All Small Six Holley 2300 Tuning

[StarDiero75]

Howdy guys!

So i believe i got my leaks sorted out, the car seems to run better and has much more power! Anyhow, I gotta tune this 2300 now and it's throwing me for a loop a bit. Its a 350cfm street avenger. So far it seems to want 64 jets to run a good cruise, but WOT is like an 11 on the wideband. I'm going to the dragstrip on Friday with some friends so I'll pick up some plugs so I can do an actual tune. In case they show up like the wideband shows, how can I lean the WOT but keep cruise the same? Also I'm running a 8.5 power valve. And should I really only look at the outermost cylinders? I ain't mr. Monopoly so I was planning on only checking and replacing 1 spark plug after each pass haha.

Thanks guys,
Ryan

 

[pmuller9]

What is the air/Fuel ratio at idle and cruise?

If everything is good except WOT then you can drill and tap for restrictors in the power valve circuit.
They use a 6-32 thread.

 

[drag-200stang]

Yes, the outer most cylinders would be the leanest. Let the MPH help guide you. Give the engine what it wants. Within common sense tuning.

 

[65coupei6]

So what is your vacuum now? Have you started from the beginning since you fixed the leaks. retuned for best vacuum and make sure the power valve is correct? Then jets.

 

[StarDiero75]

What is the air/Fuel ratio at idle and cruise?

If everything is good except WOT then you can drill and tap for restrictors in the power valve circuit.
They use a 6-32 thread.

So far I got idle to be about 12.8-13.0. Thats where its happiest. This was after letting it warm up in the garage, i haven't gotten to beat on it since, again, I'll play more with it tomorrow. When I cruised with the 63s it was about 15.5 so I'm hoping the 64s will put me a little closer to 15

Thats what I was afraid of hearing . So basically making my own jets for it? Is that on the jet side of the metering block, or the power valve side?

 

[StarDiero75]

So what is your vacuum now? Have you started from the beginning since you fixed the leaks. retuned for best vacuum and make sure the power valve is correct? Then jets.

My vacuum now is about 19. Yeah I've started from scratch. I got the timing dialed in where it likes to idle and start without the slow crank. Timing is about 16 i think, i gotta remark my balancer to be sure.

Jet wise I've gone up from originally trying 60s. Now I'm on 64s. But haven't beat on it yet. On my way to the track I'll find out if it needs to go richer or leaner for cruise.

I'm starting with a 8.5, but also have a 6.5 on the shelf. I know yoy typically start at half way, so maybe i need to go a little higher at 9.5 b/c as of now it does have a slight stutter when flooring it.

 

[StarDiero75]

Yes, the outer most cylinders would be the leanest. Let the MPH help guide you. Give the engine what it wants. Within common sense tuning.

Ok I'll just check those plugs then when confirming the richness. I'll see how rich the main jets want to go for cruising. I didn't get much of a chance to test that out too much

 

[pmuller9]

So basically making my own jets for it? Is that on the jet side of the metering block, or the power valve side?

You can purchase the restrictor jets in different sizes just like any other jet.
You can also buy blank restrictors and drill you own size restrictor hole in the jets.

They go in the power valve passages just behind the power valve.
The QF restrictors use a 6-32 threaded hole.
Quick Fuel carbs come with restrictors so you can tune the power valve circuit separately.

How to modify your Holley Power Valve Circuit - Club Cobra

Here are some pictures on how to modify your Power Valve Channel Restriction (PVCR) circuit on your Holley carb. It is not very difficult and can make

www.clubcobra.com

 

[StarDiero75]

You can purchase the restrictor jets in different sizes just like any other jet.
You can also buy blank restrictors and drill you own size restrictor hole in the jets.

They go in the power valve passages just behind the power valve.
The QF restrictors use a 6-32 threaded hole.
Quick Fuel carbs come with restrictors so you can tune the power valve circuit separately.

