Throttle plate hole

[Chryco Psycho]

picture for @71-440
you can see the hole ion the plate also #1 is the idle transfer slot , this should be partially covered at idle not fully exposed

[71-440]

Thanks Neil!

[GY3R/T]

 What was the question ?   ( i was wondering about the hole in the throttle plate )

[Strawdawg]

The question is, "What can I do to obtain my desired idle speed and maintain the function of the Idle adjustment needles?"

Google, or look in your Holley book, for detailed info

[71-440]

The question is, "What can I do to obtain my desired idle speed and maintain the function of the Idle adjustment needles?"

Google, or look in your Holley book, for detailed info

When I spoke with Neil today we discussed the problem I am having with the idle fuel adjustment screws and what I can do short of
a new carb.

[GY3R/T]

The question is, "What can I do to obtain my desired idle speed and maintain the function of the Idle adjustment needles?"

Google, or look in your Holley book, for detailed info

When I spoke with Neil today we discussed the problem I am having with the idle fuel adjustment screws and what I can do short of
a new carb.
                          Ok. But what is the hole in the throttle plate for?   Thanks.

[Brads70]

The question is, "What can I do to obtain my desired idle speed and maintain the function of the Idle adjustment needles?"

Google, or look in your Holley book, for detailed info

When I spoke with Neil today we discussed the problem I am having with the idle fuel adjustment screws and what I can do short of
a new carb.
                          Ok. But what is the hole in the throttle plate for?   Thanks.

Lets in air so it will idle on engines producing low vacuum

[Chryco Psycho]

Exactly Steve , Thanks 

the problem with low vacuum engines is you have to open the throttle a lot to keep the engine running , in some cases you have to open it so much that the idle circuit no longer works & you end up idling at 1500 rpm off the main jets , by drilling  a hole you can get enough air into the engine without uncovering the idle transfer slots & usually create a decent idle around 850-900 rpm & the idle slots still work .

[Strawdawg]

I actually had answered in more detail but I hit something by accident and it all disappeared.  LOL

[Chryco Psycho]

It is all good !
Great to see you here too 

[Strawdawg]

I'm glad to still be able to be seen   Usually, when I read the new posts, a bunch of people have already replied so I don't add another 2 cents 

I have been playing with Holleys on and off since the '60's and, to me, they are the most logical carbs out there.  With a couple fo the better books, they are really easy to understand and work on.

[Chryco Psycho]

I agree although the Proforms are more adjustable for a lower price .
we are getting into tuning season so hopefully there will be a lot more posts like this to get our teeth into !! 

[Strawdawg]

yes, I should have said Holley style...

[Priesty]

I agree although the Proforms are more adjustable for a lower price .
we are getting into tuning season so hopefully there will be a lot more posts like this to get our teeth into !! 

Sounds like an invitation, so here goes.
Have a SB360 with mild 340 like cam. Recently swapped out the 600 edelbrock for a brand new 670 Proform, vac sec, 4 corner idle. Straight out of the box I could not screw the idle speed screw below 1400rpm, it ran out of adjustment at that idle speed. Ok, I thought, I'll adjust the idle mixture screws & then reset idle speed. Ended up with all 4 corners about 1 1/4 turns out but idle at 1700rpm, no good. Grabbed trusty vac gauge & reset mixtures to highest vac reading ~17-19hg, still cannot turn idle down below 1600. Finally pulled carb off & checked transition slot in 2ndary barrels & was correct (square shape ~.025" showing). Replaced carb & tried again, only way to get idle below 1000rpm was to uncover more transition slot which then results in only front 2 idle mixture screws having any (minimal) effect, & richening mix until black smoke stinging my eyes. Read up on internet about power valve symptoms, haha I thought I had it solved, but $25 later no different. As it runs now, it will idle at around 850 rpm, light acceleration from idle flutters & dies without more acceleration & then at speed a giant bog on W.o.t before it opens up & takes off. This thing is doing my head in I'm ready to throw it in the bin & go back to the eddy, although that had a sloppy primary shaft, it ran reasonably well & would idle right down to 550-700rpm no problem. Timing is set at 14* initial, not sure on max,36 maybe ? with vac can disconnected (plugged). Plugs are black, black, black all the way around. One thing I did note on carb arrival it was missing a base gskt & the proform decals on the fuel bowls say "650" not 670 as per the box, maybe a shop return that someone had played around with ? It's a bit hard to return this stuff when you've gotta ship it back across the pacific at own cost. That's where I'm at, anyone have a magic bullet ? Seriously appreciate any input that might help.

[Strawdawg]

Normally, when one refuses to idle down, I think of a large air leak.  It could be between the base and the body, or the metering blocks are not sealing to the body due to loose bowl bolts, bad gaskets, or warpage from over tightening.  And, the simplest of all, the manifold vacuum port  is not capped off when the vacuum advance is disconnected   Some insist on capping the wrong end of the tube....

In your case, it almost sounds like the idle circuits are not supplying any fuel and you are having to open the blades and run it off the main circuit.  I am wondering if one of the passages was not drilled all the way thru or one of the idle fuel tubes has some debris in it?  You may try blowing some carb cleaner thru the various passages and see if it comes out on the other side.

Something seems contradictory in your description but I have learned that sometimes things are contradictory and it makes troubleshooting even more fun.

I would not be surprised if you got a returned carb altho they normally should smell like gas when you get one...