383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

[yellow rose]

Buying parts for it and drilling holes in it something he's committed to this questionable carburetor. He has one that works fine. you can just add $100 to what he was going to spend on this one and probably could buy a brand new one...

I don't follow your math. Butterflies are 4 bucks each. That's 8 dollars where I went to school. That's a coffee today. So what hundred dollars is he going to spend that's extra?

If he's going to do anything he should just order a Pro Form carb but he will need to tune that too. 8 dollars is cheap to try something. And it ain't hard.

 

[j par]

I don't follow your math. Butterflies are 4 bucks each. That's 8 dollars where I went to school. That's a coffee today. So what hundred dollars is he going to spend that's extra?

If he's going to do anything he should just order a Pro Form carb but he will need to tune that too. 8 dollars is cheap to try something. And it ain't hard.

listen very closely this time. He has not paid for this carburetor whatsoever. It is not working well for him seemingly no matter what he's doing. He was going to pay x amount for this carburetor. If he took x amount plus $100 he could probably buy a brand new carburetor. You also suggested he started drilling holes in it which he is already said would just make the problem probably worse. He can get out now and have no problem whatsoever.

 

[j par]

Remember as my first comment I posted I'm not opposed to a holly whatsoever and this could be a great test page that it is working great with a Holly just one that's not going to causing headaches out of the gate just for a simple tune like any carburetor will need to be tuned to its motor. Not just have headaches out of the gate.

 

[318willrun]

Remember as my first comment I posted I'm not opposed to a holly whatsoever and this could be a great test page that it is working great with a Holly just one that's not going to causing headaches out of the gate just for a simple tune like any carburetor will need to be tuned to its motor. Not just have headaches out of the gate.

Difference between a 600 eddy and a 800 DP on this engine will be about 75 hp

 

[BrokenTool]

I'm not going to speculate but, your car should idle with that carburetor. i have a .030" over 383, big valve 906 heads, 509 292 cam bumped 4 degrees, 383 torker intake, MP distributor, MSD 6AL Box and at present Holley 750 in my Dart.
it started out with a edelbrock 750 and we will not get into what manufacture is better. WOT seemed flat, i picked up a Holley 850 and set it up factory jetting and put in 3.5 PVs since my vacuum at idle is 5.5hg. she runs a bit fat but..... the ol girl likes it very much, had to move shift points from 5600 to 6000 because it was still pulling.
with that being said, i am putting a wide band in and tuning the 850 to the engine. Oh by the way, no holes drilled throttle plates yet.

 

[318willrun]

I'm not going to speculate but, your car should idle with that carburetor. i have a .030" over 383, big valve 906 heads, 509 292 cam bumped 4 degrees, 383 torker intake, MP distributor, MSD 6AL Box and at present Holley 750 in my Dart.
it started out with a edelbrock 750 and we will not get into what manufacture is better. WOT seemed flat, i picked up a Holley 850 and set it up factory jetting and put in 3.5 PVs since my vacuum at idle is 5.5hg. she runs a bit fat but..... the ol girl likes it very much, had to move shift points from 5600 to 6000 because it was still pulling.
with that being said, i am putting a wide band in and tuning the 850 to the engine. Oh by the way, no holes drilled throttle plates yet.

Boy does this support post 54 …. LOL

 

[j par]

Difference between a 600 eddy and a 800 DP on this engine will be about 75 hp

Agreed... Or your agreeing with me...

 

[yellow rose]

View attachment 1715331811 listen very closely this time. He has not paid for this carburetor whatsoever. It is not working well for him seemingly no matter what he's doing. He was going to pay x amount for this carburetor. If he took x amount plus $100 he could probably buy a brand new carburetor. You also suggested he started drilling holes in it which he is already said would just make the problem probably worse. He can get out now and have no problem whatsoever.

Ok. I said spend 8 dollars on two butterflies and drill them out. I realize it's not his carb yet. It's still just 8 bucks and some drill bits.

If I was home I'd send him two for free. But I ain't driving 3.5 hours one way for that. Maybe someone else here has some (I probably have 20 or so of them) and they can hook him up.

You math doesn't work. If he is going to spend any more money that what this carb is going to cost, plus two butterflies, he's better off buying something with removable brass. Used that's about 400-450 bucks.

