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

[318willrun]

i'm recording myself here so you can see I said I many occasions I'm not opposed to a holly...

My statement had nothing to do with Eddy vs Holley. My statement was strictly due to the fact that a 383 in the OP's form would simply like a lot more cfm's

 

[j par]

I think the op gets what I'm saying.
I'm not trying to tell anybody how to tune a Holley.

My statement had nothing to do with Eddy vs Holley. My statement was strictly due to the fact that a 383 in the OP's form would simply like a lot more cfm's

And mine as well. I agree it needs more CFM. He agrees it needs more CFM. And both of us agree it doesn't matter what carburetor it comes from. Both of us also may agree or not agree but this one is starting to giving him too much trouble for what it's worth? I certainly don't know holley's like I do Edelbrock and I'm definitely not trying to give advice on how to tune it. Nor am I trying to act like I know all about them because I read a bunch of articles.. which I know you're not trying to do because you have a lot of experience with them. I guess I'm trying to point out that if you're going to give up on a carburetor this is the perfect one to do so that you haven't putting any money into and just a little of your time. Not put good money after bad and a ton more time and keep your fingers crossed...
And if yr wants to give a money back guarantee that if he follows everything he says that this car will run perfect for him then who's going to believe that? saying to stay out of this because I can't give any name-dropping magazine advice is ludacris.. I think I'm giving great advice get out while the gettin's good...

 

[340dartley]

I appreciate everyone’s input. The point of going to this carb was not to start an Eddy vs Holley debate. I wanted to go to this carb because I need more cfm for my engine package. The 600 Eddy was just an old carb I had sitting on the shelf. I believe their is slightly more power potential with the Holley and finding an inexpensive carb in the 800 cfm range is easier. That being said the Carter AFB/AVS is less finicky. All that being said this carb was offered to me this weekend and price was right. If can make it work the. Great. Only thing I am giving up is my time and potentially a small amount of money money. I see lots of good advice here and some has to do with power and drivability. The car had no drivability issues and good power with the 600. Right now the goal is to have the car idle at a normal speed and be able to control the idle mixture with the screws. After that I will address any drivability issues that may or may not arise. I have some good things to try mentioned by many of you. I will see what I can do and report back. Cheers to all.

 

[Mattax]

FWIW here's how I see it.
There wayyyy tooo many variables in the testing so far to begin to guess whether this carb has inherent problems.
A bigger carb should make more power and torque at WOT starting around 2500 to 3000 rpm and be most noticeble in the 1/4 mile.
But bigger primary throttles and venturis are more sensitive and difficult to tune for idle and low throttle than smaller throttles.
This difference alone, may or may not explain why the 600 Eddy is more streetable out of the box than the 4780.
It certainly plays a role in making the 4780 more difficult starting point.

So the question for you (340dartly) comes down to how committed you are to a steep and somewhat long tuning adventure.
We've done our best to provide some idea of what work, tools, time, knowledge and discipline will be involved.
If not, then a carb with smaller primaries is going to be easier.

 

[fishmens67]

IT should be a debate eddy, carter vs holley on your combo. you say the eddy had no drivability issues. I say bull. I have ran pretty much the same combo as yours starting in the late 70's up until a few years ago. upgraded to 451.
my experience tells me with the purple 292, unless you have a lose convertor and at least 410 gears it is a slug when you mash the throttle . The 850 dp gives the combo the added pump shot it needs to get moving.
my combo with ported 915's 2.14 intake 1.74 exhaust, 557 purple, street dominator with 750dp. 4500 stall and 4.56 gears would et 11.30's at a buck 20 consistently in my daily driver 67 fastback.
I never got out of the 12's with a carter and 292 purple.
stick with holley, it took me over 20 years to figure that out. I was a diehard carter fan.

 

[340dartley]

FWIW here's how I see it.
There wayyyy tooo many variables in the testing so far to begin to guess whether this carb has inherent problems.
A bigger carb should make more power and torque at WOT starting around 2500 to 3000 rpm and be most noticeble in the 1/4 mile.
But bigger primary throttles and venturis are more sensitive and difficult to tune for idle and low throttle than smaller throttles.
This difference alone, may or may not explain why the 600 Eddy is more streetable out of the box than the 4180.
It certainly plays a role in making the 4180 more difficult starting point.

