Edekbrock 1403 Idle Mixture - Vintage Mustang Forums
 3Likes
Reply
 
Thread Tools
post #1 of 21 (permalink) Old 08-11-2019, 03:05 PM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
Edekbrock 1403 Idle Mixture

So, I got my 4 hole 1/2 wood Edelbrock spacer and installed it under my 1403. Under that is an old school 4 hole Shelby style intake and under that is a "mild" cam of some sort. Got my timing set to about 4 degrees retarded from pinging. Car is running well. Idles well. Carb has about 500 miles on it and I have rebuilt it with new floats, seats, needles and the stock configuration of metering rods and primary jets.



But, to get it to idle well, using a vacuum gauge and test tach, each idle screw is turned out about four and one quarter turns. This seems excessive especially when Edelbrock suggests starting at one and three quarters. This is my first car with a carb other than stock. IIRC, they generally tell you to start at two turns out and I have always landed within a half turn or so of that.


So is this normal for an Edelbrock 1403 on my set-up?


Thanks

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968

Last edited by 1968Cally; 08-11-2019 at 03:07 PM.
1968Cally is offline  
Sponsored Links
Advertisement
 
post #2 of 21 (permalink) Old 08-12-2019, 12:29 AM
Member
 
Join Date: Jul 2016
Location: NorCal
Posts: 63
For comparison: My engine
Stock 1968 J-code 302 engine ~10.5:1 compression
Dual plane manifold (stock)
4-hole phenolic spacer (for heat isolation)
12* BTDC initial timing
Vac advance hooked to manifold vacuum (adds ~15* at idle)
1403 carb (actually a 1406 carb body with the 1403 venturi boosters swapped in, which, as I understand, = 1403 carb)
Don't remember jetting and rods I finally decided on but *I think* it was the 1403 "standard setting"

With this setup, my idle screws are both out 1 + 3/8 turns. Idle AFR = 13.5. Idle RPM ~=800.
*If* I remember correctly, when I hooked vac advance to ported vacuum both screws were an additional 1/2 turn out to get the same idle quality.

So, 4 and 1/2 turns *seems* excessive even if you are using the "spec'ed" 6* BTDC initial and ported vacuum, both of which will require more fuel from the idle circuits.
P-51 is offline  
post #3 of 21 (permalink) Old 08-12-2019, 08:59 AM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
Quote:
Originally Posted by P-51 View Post
For comparison: My engine
Stock 1968 J-code 302 engine ~10.5:1 compression
Dual plane manifold (stock)
4-hole phenolic spacer (for heat isolation)
12* BTDC initial timing
Vac advance hooked to manifold vacuum (adds ~15* at idle)
1403 carb (actually a 1406 carb body with the 1403 venturi boosters swapped in, which, as I understand, = 1403 carb)
Don't remember jetting and rods I finally decided on but *I think* it was the 1403 "standard setting"

With this setup, my idle screws are both out 1 + 3/8 turns. Idle AFR = 13.5. Idle RPM ~=800.
*If* I remember correctly, when I hooked vac advance to ported vacuum both screws were an additional 1/2 turn out to get the same idle quality.

So, 4 and 1/2 turns *seems* excessive even if you are using the "spec'ed" 6* BTDC initial and ported vacuum, both of which will require more fuel from the idle circuits.
I don't understand the reasoning why you would use the manifold vacuum. By using the manifold vacuum, your idle btdc would be ~27* BTDC at idle which seems very excessive. Then as you open the throttle, you lose some (all if you go WOT) of the vacuum advance but start gaining the mechanical advance. So, they may sort of offset each other as you accelerate if I am thinking about this correctly. It also seems that ~27 btdc at idle could be damaging to the engine. But, maybe not at idle.


Anyone else with thoughts/theories?

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968
1968Cally is offline  
 
post #4 of 21 (permalink) Old 08-12-2019, 12:14 PM
Member
 
Join Date: Jul 2016
Location: NorCal
Posts: 63
Quote:
Originally Posted by 1968Cally View Post
I don't understand the reasoning why you would use the manifold vacuum. By using the manifold vacuum, your idle btdc would be ~27* BTDC at idle which seems very excessive. Then as you open the throttle, you lose some (all if you go WOT) of the vacuum advance but start gaining the mechanical advance. So, they may sort of offset each other as you accelerate if I am thinking about this correctly. It also seems that ~27 btdc at idle could be damaging to the engine. But, maybe not at idle.


