Carb/Timing

Hey all, I’ve once again found the time to jump down the rabbit hole of getting this thing running the best it can.

Since my last attempt, not sure if I mentioned it before but I found that my AOD TV Cable was adjusted pretty far off, and now that it’s correct my issues are a lot better, still not 100% however. I also looked over my spark plugs and now my #4 and #7 are not all sooty and fouled as they were before. I’ll link my previous thread for reading and the history of the issues.

I took out the plugs today to read them, and I noticed that my #1 plug was wet, not terribly but a bit, so I got out my borescope and took a picture, and even though I hadn’t driven the car for a day or two, it looks like a small amount got past the rings. I’ve never had any blue smoke or oil issues before so I’m unsure of the severity of it, perhaps just a fluke but I’m unsure. All the other plugs, the porcelain was all white on top, ground strap had a black line slightly above where it’s welded on, and the whole top “ring” was black. I looked down the porcelain further with a light and I could see that #3, #4, #7, and #8 had the darker grey/black, coating higher up on the porcelain than the other 4, so I figured the secondaries were a bit rich.

I swapped out my main jets, now I’ve got 66’s in the front, and 68’s in the back, all the idle adjustment screws out 1 full turn. The worse issues are when it’s not fully warmed up. On the 1-2 shift when it’s cold, it stumbles very bad, and takes a little bit to recover, but once it’s warm, it only has a bit of hesitation, and just some general unresponsiveness at light throttle. This is so far the best it’s been, once it’s warm its actually driveable.

I have once or twice in the past noticed that the area in the intake right under the carb is wet, as if fuel is not atomized there and just staying stuck in the waffle pattern there. This has happened whether it’s warm or cold.

Here’s the plugs


Here’s cylinders 3 and 7, all the cylinders look the same as these.


And here’s Cylinder 1, with what seems to be oil at the bottom, and on the wall.

Well, a lot of reading to get caught up. What works for me, is just basic carb stuff. Disconnect and plug the vac advance. Then adjust timing, idle speed, and bleed screws, to get the most vacuum at idle, in inches as you can. Drive, make sure it doesn’t ping, or stall on decel at a stop. Adjust idle speed if necessary.

I’ve done a lot of the basic stuff a few times, I’ve set the timing and avoided pings, tried different rates and initial timing, I drove it today with no vacuum advance, and with vacuum advance on the timing port, didn’t make a noticeable difference in my issues, which I thought was odd. I’ve had it on full vacuum before too and that’s a noticeable change, but most people have different opinions on how it should be set up. I’ve tried different jets, adjusting for the transfer slots, idle screw adjustment, I’ve made sure that my fuel pressure is constant and high enough. Fuel float level is correct, but I’ve had it lower and higher and no dice. Power valve swaps haven’t done much either. The only things I haven’t messed with is the Accelerator pump and nozzles. It doesn’t have a problem off the line, and if I floor it, as long as I am not decelerating beforehand, or in the middle of a shift, it responds fine, so I assumed accelerator pump and nozzle was fine.

The only things that I’ve noticed that I thought was odd, was that when it shifts, the vacuum drops drastically. In park I get like 12-14" of vacuum, in drive I have at least 8-10", and but when it shifts, under light acceleration, it’ll drop from 8 to 3" real quick, and take a while to recover. The car is also easier to drive at WOT than light throttle, and when I start it up, it’s easier if I floor it, as if it isn’t getting enough air. After it warms up, it can also be harder to start. Other than those things, no real issues, it’s great if I floor it, and down the road at WOT it works much better than light or medium throttle, which is where I’d mostly be since it’s going to be a semi daily driver.

It seems to me that your problem is probably related to the low level of vacuum you are getting. Without proper vacuum the carb won’t work right since vacuum is what creates the air flow necessary for proper mixture.

12-14" of vacuum at idle is not. Ideally it should be 18-20. What is your vacuum at idle with all the vacuum ports capped off (disconnect trans, PS, lights, dizzy, etc.) If it is above the 14" you are getting then you have a leak or leaks somewhere and you need to track them down (reconnect each hose one at a time). If your baseline vacuum is only 14" or less then you may have a leak around the base of the carb or the manifold may have a leak.

If I recall correctly you have a pretty radical cam. Could you remind us of the build specs?


The cam, and pistons were custom from Brent Lykins, who I was recommended to a while ago when I first started rebuilding the car. He also recommended the Edelbrock Airgap and Quick Fuel 680 Carb.

I figured with the cam I’ve got, a lower idle vacuum like that was to be expected. I’ve not checked it with everything disconnected, I’ll have to try, but I know the manifold and carb don’t have leaks, I’ve checked a few times and redone the manifold gaskets recently. Most of the hoses are new, I know the AC hose system is sealed as I’ve gone through every hose and tested them, and my vacuum headlight system works properly too, but I’ll try it out.

The low vacuum is only when it shifts, while driving I have a good amount of vacuum, and if I go from light throttle to off the gas, I see it shoot up, so I thought perhaps my low vacuum was due to the rpm drop when it shifts, perhaps a combination of the vacuum drop, and the increased load of 2nd gear. I recently swapped out my 3.00 rear gear for a 3.89, to try to bump up my rpms on the shift, but another option some people had mentioned was swapping out the torque converter for a higher stall speed, since mine is just the stock AOD, which I believe is quite low.

Swapping the torque converter is probably needed with the cam you have. It might increase vacuum by a couple inches of mercury. Not a big change in vacuum but it would help drivability a lot.

The cam that you have IMHO is made for a really aggressive 351C with a pair of 1050 CFM Dominators on a tunnel ram, with long tube open headers and a 4.56 rear gear. It likely needs 7500 RPM to peak in power. Ported heads, lots of compression, all those things go with that cam.

Yeah from what I’ve read, I thought this cam was a bit radical for what I told Brent. I’m not going for drag racing or anything of the sort, no crazy HP numbers. Although it’s my first build so I figured he would know better than I would.

If the torque converter or cam were the source of the issue, wouldn’t that cause problems equally across all temperature ranges however? It does get noticeably better once it is warmed up, not completely fixed but much better.

I don’t know how to say this delicately but if the car were mine and I planned to drive it daily I would not pick that cam. Sure it is a little better when warmed up - that’s true of any cam / engine / car.

Cams “soak up” in big cubic inch engines so for a 351 engine - maybe .030" over right? - I would be looking at a 218 - 218 cam with maybe 115 LSA and .525" lift. Then you could get by with the gears you have, with maybe a 2600 RPM converter stall speed. It would still need headers and maybe a 750 CFM carburetor. Should be capable of 16" vacuum.


Alright, well I’ll have to look into some options, I’ve already got a set of long headers on it and a larger dual exhaust on it. I don’t mind swapping out a cam, however I’ve not messed with the whole valve train, I had a machine shop assemble it, and they put those newer honeycomb style springs on it, would there be an issue since those springs are setup for the extreme lift it has now?

I’ll have to look at all the parts on there but the whole valve train was upgraded for this cam, so I figure going with an milder cam wouldn’t give me issues, but I’m not familiar with this stuff too much.

The lifters, springs, and pushrods ought to be fine. Going with a smaller cam with less lift and duration will make boatloads of low and mid range torque - the car will be fun to drive, and probably faster than it is now.


Alright well I guess I’ll get looking at some cams. Any rules of thumb to follow? I figure higher than 111 LSA, between 215 and 225 on the duration, and somewhere between .510 and .540? Not sure if there’s any secrets the 351C has that might be useful.

From what I’m searching up there’s not too many cams with a lower lift for a hydraulic roller cam setup. Looking up some CompCams, the lowest they’ve got is either below .510 or .566 and up. Must be out of stock on a lot of stuff to not even see the listings. The closest one that isn’t months away is a CompCams 284HR, but even that is in that .566 range.

Don’t get too fixated on vacuum numbers. For that cam, the vac numbers look pretty good. That cam isn’t that radical. It’ll give good sound and street performance. You probably wouldn’t want much more for the street. My station wagon has a similarly sized can 227/227 with a 113 lobe separation. There is sufficient vacuum to operate power brakes. The idle quality is very good and it has great performance.
What you need to focus on is your timing curve. Your initial timing without vacuum should be set just shy of kicking back during starting after a hot soak on a hot day. You will probably be looking for 34-36 degrees of total timing. To keep a high initial setting and not exceed your total will require narrowing the range of the mechanical curve in the distributor. Depending on other components of the vehicle will determine how quickly your mechanical advance swings out. Then add vacuum advance as needed with an adjustable advance unit. I find somewhere between 8-14 degrees on a street engine works pretty well. Don’t be the guy that has an advance unit that is not adjustable and pulls 20 degrees-----and you are detuning other parameters to accommodate. Timing is an essential operating parameter. As far as running your vac advance off manifold vacuum, it generally gives you a smoother idle an allows you to close your throttle blades a bit more-----which should increase vacuum.
For the trans, a 2500-3000 stall convertor, like a really tight 10" would be a nice compliment. Note: on a street driven AOD that sees cruising miles --and— has a high stall convertor, you should retain the direct shaft. When retaining the direct shaft, it doesn’t matter how much convertor stall you have. If your AOD has a one piece direct shaft, you will have to be more conservative with stall speed. Stay down around 2000-2300. It also depends on your gear and what your cruising rpm will be. Tell me about your AOD and what rear gear do you have?
About Brent Lykins… The Ford engine community is lucky to have a guy like him. I’ve dealt with multiple people who either don’t know or are only looking to pedal parts telling you what you want to hear. Brent is a great listener and puts a lot of effort into finding the best possible solution for your application. Super knowledgeable guy that talks accurate info in a good-neighbor fashion.

Can you mention where your ignition timing events are set at:

Initial:_______
Total mechanical:______
Total mechanical is all in by this rpm:______
Vacuum Advance range:______

Vac Advance is via manifold or ported?

Explain your method to view where these events of timing are set.

Over a long period of time I’ve tried a lot of different timing curves.

Currently my initial is around 12-14, total mechanical is 35, total is all in by 3000, the vacuum advance range seems to be about 10 degrees, perhaps 12. I’ve got the vacuum on ported currently.

I drove it on the freeway yesterday for a friend’s music video shoot, and I’ll most likely take it off the ported vacuum as it was pinging at highway speed whenever I’d get on the throttle. Or just change it to a lower advance amount.

Over the months I’ve tried slower curves, faster curves, the smallest advance bushing which is only 18 degrees, with an initial of 17, I’ve tried the opposite with 10 degrees initial and the silver bushing which is 25 degrees. I’ve read different people’s ideas on ported or full, I’ve tried both of them, and tried not having it at all and while I obviously notice the full port is active all the time, even with my timing adjusted around that, no issues got fixed.

Other than the pinging at highway speed I’ve not had trouble with timing, or at least it’s never fixed any issues I’ve had. No matter the timing setup I still get bad hesitation on shifts, and when it’s cold, popping out of the carb.

I’ve got a timing light, and it’s an MSD distributor that came with the parts and a graph of the curves with different springs/bushings, but I have seen it get to the correct total timing at 3000 like the graph says it should.

The AOD is a rebuilt unit, 2 piece input shaft, it has a shift kit in it, not that I was really looking for one but that was the closest available rebuilt AOD. I’ve set the TV pressure correctly according to procedures online and on the Lokar paperwork. It has the stock converter that came with it, which is one of the other suspects, I just figured since the problem got better as the car warms up that it might not be that.

I’ve got a pretty standard 9" rear, with a TruTrac and 3.89 gears. All new, less than 150 miles on the rear.

When you get off the gas the vacuum signal in the carb goes to zero, maybe even slightly negative. The cam you have is designed to produce horsepower at high RPM and I bet it does a good job of that. Everything you are describing is not full throttle acceleration and typically what you sacrifice to get big horsepower number out of your engine. The more you build this thing into what works around the cam the better it will behave.

You have to remember that the engineers in the '60s had to make all kinds of trade offs to make these cars start and run in cold weather, run half way decent while warming up, not over heat in summer, and then to make some power at the same time. For some reason people think that the engineers left a lot of “no sacrifices” power on the table, and that you can bolt on some stuff and get all this free power. Man I wish it worked like that.

Modern engines use variable valve timing, electronic fuel injection with multiple downstream sensors, fully electronic ignition that independently fires each cylinder with active knock sensing and sensing for every environmental condition. This is how the Coyote can get incredible output per cubic inch while being street-able at the same time. So far, using technology from the 1960s just can’t match this.

I know this sucks after you have spent the money and done the work. No advertising ever claimed: 50 more horses that you will never be able to use. Decrease your gas mileage, make it harder to start, eliminate your low end torque, and make it ping with anything less than race gas and a 72 degree day. But there you have it.

Probably your best bet is to go with as much modern magic as possible: Sniper or other EFI that can also control ignition. Even then most Sniper issues arise from too much cam and too high of an expectation of what is possible.

I appreciate the honesty and I do agree that the cam could be/probably is the issue, nothing against Brett and he did help me out with other things and he seems to be a great guy, but just about everyone I’ve talked to agrees that it is a radical cam, at least lift wise.

At this point I’m willing to try anything else someone here advises, such as what 9F91H581221 was saying, but I’d rather try the cam swap than get into the modern EFI stuff and all that. Perhaps down the road but not now.

Thanks for the ballpark specs on the cam Bill, I’ll keep looking to to find something around what you mentioned, even though there doesn’t seem to be anything too close. I’ll probably keep fiddling around until I bite the bullet and get a different cam.

Your ignition timing sounds pretty good. However, pinging says there is something a bit off.

You’ve been at this a while. However, you still need to do further testing and charting out timing curve at 500 rpm intervals with your timing light to know where the timing actually is at what rpm. What vac levels does your advance start to pull and top out? Run a vacuum gauge in your car or tape it to the windshield. Then pay attention to at what rpm your engine pings and whether your vacuum advance was being pulled or if it didn’t matter because engine vacuum was below your “start vacuum”. If you plug the vac advance, does it still ping on the highway? If so, you may want to take a few degrees out of the vac.

The replacement cam specs you mentioned of 215-225 with a 111 lobe sep is about as much cam as what you currently have…since the current cam is 225/233 with a 113. The 113 is going to give you better idle characteristics than a 111. The lobes are not that aggressive. This is sometimes done to bleed off a little low end compression to help suppress detonation. Are your heads 2v open chamber? If so, and you reduce duration to help low end, it will ping worse. It’s funny how the closed chamber heads can run another point of compression on the same octane.

Your cam is moderate. It is by no means radical. It probably tops out at 5700-6000 rpm.

Lift has ZERO to do with your problems. You can reduce lift by putting on 1.5 or 1.6 rockers instead of the 1.73. Not sure if there is a rocker in that ratio that fits a 351c.

What temp is your thermostat? Does you engine run at that temp?

What RPM does the pinging on the highway happen? What gear are you in? Depending on the rpm you may need to tighten spring for mech curve and widen the vac range. Mechanical advance is solely based on rpm. Vacuum is dependent on engine load.

When the AOD is in 3rd or 4th it really harnesses down engine rpm exactly the same as a manual trans. It is a direct mechanical connection. No floating around rpms in a fluid connection like in 1st and 2nd. If shift timing is not set up correctly —for example if the cable is set too loose, it will be like driving in too high of a gear and not kick down for passing gear when sufficient throttle is applied. You would be better off to sway towards the cable being too tight for later shifts and easier kickdowns. Or change the governor for higher rpm shifts.


Go on ebay or Amazon and look for the book Dr. Jacobs Guide to Optimizing your Ignition. It’s from the 1980’s, but it’s not outdated for the procedure in finding the correct ignition curve for your engine in your vehicle.

Popping out of the carb is often referred to as a lean sneeze. There are probably other causes, like ignition crossfire or valve sealing that may promote popping. No vacuum leaks? Might be a stretch to consider doing a cylinder leak-down test. One thing that doesn’t take a lot of time is find a totally dark area to open you hood and look for spark leakage from the cap, wires and plugs. Let your eyes adjust for a bit. It’s surprising you can see the spark going through the porcelain plugs.

I’ve never used an Air Gap intake. My thought is carb temp is going to be hard to control. Heats up in traffic, cools off while cruising. Which do you tune for? Maybe this is where a self tuning EFI will help.

Hesitation on shifts. Are you talking the 1-2 shift? Or, 2-3? It is characteristic of the AOD to cause an engine to fall on it’s face on the 2-3 shift…because it totally takes away convertor stall. Higher shift points will help this.

You have a lot of stuff weighing in on this narrow balancing act. I say narrow because certain things will require tuning to be more spot-on than just being in the ball park. AOD, Air-Gap, moderate cam, compression on the edge of available octane. Glad you got rid of the 3.00 gear.

You’re kinda far. Too bad you weren’t coming to Carlisle. I’d like to road-test your Cougar.

What does your current AOD convertor stall at if you foot brake it? I would suspect 1800 perhaps 2000?