Ok. Here is what I have setup on the old beast. I do not want to get into the big debate over ported vs manifold for the dizzy! I have it setup as stock vacuum diagrams indicate so for my truck that is manifold vacuum with restrictor. I have the base timing set at 10* BTDC. I used the 1/8" allen screw in the dizzy to back off the vacuum advance I was getting there because whoever owned this truck before had the screw turned all the way in! Now I am getting 10* base + 12* from the dizzy at idle = 22* total at idle. This is down 10* from how it was before I dialed back the dizzy. My thoughts were that 32* at idle was a bit high ... not to mention I couldn't get the idle down. My questions for all you experts here is ... what do you think about my changes ... my reasoning? Is 22* at idle better than the 32* or did I miss something? Keep in mind this is a stock Ford F250 4x4 460 with the CA emissions 4180c carb.

Thanks

 

Your timing will be high like that if you have vacuum on the dist at idle. Obviously you do if you are messing with the vacuum adjustment and getting it to come down.

From what I understand on the 460 this is not correct, they only put vacuum on the dist at idle when the engine is overheating. But there are other guys on here who know more about the 460 setup than I do so maybe they will come in and comment. But I would not worry where the advance is at idle if you have vacuum on the dist, you will not really be able to control it. Idle speed, engine load(in drive or not) will all vary the vacuum and thus the timing you will get.

 

The way my engine was setup .... stock .... according to the vacuum diagram is that it runs full manifold vacuum to a temperature switch that gives restricted manifold vacuum to the dizzy under normal conditions and switches to full manifold vacuum when the engine gets too hot. I have eliminated the temp switch because I installed a new thermostat housing (old one cracked) and could not salvage the old temp switch. I have the dizzy running through the restricted line to manifold vacuum so essentially it is the same as it was and it is the way Ford set it up. Now my issue is that I think whoever owned the vehicle before me messed with the dizzy too much because even with vacuum advance at idle 32-34* was too much (in my opinion) .... so all I did was dial down the dizzy spring so the total base+vacuum advance at idle is 22* now. Still idles high but not as bad ... and it still follows the factory setup. I guess my only reason for posting this was to get opinions on what I did and if 22* at idle is a better number than the 32-34* .... basically just asking someone with more knowledge to 'check my math' I hate these damned CA emissions setups but I have to keep it this way if I wanna pass smog in October.

 

Ok . I have read for hours today through the forums and I can see the debate over ported vs manifold vacuum is still going strong so I will toss my situation into the ring and see what shakes loose. Just because my stock vacuum diagram shows my dizzy being run from manifold vacuum doesn't necessarily mean I am adverse to change. Would it be worth it to switch to the ported nipple on the carb (Holley 4180c)? First off I know I would be able to achieve a lower RPM at idle because currently I have the curb idle screw backed all the way out and I am still a little high rpm at idle .... likely because I am at 22* BTDC at idle (base+vacuum advance). I realize I would likely have to switch it all back to stock for my smog test in October but I am ok with that if I can make changes today that will help the truck run better the other 364 days out of the year. Open to all suggestions folks Thanks

 

I was going to bow out and wait for someone else with more knowledge on the 460 system to come by, but they must be busy.

Since you have a manual transmission you could go either way on the vacuum hook-up. I am suspicious though that something is still not correct with your hook-up, but I don't have the diagram for your engine handy and if I remember correctly, the one I saw was pretty complicated. What I don't understand is your reference to a "restriction" in the path to the distributor. In my mind a restriction would definitely slow the reaction of the device it was controlling, but over time you would end up with the same vacuum as manifold wouldn't you? Unless there was a way that it bled the vacuum off?

I would try the ported vacuum just as a experiment. I don't think it would hurt your emissions, it actually sounds like it would help it. Getting rid of that timing will let you open the carb back up letting more air in, and giving you better adjustment on your idle air mixture screws.

 

Here is the vac diagram under the hood. You can see the vacuum advance is run to a valve on the radiator thermostat housing and connected to manifold vacuum... one line out to the dizzy is full manifold vac while the other has a small in-line restricter but is still manifold vacuum. As I understand it the reason for this is that at normal operating temp the dizzy gets the restricted manifold vac but when temp rises above the valve set point it switches to the full manifold vac to raise RPM's further to help cool the engine by way of more advance.... I have removed this thermostat housing valve and have the dizzy hooked up to manifold vac through the restricted vac line so essentially it is the same as stock. The only thing I have done in addition is dial back the spring screw in the dizzy vac pot to bring the additional advance from vacuum down to about 12* for a total advance at idle of 22* (10*base+12*vacuum advance). However .... before I installed the remanufactured 4180c carb I was able to get the idle down further by using the curb idle screw .... now I have the curb idle screw all the way backed out and I am still getting to high of RPM's at idle .... and that is with less advance at idle as well so that confuses me even more ... I thought since the advance at idle is about 10* less than it was when I had the other carb and was able to get use from the curb idle screw then it would actually result in lower rpm's now but that is exactly the opposite of what I am experiencing confused as h*ll over this one at the moment

 

Tkc, see if this post helps you:

https://www.ford-trucks.com/forums/1...l#post11162043

Ralph (81-F-150-Explorer) is/was in California and had a boatload of knowledge he shared with folks here on this stuff (he corrected my misinformation more than once); using the Advanced Search on this forum for posts authored by him that contain maybe "vcv" wouldn't be a bad thing for you to do.