How to modify your Holley Power Valve Circuit - Club Cobra

Here are some pictures on how to modify your Power Valve Channel Restriction (PVCR) circuit on your Holley carb. It is not very difficult and can make

www.clubcobra.com

This is very similar to the trick on the Autolite carbs. I haven't done it but I'll definitely try this one. If my WOT is 11, what size restrictor would you recommend to start with? I should probably measure the factory hole before I drill and tap so I know what size I'm starting with too.

 

[StarDiero75]

So the drag strip got rained out so I took it out for a drive and kept having lean issues at cruise and even reving up in neutral. At WOT is ran real fat at high 11s to 12.
So new development.... It seems after setting my idle mixture screws at idle to about 12.5-13 AFR, when I hold the gas in neutral to it leans out in the 1500-2000rpm range and richens up about 2500-3000 to more normal levels. So finally i try this, I set the idle to about 1800rpm then between my vacuum gauge, ear, and wideband, i adjust the screws to bring home a SOLID (its never been solid due to missing from going lean) reading of 22inches and an AFR of 13.7-14.2. Solid, runs very nicely at that. Actually the first time of having a carb on this and it being great. Problem now, at idle i have an AFR of like 11.1. So here's my questions:
1. On a holley, how long do the idle mixture screws actually control the fuel delivery for? B/c up till now, increasing jet size hasn't really richened my lower level RPM AFR. Which this would explain this discovery today.
2. To lean my idle now, do I need to drill and tap the metering block for the idle feed restrictors? Or do I actually need to richen the circuit so off idle is richer and thus lean out actual idle? My idle now is much more consistent and the vacuum holds much steadier at 19 inches

I'll be taking it out for a highway drive tomorrow so I'll find out what my cruise AFR is now. I know it has to be richer than it was lol. From there I'll tune the main jets to try to make it richer/leaner.

 

[bubba22349]

At 1800 RPM you are already way out of the Carbs Idle Circuit. For example on a stock Cam'ed street Six will easily Idle at 600 or even less RPM. So unless you have a really big performance cam installed would you ever need to raise the RPM a little higher and even then it would be something in the range of 700 to maybe as much 850 RPM with one of the biggest street-able Cam's, note that a strictly Race engine would be much different still.

To start your tuning you need to first check all the things that effect the Carbs Idle circuit the major one is the fuel level in the bowl so be sure that the float level is set right. Another area that effects the Idle Circuit is the amount of the Idle Transition slot that is uncovered at idle by the Carb's Throttle Blade this should range from 0.040 to a maximum of 0.060 inch, as close as you can get to that lower amount the better. Again depending on the engine build at the most the idle mixture screws would only be 1 1/2 to a max of 2 turns out. When the idle jetting is about right it will have a mixture that is a bit on the rich side.

If you really want to tune the idle and transition circuits for best results and fuel economy you need to Mod the carb's metering block for replaceable air bleeds, I would look into reducing these Air Bleed'sand installing the Power Valve screw in restricter s that PMuller9 told you about in his the above post before you start changing or drilling out the Idle and Main Jets. Best of luck on your Holley tuning

 

[wsa111]

So far I got idle to be about 12.8-13.0. Thats where its happiest. This was after letting it warm up in the garage, i haven't gotten to beat on it since, again, I'll play more with it tomorrow. When I cruised with the 63s it was about 15.5 so I'm hoping the 64s will put me a little closer to 15

Thats what I was afraid of hearing . So basically making my own jets for it? Is that on the jet side of the metering block, or the power valve side?

Under the power valve. You need to measure what you have. You need to get some 6-32 brass set screws & install a screw in jet smaller than what you have.

 

[StarDiero75]

So i went ahead and took the carb off, reduced the main jets to 62s, turned the mixture screws out 1.5 turns, and set the idle with just a hair of the transfer slot showing and the idle was super high, like 1800. So I had to back off the timing. I finally had to back off on the idle a hair and got the idle down to 1100 ish. I'm about to disconnect the PCV valve and see what that does. Not quite sure what happening, unless this means my vacuum leak is still there....