Anyone else with thoughts/theories?
This topic has been discussed to death on the forums. Search for "ported vs manifold vacuum" (or something similar) on VMF for some entertaining exchanges/"religious debates". IMO, here are the most definitive articles that cover the topics of timing and vacuum advance. If you understand these two articles you pretty much understand how all the timing parameters (eg "initial", "total", etc), controls (eg mechanical advance, vac advance), and tradeoffs (eg ported vs manifold vac) work.

Timing and Vacuum advance:
http://www.camaros.org/pdf/timing101.pdf

General timing overview:
https://www.fordmuscle.com/archives/2000/03/timing/
P-51 is offline  
post #5 of 21 (permalink) Old 08-12-2019, 02:41 PM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
Quote:
Originally Posted by P-51 View Post
This topic has been discussed to death on the forums. Search for "ported vs manifold vacuum" (or something similar) on VMF for some entertaining exchanges/"religious debates". IMO, here are the most definitive articles that cover the topics of timing and vacuum advance. If you understand these two articles you pretty much understand how all the timing parameters (eg "initial", "total", etc), controls (eg mechanical advance, vac advance), and tradeoffs (eg ported vs manifold vac) work.

Timing and Vacuum advance:
http://www.camaros.org/pdf/timing101.pdf

General timing overview:
https://www.fordmuscle.com/archives/2000/03/timing/
Okay, I think I am beginning to "get it." Those articles are really good - thanks for sharing and insight. I will put off reading those other threads for now as they would probably mess to much with my head. I think I now know that using the manifold vacuum is not necessarily a "bad" thing. Do you think Edelbrock indicates to use ported vacuum so that they do not run afoul of the EPA? Classic cars here in Illinois are exempt from emission testing.



So here are my takeaways, comments and questions.
1) A lot of advance timing is required at idle. Much more than just 6*BTDC. And this is why folks really bump up their initial timing anywhere (from what I have read in threads here) all the way up to 20* BTDC. I assume that these people are using ported vacuum. And, at idle there is no ported vacuum so it does not matter if they disconnect and plug the hose.

2) When you are using ported vacuum and have a high initial timing of say 15* BTDC, when you accelerate, you get the initial + Vacuum + increasing centrifugal advance which will give you a whole lot of total timing advance. This would seem to give you more than needed or desired.

3) If you use manifold vacuum for advance and you set your initial timing to 6* BTDC (with the vacuum hose disconnected and plugged) you will wind up with your idle timing at about 20* BTDC.
4) Given the scenario 3 above, this would allow for (and the engine would like) a leaner idle mixture adjustment. So, maybe ~two turns out versus my current of 4 plus turns out).
5) In 1968, Ford used the dual diaphragm advance. I am using just a single advance. Does this really change anything in the conversation?
6) With my vacuum currently using ported and my initial at about 11 degrees, the car accelerates and cruises very nicely with no pinging. But, a smooth idle is a little elusive and the idle mixture being so rich troubles me. I use 10% ethanol 89 octane fuel. Nearest non- ethanol gas is about 50 miles away.
7) So, should I try the manifold vacuum and if so, should I set initial timing to 6* BTDC with the line disconnected and plugged? And then maybe start with a mixture of two turns out?


Thanks so much for the help and education, P51.

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968
1968Cally is offline  
post #6 of 21 (permalink) Old 08-12-2019, 03:03 PM
Senior Member
 
kenash's Avatar
 
Join Date: Dec 2006
Location: Severna Park, MD
Posts: 6,057
Garage
I go by the thinking "Ported" Vac is for emission controlled vehicles, "Full" is for non. I chose the "Non".

OK, please let this lie dormant. We all know the stories and the thinking behind each and as has been noted, beat to living death. If there is such a thing LOL!

KenA..
64 1/2 Poppy Red Cvt. Resto-Mod
333 Cu.in. T5z, 3:55, Dual 40 mm DCOE Webers
Performer RPM, CI cam, TFS/TWs, Tri-Ys, Discs w/Shelby Drums
Severna Park, Maryland
kenash is offline  
post #7 of 21 (permalink) Old 08-12-2019, 07:06 PM
Member
 
Join Date: Jul 2016
Location: NorCal
Posts: 63
Quote:
Originally Posted by 1968Cally View Post
Okay, I think I am beginning to "get it." Those articles are really good - thanks for sharing and insight. I will put off reading those other threads for now as they would probably mess to much with my head. I think I now know that using the manifold vacuum is not necessarily a "bad" thing. Do you think Edelbrock indicates to use ported vacuum so that they do not run afoul of the EPA? Classic cars here in Illinois are exempt from emission testing.