 

[yellow rose]

I'm not going to speculate but, your car should idle with that carburetor. i have a .030" over 383, big valve 906 heads, 509 292 cam bumped 4 degrees, 383 torker intake, MP distributor, MSD 6AL Box and at present Holley 750 in my Dart.
it started out with a edelbrock 750 and we will not get into what manufacture is better. WOT seemed flat, i picked up a Holley 850 and set it up factory jetting and put in 3.5 PVs since my vacuum at idle is 5.5hg. she runs a bit fat but..... the ol girl likes it very much, had to move shift points from 5600 to 6000 because it was still pulling.
with that being said, i am putting a wide band in and tuning the 850 to the engine. Oh by the way, no holes drilled throttle plates yet.

Check your manifold vacuum at cruise and set the power valve opening from that, not idle. You'll be able to see with the O2 sensor that the power valve can be set to open much sooner. It doesn't affect idle.

If you do that, you can use less squirter because it will get on the enrichment curcuit sooner, like it should. Set your cruise A/F ratio with the main jet and set WOT with the power valve restricter channel and secondary main jet.

 

[340dartley]

Even if I do not keep this carburetor, I will be going to an 800 or 850 cfm carb. That was part of the plan since the build started.

 

[340dartley]

This is the carb number I took the picture the other day while I was going through it. The price of the carb, if I decide to keep it is $100.

 

[BrokenTool]

Check your manifold vacuum at cruise and set the power valve opening from that, not idle. You'll be able to see with the O2 sensor that the power valve can be set to open much sooner. It doesn't affect idle.

I'm quite you are correct in your application but..... this is the rule i used to set up my 850dp and it works very well.

The Truth About Power Valves Used with Holley Carburetors - Engine Builder Magazine
An accurate vacuum gauge, such as Holley P/N 26-501, should be used
when determining the correct power valve to use. A competition or race
engine which has a long duration high overlap camshaft will have low
manifold vacuum at idle speeds. If the vehicle has a manual
transmission, take the vacuum reading with the engine thoroughly warmed
up and at idle.
If the vehicle is equipped with an automatic transmission, take the
vacuum reading with the engine thoroughly warmed up and idling in gear.
In either case, the power valve selected should be 1/2 the intake
manifold vacuum reading taken. EXAMPLE: 13? Hg vacuum reading divided
by 2 = 6.5 power valve. If your reading divided by 2 lands on an even
number you should select the next lowest power valve. EXAMPLE: 8? Hg
vacuum reading divided by 2 = 4 power valve. Since there is no #4 power
valve you should use a 3.5.

 

[yellow rose]

I can tell you that is wrong. And has always been wrong. I just went on YouTube to try and find the video Mark Whitener made where he proves, with an A/F gauge hooked up that you can open the PV at idle and it makes ZERO difference. You can watch it on the A/F gauge. If you open the PV and the A/F ratio doesn't change it means power valve opening using idle vacuum is wrong. Unless the diaphragm is ruptured the PV won't make a difference at idle


You are only delaying the power enrichment circuit, which is really what the function of the power valve is. They should have called it the economizer valve, but that wouldn't have been as cool. But that's what it does. It only adds fuel for WOT.

If you can find that video it would help. I still can't believe guys are still doing this wrong.

 

[yellow rose]

BTW, I read the link and it's Holley still telling people to do it wrong. No wonder Holley fought like hell to keep people from making carbs based on that architecture. They are just that ignorant. And to admit they had it wrong now would be a black eye on them.

Think about this. The power valve adds fuel under load. If you are cruising at 15 inches and you use a 4.5 PV, look how long a delay you have to get the enrichment system going. You should be at least 8.5 and 10.5 would be better. That way, you aren't using accelerator pump shot to cover a hole in the fuel curve that is caused by late PV opening.

Yes, I'm saying the link is wrong. Holley is wrong.

 

[Mattax]

If you can find that video it would help. I still can't believe guys are still doing this wrong.

Sure you can.
There's more nonsense out there now than when I began, and you've been in this game longer than me.
The magazine writers just regurgitate what they are told. Very very few have even heard of Larew, Taylor or Obert. Never mind knowing what research information is in their books.

