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post #11 of (permalink) Old 05-11-2009, 11:22 PM Thread Starter
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Carb is a 7448-1 (at least that is what is above the date code on the air horn). I believe it came 'stock' with 8.5 power valve and 61 jets.

Ended up taking the carb apart and cleaning it with nearly a whole can of carb cleaner. All the passages in metering plate and airhorn.

Now the engine seems almost ready to catch and run, but I ran out of time. Stuck out in Idaho for the next week an a half, while the jeep is in NC. Hope it is just a timing issue now and can get started when I get back.

Can you think of a reason why it wouldn't start at idle, and would only start at part throttle, but limp along with lots of black smoke?

Thanks again for all the help.
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post #12 of (permalink) Old 05-15-2009, 09:10 PM
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Quote:
Originally Posted by mdn86cj7 View Post
Carb is a 7448-1 (at least that is what is above the date code on the air horn).
I believe it came 'stock' with 8.5 power valve and 61 jets.
List 7448-1 (now we are getting somewhere!)
What it is, and what it came with from Holley...

Model 2300,
350 CFM,
Renew Kit 37-1536,

Trick Kit 37-933,

Needle & Seat 6-504 (off road p/n 6-513 recommended)
Holley 6-513 - Holley Needle and Seat Assemblies

Primary Main Jet 122-61 (That's a 61 jet for the layman)

Primary Metering Block 134-203

Power Valve 125-85 (that's an 8.5 In.Hg. Closing Point Power valve)
You should get a part throttle cruise vacuum reading and put in the proper power valve...

Accelerator Pump Discharge Nozzle 0.031"

Primary Bowl Gasket 108-83-2

Primary Metering Block Gasket 108-89-2

Primary Fuel Bowl 134-103
(Center Pivot, not the best for off road applications)

Throttle Body & Shaft Assembly 12R11070A

Venturi Diameter 1-3/16"

Throttle Bore Diameter 1-1/2"

This should be a 350 CFM, 2 barrel with CENTER PIVOT float bowls... and it's a 'Universal Application' unit.

Up until now, I wasn't sure if it was 2 or 4 barrel, vacuum secondary or mechanical secondaries if it was a 4 barrel.
All Holley correspondence should start with the 'LIST' number first and foremost!
-------------------------------------------------------

Quote:
Ended up taking the carb apart and cleaning it with nearly a whole can of carb cleaner. All the passages in metering plate and airhorn.
You really should use carb cleaner 'DIP' for cleaning the carb.
The stuff in the spray cans is mostly just to take the dust off the outside.

Quote:
Can you think of a reason why it wouldn't start at idle, and would only start at part throttle, but limp along with lots of black smoke?
Covered this before...
My first though is way too much fuel pressure.
This carb should see a MAXIMUM of about 6 PSIG,
And it will probably run better with about 3 PSIG.

The second thing I would check is the throttle cable to make sure it's not holding the blades open.

The third thing I would check is the CURB IDLE screw to make sure it's not holding idle open to the point of uncovering the transfer slots (Which will make it run WAY too rich at idle)...

The fourth thing I'd check is to make sure the throttle blades aren't closing completely.
Bent or mis-adjusted linkage will cause the blades to seal in the bores, cutting off air, and the vehicle won't idle.

My FIFTH thought is to adjust the fuel inlet float as directed earlier.

Sixth, adjust the idle mixture as directed earlier...

Then I'd adjust the POWER VALVE as described earlier...

If I had the carb off (like for adjusting the blade opening at idle) I would check for, and install if necessary, a 'Back Fire' valve in the throttle plate.

It's VERY easy to tune a Holley if you follow the directions and pay attention to the details...
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post #13 of (permalink) Old 05-15-2009, 11:41 PM
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TR - you say the center pivot bowls are NOT the best for off road?
Why?

Seems like the side pivot types on a sidehill leaning one way it'd go too rich, the other way too lean.

For up and downhill, I've always installed the jet and vent extenders (inside the bowls) for off road use. What am I missing?

