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Thread: Holley Carb ?'s
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post #3 of (permalink) Old 05-08-2009, 08:56 AM
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Originally Posted by mdn86cj7 View Post
I saw a post on the forums from year 2000 from a guest that had almost the same setup as I did (258 w/ Crane 260 cam, Clifford intake and exhaust, and Holley 2300 7448 carb). Just wondering if that person is around or if anybody has a similar setup and could let me know what tuning they had done to the carb?

Mine came with 8.5 powervalve and 61 jets. Just wondering if that has worked for folks on the 258.

How about I tell you how to tune your Holley so it works with YOUR engine?

First off, you need a VACUUM GAUGE.

You need a vacuum gauge to set the idle mixture,
And to determine the correct power valve to use.

There are a number of steps to tuning a Holley correctly, and you should do them all so your Holley does what it's supposed to do!

Start with checking the base plate for vacuum leaks!
Any vacuum leak will cause problems with everything from idle mixture to power brakes!


Secondly, Throttle linkage adjustment.
Make sure you have some slack in the throttle linkage so when you put the jeep in a bind, it doesn't pull the throttle linkage open.

Don't just stand beside carb and open linkage,
Actually have someone push the pedal down!


Third, Check your accelerator pump linkage, make sure it starts to move the INSTANT the throttle blades start to move!
If there is any 'Gap', you will get a 'Bog' or 'Stumble' when you try and move from a stop.


Fourth, Take the SIGHT PLUG screw out of the float bowl(s)...
So when you start the engine, you can adjust your fuel float level.

The SCREW in the adjuster is the LOCK SCREW,
And the 'NUT' is the adjuster!

Most 'Off Road' guys wan the fuel level to be just barely getting into the threads of the sight plug hole,
Serious off roaders will want fuel level about 1/16" to 1/8" below the threads.

Engine (or fuel pump if you have electric) MUST be running before you can adjust the fuel level,
And you should NEVER adjust fuel level INDOORS!
Always have a fire extingusher handy!


[b]Fifth[b], Screw in the idle mixture screws LIGHTLY, then back out about 1.5 turns.

Hook up the vacuum gauge to base plate vacuum, and turn the idle mixture screws TOGETHER (ALWAYS TOGETHER!) 'IN' until you get the highest STEADY vacuum.

If you go too far in, the idle will move around, and the vacuum will NOT be steady.
If you go even farther in, the engine will die.

You are looking for the highest STEADY vacuum, and you are looking to have the screws EVEN, both the same amount 'Out'.


Use that vacuum gauge with LONG HOSE, and place it so you can see the gauge while driving.
Find a flat, long stright stretch where you can drive and keep an eye on the vacuum gauge...

Get up to 55 MPH, keep the throttle STEADY and just CRUISE down the highway.
This is called 'Part Throttle Cruise', and you want to take the vacuum reading at 'Part Throttle Cruise'.

That vacuum reading at PTC will determine the correct size Power Valve...
Most people want the Power Valve 1.5 to 2.0 In.Hg. LOWER than the PTC vacuum reading.
IE: If your vacuum at PTC is 8.5 In.Hg., most people would want a 6.5 In.Hg. power valve.

Street rodders will want to get CLOSER to the vacuum reading, so the power valve opens sooner and gives extra fuel.

Average commuters will want the power valve to open about 2.0 In.Hg. below the PTC vacuum reading, so it saves fuel, but still does it's job.

Serious off roaders will often go 2.5 to 3.0 In.Hg. below the PTC vacuum reading, so the Power Valve doesn't open on the trail when they are trying to 'Finesse' an obstacle at low RPM/Speed...


Make sure your distributor is hooked up to SPARK PORTED VACUUM!
If you don't, your distributor vacuum advance will not function correctly...
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