So the question for you (340dartly) comes down to how committed you are to a steep and somewhat long tuning adventure.
We've done our best to provide some idea of what work, tools, time, knowledge and discipline will be involved.
If not, then a carb with smaller primaries is going to be easier.

I have no problem tuning a carburetor. I have no problem learning what I don’t know. I am still not sure if there is something wrong with this carburetor that has nothing to do with the normal idiosyncrasies of this model of carb.

 

[340dartley]

IT should be a debate eddy, carter vs holley on your combo. you say the eddy had no drivability issues. I say bull. I have ran pretty much the same combo as yours starting in the late 70's up until a few years ago. upgraded to 451.
my experience tells me with the purple 292, unless you have a lose convertor and at least 410 gears it is a slug when you mash the throttle . The 850 dp gives the combo the added pump shot it needs to get moving.
my combo with ported 915's 2.14 intake 1.74 exhaust, 557 purple, street dominator with 750dp. 4500 stall and 4.56 gears would et 11.30's at a buck 20 consistently in my daily driver 67 fastback.
I never got out of the 12's with a carter and 292 purple.
stick with holley, it took me over 20 years to figure that out. I was a diehard carter fan.

I meant MY Eddy on this engine has no drivability problems. It starts on first crank. Has a nice lope from the cam. No hesitation weather I stand on the gas or slowly apply throttle. Runs smooth up until I shift gears. I was not saying all The Eddys have no drivability problems. I also was not talking about weather the car might be able to pick up a tenth on its 60 foot time. So yes on my car it has no drivability issues. Oh and as mentioned earlier, I do have a loose converter and 3.90 gears. I only planned on the larger carburetor because my combination is giving up a ton of potential power because of the small carb. I am not to the drivability part yet. Just trying to get it to idle and control the mixture with the mixture screws.

 

[fishmens67]

have you tried a 1" spacer ?

 

[j par]

IT should be a debate eddy, carter vs holley on your combo. you say the eddy had no drivability issues. I say bull. I have ran pretty much the same combo as yours starting in the late 70's up until a few years ago. upgraded to 451.
my experience tells me with the purple 292, unless you have a lose convertor and at least 410 gears it is a slug when you mash the throttle . The 850 dp gives the combo the added pump shot it needs to get moving.
my combo with ported 915's 2.14 intake 1.74 exhaust, 557 purple, street dominator with 750dp. 4500 stall and 4.56 gears would et 11.30's at a buck 20 consistently in my daily driver 67 fastback.
I never got out of the 12's with a carter and 292 purple.
stick with holley, it took me over 20 years to figure that out. I was a diehard carter fan.

I think a lot of stuff gets lost in this writing stuff out on the internet instead of straight talkin on the phone or something like that or in person. I don't think myself being a Edelbrock fan and 318willrun being a Holley fan we're in any odds with each other whatsoever over the brand. Both us and 340dartley do agree that more CFM is what he needs. And I agree on a holley for an all-out effor. I don't build my car for all out effort anymore it's more Street and strip. Now while I don't suggest this to 340dartley mostly because I'm not trying to cyber spend his money, but as far as I'm concerned I'm sure I get plenty of pump squirt off of two Edelbrock carburetors especially them linked one to one..
I sure appreciate him doing all these adjustments and sharing all the results with us... Not suggesting staying with the 600 CFM carburetor as we all know there's horsepower being left on the table big time. But to put it back on there and drive it for a while longer until the correct carburetor can be afforded wouldn't hurt and just like he's doing in the meantime see if he can't make something happen with this one. Just hoping he doesn't beat himself to death with a hopeless carburetor. And I'm speaking of this individual carburetor itself not all Holley carburetors not all carburetors identical to his but just the specific one. Sometimes it happens and you get a bum carburetor. And also not doing anything that's going to get him locked into it by Taking Chances...

 

[j par]

have you tried a 1" spacer ?

Almost positive that's one of the first things he said he tried....

 

[340dartley]

have you tried a 1" spacer ?

Yes. I put one on as I was at the parts store buying gaskets anyway and there was some intake clearance issues.