Good info on his!
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post #14 of (permalink) Old 05-16-2009, 10:47 AM Thread Starter
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TR -

Thanks for the info. I have been using the gaskets and parts from the Trick kit in the rebuild. Only change is that the trick kit came with 5.5, 6.5, 7.5 power valves. If I could get it started I would be able to do about the second half of what you said.

One other thought I had is that timing is still off. If I am seeing about 10 degrees BTDC just cranking with the starter that is probably too much advance (at least I think). No vacuum advance hooked up, so the mechanical advance is probably not really kicking in, but once it idles the RPM will climb and I'll get some more advance maybe putting me in the 16-20 range?

Thanks for all the info again.

Mark
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post #15 of (permalink) Old 05-16-2009, 01:25 PM
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carb

i got a 500cfm 2bl sitting on a built 350 chevy in a cj5 i think maybe the compression was to high it burns rich , why would ya need 4bl carb and a passing gear in a jeep but im 3 speed , just a saturday night cruze with big cam , jet it down but lean is bad news!

ROLLIN'THUNDER
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post #16 of (permalink) Old 05-16-2009, 01:56 PM
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10 at cranking should be OK, once it starts it shouldn't advance much at idle unless the springs are worn. 6-8 cranking may be better, 8 idle, but you are close. At this stage, it's not a problem.

Get the fuel working first.
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post #17 of (permalink) Old 05-18-2009, 12:11 PM
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Quote:
Originally Posted by RRich View Post
TR - you say the center pivot bowls are NOT the best for off road?
Why?
Because center pivot bowls have big wide flat bottom floats that like to end load when you are in off camber situations.
(Float is Up-Side-Down in this picture)




Side pivot float bowls have rounded floats that don't side load, and do a MUCH better job in off camber situations.
Float is up-side-down in this picture...


------------------------------------------------

Quote:
Seems like the side pivot types on a sidehill leaning one way it'd go too rich, the other way too lean.
You would be assuming the float in a side pivot was mounted off center so the varying fuel level on one side or the other effected it directly...

That ASSUMPTION would be incorrect.
Side pivot still has the ROUNDED float bottom centered in the bowl, so the fuel inlet metering is pretty well regulated until you uncover one of the Main Jets or Idle Fuel Pickup Tubes...


(Image Courtesy Of HOLLY CARBS! Thanks Holley!)

This image of a side pivot float bowl is a little biased,
Remember, if you look dead on at the end, instead of this angled shot,
The float will be MUCH more to the center of the bowl, and the rounded bottom will work MUCH better at off camber angles!
----------------------------------------

Quote:
For up and downhill, I've always installed the jet and vent extenders (inside the bowls) for off road use. What am I missing?
Not much with the vent 'Whistles', I recommend them myself...
Holley 26-89 - Holley Fuel Bowl Vent Baffle


And a Vent Screen will help slow down any fuel escaping from the float bowls, without getting in the way of venting the bowl...
Holley 26-39 - Holley Fuel Bowl Vent Screens


As far as jet extension go,
Remember, if you have a CENTER PIVOT float bowl, and you want to use Jet Extensions,
YOU MUST USE A FLOAT WITH THE CORRECT 'NOTCHES' IN IT TO CLEAR THE JET/EXTENSIONS!
Holley 116-10 - Holley Carburetor Float Kits


Here are the 'Short' Jet extensions, which I like the best for off road use,
Holley 122-5000 - Holley Main Jet Extensions


YOU DO NOT NEED A SPECIAL FLOAT IF YOU HAVE A SIDE PIVOT FLOAT BOWL!
The Jet Extensions/Jets will clear the float without special floats in side pivot bowls.
----------------------------

Back to the vents...

If you look up some of my posts from 10 years ago concerning Holleys, you will find I show several ways to raise the vent tubes up off the Venturi bodes...

We have used everything from copper tubing to raise the float vents up (so fuel doesn't leak out on steep 'UP/DOWN' hill climbs/desents,
To rubber tubing slipped over the slash cut vent tubes...