So here are my takeaways, comments and questions.
1) A lot of advance timing is required at idle. Much more than just 6*BTDC. And this is why folks really bump up their initial timing anywhere (from what I have read in threads here) all the way up to 20* BTDC. I assume that these people are using ported vacuum. And, at idle there is no ported vacuum so it does not matter if they disconnect and plug the hose.

2) When you are using ported vacuum and have a high initial timing of say 15* BTDC, when you accelerate, you get the initial + Vacuum + increasing centrifugal advance which will give you a whole lot of total timing advance. This would seem to give you more than needed or desired.

3) If you use manifold vacuum for advance and you set your initial timing to 6* BTDC (with the vacuum hose disconnected and plugged) you will wind up with your idle timing at about 20* BTDC.
4) Given the scenario 3 above, this would allow for (and the engine would like) a leaner idle mixture adjustment. So, maybe ~two turns out versus my current of 4 plus turns out).
5) In 1968, Ford used the dual diaphragm advance. I am using just a single advance. Does this really change anything in the conversation?
6) With my vacuum currently using ported and my initial at about 11 degrees, the car accelerates and cruises very nicely with no pinging. But, a smooth idle is a little elusive and the idle mixture being so rich troubles me. I use 10% ethanol 89 octane fuel. Nearest non- ethanol gas is about 50 miles away.
7) So, should I try the manifold vacuum and if so, should I set initial timing to 6* BTDC with the line disconnected and plugged? And then maybe start with a mixture of two turns out?


Thanks so much for the help and education, P51.
I'm not sure I can exactly answer all your questions accurately but here is how I understand it:

When you have the vac advance canister hooked up, the only difference between ported and manifold is at idle. Once you crack the throttle blades even a little (enough to expose the ported vac port to the manifold vacuum), the vac advance is the same whether you are using manifold or ported vacuum. So, the only question is whether you want the advance engaged at idle or not. Some engines do fine with manifold vac, some do not. For example, if you have loppy cam with very low or highly-varying vacuum, using manifold vac will not give you a good idle. With a highly-varying manifold vac at idle the advance would be going "in and out". Or if you have low manifold vac, the vac advance might be partly engaged causing it to act squirrelly. But for a stock engine with >15" *steady* vacuum, hooking the vac advance to manifold vac should work.
Bottom line: Manifold vacuum uses less fuel, engine runs cooler, and it produces more emissions. But ported vac is a lot more forgiving.

As for " initial + Vacuum + increasing centrifugal advance" (per above) being very high, you see that at idle when rev'ing the engine because the engine is not under any load. When you're actually driving and accelerating the load on the engine is much higher, your throttle blades are open a lot more, and, therefore, your vac advance has likely *dropped out mostly or completely*. So, you will only be seeing approximately "initial + centrifugal" when the engine is under load. When cruising you are not loading the engine much (just keeping the car moving at a set speed doesn't take all that much hp), the throttle blades a just cracked a little, and the vac advance is again engaged (it is the same whether using either manifold or ported vac). Yes the advance seems large but the amount of fuel being consumed by the engine is so low in this case that the time it takes to burn in the combustion chamber is longer allowing for much more advance (refer to the the Timing 101 article Timing)

As for setting the initial to 6* BTDC, I personally would leave it at 11* as you now have it and then try both manifold and ported vac to the distributor to see what you engine "likes" better. One thing to check is manifold vac (with a vac gauge) at idle 11* initial with vac canister disconnected. If the vac is lower than ~15" or if it is bouncing around a lot it may mean that you have a vac leak (which might explain the idle screw setting??). If you don't have a steady vacuum you may be better off with using ported vac to the disti.

Edit - As to your question "Do you think Edelbrock indicates to use ported vacuum so that they do not run afoul of the EPA?"
I think that given that hooking the vac advance to ported vacuum "just works" for a large variety of engines/mods, Edelbrock recommends it so that it doesn't get as many calls to their tech support and/or people complaining that their product doesn't work.