 

[fishmens67]

I'm just stating my experience dealing with single carter combo, unless you have strip kits and springs it is very hard to optimize/ drivability with a single plane on the street. I do not believe the combo is leaving much HP on the table with the 600.

 

[yellow rose]

I think the op gets what I'm saying.
I'm not trying to tell anybody how to tune a Holley.

And mine as well. I agree it needs more CFM. He agrees it needs more CFM. And both of us agree it doesn't matter what carburetor it comes from. Both of us also may agree or not agree but this one is starting to giving him too much trouble for what it's worth? I certainly don't know holley's like I do Edelbrock and I'm definitely not trying to give advice on how to tune it. Nor am I trying to act like I know all about them because I read a bunch of articles.. which I know you're not trying to do because you have a lot of experience with them. I guess I'm trying to point out that if you're going to give up on a carburetor this is the perfect one to do so that you haven't putting any money into and just a little of your time. Not put good money after bad and a ton more time and keep your fingers crossed...
And if yr wants to give a money back guarantee that if he follows everything he says that this car will run perfect for him then who's going to believe that? saying to stay out of this because I can't give any name-dropping magazine advice is ludacris.. I think I'm giving great advice get out while the gettin's good...

Your mouthy remarks about magazines is hilarious. And stupid.

I told the OP what I did based on years of doing this ****. Did you read what AJ posted? If you did, he said exactly what I said, except no way in hell am I typing that all out. Never. I'd rather give the OP my number and walk him through it on the phone. It's quicker.

His issue isn't something new. Or never heard of. I forgot to mention the PCV valve MUST be hooked up and functioning, but AJ covered that. As he pointed out, if the carb has the outlet for it, it is calibrated for that air leak. If you don't use it, you make the idle pig rich.

I was doing this **** in 1980. And getting paid for it. Maybe you should stop typing, start reading and see if you can learn something.

 

[j par]

Your mouthy remarks about magazines is hilarious. And stupid.

I told the OP what I did based on years of doing this ****. Did you read what AJ posted? If you did, he said exactly what I said, except no way in hell am I typing that all out. Never. I'd rather give the OP my number and walk him through it on the phone. It's quicker.

His issue isn't something new. Or never heard of. I forgot to mention the PCV valve MUST be hooked up and functioning, but AJ covered that. As he pointed out, if the carb has the outlet for it, it is calibrated for that air leak. If you don't use it, you make the idle pig rich.

I was doing this **** in 1980. And getting paid for it. Maybe you should stop typing, start reading and see if you can learn something.

Does anybody read what AJ says? You got to be joking me! he dribbles on from one thing to the other and it goes on and on and on good Lord no I don't read what he says most of the time. I for one don't believe anything you say and don't have any reason too...
For the last time I gave no advice on how to tune his carburetor.
Please stop trying to make this about you and me which I don't care to try and do, I'm just giving him my best advice from my real experience... No matter what is done some carbs you just can't reach..

 

[fishmens67]

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

I don't think so.

 

[318willrun]

I don't think so.

you think more? 100 hp ?

 

[Mattax]

IMO 75 Hp was a good guestimate, but prob less.
Both tuned in; that is flat AFR through the top, jetted for max power and torque, etc.
Disconnecting the secondaries on a '750', my 340 lost 25 - 30 hp, and the peak dropped from 5500 to 5250. The difference should be higher than that but ran out of time to tune in the secondaries. So that's a real life, but imperfect example of halving carb size.

 

[Mattax]

OK. It seems like you'ld like to keep this carb rather than hunt a 800ish Carterbrock or such.

