Metering block , Missing restrictors

[6cyl]

It seems my holley metering block is missing some restrictors . I would like to have put a pcture up but the file was to large . So i'll explane best I can.
Each side of the power valve there is a hole , well it's actually two holes ,one of them I think connects to PV Restritors . The other one 'I think' is the low speed jet or something like that, This is the one where It would normaly have a restrictor but there is none , on both front and rear metering blocks ! why is this so .
The carb is an AED 650 HO that I puchased new . 60 MPH cruise @ 3400RPM is way rich 12.0 AFR.

[jmarkaudio]

The two underneath the PV are your PVCR's, the power valve channel restrictors. They only pass fuel when the engine vacuum drops enough to open the power valve. With a power valve losed not likely you issue. The others are your idle feed restrictions. They supply fuel to the idle and transition circuits. Prior to the start of the mains at low cruising RPM they will cause an over rich condition. Sounds like someone took them out before selling you the carb if used, or it was intended to be for methanol. I'd try about .032 in those, and for the PVCR's anywhere from .059 to .080 will work to start.

[Shaker455]

The metering blocks may have emulsion tubes inside and there would be no need for the idle feed restriction in the normal spot.

If you look at the outside top of the blocks the main well plugs will have caps flush with the top.

Also, the restriction may be in the other high up location so take a close look at the blocks again.

[jmarkaudio]

The metering blocks may have emulsion tubes inside and there would be no need for the idle feed restriction in the normal spot.

If you look at the outside top of the blocks the main well plugs will have caps flush with the top.

Also, the restriction may be in the other high up location so take a close look at the blocks again.

The restriction can be either at the bottom of the mainwell below the emulsion channel or up top next to the mainwell exit. However don't confuse an emulsion tube with an idle feed tube, they both are placed in the mainwell but serve two entirely different purposes. An idle feed tube is primarily used in the mainwell of a 3 circuit Dominator, on the early ones the tube is pinched at the end and drilled a set amount to be the restriction. Later ones use an open hole and restrict it in the metering block at the top like some of the later 2 circuit blocks.an emulsion tube provides air from the main air bleed to set the fuel curve, sometimes in addition to the emulsion well. It has no bearing on idle fuel.

[6cyl]

When I ordered this carb from AED , I was clear with vehicle specs and usage , Drag racing & street use , on gasoline fuel . Maybe they leaned more towards the Drag use than the street .
The 650 HO is a fairly basic carburettor but I ordered it with a few extras as follows , removable PVRC
'' idle restictors
" idle bleeds
On the spec sheet that came with the Carb I noticed next to the headings 'interm restriction & interim air bleed , it reads N/A .
Is this the restrictor that I think is missing ,
I,m going to send an email to AED to see what thay say.
Thanks for help so far I still have a lot to learn about carburettors.

[jmarkaudio]

That would be the intermediate air bleed and restrictor, a 650 does not have an intermediate circuit. They are used on a 3 circuit Dominator.

As far as the idle feed, it can be at either position in the picture, and the other will be left open. The original Holley carbs were located at the bottom, later Holley and aftermarket blocks come in the upper position. I prefer the lower, at low metering signals (race engine with a low vacuum cam) fuel delivery is more stable and consistent when the metering jet is in a submerged position.

[6cyl]

Thanks for the picture and explanation Mark, mine has removable idle restrictors where the top arrows point in your picture ,and is open at the lower arrows .
What I have in the Carb at the moment is.
.031 Idle restictors front and back
.081 Idle air bleeds front and back
.063 PVCR's , 7.5 PV
Main jets 62 front , 73 rear , mixture screws 1 1/8 turns out all round , throttle blades adjusted so there is basicly a square of the transition slot visable under the throttle blades.
Idle vacuum @ 1000 rpm in neutral is 7.5 - 8 with 23' timing , total timing 28' all in by 1600rpm , no vac advance .
As i mentioned earlier the hwy cruise is too rich , 60 mph @ 3400 rpm 19 - 20 in hg vacuum im getting 12.0 AFR's , very slight increase of throttle it will go leaner 13 14 15 afr's
a slight lift of the throttle it goes richer 11's 10's .
A little about my combo , It's an inline six banger, Australian 265 cu.in Chrysler Iron block & cyl head , 10.9:1 comp ,252 / 257 @ .050 , 4.11 gears 4800 convertor , vehicle weight with driver 3320 lbs , the 1/4 mph and vehicle weight works out to around 320 hp.
I've given this information in the hope that you or someone might see if theres anything that i've done wrong to cause this rich cruise condition .
Thanks Andrew.

[jmarkaudio]

One thing you can try is change the location of the idle feed restrictor, it can make the idle and transition fuel delivery more stable. It's interesting that it is rich until you put a light load on it, where does it cruise at at lower RPM's, 1800-2400 range before the mains come in?

[6cyl]

Tried it in those ranges got 1800rpm - 12 in Hg - 12.8 afr , 2000rpm - 12.5 in Hg - 12.8afr , 2400rpm - 13 in Hg - 13.2afr .
These aren't dead accurate because its so difficult to maintane a constant RPM or more important a constant vacuum reading . My front main jets are a little on the small side at the moment which would explane the the leaning off that I mentioned earlier ( as the throttle is opened further ).
I Will need to buy a 6-32 tap ( I think ) to relocate those idle restictors , In the mean time I might try smaller .070 IAB's and see what happens.

[jmarkaudio]

Try a smaller idle feed or larger idle air bleed, a smaller idle bleed will make it richer.

[6cyl]

Thats something I actually do know , I just wanted to try it to see at what point there was a change and how much . Got a 6-32 tap today so i'll move the idle jets into the lower position and plug the originals before I try anything else.

[jmarkaudio]

You don't plug the others, take the restrictions out and leave it open. They are both part of the idle circuit passage, the only difference is where the restriction is placed. Early research in carburetor design found that metering fuel through a submerged restriction was more stable and consistent, especially when the signal drawing it is low like in a performance engine with a larger cam/low manifold vacuum.

[6cyl]

Ok I tried out the idle feed re-location as you described , Not any notacable change in the problem areas . I did notice the Afr's were more steady throuought the cruise range , I would have to convert it back the other way to be sure I was not suffering the placebo effect.
It's mostly in the 13 - 18 in Hg vacuum range where it's the richest , and anything I do to the idle circut to lean it off in that area , just ruins the idle quality .

[jmarkaudio]

Not sure why you would have an issue on a 4150 but you can try another route. On Dominators it is typical to have too much t-slot area. The fix is to use t-slot restrictors. The picture shows the position, find the appropriate size to thread the hole and use brass set screws. Start at .050 and go up or down from there.

[jmarkaudio]

One other thing, for testing purposes plug the power valve and see how it responds to cruise and small throttle changes. No WOT romps while testing this, it will leave you lean. See how the primary jet by itself affects it by making changes.