When that 'rule of thumb' works, its just dumb luck. At least the rule of thumb based on highway vacuum has some logic behind it.
The right way to know when an engine's part throttle load is such that it needs to go richer is by testing when the combustion changes. Since most of us don't have that sort of equipment, we have test in more practical ways. Anyway, getting way off topic and covered this in other threads.

 

[yellow rose]

This is the carb number I took the picture the other day while I was going through it. The price of the carb, if I decide to keep it is $100.

View attachment 1715331904

IIRC, that carb was made on the 41st day of 1998.

One more suggestion...Id spend the money for Superformance gaskets for that carb. They not only seal better, they last longer and can be reused many times.

100 bucks for that ain't bad. Mill the choke horn off (you can do it at home with a hacksaw and a file if you are careful) and it will help with airflow across the boosters. Especially when you run an air cleaner.

Then do the simple stuff. Make sure the main body is flat. They never are. Carefully draw file it until it's flat. Make damn sure you can put the metering block on the main body with the power valve installed and no gasket on the main body and make sure the power valve doesn't hit the boss in the power valve well. Seen it dozens of times and it will let fuel leak into the engine. You won't have an external leak either. And then the power valve gets blamed.

Make sure all the emulsion holes are open, and the air bleeds. Blow them out with compressed air. It doesn't take much to plug or partially plug an .028 hole.

Also, check the size of the idle feed restriction. It's probably too damn big. You can either buy brass from someone like BLP or pull the brass out that Holley used and carefully drill and tap the metering block for a brass set screw and make your own restricters. You may need to open up the idle air bleed a bit as well. .004 bigger is a good start. After that .002 is the next move.

That's all simple stuff you can do that is cheap and easy.

 

[j par]

Ok. I said spend 8 dollars on two butterflies and drill them out. I realize it's not his carb yet. It's still just 8 bucks and some drill bits.

If I was home I'd send him two for free. But I ain't driving 3.5 hours one way for that. Maybe someone else here has some (I probably have 20 or so of them) and they can hook him up.

You math doesn't work. If he is going to spend any more money that what this carb is going to cost, plus two butterflies, he's better off buying something with removable brass. Used that's about 400-450 bucks.

So a friend gives you a carburetor on the pretense that you're going to try it and you start buying parts for it and drilling holes in it and then decide it's no good and give it back? I reckon when he starts drilling he's pretty committed to making sure this thing's going to work perfectly for him. All I'm recommending just from experience is when something starts going wrong throwing money and internet ideas at it sometimes ain't the answer....

 

[Mattax]

This is the carb number I took the picture the other day while I was going through it. The price of the carb, if I decide to keep it is $100.

View attachment 1715331904

OK. If its not been molested or abused, its decent carb if your engine can use it.
https://documents.holley.com/techlibrary_carb_numerical_listing.pdf
Downleg boosters on all 4 bores?
There will be a learning curve, don't kid yourself. And there will be plenty of time and iterations on tuning. But if you want to do it, at least its not a wacky configuration from the get go.

Check each metering block. Make sure they match.
You probably don't have micro drills (yet). But look at each drilling and see that its not been messed with. Or post photos up and we can walk you through it and hopefully help you avoid a damaged unit.

 

[Mattax]

This is the carb number I took the picture the other day while I was going through it. The price of the carb, if I decide to keep it is $100.

View attachment 1715331904

If you're going to go with this carb, or any other Holley 4150 type, get yourself a cheap used copy of Urich and Fisher's Holley Carburetors and Manifolds. Some of it is marketing BS, but the fundementals of how the circuits work is invaluable. So is the explanation of transfer slots and drilling holes if need. Also their tips on road racing can be translated to street/general purpose tuning if you have your thinking cap on. The smaller Holley 4150 book by Urich covers the basics - so that's an alternative.

Trick kit is getting expensive but I like the fact they come with lots of gaskets large and small. Otherwise I buy the blue metering block and bowl gaskets as 10 packs. Buying in 2 packs and such will kill your wallet. A little WD40 or other similar kills the sticky and they work fine. Torque the bowl screws carefully. Earlier carbs have slot screws, later ones have hex heads. Harder to strip out the slotted ones.