Four *full* 360* turns out (not "half turns") on the idle screws still seems very excessive to me. I have never seem much more than 2.5 full turns out.

Aside: I also only have a single-port vac advance canister on my disti

Last edited by P-51; 08-12-2019 at 07:19 PM.
P-51 is offline  
post #8 of 21 (permalink) Old 08-12-2019, 09:57 PM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
Again P51, thanks! I think I got it now along with the pros and cons (fact and opinion) on similar threads here and other forums. Yes, the debate can get spirited.


My vacuum with the currently ported advance and initial at 11* BTDC and idle at about 700 (not in drive) is a steady 16 hg. I think that reinforces that I do have a mild cam as the PO told me as that is what his PO told him. My compression varies from 177 to 183 with five of the cylinders right at 180. This was done with the engine cold, all plugs out and the throttle and choke wide open.


So tomorrow I have all day to play with this issue. I will first move the advance to manifold vacuum and see how that affects the mixture setting. I am almost betting this will allow me to go leaner. Then, if idle and drivability are both good, I will leave my 11* initial. But, I reserve the right to play with it a little!


Now, I hate to bother you with another issue that does sort of relate to vacuum. And that is the PCV Valve. In reading through the other threads, I came across a post or two about where the PCV valve hose should be connected. It indicates that for my Edelbrock, it should be connected to the center front port of the carb that Edelbrock identifies as for the PCV as this will better distribute the crankcase gases into the intake. That makes sense and I believe the stock 4 bbl. configuration used a spacer with the port for the PCV.



Currently, I have two ports on the passenger side rear of the intake right next to each other. See picture. The PCV goes into a single barbed fitting. The other fitting is multi-purpose. The metal line for the brake booster (which transitions to a rubber hose), then another port is for the tranny modulator and yet another port is for the HVAC actuators. So am I okay moving the PCV to the front of the carburetor and plugging that port and leaving the multi purpose port as is? I would think so but maybe the brake booster should be the only thing on one of the ports. I want to get this correct before I move to the manifold vacuum tomorrow.



Thanks.
Attached Images
File Type: jpg IMG_1618.jpg (428.2 KB, 1 views)

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968
1968Cally is offline  
post #9 of 21 (permalink) Old 08-12-2019, 10:54 PM
Member
 
Join Date: Jul 2016
Location: NorCal
Posts: 63
Quote:
Originally Posted by 1968Cally View Post

... Now, I hate to bother you with another issue that does sort of relate to vacuum. And that is the PCV Valve. In reading through the other threads, I came across a post or two about where the PCV valve hose should be connected. It indicates that for my Edelbrock, it should be connected to the center front port of the carb that Edelbrock identifies as for the PCV as this will better distribute the crankcase gases into the intake. That makes sense and I believe the stock 4 bbl. configuration used a spacer with the port for the PCV.

Currently, I have two ports on the passenger side rear of the intake right next to each other. See picture. The PCV goes into a single barbed fitting. The other fitting is multi-purpose. The metal line for the brake booster (which transitions to a rubber hose), then another port is for the tranny modulator and yet another port is for the HVAC actuators. So am I okay moving the PCV to the front of the carburetor and plugging that port and leaving the multi purpose port as is? I would think so but maybe the brake booster should be the only thing on one of the ports. I want to get this correct before I move to the manifold vacuum tomorrow.

Thanks.
I'm probably not the best one to answer this as I just ignored what Edelbrock said about hooking the PCV to the front and instead hooked it straight to the back manifold vac port on the carb (the one for the brake booster - I don't have power brakes). The reasoning... before getting the phenolic spacer I had a stock? metal spacer with a port on the back that the PCV hooked up to and this seemed to be almost (not exactly) the same setup. To me, manifold vacuum is manifold vacuum no matter where you tap it so my answer is that it won't cause any issues moving around connections to manifold vacuum. Having said that, my guess is that someone on this forum has a much better idea about why certain manifold ports are "better" than others for various functions... but that person is not me. Sorry.
P-51 is offline  
post #10 of 21 (permalink) Old 08-13-2019, 12:05 AM
Senior Member
 
66ryan's Avatar
 
Join Date: Apr 2016
Location: Raleigh NC
Posts: 275
Quote:
Originally Posted by 1968Cally View Post
So am I okay moving the PCV to the front of the carburetor and plugging that port and leaving the multi purpose port as is?
Yes. As you already wrote, Edelbrock suggests this configuration. I have the same carb and set it up this way and it works well. As expected, since it was in their instructions

