351C where to start?

[Cleveland Crush]

+1 on an AF gauge (wideband). Pull a couple spark plugs to get a read on them. Post some good quality photos of your spark plugs and we can offer some help.

 

[boilermaster]

351mach1,
never seen a cleveland need smaller than a .031 primary squirter, get a .033' and a .035''
you want just enough and no more.
Boilermaster

 

[Stanglover]

Now that I am a Holley tuning "expert" after 30 minutes of youtube this morning, I think my choice of carb is just fine for my stockish motor with auto trans. 600 CFM may be a bit small if I ever go with more power but for now its fine. the 4160 doesn't have a secondary metering block which is apparently beneficial for a stock engine with auto trans. If I ever drop the 5 speed in and rebuild the motor, I can add the secondary metering block via a kit but I personally would probably just be purchasing a larger carb (likely a 700 CFM 4150). Drilling holes in the throttle plates is generally for motors with very large cams that have issues idling. Probably not my case. My carb is currently sitting at 15" of vacuum.

I have an awful smell of gasoline inside of the car while driving. I thought it was a major exhaust leak but now I am thinking I am just running ridiculously rich. I think its time I purchase a timing light with tach so I can dial in the dizzy recurve myself and then really dig into the carb tuning. I don't really like paying mechanics for things I can figure out myself so I still have a lot more patience on this before giving up. I also very much enjoy becoming more knowledgeable on what I am running. If it gets to the point where I need to mess with the power valves I may enlist an expert but I think I should be able to get it pretty darn close with normal tuning and possibly swapping out the accelerator pump nozzles.

I am still learning if I actually need a smaller nozzle or a larger nozzle. I may purchase a .025 and a .035 and see how they each affect driveability. I could also play with a different accelerator pump cam but that will probably be the last thing I try to do.

Edit: maybe also worth investing in an air/fuel ratio meter

Messing around and learning as we go is a big part of the fun of owning one of these beasts. I knew practically nothing when I joined this forum and now I know almost nothing.......... and that's a big improvement.
As for the drilling of holes, my "guy" told me it was because Holley carbs tend to be too rich on the idle circuit and these big valve engine need that extra air. I do have AFR bungs welded into my exhausts and I did use an AFR which shows an almost perfect ratio. The plug read confirms that.
I also tried different pump cams but ended up with the original one, which seems to be the best option. I have tried differing choke settings, but again went back to a stock setup.
Have fun.

 

[73 SGM Mach]

Just a thought since your car has amnesia, it’s possible your symptoms point to a contamination fuel tank. I know you changed the carb, but did you trace back to the pump and the tank to verify clear fuel flow? Since the PO didn’t give you the straight story, what else did they fail to mention? Just to alleviate worry, I would check that out. Good luck.

I had a lot of issues with my car also that were similar. I threw alot of parts and money at it to fix it but it all boiled down to a gas tank full of crud. Fyi there is alot of good people in here that can help you out. Just keep plugging away at it!
Jeff

 

[351mach1]

I had a lot of issues with my car also that were similar. I threw alot of parts and money at it to fix it but it all boiled down to a gas tank full of crud. Fyi there is alot of good people in here that can help you out. Just keep plugging away at it!
Jeff

I have come to the conclusion that I would be foolish to not replace the fuel tank. It's on the list now!

 

[351mach1]

Installed a new fuel tank. The old one was way nastier than I had thought. I now have fresh clean fuel and fuel filters.

SO: I am still having a little off idle stumble that I can't seem to tune out. I am not sure what else to check. Anyone have any advice?

-I re-checked the timing. I am at 16* initial with 36* all in at 3000 RPM. Timing is steady at idle and at 3000 RPM
-I have 15 inches of vacuum at idle. Vacuum is steady
-I don't have a way to check the AF mix so I am just going by vacuum reading
-I am about a full turn out on the Fuel mixture screws. It doesn't seem to like going much more lean than there.
-I reset the transfer slots to the proper amount recommended. When I did this I was idling at 600 RPM and it was way too low. After a few adjustments I can get the engine to idle very nicely at 720 RPM. I have been mostly driving with the idle set at ~700 RPM but I thought maybe it wants a higher idle so turned the idle screw to ~820 RPM
-I tried a .035 accelerator pump nozzle but that seems to make the stumble worse. I haven't tried the .033 and I went back to the .031. I don't seem to be getting a super solid stream out of the nozzles.
-The accelerator pump is adjusted correctly.

Not sure where to go from here. The only thing I can think of is that some dirty fuel got in the carb but even with the dirty tank I was running 2 brand new fuel filters so I don't thank any major debris could have gotten in. I almost want to try swapping carbs but I know carbs are generally user era and that there is likely nothing wrong with my brand new carb.

 

[Cleveland Crush]

Installed a new fuel tank. The old one was way nastier than I had thought. I now have fresh clean fuel and fuel filters.

SO: I am still having a little off idle stumble that I can't seem to tune out. I am not sure what else to check. Anyone have any advice?

-I re-checked the timing. I am at 16* initial with 36* all in at 3000 RPM. Timing is steady at idle and at 3000 RPM
-I have 15 inches of vacuum at idle. Vacuum is steady
-I don't have a way to check the AF mix so I am just going by vacuum reading
-I am about a full turn out on the Fuel mixture screws. It doesn't seem to like going much more lean than there.
-I reset the transfer slots to the proper amount recommended. When I did this I was idling at 600 RPM and it was way too low. After a few adjustments I can get the engine to idle very nicely at 720 RPM. I have been mostly driving with the idle set at ~700 RPM but I thought maybe it wants a higher idle so turned the idle screw to ~820 RPM
-I tried a .035 accelerator pump nozzle but that seems to make the stumble worse. I haven't tried the .033 and I went back to the .031. I don't seem to be getting a super solid stream out of the nozzles.
-The accelerator pump is adjusted correctly.

Not sure where to go from here. The only thing I can think of is that some dirty fuel got in the carb but even with the dirty tank I was running 2 brand new fuel filters so I don't thank any major debris could have gotten in. I almost want to try swapping carbs but I know carbs are generally user era and that there is likely nothing wrong with my brand new carb.

Simple things first:
Back the idle screws out (counter clock) 1/4 turn. If that cleans your stumble either leave it alone or go back in 1/8th turn to see what your engine likes. Sounds like your close to nailing it!

 

[Q1SVT]

SO: I am still having a little off idle stumble that I can't seem to tune out. I am not sure what else to check. Anyone have any advice?

-I re-checked the timing. I am at 16* initial with 36* all in at 3000 RPM. Timing is steady at idle and at 3000 RPM

-I tried a .035 accelerator pump nozzle but that seems to make the stumble worse. I haven't tried the .033 and I went back to the .031. I don't seem to be getting a super solid stream out of the nozzles.
-The accelerator pump is adjusted correctly.

Not sure where to go from here.

I posted this youtube link before, but you might find the tuning part helpful...

Great tuning info.

If you change the fuel tank hopefully you changed out the fuel lines?

Open chamber heads seem to like a lot of tining... UT took 42*

UT showed the accelerator pump cam change helped a lot.

jm2c

 

[351mach1]

Great video!

I'll keep working on the accelerator pump and nozzle adjustments. I think I'll try to give it some more timing too. Most of the research I have done says to never go more than 38* on a Cleveland.

I did not replace the steel fuel line but did blow it out with compressed air.

 

[boilermaster]

351mach1,
what color accelerator pump cam are you using and at what position is the pump cam installed ?
Please be aware that you change cam or position you will need to re tailor pump clearance each time a change is made.
same goes for removal of the float bowl.
Boilermaster

 

[Sheriff41]

Does the stumble occur under normal acceleration or just under hard acceleration?

 

[351mach1]

Turns out a lot of dirty fuel got into the carb. I disassembled and cleaned the carb and I was oh so close. I took it on an hours drive on the highway and everything was feeling great. The stumble was about 99% gone; just a little blip on hard acceleration from a stop. I had the .033 nozzle in there so I decided to tinker a bit trying all three nozzle sizes. Things got progressively worse from there. I felt like the .035 was performing the best so I stuck with that and went for a test drive. I was trying to figure out under what conditions the hesitation was the worst. The hesitation is the worst under hard acceleration especially from a stop. If I ease into the throttle and then accelerate hard, there is essentially no stumble. There is essentially no stumble under normal acceleration.

While I was testing, I was cruising at about 40 mph and stabbed the gas to feel for the hesitation. It immediately stalled out. I pulled over onto the side of the highway and tried to restart but it wouldn't start. After about 5 minutes of sitting, it started up like nothing was wrong. I took it home and checked things out but couldn't find anything wrong. It was starting and driving without trouble so I figured it was a fluke and decided to drive out to the mountains for the sunset. I was aggressive on the throttle leaving town trying to discern the stumble. I was cruising about 50mph and stabbed the gas to WOT. Again, it immediately stalled out. I pulled over and had another crank with no start. This time it took about 30 minutes before it finally started. I was about 5 minutes away from abandoning it on the side of the highway for the night. I limped home with my tail between my legs.

I know I am getting close but now what is going on? Am I flooding the engine when stabbing the throttle causing it to not want to restart? Is there anyway I could have damaged the carb with dirty fuel or when it was backfiring previously? Damaged power valve? I am definitely learning a lot about Holley carbs

Couple other tidbits:
-I have the orange pump cam in position 1
-I backed off my timing to 14* initial and 34* total. I did not try moving it up as it seems to be running the best that is has been but I may try tweaking it forward next time I play with it.
-I still don't have a way to check AFRs so still just going by Vacuum/Rpms

 

[Q1SVT]

I was cruising at about 40 mph and stabbed the gas to feel for the hesitation. It immediately stalled out.

I was cruising about 50mph and stabbed the gas to WOT. Again, it immediately stalled out.

… she needs more fuel from the accelerator pump CAM, sooner/faster. Adjust the cam or change to a bigger cam. The video shows how to test for your issue. If that fix’s the issue, I would then install the .033 and then retune fuel.

 

[351mach1]

… she needs more fuel from the accelerator pump CAM, sooner/faster. Adjust the cam or change to a bigger cam. The video shows how to test for your issue. If that fix’s the issue, I would then install the .033 and then retune fuel.

Ok I get that and will try a different cam but what I don't understand is what is causing the no start issue after stalling?

 

[Q1SVT]

Many things can cause non start.
After driving and engine is fully warmed upped, if turned off does she start right away? Or is the same as after she stalled…

“It immediately stalled out.”
Generally a lean problem
If there is bogging of the engine, generally too much fuel.

EDITED: Took a little time to read through your thread.
Think you have a fueling issue... 1) Heat sink - trouble restarting 2) not enough fuel at higher speeds

You installed a new intake, but bolted carb directly to the intake.
Would reinstall your carb spacer and a thicker heat gasket between them. Google for a Ford 428/429 carb gasket generally they are about 1/8-3/16 thick four holes.
jm2c all carbs bolted to a two hole intake should run a four hole spacer.
Improves carbs ability to get a good signal...


Fuel issues... you replaced tank and a carb, this crud in the carb is BAD...
Need to replace all fuel lines and clean fuel pump. Check routing to prevent heat sink issues



Maybe need to replace fuel pump? pic below and above shows an OLD pump [cannot tell brand or GPH spec. not all pumps deliver enough fuel for modified engines, performance level

 

[basstrix]

IMO, your stalling issue is the first order of business. Has the gas tank been replaced with new or, at least, thoroughly cleaned? What do you have for fuel filters? If filters are in place, you should not be getting sediment into the carb. I suspect you have a fuel filter, but it's partially plugged and is passing some sediment. My suspicion is that while cruising, you're getting enough fuel to keep it going, but when you're aggressively accelerating, fuel in the bowls gets depleted....sitting and waiting, allows some fuel to seep past the plugged filter and into the bowl enough to get you started up again.

1. Check fuel filter(s). You need 1 between the fuel pump and carb.
2. If the tank hasn't been replaced, I highly recommend removing it and looking inside to confirm that the zinc coating is intact. If it's not, replace it. It's a couple hundred bucks well spent.
3. What power valve are you running? The typcial PV is 6.5. My preference is an 8.5 to get the enrichment going at a slightly higher vacuum level. It won't affect your cruise air fuel ratio because you'll be at much higher vacuum than 8.5". I also like the Pink cam for 4v clevelands. What cam are you running?

I saw on another post that you have an electrical issue? That sounds kinda scary....our group expert is Midlife....he's your best resource, but to me it sounds like the harness may be getting ground through the cigarette lighter circuit....we don't want to read about you having a fire under the dash and losing that beautiful mustang, so please....get that properly resolved.

 

[boilermaster]

351mach1,
Still got that aftermarket ignition module bolted to the shock tower ?.
Boilermaster

 

[351mach1]

Stellar info! Thank you fellas! Lots of info to sift through and I'll try to answer it all. First off, I went back to the .033 and advanced my timing to 16* initial and its running great. I still have the pesky stumble but it only stalled once when I stabbed the gas and it was when I was really beating on it. It started right back up after it stalled though. I haven't had any hot start issues up to this point. Also its been generally between 45-70 degrees when I have been working on this car so not crazy ambient temps. To me, I feel like I am over fueling and flooding the engine when I stab the gas but I am probably wrong!

I have replaced everything in the fuel system except the fuel pump and steel line (which appears to be in good condition from the outside). I think you are onto something with the fuel pump. I ran new filters before and after replacing the fuel tank. After replacing the fuel tank, I blew out the steel line with compressed air and have 2 filters, one normal metal can (WIX) before the fuel pump and one clear one (edelbrock) going into the carb. The clear one going to the carb shows clear clean gas coming in. There is one or 2 specs of dirt in it that are probably remaining from the fuel pump since I did not change the fuel pump out. I was planning to run 2-3 tanks of gas through the system and replace the fuel filters again.

I didn't think that much crap could get through 2 brand new filters in a row but the carb says otherwise.

-Everything in the fuel system is new and clean except the pump and steel line
-I am running this carb spacer https://www.summitracing.com/parts/EDL-8725
-I am using Edelbrock performer intake
-the ignition box is still on the shock tower
-I am running orange accelerator pump cam in position 1
-I am pretty sure I have the 6.5 power valve (forgot to snag a picture but remember seeing a 6)
-Videos of hesitation: https://photos.app.goo.gl/QHqbxMKFY6uEeiqb8

Plan of action:
-Replace fuel pump
-Replace steel fuel line
-Check Fuel pressure
-Run a tank of gas and replace fuel filters
-re clean carb
-Move ignition box into the grill somewhere
-Potentially try pink pump cam and or 8.5 power valve
-Get wiring refurbished by midlife