He disappeared from here a few years ago and nobody knows why...

 

Good reads .... still reading. Serious wealth of information. Thanks for the heads up on this one.

 

Ok ... update. Finally managed to get the idle and everything perfect on the old beast. Actually had to reverse some of the adjustments I did on the vac advance can to get things just right. Then I took it for a drive up to my Dad's place .... plenty of hill climbing to really test out the carb, etc.... AND now I have a new issue that is completely puzzling. Keeping in mind the truck was idling perfect and was driving perfect .... after about 15 min of driving I came to my exit and coasted to a stop only to hear my RPM's drop down to almost nothing and the truck just about died ... sounded like one of those big loppy cammed engines .... was not idling the way it had been in the driveway 15 min prior. So I pulled over and popped the hood and immediately hooked up my vac gauge (took it with me for the test run just because).... and I was only getting 13-14hg and a crappy idle when 15 min prior I was getting 20-21hg and a perfect idle. Now here's the even weirder part .... letting it sit like that idling all crappy .... within about 5 min it slowly idled back up and was running like it had been in the driveway ... great idle and 20hg of vac ? ? ? So dropped the hood and took off again .... needless to say it happened again the very next time I had to come to a stop ... this time I decided to continue on to my Dads place before messing with it again. This is where I found that with very very light throttle from a stop it hesitated/stumbled but if I pushed the peddle down enough to engage the accelerator pump it jumped to life and ran great. So it seems like its isolated to an idle/very light throttle issue ? ? ? Done with it for tonight ... just doing my research online to try and see where to start on it tomorrow. Kind of sounds like a vacuum leak as well but then it wouldn't correct itself if let alone for 5 minutes would it? I have also heard stories of those spungy 1/4" mounting gaskets causing issues vs a thin mounting gasket .... could this be part of the issue? As you can see I am grasping at straws and looking for ideas on where to start my investigation tomorrow. I truly appreciate all the help I have gotten thus far from everyone on this site .... sorry to be back asking for more but here be the knowledge I seek

 

Speaking of grasping at straws...

The two idle circuit air bleeds are located on the top of the carburetor, at the front, At the base of the choke flap air horn. If these become clogged if will mess up your idle.

Do you have dual air pumps? If so you have two vacuum operated valves controlling the air flow, and vacuum controlled valves can leak and give you a vacuum leak.

How about your EGR valve? If it was sticking open, or getting vacuum when it wasn't supposed to, that could raise heck with your idle... Since it's just like a big ole vacuum leak, only it leaks exhaust gasses into your intake stream...

Now my gut is saying start with EGR.

 

Yeah I am leaning toward a vacuum leak somewhere. The idle is dropping to almost nothing when I stop now ... no longer a high idle issue. Tomorrow I am going to check the carb mounting gasket area first ... since I just put this reman carb on a couple days ago and used the 1/4" spongy gasket that it came with. Torqued it down to 11lbs ... was afraid to go any tighter with that spongy gasket because they can compress at the four corners and put stress on the mounting ears .... broke a mounting ear off my old carb that way. IF I find this gasket to be the issue I think I will replace it with the standard thin gasket .... only potential issue then will be possible vapor lock from heating up the fuel. Still grasping at straws trying to figure this mess out. Don't really want to blame the carb since its essentially brand new from a reputable reman company ... but didn't have any of these issues with the old carb .... just a broken mounting ear. hmmm so tomorrow morning I will go vacuum leak hunting

 

Simple enough to disconnect the EGR vacuum line and plug it. Might ping under light acceleration at highway speed though if you do.

 

Could be the float levels in the carb are set too high. When braking fuel could be sloshing and dripping over into the engine. After is runs a little bit it clears up. This is all theory also, but you could test this by looking down the carb throat when it's messing up and look for any liquid fuel dripping into the engine. If you see liquid fuel, your float level is too high.

Dirt can also cause this, making the needle hang in the seat and not seal off, causing the fuel level to be too high in the carb.

 

I thought about the float levels early on with this problem. But the issues are occurring even after only driving a short distance at low speed with no hard braking. Checked the floats anyway just to be sure and they are both sitting just at the sight window ... only trickles out with a slight rocking of the truck. So I think they're all good. Still leaning toward an exhaust leak that only comes into serious effect when the engine is hot ... so I am about to pop the hood now and have a look

 

ok. Here is what I have found. Popped the hood and did a visual inspection ... no obvious sources of vac leak. Tightened the carb down to torque specs just in case. Started it up and got it going and idling perfect (once again). Hopped in and drove 3 miles to O'Reilly to get a can of carb cleaner ... soon as I got to the bottom of the freeway exit the issue started up again. Choppy low loppy idle and poor off idle throttle response at least until the accelerator pump kicks in. So I got home and started the carb cleaner vac leak hunt. What I found was when I spray carb cleaner lightly around the choke cap where it meets the choke housing I get the tell-tale idle increase from the carb cleaner ... vac leak! Small but its there. I had also hooked up my vac gauge to confirm things and I was getting 13hg when before I started driving down the road I was getting 20hg .... so curious why this only starts to leak when its been run down the road .... choke cap heats up? Weird because I had it at full operating temp in the driveway with the choke working fine and fully disengaged and everything was fine. So confused