 

[StarDiero75]

Well i finally decided to try this trick, i leaned out the mixture pretty good and started spraying brake cleaner arpund the base, apparently there is still a leak. I finally take the carb off again (i thought it looked funny earlier but was doubting myself) and it's definitely leaking. I'm thinking over about JB welding my 1" spacer plate to the bottom plate (since the bottom is already JB welded to the head). This way I only have 1 gasket to worry about. Then i can look into getting a real thick gasket for the upper one. Not sure why I can never really get rid of my leaks....

 

[frozenrabbit]

I'd hand true the mating surfaces. Good flat wide piece of bar stock, with 400 grit.

 

[StarDiero75]

So I lapped the spacer, then copper coated the flange gaskets with 3 coats. The spacer had no rock at all on the carb or adapter plate to the head. Set the transfer slot at .030" and mixture screws at 1.5 turns. Fired her up and it ran great..... but after the choke came off the idle doesn't change from 1800. Finally backed off on the idle screw and got it down to about 750. Played with the mixture screws. About 12.3 AFR and 0.75 turns out on both..... whats happening here? Why can't i get near where I'm supposed to be? Is there too much fuel in the idle circuit causing the idle to be too high? With the .030" transfer slot exposed, mixture screws at 1.5 turns out, and idle at 1800rpm, my AFR was 12.5. I don't know if this helps any.

 

[bubba22349]

What is the Vacuum Reading your getting and is it a steady reading?

 

[bubba22349]

All right so assuming that the Float Level has first been correctly set the next step is to try and do some more fine tuning to your above mixture screw setting. From your current above setting you should now try adjusting one side's mixture screw by turning it in clockwise (this Leans it) but only about an 1/8th of a turn watch what your Vacuum Gauge reading does. Now does the Vacuum Gauge reading or the engine's RPM increase? If the Vacuum goes up then next try adjusting the other sides mixture screw in 1/8 turn and again watch the Vacuum Gauge reading.

If after this first adjustment of that first idle mixture screw the engine vacuum dropped, then return to the base setting and then turn the mixture screw out an 1/8th turn what did the Vacuum reading do? Otherwise if Vacuum reading is going up then go back to the first mixture screw and do another 1/8 turn and so on doing these small adjustments to the mixture screws always watching the Vacuum Gauge readings. When the Vacuum Reading starts dropping go back to the highest Vacuum reading, this is when you are really close to your final Mixture Setting, so take your time here. The goal is to get to the highest Idle Vacuum Gauge reading you can! If after these settings if the idle RPM rises above your starting 750 RPM then reset the Curb Idle RPM again back to 750. This will then more than likely lower the Idle Vacuum reading some but that is normal. I usually go through this a couple or more times to see if there's any more left in it to fine tune. If it doesn't get any better on the AFR than the Idle jetting is to rich and its time to start Modding the Metering Block. Good luck.

 

[wsa111]

So I lapped the spacer, then copper coated the flange gaskets with 3 coats. The spacer had no rock at all on the carb or adapter plate to the head. Set the transfer slot at .030" and mixture screws at 1.5 turns. Fired her up and it ran great..... but after the choke came off the idle doesn't change from 1800. Finally backed off on the idle screw and got it down to about 750. Played with the mixture screws. About 12.3 AFR and 0.75 turns out on both..... whats happening here? Why can't i get near where I'm supposed to be? Is there too much fuel in the idle circuit causing the idle to be too high? With the .030" transfer slot exposed, mixture screws at 1.5 turns out, and idle at 1800rpm, my AFR was 12.5. I don't know if this helps any.

Set your idle AFR to close to 13-1.
If your A/F is still rich at part throttle, the idle jet in the metering block may be too large. Most of the time this is a fixed diameter. The only way to make it small is a screw in orifice .003" smaller.
But this operation should be done by a professional.
The best test is drive at a very low speed with your wideband to check the slightly off idle mixture, most of the Holleys are calibrated for a larger engine thats the cause of your condition.