In priority order:
1. get yourself a cheap used copy of Urich and Fisher's Holley Carburetors and Manifolds.
2. Write down everything on a build sheet, starting with Carb list number and revision. Then block Numbers, then all the restrictions (jets & bleeds) etc. Check each metering block, the base - whether it has a snake channel, PV, accel pump cams, shooters. You'll need a drill set(s) into the high numbers (small sizes) or pin gages to measure but you can eyeball with wire type spark plug feeler gages
3. Write down the amount the transfer slots are now visible below the throttles. (the last test you did on the engine).
4. Check the Fuel level in the bowls. (offthe engine, this means checking float setting, on the engine you know what to do)
5. Make sure your PCV is hooked up and working; it is your firstline idle-air bypass. Assuming its OK since the Eddy worked OK.
6. You have to set the Transfer-slot exposure first....... then set the idle speed with bypass air and timing.
6. 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.
6 WRITE DOWN how many turns of the idle stop screw it takes to reveal .020. .030 and .040 of the transfer slot. When on the engine, it should be no more than .040 once its warmed up.
7. Check timing at idle and off idle rpms with the Eddy so you know the curve.
8. Install carb and once its running recheck fuel level. When its warmed up, adjust the p transfer slot so its no more than .040 once its warmed up. Don't care what you need to do to do this. Increase timing a little if it makes sense, Open the secondaries if thats convenient. Stick wires in the PIABs. write down what you do. Listen, smell, and check the spark plugs for clues. None of this is the setup, just experimenting to see what it takes to get the proper primary idle throttle.

 

[AJ/FormS]

I agree the small carb is giving up power; but as a streeter; ask yourself when is the power lost and does it matter.
With 3.91s and a TF trans, you are gonna be, or should be, spinning the tires right thru first gear anyway, probably with half as much carb. That puts you at say 6000= 48mph in first. Going to 3700 in second. Now, 60mph will be about 4650rpm,not even getting on the power curve of that big cam.
Ok so now with a 60mph limit and 3.91s, you could probably give up 2 cam sizes and not be much slower; just have a lil less tirespin......... because the smaller cam will power peak closer to60mph than the 292, and very possibly have more power at lower rpms, so the average power delivered in second gear, up to 60mph, could easily be the same.
As a real world comparison; I switched from that 292/292/108 to a 270/276/110 and never missed that big cam; that's 3 cam sizes by advertised/3.5 by the .050s. Well; I did miss the idle-lope,lol. And yes I'm sure the 292 would have been quicker in a drag race to 110mph. 3 years later when that 270 died, I moved up to a 276/286/110, and sorely missed the 270. It took a lot of work and a lower first gear to be finally happy with the 276 cam. A 750DP, and 3.55s were constants, and the cylinder pressure was adjusted to be nearly so.And in the meantime, I saved thousands of dollars in fuel costs over time. As a DD that 292 was hurting me bad.
So the point is IMO, yes, you are leaving power on the table with the smaller carb, but are you gonna see the difference in zero to 60 times? And if yes, then how much? and finally is it worth it?

To be fair, a 600 is pretty small for over 360 cubes. A DP carb, even if it isn't any quicker, it will sure feel quicker,lol. My 750DP was easy to tune, and will idle down to 550 with the T-slot sync set right, and the timing retarded to 5*. I usually have the idle at 750 by cranking the timing to 14 from 5, and the 367 will take full throttle almost right off idle with a 10.97 starter gear....... cuz the tires spin right away. I only retard it because I have the dial-back computer in the cab, and at 5*/550 rpm it pulls itself at 4mph, around the parking lot, being the slowest it can go with 3.55s.

 

[318willrun]

I agree the small carb is giving up power; but as a streeter; ask yourself when is the power lost and does it matter.

When is the power lost? Answer: right from the word "GO"

 

[yellow rose]

Does anybody read what AJ says? You got to be joking me! he dribbles on from one thing to the other and it goes on and on and on good Lord no I don't read what he says most of the time. I for one don't believe anything you say and don't have any reason too...
For the last time I gave no advice on how to tune his carburetor.
Please stop trying to make this about you and me which I don't care to try and do, I'm just giving him my best advice from my real experience... No matter what is done some carbs you just can't reach..

LOL.

 

[340dartley]

Well I may have found the main issue with the idle mixture screw issue on the carburetor. It seems fairly obvious now. It had the incorrect base to main body gaskets and it was blocking flow from the main airhorn to the ports on the base plate. Here is a picture of the base gasket next to another Holley base plate with the same port configuration. You can see the indent of where the port is supposed to be on the new gasket. I Made some holes in the gasket to try it out. Low and behold the idle screws do something now. The idle is still hunting a bit but at least I can kill the engine by turning the idle screws in. It may still need holes drilled in the throttle plates and other tuning tricks but at least I have the idle ports opened up. I am going to order a new base gasket / rebuild kit. What is good kit that is tolerant of California crappy fur blends and potentially could be taken apart and reassembled with out gasket damage?

