Both will effect idle air quantity and that effects not only idle, but also how the transition phase operates.
 
nm9stheham said:
I am not sure if this is referring to the primary or secondary side, but the secondary side will have a stop screw that sets the 'at rest' secondary throttle opening. You will want to set that stop screw so that the secondary transition slots are showing about as much height as width when the secondaries are fully closed. (I.e.: Slot exposure is 'square'.)
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No. I don't want him to touch the secondary side. Especially not with the information provided. Usually the factory is OK on the secondary side and even if not, the t-slots are often high in bore and in those cases secondary idle position idle can't be judged by t-slot exposure. We can come back to this if needed once we know what the carb is, and how it runs on this particular engine.
 
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yellow rose said:
If that's 15 inches at idle it doesn't matter. Don't set PV opening from idle vacuum. Do it from cruise vacuum.
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OK I always thought it was idle vacuum . I will have to check my BB 500 motor as I have 7" at idle and I put a 3.5? ( Have to check my paperwork from that set up) runs great though.
Anyways I will post some pics once I get it. He's still digging around for it.
 
Mattax said:
No. I don't want him to touch the secondary side. Especially not with the information provided. Usually the factory is OK on the secondary side and even if not, the t-slots are often high in bore and in those cases secondary idle position idle can't be judged by t-slot exposure. We can come back to this if needed once we know what the carb is, and how it runs on this particular engine.
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OK, you are setting out a plan... good. I just want him to be aware of that secondary setting... it is ususally important when you get down to the last steps of fine tuning for smooth street/cruise operation. And it ought to be checked now just to be sure it is at the nomimal setting (square t-slot exposure with secondaries closed) to start with.. someone could have monkeyed with it and got it all out of whack and nowhere close to factory nominal setting.
 
Yes. I'm trying to keep to initial basics and small steps.

I'm assuming its high likelyhood that when the engine is first started, someone may crank the idle speed screw in to keep it running. Figured after its running, kendog can then readjust the primary thottle position to be between .020 and .040"
Agree that will look close to square.
If someone needs a picture, here's the amount a primary throttle slot is visible compared to a drill bit shank.
The big hole above the bit is the idle discharge port.
The small squareish cavity by the end of the bit is the transfer slot.
upload_2019-5-12_18-32-39.png

Now off the top of my head, I sure don't remember what size that bit is! That's why notes are so important.

Below is the secondary side of the same carb.
A very small drill bit is sticking out of the secondary idle port.
Its very small for two reasons:
The hole itself is the idle port restriction. There's no needle valve (idle mixture screw) on the secondary side.
It's provides only a little fuel, and most consider its main job is as a weep so the secondary fuel doesn't get stale.
Off the top of my head, the holes here are around .020" diameter - I'd have to check my notes... :)
upload_2019-5-12_18-39-10.png
 
Mattax said:
Yes. I'm trying to keep to initial basics and small steps.

I'm assuming its high likelyhood that when the engine is first started, someone may crank the idle speed screw in to keep it running. Figured after its running, kendog can then readjust the primary thottle position to be between .020 and .040"
Agree that will look close to square.
If someone needs a picture, here's the amount a primary throttle slot is visible compared to a drill bit shank.
The big hole above the bit is the idle discharge port.
The small squareish cavity by the end of the bit is the transfer slot.
View attachment 1715334348
Now off the top of my head, I sure don't remember what size that bit is! That's why notes are so important.

Below is the secondary side of the same carb.
A very small drill bit is sticking out of the secondary idle port.
Its very small for two reasons:
The hole itself is the idle port restriction. There's no needle valve (idle mixture screw) on the secondary side.
It's provides only a little fuel, and most consider its main job is as a weep so the secondary fuel doesn't get stale.
Off the top of my head, the holes here are around .020" diameter - I'd have to check my notes... :)
View attachment 1715334351
Click to expand...



That .020 sounds close. With what you can buy today for so cheap there's no reason to get a carb with 4 corner idle. Then you can control the secondary idle side better.
 
yellow rose said:
That .020 sounds close. With what you can buy today for so cheap there's no reason to get a carb with 4 corner idle. Then you can control the secondary idle side better.
Click to expand...
Now you made me look. :p 0.024" dia.
upload_2019-5-13_0-31-15.png


It's just sitting in the box now. Waiting for me to get around to swapping it on. Very curious to see how it responds at mid throttle with kill bleed location corrected.
 
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yellow rose said:
So it has 2 kill bleeds???? Hmmmmmm.
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LOL. It had a kill bleed on each corner up in the doglegs. That's why I have a note there is no tube in the main wells.
So I plugged the holes, and drilled new a one into each angle channel.

Before:
upload_2019-5-13_0-37-59.png


After:
upload_2019-5-13_0-40-30.png
 
Mattax said:
LOL. It had a kill bleed on each corner up in the doglegs. That's why I have a note there is no tube in the main wells.
So I plugged the holes, and drilled new a one into each angle channel.

Before:
View attachment 1715334513

After:
View attachment 1715334515
Click to expand...


Hmmm. I must have not been paying attention. That's the first kill bleed I've seen that high. BUT...I didn't do much with carbs from 1988-2000 so I got behind a bit.
 
Get a wideband while your at it. They are like $139 now. If your being given the carb, your already money ahead.
 
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