Secondary transfer slot idle setting

[rdorman]

I have read over and over that the transfer slot on the primary side of a Holley should be exposed .040 to .060 at idle, but what about the secondary transfer slots? Exposed? If so, how much? Getting the front slots uncovered the correct amount had very gratifying results but in order to do so I had to uncover the rear transfer slots. Thinking perhaps I need to shut them back down and just drill the front plates.

Rick

[Mr.Fixit]

If it has four corner idle screws, do the fronts and rears the same.

[rdorman]

There is Fixit again! It only has two corner idle. So what should I do in this case?
Thanks
Rick

[BB427]

Rick,

How is the car acting? If is it rich at idle and wants to load up.
This could be a result of an insufficient signal to the front idle slot. To fix it, open the secondary throttle blades slightly. This allows more air into the engine at idle and allows you to close the primary throttle blades. This also reduces the signal to the idle transfer slot and makes the idle mixture screws more sensitive to adjustment. If you only have two corner idle adjustment you need the primarys to be sensative to adjustments.

Brent

[rdorman]

Actually it is acting fine. The question is simply so I know how much ideally of the secondary transfer slots should be exposed.
Thanks
Rick

[auto10x]

If it ain't broke don't fix it.
auto10x
Bill

[rdorman]

So it appears as though I am not the only one that does not know the answer!

Rick

[Mike Simard]

Rick, how many of us have a carb that is properly sized and could follow a general transfer slot size rule? I've found that transfer slots in general like to be exposed a very small amount, just enough to keep the circuit active at idle so that it immediatly flows when the throttle opens. Most motors like ours have a tendancy for off idle stumble unless idle were too rich and would usually want a stronger transfer circuit anyway. If the slot were too far exposed, it wouldn't have much to add to the transfer. I set my primary transfer slot at their ideal setting and then adjust the idle with the secondary butterflys, it's just luck that they come out with similar exposure to the primarys. Of course none of this matters for anyone else because my carb is horribly oversized anyway ;-)

[rdorman]

So the answer is, set them the same/similar........... if you can? I was wondering if the secondaries need to exposed at all but .......

Thanks
Rick

[Hotfingrs]

The rule on transfer slots is open the same as the width of the slot. You should see a square opening when they are set right. Any more and you have problems elsewhere.

[Jack21]

When setting the idle on a Holley, if the primary idle transfer slot is open too far resulting in off-idle stumble, and it seems like drilling holes in the primary butterflies is next; try this.

I replaced the secondary butterfly adjustment screw with an allen wrench setscrew. This allowed minute adjustments with the carb on the car, and the engine running. This allowed me to adjust the idle mixture with the primaries (correct slot opening), and the idle speed by opening the secondaries.

I must admit that I became frustrated with this, and in desparation, replaced the Holley with a BG Speed Demon. What an improvement! The engine even sounded better. And my eyes weren't burning anymore. I'll never put another Holley on a Hi Po engine again.

[Michael C Henry]

I have dual fours 1860.vacum secondaries, no metering block on the secondaries.I installed the allen socket set screw 10x32 in the secondary throttle plate stop.It fit too freely.I dropped some super glue into the hole and let it dry now it has some drag so it won't rattel loose.The original screw was wedged open at the screw drive slot providing drag.Now adjusting the secondaries as a starting point, expose the slot as much as it is wide? correct?Problem is it is over fueling to the point twenty minutes or street driving fouls the plugs.

[Hotfingrs]

What vacuum do you have at idle and what PV's are you using?

[Michael C Henry]

I can carry 8.I tried 8.5 too high.Had to tow the car home .I have it covered with a 3.5g but had other issues .A twenty minute run out to Lakewood. Plugs fouling but were able to drive it hme .That is why I'm cleaning everything now.I now have a selection of pv's from 2.5 to 8.5 in pairs.

[Rick Parker]

Hotfingers is right on! There should be enough of the slot exposed to create a "small square" visable with the carb upside down. This way there is a small amount of emulsification taking place in the metering block already and fuel is already being mixed, although in a very small volume. This set things in motion so when the secondaries are opened they can come online immediately with a minimum of hesitation, the balance of the manifold depression being overcome by adjusting the accelerator pumps, the squirters sizing and their timed delivery. It's all a compromise at best.

Rick

[Michael C Henry]

Found a wrong gasket on one carb .between mainbody and basepate.outer edges of both sides came inward at midel exposing a curved slot on either side that connected primaries and secondaries.I bought a whole trick kit to get that gasket.One of four baseplate to mainbody gaskets in the kit .By the way what is the original PV that comes with a kit rated at?I got so involved with that gasket that I foregot the gasket between the primary metering block and mainbody on the rear carb , the gas came right out.

[Hotfingrs]

Holley usually puts 6.5 as standard...you have to adjust from there. I generally run 2.5 or 3.5

[Michael C Henry]

I figure that 3.5g pv's I have installed now will be closed earlier in the prosces.I'll get everything under control and get a good baseline for vacum. I figure there is power to be gained by the pv's staying open a little longer. There is a 6 and a 5 stamped aruond the brass disk 90° apart.Very small .I had a problem reading it even with my glasses and good lite.I bought a selection ,in pairs,of power valves ranging from 2.5g to 8.5g from Quick Fuel Technology. I was sure that I could support a 5.5g pv's.I may be able to get 6.5g's pv to close at idle-cruise.the better the timing and the less fouled the plugs the better the vacum.That means that if I get too high a"g" Pv's if it goes sour ,It wiil snowball quickly.

[Hotfingrs]

You don't want to big a PV...Stop and go driving will open the PV because vacuum drops at take off, even if you're not at WOT, so you're just dumping raw fuel into the engiine and not burning it. Even with a 2.5 PV at WOT you'll be well past 150 mph before it even thinks about closing, if everything else is sized right.

[Michael C Henry]

Now a question .On a dual four setup 600cfm 1860 holleys.They came to me with light blue accelerater pump cams and 30 cc pumps.They stroked out real quickily in the first part of the throttle movement leaving nowhere to go in the rest of the throttle travel.The 50 cc pumps have a slightly smaller disk in it's diaphram (to make room for the pleats) than the 30 cc diaphram . The 50 cc pump kit came with a brown cam #664 it appears to be identical profile to #336 but with a wider ramp for the lever to rub on.It is a gradual lift untill full throttle.so any farther application would have a squirt.It appears to be identical to the Light blue cam and 30 cc pump but it keeps squirting untill full throttle.I haven't changed squirters. Any experience out there?