Now Holley is producing the 'Truck Avenger' carb for 'Off Road' use, and it comes with a raised vent tubes over choke horn...

Look at the tube crossing the Venturi Opening with the holes drilled in it....
This is the same thing we did with copper tubing and brake line for years, good to see Holley started doing it!



Also notice the side pivot float bowls on this 'Off Road' carb,
Along with a removable top for the vacuum secondary spring change!
Man, it was a REAL pain in the butt to change vacuum secondary springs before this little gadget came along!

Holley 20-59 - Holley Vacuum Secondary Carburetor Accessories



Once you get the vent point moved to the center of the bowl (instead of the back wall) you don't get NEARLY as much flooding from the front bowl when going UP hill,

Get the opening of the vents up off the Venturi body and the fuel can't spill into the Venturis like it did before

Get the Jets to the center of the bowl, you don't get the Jets being UNCOVERED when you go DOWN a hill,

And get the Leverage Force point to the center of the bowl with a round float you don't have nearly the Side Loaded fuel problems anymore...

Reduce the opening point for the power valve, and you don't get flooding when you are trying to 'Finesse' an obstacle and the vacuum drops under load,

Get a spring loaded needle and set in there so washboards or hard drops off things don't let too much fuel in...

And the Holley becomes a seriously FORMIDABLE off road carb!
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post #18 of (permalink) Old 05-18-2009, 12:39 PM
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Quote:
Originally Posted by mdn86cj7 View Post
TR -

Thanks for the info. I have been using the gaskets and parts from the Trick kit in the rebuild. Only change is that the trick kit came with 5.5, 6.5, 7.5 power valves. If I could get it started I would be able to do about the second half of what you said.
If I were you,
I'd start with a big, honkin' fuel filter!
No such thing as 'Too Clean' of fuel!

I use the large 'See Through' plastic fuel filters.
Since I change them OFTEN, they don't get a chance to get cloudy or get old and crack.

'See Through', or 'See Into' fuel filters will allow you to observe if fuel is getting into/through your system correctly,
And you can look for things like bubbles that would indicate leaks in the lines or holes in the fuel pump diaphragm.

A fuel pressure gauge AFTER the FILTER, as in between filter and carb,
Is ALWAYS a good idea!
See Through filter lets you know you ARE getting fuel,
The gauge lets you know if the fuel is getting THROUGH the filter and if the pressure is correct from the pump...
-----------------------------

The second thing I would do is make sure your throttle blades aren't opening to the point of uncovering the transfer slots when the engine is running.

I posted pictures of the transfer slots, and where they will be located in the throttle body bores...

If you uncover the transfer slots too soon, you will get WAY too much fuel...
---------------------------------

Another through that crosses my mind,
Which gasket did you use for the Metering Block to Venturi Body?

The wrong metering block gasket,
Or not remembering to put on fresh 'O' rings on the transfer tube (if you have one) will cause MAJOR fuel metering problems!
----------------------------------



Quote:
One other thought I had is that timing is still off. If I am seeing about 10 degrees BTDC just cranking with the starter that is probably too much advance (at least I think). No vacuum advance hooked up, so the mechanical advance is probably not really kicking in, but once it idles the RPM will climb and I'll get some more advance maybe putting me in the 16-20 range?
I would start from SCRATCH, and VERIFY the ignition timing before I went any farther...

It's VERY easy to do, takes basic tools, and will make things MUCH easer to diagnose!

Simply take the #1 spark plug out,
Turn the engine over BY HAND with a wrench/socket on the center bolt of the crankshaft...

Find when COMPRESSION stroke starts by putting your finger over the #1 spark plug hole, and turning the engine BY HAND!

If you use the starter, more than likey the momentum of the crank will carry your engine PAST compression stroke of #1 since there is no COMPRESSION BACKPRESSURE to slow the crank down...
SO DO NOT USE THE STARTER TO TURN THE ENGINE OVER!

Once you have VERIFIED COMPRESSION STROKE STARTING on #1 Cylinder,

Then stick a chop stick, wooden dowel rod, ect. in the spark plug hole.
DO NOT USE METAL!
You would be Amazed how fast a metal object can screw up cylinder walls, piston top, spark plug threads, ect.

Use the wooden dowel rod to locate the top of the piston,
You crank the engine BY HAND to look for the highest point of the piston on COMPRESSION STROKE!

This is VERIFYING TDC OF COMPRESSION STROKE.

Now that you have MANUALLY VERIFIED TDC OF COMPRESSION, and there is NO QUESTION you have TDC of Compression stroke,

Take a look at the balancer 'Hash' mark, and see if it lines up (roughly) with the 0 (zero) mark on your timing tab on the front cover.

*IF*...
The balancer 'Hash' mark lines up with the 0 mark (within two or three degrees) you have a balancer that hasn't had the outer ring slip on the hub yet.

Balancer outer rings are suspended in rubber between hub and ring... The rubber degrades and the outer ring slips, and causes no end of problems with timing!
You are reading 8 of advance, but if the balancer ring slipped, you might have 18 degrees of initial advance!

VERIFY THE RING 'HASH' MARK AT ROUGHLY 0 WITH THE CRANK AT TDC OF COMPRESSION.

Then locate the #1 plug wire on the distributor cap,
Follow that plug to it's terminal on the distributor cap,
Then mark the location of that terminal on the distributor base so you know where the #1 plug terminal is when the cap is off.

Flip the distributor cap, and have a look at the rotor.
It should be pointing (ROUGHLY) at the mark you made for #1 terminal on the distributor base.

If it's NOT pointing at the mark you made, you have a problem with where the distributor is set, and you need to lift the distributor and correct for #1.

Once you do these simple things,
VERIFY Compression,
VERIFY TDC,
VERIFY Balancer,
VERIFY Distributor,
You don't have to worry about the IGNITION anymore!

MUCH better to waste 20 minutes to VERIFY the ignition than to wonder if that is the problem or not!
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post #19 of (permalink) Old 05-18-2009, 12:45 PM
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Quote:
Originally Posted by Dex View Post
i got a 500cfm 2bl sitting on a built 350 chevy in a cj5 i think maybe the compression was to high it burns rich , why would ya need 4bl carb and a passing gear in a jeep but im 3 speed , just a saturday night cruze with big cam , jet it down but lean is bad news!
Didn't see a 'Question' in there...

If it's 'Rich', when is it 'Rich'?
When it's idling?

Over 'RICH' can also be float level being too high and forcing fuel into the idle and main jets...
Make sure you adjust the fuel/float level before you start messing with idle mixture...

If it's 'RICH' at idle, lean out the idle mixture a little with the idle mixture screws,
And check to make sure the power valve isn't blown while doing so.

Use vacuum gauge as described before to set idle mixture correctly.

If the 'RICH' happens when you are above about 800 RPM, then the problem is main jets being too big,
or it's a power valve opening point problem.

Power valve is EASY to determine what you need with a vacuum gauge,
And smaller jets are EASY to install.
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post #20 of (permalink) Old 05-18-2009, 12:49 PM
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Quote:
Originally Posted by RRich View Post
10 at cranking should be OK, once it starts it shouldn't advance much at idle unless the springs are worn. 6-8 cranking may be better, 8 idle, but you are close. At this stage, it's not a problem.

Get the fuel working first.
I don't agree.
I say to VERIFY the igntion, since it's the easitest to check out....

VERIFY Compression,
VERIFY TDC,
VERIFY The Balancer is correct,
VERIFY The distributor placement,
Then you don't have to worry about ignition...

Besides, it sounds like the distributor is working correctly for centrifugal advance,
he's getting about the correct amount of advance,
And correct advance timing if the engine speed is moving up to over 1,000 RPM...

I'd start with ignition, VERIFY the ignition,
Then move to the carb again...
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