 

[yellow rose]

So a friend gives you a carburetor on the pretense that you're going to try it and you start buying parts for it and drilling holes in it and then decide it's no good and give it back? I reckon when he starts drilling he's pretty committed to making sure this thing's going to work perfectly for him. All I'm recommending just from experience is when something starts going wrong throwing money and internet ideas at it sometimes ain't the answer....

How is getting two butterflies, drilling holes in them, and if it doesn't work, replacing the originals doing anything wrong? I didn't say to permanently modify a carb he doesn't own. How can you not grasp that? It's a simple modification that can be easily undone. For about 8 dollars at most.

You're trying to stir **** or you have no idea WTF you are talking about.

Either way, step out of the discussion as you have nothing to offer the OP.

 

[AJ/FormS]

When I ran the 292/292/108 in my 11.3Scr 367back in 2000; on my ancient circa 70s 750DP, I closed the secondaries up tight but not sticking, and drilled the blades . First 1/16, then 3/32, and so on until the idle speed was over 800 with the transfer exposure set to slightly taller than wide, and the idle-timing at 16*. Then I backed the idle speed down with the speed screw. This introduced a small tip-in hesitation, so I restored the TP exposure and took out 2 degrees timing. and off I went on the roadtest. That was the baseline tune. It didn't end there. It started there.
I think that engine idled at about 8" or a wee bit more, but I learned a lot about PVs with this engine. I found out too, that Holley was dead wrong about choosing a PV. I plugged the PV and road tested it to find out that the mains were good to about 10" of vacuum, and then the engine went lean. With no AFR gauge, how did I know? Well go out and try it; you wont need a gauge. So I installed several higher than 3.5/4.5 PVs and discovered that the 10.5 had the best roll-on characteristics, and allowed me to run less mainjet.... And you know how hard on gas that 292/108 can be. So all my other iterations (2 others,lol) since, have begun their tunes with a 10.5 PVs.
I think that 292 ended up with 1/8" holes(.125), which was too much. I chamfered the holes and dropped a solder plug into them; then moved over and downsized to 7/64 IIRC, which maths to .109... This was on a 367 SBM, true Zero-deck with flat-top KB 107s, .028 gaskets, and OOTB Eddies.
The solder plugs have never moved.
Make sure your PCV is hooked up and working; it is your firstline idle-air bypass. And I'll say it again, make sure you have no vacuum leaks. If you half-decent get it running with an un-discovered vacuum leak...... and later discover it, well then you get to start all over.This includes valves that don't seal.I know you said it runs fine on the Eddie carb, but who knows how that one is set up.
And I for one, would trade that no-Vcan D for one that does have it, and then I would fix that too short, too fast curve; 3000TC be derned. With aluminum heads, and tightQ, I bet you can get it to run on 87E10 like mine did. Without the tightQ it should still run on pump gas. I mean with a true measured 11.5Scr and the cam in at 104 for an Ica of 70*, your pressure is only predicted to be 180psi at 250ft elevation. Aluminum heads should handle that with ease on pumpgas;there are guys here on FABO claiming to run their stroker SBMs at about 200psi still on pumpgas.

Post 50 is on the money; you are just swapping rear air to the front or vice versa; You have to set the Transfer-slot exposure first....... then set the idle speed with bypass air and timing. If you open the secondaries and do not have a 4 corner idle, then the rear air will be dry, and it will run like crap.Ok maybe crap is too strong, but it sure won't take throttle properly.
If you do have 4-corner idle, then you need to put a little fuel into that rear air. If you put too much fuel/air in the back then the fronts won't respond properly.
IMO, the 292/292/108 cam is right on the borderline of needing a 4-corner idle, but with very little effort can be made to run on a standard carb. Just don't try to run it on a 600Vsec,1850, lol.( yeah I tried that with 3.55s and a clutch. I told you; that cam sucks gas like a fish sucks water,lol, and I was desperate).
I no longer use secondary cracking for idle air bypass, on a standard carb. Instead, I introduce air thru another external circuit, thru a pair of calibrated holes,delivering under the butterflies; then drill as may be required; works every time........ but you still have to establish transfer-slot exposure and the idle-timing first. And then you can use the speedscrew as a trimmer. If you change the idle-timing, well, back to square-one. And if the timing is unstable, fix that FIRST.
Happy HotRodding

Ya know what; try this; run the engine up to 1500rpm and stick your fingers down the carb and block off the boosters killing the mains. Repeat at 1800,2100,and 2400. When it starts to make a difference in base speed is when the mains have begun to flow. If it starts at 1500, something is not right. That cam vacuum-plateaued at about 2100 in my 367 IIRC, still on the transfers. Ima thinking a properly tuned 383 will go slightly lower to plateau; especially with your early all-in timing.

 

[318willrun]

Agreed... Or your agreeing with me...

I missed your post if you said that already...

 

[j par]

How is getting two butterflies, drilling holes in them, and if it doesn't work, replacing the originals doing anything wrong? I didn't say to permanently modify a carb he doesn't own. How can you not grasp that? It's a simple modification that can be easily undone. For about 8 dollars at most.

You're trying to stir **** or you have no idea WTF you are talking about.

Either way, step out of the discussion as you have nothing to offer the OP.

Carburetor experience is what I have to offer. Not a bunch of magazine name dropping. Look you can't fix everything every single time. Are you saying there's no way there could be some kind of internal unseen problem in this carburetor? The fact that it could be warped or something like that? These things are generally unlikely I mean you have dealt with enough carburetors to where there was one or two out of every few hundred that just whatever you did you couldn't get to run right. What is your magic unicorn wand work in a different way?

I got to laugh "Holly people" LOL I think either carb works well if it's in good condition. I personally like Edelbrock's cuz they seem less finicky.
now I thought I was pretty damn good at those 1406 s and have a couple myself. I've taken them down to nothing and put them back together with kits and have had great results. But this last 1406 that I had same problem, ran fine but wouldn't idle said the last person that I owned it. I went out bought a brand new rebuild kit and dipped in a vat of carburetor cleaner. Then cleaned every orifice out with spray carburetor cleaner. Then assembled it and it was shining like a brand new penny. Put it on my car and it ran fine like before but could not hold an idle. I sold it at the last swap meet for $60 with the receipt for the $50 rebuild kit and put it out of my life...

If you start "drilling holes" in this highly suspect carb you'll own it...
I suggest NOT...

...

Understand he's saying he has not paid for the carburetor and if he just takes it back he doesn't have to use it...

Remember as my first comment I posted I'm not opposed to a holly whatsoever and this could be a great test page that it is working great with a Holly just one that's not going to causing headaches out of the gate just for a simple tune like any carburetor will need to be tuned to its motor. Not just have headaches out of the gate.

Agreed... Or your agreeing with me...

I'm recording myself here so you can see I said I many occasions I'm not opposed to a holly. It can be a 1 in 500 carburetor that just no matter what you do has some kind of internal problem. kind of the reason his friend might have just said here give it a try. No strings attached. The gold telling people to start drilling and and find parts for a carburetor that isn't there's no matter how inexpensive it is. I just don't think it's good advice.
If the original poster is married to the idea of definitely having that carburetor at least get a good known running one or a new one and start turning it to his needs. Again that's just comes off the hills of the same exact problem I was having with a carburetor myself. Grant you it wasn't a holly but it was definitely a carburetor I know well.... I definitely agree was upgrading to a bigger carburetor. And of course it's no mystery that I do prefer Edelbrocks. and yes recently one time out of all of the carburetors of the same exact caliber I've tuned and rebuilt I had one finally that was just not worth the trouble.. you can't win them all...

I missed your post if you said that already...

 

[j par]

I don't follow your math. Butterflies are 4 bucks each. That's 8 dollars where I went to school. That's a coffee today. So what hundred dollars is he going to spend that's extra?

If he's going to do anything he should just order a Pro Form carb but he will need to tune that too. 8 dollars is cheap to try something. And it ain't hard.

and of course I agree with all that it's cheap and all that but now tearing this carburetor apart and putting it back together and also I agree that any carburetor he gets he's going to have to tune to his car. If you're getting a free chance at it that's great but now you're throwing good money after bad and another gamble what if you're wrong and that's not the problem? Then he's out $8 and a bunch of his time when he could just start or something better. Honest to goodness I hope he just hits The Sweet Spot on this carb and all is well...

 

[AJ/FormS]

Here's another tip;
Run the car . Then stop it, and drain the front bowl,without disturbing the M-block; then remove the PV.
If there is fuel in the cavity behind it, then throw the PV away, she's a leaker.