Oh for the record I took it out for a short test drive. It didn’t like to idle in gear but it made a huge improvement on power. I am thinking the 75 hp estimate may be pretty close. Timing is set at 18 initial right now with 34 total. I didn’t detect much in the way of pinging when I ran it either.

 

[yellow rose]

Well I may have found the main issue with the idle mixture screw issue on the carburetor. It seems fairly obvious now. It had the incorrect base to main body gaskets and it was blocking flow from the main airhorn to the ports on the base plate. Here is a picture of the base gasket next to another Holley base plate with the same port configuration. You can see the indent of where the port is supposed to be on the new gasket. I Made some holes in the gasket to try it out. Low and behold the idle screws do something now. The idle is still hunting a bit but at least I can kill the engine by turning the idle screws in. It may still need holes drilled in the throttle plates and other tuning tricks but at least I have the idle ports opened up. I am going to order a new base gasket / rebuild kit. What is good kit that is tolerant of California crappy fur blends and potentially could be taken apart and reassembled with out gasket damage?

Oh for the record I took it out for a short test drive. It didn’t like to idle in gear but it made a huge improvement on power. I am thinking the 75 hp estimate may be pretty close. Timing is set at 18 initial right now with 34 total. I didn’t detect much in the way of pinging when I ran it either.

View attachment 1715334289

Without the book in front of me, I don't remember all the specs of the 4780. IIRC (that's a big IF) that 4780 is essentially a 750 main body (Venturi diameter) with an 850 baseplate. Again, IIRC. But that was by far the best combo of that series of universal Holley carbs. I never really cared for the 4781 on the small block because you had the HUGE Venturi with the 1.75 base plate.

The real pile of **** carb was the 830 annular discharge carb that I can't think of the number. It was an 850 Venturi with the 750 (1 11/16) base plate. A steaming pile of monkey crap.

So, you didn't waste any money and have a carb that will work with some tuning. I still say you'll need to drill some holes in the butterflies to make it correct. If you can wait, I may be home by the end of the week I can send you a pair. Won't even cost you a cent.

Let me know.

 

[340dartley]

Without the book in front of me, I don't remember all the specs of the 4780. IIRC (that's a big IF) that 4780 is essentially a 750 main body (Venturi diameter) with an 850 baseplate. Again, IIRC. But that was by far the best combo of that series of universal Holley carbs. I never really cared for the 4781 on the small block because you had the HUGE Venturi with the 1.75 base plate.

The real pile of **** carb was the 830 annular discharge carb that I can't think of the number. It was an 850 Venturi with the 750 (1 11/16) base plate. A steaming pile of monkey crap.

So, you didn't waste any money and have a carb that will work with some tuning. I still say you'll need to drill some holes in the butterflies to make it correct. If you can wait, I may be home by the end of the week I can send you a pair. Won't even cost you a cent.

Let me know.

Thank you. I think I will be ok though. I have a junk old 750 vac secondary carb in the garage and I measured the primary butterflies. They are the same size. I can install them out of it if I need. Thank you for the offer though. Ironically I was looking at an old 600 vac secondary Holley that was an oem carb from a 383 and it has holes in the butterflies from the factory.

 

[AJ/FormS]

I can't imagine an 850 Vacuum secondary on my 367,
because as a streeter, even the 780 I didn't like.
I have a manual trans so when the secondaries started coming in, in the middle of a turn, sometimes completing the turn was an event by itself. It didn't matter what spring I put into the pod, cuz every turn was different and always exciting, often ending up with me facing the wrong way, somewhere in the weeds, or up on the center divider.
Switching to a 750DP,I left all that behavior behind. I'm never going back to a Vsec/manual trans combo. But someday, I would like to tune a bigger DPcarb on my 367, just for the experience.

As to the holes in the throttles; I have seen them in garden tillers,snowblowers,string-trimmers, lawnmowers,etc. And especially in 2-cycle marine carbs; where they can be pretty large. Also in Marine Apps, they retard the timing a long ways to control the idle speed, else you might plow into something,lol.