66ryan is offline  
post #11 of 21 (permalink) Old 08-13-2019, 08:33 AM
Senior Member
 
Join Date: Dec 2013
Location: Knoxville, TN
Posts: 652
I would not move the PCV hose because it looks better where it is and I don't really think it will make a functional difference.
Rufus68 is online now  
post #12 of 21 (permalink) Old 08-13-2019, 09:15 AM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
Quote:
Originally Posted by Rufus68 View Post
I would not move the PCV hose because it looks better where it is and I don't really think it will make a functional difference.
I just read in another forum that putting it in a manifold port like I have now can "lean out" one of the cylinders. But, hooking it to the designated port on your carb or carb spacer, distributes the gases pulled from the crankcase evenly to all cylinders. That makes sense. But, I am not sure as you say, how much of a difference that really makes. I am going to hook it to the front of my Edelbrock as that is the right way to do it.

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968
1968Cally is offline  
post #13 of 21 (permalink) Old 08-13-2019, 04:02 PM Thread Starter
Senior Member
 
1968Cally's Avatar
 
Join Date: Dec 2017
Location: Hawthorn Woods, Illinois
Posts: 551
Garage
So today I got a PCV Valve with a 3/8" nipple and hose and it in now plugged into the 1403s front center PCV fitting.


Left my initial timing at 11* and moved the vacuum advance to the manifold vacuum port in front. That made the timing at idle reach 25*. So, that would be the expected result. Using the timing light, when I rev it up from idle, the timing retards about 10* for a split second and then increases to over 25* as the centrifugal advance takes over. Also expected. But, I still need to have the mixture screws out about 4.5 full turns for best idle. Also need to have the idle rpm set to about 800 so that it will not start shaking a lot and come near to stalling when dropping it into drive. As far as drivability goes, it remains very good although perhaps a little less power which is fine with me. No pinging.

The idle mixture screws really do very little once I get them 3.5 turns out. I am wondering if that is where you reach maximum richness and after that, you are just un-threading them further out.

I did check (again) for a vacuum leak with starting fluid but could not find anything.

This all started when I was smelling richness in the exhaust when stopped at a light for a little bit. I tried adjusting the mixture but there was not much difference. I took the mixture screws out and put a little carb cleaner down the holes and blew them out. Then I took the top off and adjusted the floats which were not that far off. I have since been told (on the forum) that smelling a rich exhaust is sort of normal for the high compression 302.

Then, being new to modern 4 bbl. carbs, I made a fatal stupid mistake. I put the air horn back on without first removing the metering rods. Put the top back on totally missing the jet holes and bending over the tips of both metering rods. I guess I really mashed the air horn down using a 1/4 ratchet. So, I bought a rebuild kit, new stock metering rods, springs and primary jets. I also bought new floats while I was at it. I only used the new needles and seats, air horn gasket and accelerator pump from the rebuild kit as I left everything alone (except for the new jets) in the body of the carb.

Not sure what next step should be. I can drop $400 on a new 1403 or maybe a new 1406. Or, just live with it. Any other ideas? I do have the original 4300 carb which I could rebuild and try. Would have to get a stock spacer though.

Dave
'68 GTCS
8R01J
C4/PS/PB/AC
2/8/1968

Last edited by 1968Cally; 08-13-2019 at 04:24 PM.
1968Cally is offline  
post #14 of 21 (permalink) Old 08-13-2019, 04:09 PM
Senior Member
 
Join Date: Dec 2013
Location: Knoxville, TN
Posts: 652
It really sounds like something is restricting the flow of fuel through your idle circuit. Backing out the screws on my 1403 shows up right away on the AFR gauge. For some reason your carb must not be flowing the fuel properly through there.
Rufus68 is online now  
post #15 of 21 (permalink) Old 08-13-2019, 04:36 PM
Senior Member
 
Join Date: Dec 2013
Location: Knoxville, TN
Posts: 652
I was reading on the Edelbrock FAQ page for carburetors and it said to check the vacuum on your timed port at idle. There should not be any vacuum at all. If you have any vacuum there then you have the throttle blades open too much and you've moved out of the idle circuit. Have you connected your vacuum gauge to the timed port?
RV6 likes this.
Rufus68 is online now  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Vintage Mustang Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome