427 Stroker. Hard Starting. Need advice

[robertjamesellis]

Need any advice folks can offer on how to get this 427 Stroker into final tune so its easier to start. Here are the specs
Ford Z Head 427 Stroker off 351w.
QuickFuel Carb HR-680. Primary Main Jet: 70. Secondary Jet: 74. Power Valve 6.5.
AGSP32 Motorcraft plugs as recommended.
Timing set at 32 @ 4200 rpm as recommended.
Cam Lobe: 110. Duration: 242. Lift .594/.618
Using 91 Octane Fuel.
Live in San Francisco bay so I'm at sea level.

I sensed it was running rich as I could smell some gas vapors in exhaust. Pulled all the plugs and each one was black with soot. Rich condition was confirmed. Replaced with new plugs.
Installed PE Wideband lambda O2 sensor on drivers side pipe. Again, confirmed I was running richer than needed. Meter is set Set for 14.7:1. Was at ~ 0.95 at idle and in 0.80's at high rpm's.
Then I set all idle bleed screws to max vac. not all set at exact same turns. I'm at about 1 1/4 turns out but I don't know exactly.
Now O2 says I'm running at ~1.15 at idle. Running ~0.90 at highway cruise. ~3,000 rpms'.
Definitely runs better now but still hard to start. Has tons of pull but at highway cruise when I give it a hard push on the gas I get slight bumping as it accelerates. Not smooth like I would expect.

Typically, to start I push in gas pedal 2-3 times, take my foot off the accelerator and turn it over. If it doesn't catch, I repeat. I think I'm flooding at that point as I usually have to give it some pedal before the engine will catch. I checked the electric choke and set that to just closed at cold and that hasn't seemed to help with the starting. On the positive note, once its warmed up it will immediately restart with barely a turn of the key. Whether its cold outside or warm doesn't seem to have too much affect although I would say it cooperates more in warm weather.

I checked float bowls and both are right on the site lines as recommended by QuckFuel. I also have a fuel pressure meter installed right before the carb and its running at 6psi. I don't think getting gas is the problem. I'm thinking its not getting the air but I'm learning as I go.

Once started it will idle fine although it tends to want to stay at a higher idle speed to keep running somewhere around 1,100 according to my rpm meter, not the dash meter. And thats after it warms up.

It feels like I'm close but I can't get a good easy start and running perfectly smooth at fast acceleration and was hoping I could find some advice among the carb experts here. What should I do next? Is there anything else I can do or is this just the nature of the beast? All advice appreciated.

Thanks,
Rob

[mike223]

393W / 10.5:1 / 750DP here.


I removed the choke plate and only use the choke (manual) to set a high idle while I'm warming up.


Is yours hard to crank?


I have separate starter and ignition switches - Engage the starter, get the engine turning over, and then flip the ignition on.

That's an old race car starting trick - useful when you end up with a little too much compression + significant low RPM timing advance.

[rich grsc]

Sounds like the timing is off. Whats your base timing at idle?
Your thread title says hard starting, but you say "warmed up it will immediately restart with barely a turn of the key". I wouldn't consider that as hard starting??

[Jim1855]

Base timing, probably about 15-18 degrees at 1,000. Then all in at 3,200 to 3,600
Start at 1 pump but that was with a double pumper, lots easier to add gas than wait for it to evaporate. The extra fuel floods the engine and washes down the cylinder walls.
I don't know anything about chokes, haven't run one in years. Since these are normally warm weather cars not sure about the concern for a choke.

Jim

[OVCobra]

Rob
I am using a Quickfuel BDQ-650 (has no choke) and your starting method is very similar to mine...pump a couple times/turn over/repeat until it catches. It seems that you are not creating a rich enough mixture for a cold start likely due to the choke not being fully closed.
My recollection with electric choke Holley carbs is that you should only push the accelerator to the floor once and then try to start it it. While I am not certain I believe the multiple pumps may release the choke from full choke to partial.
Good luck.

[NAZ]

I’ve never worked with the QFT HR-680 but can give you some basic suggestions. First, what is your base timing (no vacuum advance and at hot idle RPM which you could hopefully get closer to 700 RPM)?

Your idle AFR of 16.91 (1.15 lambda) is supper lean and going to need more advance to fire the lean mixture than a typical carb idle AFR which is usually on the rich side (~12.0-13.0 AFR or .82-.88 lambda on your meter). Your high idle RPM sweet spot is likely a result of the lean idle.

The 3,000 RPM cruise AFR of 13.23 is a bit rich for light cruise, I would prefer that your idle and cruise AFR readings were reversed. The 13.2 AFR would make good power at WOT under heavy load but not the most economic light cruise AFR. BTW, I hate dealing with lambda – so used to AFR numbers I have to get a calculator out.

For now, I suggest you adjust the e-choke full open when cold to eliminate a variable during troubleshooting. I live at 7,000’ ASL and it’s cold here in the winter but I don’t have choke on my hot rod, don’t need it!

Did you check the idle transfer slot opening on secondary side (does that carb even have one??)? On a Holley or QFT that uses an idle transfer slot you don’t want more than ~.040” uncovered at idle (approximately square) or you start losing your idle AFR adjustment. And don’t be surprised if one side is uncovered more than the other due to quality control issues so I use an average between the two on each end of the carb for initial set-up.

Your hard starting condition is likely due to the lean idle condition. A lean idle condition may be caused by a vacuum leak allowing air to bypass the idle circuit. Check for vacuum leaks before increasing the size of the idle jet. But do what it takes to richen up the idle. Once the idle and hard start condition is solved, work on the light cruise AFR and get this closer to 15.0-16.0 AFR (leaner is better) and no you won’t hurt the engine under light cruise lean conditions – this is not the same as WOT under load lean.

[CFranks]

I had similar symptoms on mine (also a ford racing 427 but with x heads and a 680 QF carb). Not sure how long yours has been sitting, my issue was the gas gunked up inside the carb since it was sitting before I bought it with untreated pump gas. Once the carb was cleaned out, haven't had a problem since. Not sure if yours has been sitting with untreated gas for a period of time, if so something to consider or possibly other dirt in there.

[robertjamesellis]

Its definitely hard to crank. Burnt up my first starter trying to get it running. This second one now gets hot if I crank over more than 4 times.

Not sure if I'm ready for the separate ignition and starter switches yet, but I'll keep that in mind. Thanks for the tip!

[robertjamesellis]

Base timing is at 11 degrees. Thats at ~1100 rpm idle and vacuum advance off.

[robertjamesellis]

I agree. I'm going to a single pump and then a crank.

[robertjamesellis]

Thanks for the help Naz. Just looked at base timing and its at 11 degrees at idle (1100 rpm) and advance disconnected.

Tried to open choke all the way to start and not even a sign it wanted to. Then closed the choke all the way and it fired up.

Thanks for the guidance on idle AFR. I'm going to reset idle mixture screws to get AFR into range. But worried it will push a way too rich condition under cruise which is where I started with all the soot. I know the idle screws shouldn't affect AFR under power but it did when I set them. I would guess the way to adjust after getting idle into range is to adjust the metering jets to get higher rpm AFR into range. Let me know if I'm thinking about this wrong.

Idle transfer slots are more than .040 by looking at them. I'll have to study up on how to adjust. I can say both primary and secondary ( 4 barrel carb for QFT 680) look about the same. They are deep though so not easy to really measure.

As for vacuum leaks, I've looked all over and pushed all hoses in place to double check. I've also sprayed carb cleaner around the engine when running and no signs of a leak with rpm change. Can't find anything if there is one.

Appreciate all the help. My next step is to get idle AFR into range and hopefully get idle rpm down a little as well by adjusting idle mixture screws and transfer slot if I can.

[robertjamesellis]

The engine was sitting for about a year before I installed and fired it up. It ran nice out of the crate but was always hard to start when cold. I will give it a once over though and make sure its not gunked up anywhere. Thanks for the help.

[NAZ]

Thanks for the help Naz. Just looked at base timing and its at 11 degrees at idle (1100 rpm) and advance disconnected.

Tried to open choke all the way to start and not even a sign it wanted to. Then closed the choke all the way and it fired up.

Thanks for the guidance on idle AFR. I'm going to reset idle mixture screws to get AFR into range. But worried it will push a way too rich condition under cruise which is where I started with all the soot. I know the idle screws shouldn't affect AFR under power but it did when I set them. I would guess the way to adjust after getting idle into range is to adjust the metering jets to get higher rpm AFR into range. Let me know if I'm thinking about this wrong.

Idle transfer slots are more than .040 by looking at them. I'll have to study up on how to adjust. I can say both primary and secondary ( 4 barrel carb for QFT 680) look about the same. They are deep though so not easy to really measure.

As for vacuum leaks, I've looked all over and pushed all hoses in place to double check. I've also sprayed carb cleaner around the engine when running and no signs of a leak with rpm change. Can't find anything if there is one.

Appreciate all the help. My next step is to get idle AFR into range and hopefully get idle rpm down a little as well by adjusting idle mixture screws and transfer slot if I can.

The next step is to pull the carb and ensure the transfer slots are uncovered no more than .040" (they will appear more like squares than rectangles when at .040"). This is done by adjusting the idle speed screws while the carb is inverted. On some cams you may have to open the secondaries a bit more to close down the primaries to achieve a reasonable idle speed. Still others, like mine, I had to drill bleed holes in the primary butterflies to close off the transfer slots where only .040" was uncovered. If these slots are uncovered too much you will lose idle mixture screw authority and turning the screws will do little to nothing. After the transfer slot adjustments are done, then you can start tuning the idle mixture screws to fatten up the idle mixture. Your 11-degrees of ignition lead at idle should work much better once you fatten up the idle mixture. Lean mixtures are slower burning and require more timing advance to shift peak cylinder pressure where it belongs.

Thought I'd add a couple links that you may be interested in. The first one is a short article on tuning Holley carbs: https://www.hotrod.com/articles/tuni...arb-made-easy/

The second is a link to a book that Dvid Vizard wrote on tuning and modifying Holley carbs. David is a very sharp guy when it comes to carbs of all kinds: https://www.amazon.com/Vizards-Modif.../dp/1934709654

[SJDave]

I went thru a similar process on my engine and got it pretty close to acting like a fuel injected car, but still had some stalling issues at idle, especially when letting it wind down from high rpm and coming to a stop. I can't remember where I found the information on the WAGNER PCV valve, but after installing and adjusting using a manifold vacuum gage, all my stalling problems are gone and the idle jet adjustments are in normal range now. It's not cheap, $130 as I remember, but with it's dual circuit design it works really well especially if your running a big cam and low idle vacuum (under 12 " of HG).

I graduated to a Powermaster gear reduction starter motor on my 427 build and upgraded the wire gage from the battery to the starter motor to 1 gage. No cranking issues after that!

HTH,
Dave

[mike223]

I can't remember where I found the information on the WAGNER PCV valve, but after installing and adjusting using a manifold vacuum gage, all my stalling problems are gone and the idle jet adjustments are in normal range now. It's not cheap, $130 as I remember, but with it's dual circuit design it works really well especially if your running a big cam and low idle vacuum (under 12 " of HG).

That's a good catch - I had forgotten trying to run a conventional PCV valve.

The one I tried was for about a 1966 427 Corvette.

Didn't work - wouldn't idle - too big a vacuum leak.



I plumbed the breather ports off the valve covers into the air cleaner and called it "good enough" crankcase ventilation.


Adjustable PCV valves (like Dave is talking about) are another option.


Like Dave, I've been tuning the carb for a couple years now using a wideband AFR meter, and just about have it running like efi - but I learned way more than I wanted to know about it.


Many EFI systems are the same way - you're going to end up knowing a lot more about it than you wanted to...

[NAZ]

Yes Dave, that is a good catch. Been so long since I've worked on a real street car I've forgotten about the smog control stuff (and I used to have a CA smog license). Robert, the easy way to eliminate that as a vacuum leak is to simply plug the PCV port on the intake manifold and observe the effect. If AFR increases and idle RPM decreases significantly then you should consider the unit that Dave used with success. But I disagree with Dave's comment about the Wagner unit not being "cheap" -- $130 to fix an intake issue is money well spent if it works.

[robertjamesellis]

I went thru a similar process on my engine and got it pretty close to acting like a fuel injected car, but still had some stalling issues at idle, especially when letting it wind down from high rpm and coming to a stop. I can't remember where I found the information on the WAGNER PCV valve, but after installing and adjusting using a manifold vacuum gage, all my stalling problems are gone and the idle jet adjustments are in normal range now. It's not cheap, $130 as I remember, but with it's dual circuit design it works really well especially if your running a big cam and low idle vacuum (under 12 " of HG).

I graduated to a Powermaster gear reduction starter motor on my 427 build and upgraded the wire gage from the battery to the starter motor to 1 gage. No cranking issues after that!

HTH,
Dave

Hey Dave,
I know I can get there too, just need some patience! I'm going to check out the wagner PCV and see it that will help. I'm definitely pulling low idle vacuum. Also looking to upgrade the starter like you did. I was waiting until I pulled the body off again to start bodywork but want to do exactly what you did. Upgrade the starter and the wiring and be done with it! Thanks for the tips.

Rob

[robertjamesellis]

Yes Dave, that is a good catch. Been so long since I've worked on a real street car I've forgotten about the smog control stuff (and I used to have a CA smog license). Robert, the easy way to eliminate that as a vacuum leak is to simply plug the PCV port on the intake manifold and observe the effect. If AFR increases and idle RPM decreases significantly then you should consider the unit that Dave used with success. But I disagree with Dave's comment about the Wagner unit not being "cheap" -- $130 to fix an intake issue is money well spent if it works.

Naz,

Great tip. I'll give that a shot today. Also agree $130 ain't much if I can get this running great. I took a fresh look at the idle transfer slots and think you have nailed it. I'll take pictures later but they look like long rectangles now and not close to square. So I'm eager to fix that, plug the PCV and see what happens. Again, appreciate the assistance!

Rob

[robertjamesellis]

Here's the latest. I went ahead and pulled the carb to check the idle transfer slots. As NAZ predicted, the primary was too open and the secondary was completely closed. I made the adjustment so both were just square. I kept secondary even slightly tighter than the primary. I then put the carb back on. It took a few turns of the key to get the floats filled back up (mechanical pump) but once they were full, it gave one cough, then started up on the next turn of the key. It was idling very high at that point so I let it warm up. Without thinking of what I was doing, I then turned the idle screw back down and probably undid my work at least on the primary side.

I adjusted all the idle screws to max vacuum and was able to pull at 16 which was better than where it was before. I could turn the screws in and see a noticeable drop in rpm's and vacuum. The lowest I could get the idle was to ~920. But it was a steady 920.

I checked the vacuum by pulling the PCV hose and putting my finger over the vacuum hole. I didn't see much difference in vacuum on the gauge though so not sure the Wagner will make much difference. At idle AFR was at 92 lambda which is a 13.5 AFR. Runs just a little rich at idle as NAZ indicated. I then took it out on the road. Running at around 2200 rpm it was showing 15.5 AFR which is leaner than it was at before. At 80 on the freeway which gets me to 3100rpms, it was running lean again at 13.5. So still a little rich at higher RPM's

It was responding better overall and had some noticeable increase in pep. Spun the tires on takeoff a couple times without trying. So this was definitely an improvement.

Question for you NAZ. Since I adjusted the primary idle screw should I reset the primary idle transfer slots back to .04 or roughly square and dial in the idle mixture screws to compensate?
Any advice on how to lean it up a little at higher rpms? is it now time to work are adjusting air bleeds?

BTW. Thanks for all the help and this education. This is all making sense now and I'm feeling good about getting this baby tuned! I'm anxious to try and start once its cold again and see what difference this made.

Thanks,
Rob


Here are the primarys before and after adjustment



Here are the secondarys before and after adjustment

[NAZ]

Rob, good to hear you’re making progress. Tuning can be challenging and personally rewarding.

About the idle RPM, some engines won’t idle as low as a mild-mannered OEM but with your cam specs I’m surprised you can’t get it below 900. My hot rod idles at 1,100 but it has a very aggressive nitrous cam. There’s nothing wrong with a 920 RPM idle if the engine is happy. And your AFR at idle looks good.


When you set the idle transfer slot adjustment to ~.040” that’s about as far uncovered at idle as you want. This adjustment will usually end up with a fast idle when the engine is warm and when you adjust the idle down to your normal idle RPM you end up with the transfer slots uncovered less than .040” which is a good thing. With my cam, I couldn’t get the thing to idle with the transfer slots uncovered .040” and had to open the primary butterflies way more (and uncovering much more than .040”) to get the engine to idle. So, to maintain idle mixture authority I had to drill bleed holes in my primary butterflies so I could turn the idle speed adjustment down and cover more of the idle transfer slot. This is a more advanced tuning technique. Sounds like your adjustment is working so don’t sweat the idle. You have some other tuning opportunities to work on.

The light cruise AFR is also good at 15.5. Now to work on the highway cruise rich mixture. At around 2000 - 2500 RPM the idle transfer circuit starts to fade and the main jets start to take over fuel metering. The 13.5 AFR you saw at 3100 RPM cruising the freeway is on the rich side. If you have the typical progressive linkage you probably haven’t reached the point that the secondary butterflies have opened yet. So, we would adjust the rich mixture with the main jets on the primary side. But first we need to know what PV you have and how much manifold vacuum the engine is creating at 3100 RPM freeway cruise. The PVs are marked with the vacuum rating in inches that is required to close them.

If the PV is opening at freeway cruise then besides the main jets, the PVCR (Power Valve Channel Restrictor) circuit is providing supplemental fuel. There are two tiny removable jets (or fixed restrictors on the less expensive carbs) under the PV that add fuel during times when more power is needed. At somewhere around half-throttle or more, the vacuum will drop enough to open the PV. To make best power safely at WOT under load we need between 12.5 to 13.5 AFR but we don’t need that at freeway cruise.

As for the high-speed air bleeds, these are used to change the AFR slope, an advanced tuning technique for fine tuning AFR at higher throttle openings and RPMs. They really come in handy when you have ram air induction like an air scoop that will change the air pressure exponentially as vehicle speed increases.

[BRRT]

Great carb tuning info! Thank you!

[johnnybgoode]

Here's the latest. I went ahead and pulled the carb to check the idle transfer slots. As NAZ predicted, the primary was too open and the secondary was completely closed. I made the adjustment so both were just square. I kept secondary even slightly tighter than the primary. I then put the carb back on. It took a few turns of the key to get the floats filled back up (mechanical pump) but once they were full, it gave one cough, then started up on the next turn of the key. It was idling very high at that point so I let it warm up. Without thinking of what I was doing, I then turned the idle screw back down and probably undid my work at least on the primary side.

I adjusted all the idle screws to max vacuum and was able to pull at 16 which was better than where it was before. I could turn the screws in and see a noticeable drop in rpm's and vacuum. The lowest I could get the idle was to ~920. But it was a steady 920.

I checked the vacuum by pulling the PCV hose and putting my finger over the vacuum hole. I didn't see much difference in vacuum on the gauge though so not sure the Wagner will make much difference. At idle AFR was at 92 lambda which is a 13.5 AFR. Runs just a little rich at idle as NAZ indicated. I then took it out on the road. Running at around 2200 rpm it was showing 15.5 AFR which is leaner than it was at before. At 80 on the freeway which gets me to 3100rpms, it was running lean again at 13.5. So still a little rich at higher RPM's

It was responding better overall and had some noticeable increase in pep. Spun the tires on takeoff a couple times without trying. So this was definitely an improvement.

Question for you NAZ. Since I adjusted the primary idle screw should I reset the primary idle transfer slots back to .04 or roughly square and dial in the idle mixture screws to compensate?
Any advice on how to lean it up a little at higher rpms? is it now time to work are adjusting air bleeds?

BTW. Thanks for all the help and this education. This is all making sense now and I'm feeling good about getting this baby tuned! I'm anxious to try and start once its cold again and see what difference this made.

Thanks,
Rob


Here are the primarys before and after adjustment



Here are the secondarys before and after adjustment

Good advice in this thread will try to add a bit. Once I get my primary T-slot adjusted I use the secondary throttle stop grub screw to fine-tune the curb idle. QF sells an adjuster you can add to your carb to make this easier or you can try getting a small allen key under the carb to adjust or reverse the grub screw (take it out and reinstall from the top of the base plate) so you can adjust from the top of the carb (hold the throttle wide open with the ignition off and give the grub screw a 1/8 of a turn). Tuning carbs and timing curves is part of the enjoyment of these cars in my opinion. Good Luck. Scott

[robertjamesellis]

Naz. Ok. I won't worry about idle right now. My PV is 6.5. I'm not sure of the vacuum at higher rpms. I'll have to check again. I'm out of town until wednesday but will check then. If I'm understanding your thinking the power valve may be opening too soon causing the rich condition and the theory is a lower value PV might help. Let me know if I'm not thinking about this correctly.

I did go out and try to start it cold. It was a no go. It gave a cough but that was it. I'm suspecting that I'm burning up my starter and will need to replace that. The wire that goes into the starter got really hot and was melting away the insulation. And it doesn't give the solid turnover it used to. I'm going to replace and upgrade wiring just so I can put that behind me and just focus on tuning.

Scott. Thanks for the tip on turning the screw upside down. I'll see if that works on mine.

To all that have contributed. If you find yourself in San Ramon anytime, the beers are on me!

Rob

[NAZ]

[QUOTE=robertjamesellis;442621]Naz. Ok. I won't worry about idle right now. My PV is 6.5. I'm not sure of the vacuum at higher rpms. I'll have to check again. I'm out of town until wednesday but will check then. If I'm understanding your thinking the power valve may be opening too soon causing the rich condition and the theory is a lower value PV might help. Let me know if I'm not thinking about this correctly.

Yes, that's exactly what can happen but you'll only know for sure by test driving it at freeway speed and watching the AFR & Vacuum. If your 80 MPH @ 3100 RPM was pulling less than 6.5" of vacuum then I would want to see something close to 13.0 AFR. So if that was the case, note the Vacuum at that cruise condition and you may consider replacing the PV with one .5" lower than that cruise vacuum reading and make another road test to evaluate your changes. Carb tuning is an iterative process.

I run a 3.0 PV on the street (and no PV on the track) but my idle vacuum is 4.5" - 5.0". I look at the way a carb is configured out of the box as a suggestion only -- they always seem to require some tuning to get them dialed in perfectly. So don't be afraid of making changes and experimenting, but one change at a time and keep a good record of the changes. I have a tuning record of every race at each track including the weather conditions.

[CraigS]

Looks like you are very close to having your carb sorted. I want to add a little of my experience re; idle mix screws. I was dealing w/ a super lean cruise on my 351 w/ SS650AN carb. I call QF and talked to one of their tech guys. His comment was that the idle circuit can have an affect up to 2000rpm and he thought that might be the cause of my problem at about 1400 in 5th. He suggested a test. Change idle screw adjustment from lean best idle (or max vac) setting by opening all four 1/2 turn. Don't pay attention to the idle just the cruise. Try it and then open another 1/2 turn. And maybe even a third 1/2 turn. If this fixes, or at least improves, the lean cruise then you know that you need to work w/ the idle system jets. It did fix it so I ordered jets. It was very interesting to me that he was correct, I could see the change in idle screw affecting the mixture on my meter way higher than just at idle. I also had problems w/ my electric choke. If I set it so it started well, then it would open way too soon, I would lose the higher idle, and I would have to jazz the pedal at the stop sign about 3 miles from my house. I ended up drilling a bunch of holes in the choke plate so I could set it so it would stay on longer while all the holes allowed enough air to pass through that it wasn't super rich. I finally converted it to a manual choke.
CHOKE Manual by craig stuard, on Flickr
Got a generic push/pull cable and cut to fit and put a loop bend in the end. Then I removed the spring and cut a slot in the black plastic cover for the cable to slip though.

[robertjamesellis]

Here's the latest update. To fix the starting issue, I purchased an powermaster ultra torque starter and upgraded my wire to 1/0. And that did it. It turns over great right now and seems to start up well with just a double pump of the pedal before I crank. Likely that was the issue to begin.

As for the carb. I haven't rigured out how to check vacuum while driving, so I've been swapping out Power Valves and worked my way down from the original 6.5 to a 6.0, then a 5.0 and now a 4.5. None of them had any noticeable affect. I did make a few runs today on the 4.5 and it seemed to be running a littler rougher. However, I noticed it was running a little rich again at all rpm's. So I hooked up the vacuum gauge again and gave the idle set screws about a 1/8 turn in. I could see my O2 sensor react quickly as it leaned up. There wasn't any appreciable difference in rpm though so I thought I would give it another run. At Idle I was running 15.0 AFR, at 2200 it was right at 14.7 and still at higher rpms around 3200 it was still running rich at 13.5. Now the good part is the car seemed to be running great. No hesitation and I could feel the power. What was interesting is that there was a noticeable difference in just a 1/8 turn of the idle screws in performance.

My thinking now is that I may need to dial down the main jets and see how that effects the higher RPM AFR. Time to place an order.

[robertjamesellis]

With all the help here I got this whipped!

I did attack the PV first. I went sequentially and lowered the PV from 6.5, to 6.0, then 5.0 and finally 4.5. No difference in performance or AFR. Well I went back and reread Naz's advice and he distinctly advised to check the Vacuum under load. So I hooked up a longer hose to my vacuum gauge, taped it to the windshield so I could read it from the drivers seat, and blocked up the hood a little so it wouldn't pinch the hose. then took it out for a spin, and what do ya know, the Vacuum was pulling 20 while cruising along around 3,000 RPM's. So yeah, lowering the PV wouldn't change a thing. Lesson learned.

So I put the 6.5 PV back in and started working on the main jets. I again went sequentially and lowered then from the original .70 to a .69. No real change in AFR. Next I did a .68, and some a slight improvement at 3200 rpm's. Next I went to .67 and then .66 where I came close to AFR goals. Idle was just slightly rich at 14.4. Mid range (2200 rpms') was lean at 15.6 and higher rpms (3200) a slight lean at 14.9. I think I could get slightly better performance by trying a .65 and upping the idle screws a 1/8 turn or so and get a better rich idle mixture and lean cruising mixtures.

I did end up with the secondary idle screws turned out 1/8 more than the primary idle screws. This allowed me to get a richer idle with a leaner cruise AFR.

In the end there was a noticeable performance difference when driving. It now accelerates smoothly and quickly. No jerks during acceleration. My wife says it also is a little quieter now which she likes. If drives like the beast it was meant to be! With the wire and starter upgrade along with the tuning, it starts much easier as well. I learned a lot doing this and ended up loving the carb and tuning. I didn't get the EFI for the classic look and feel and wouldn't change a thing right now. What a fun ride this is!

[GoDadGo]

I don't know if this will help, but I hadn't driven a carbureted car since 2005 so I forgot the Pre-Start Pump-It Practice!
This old practice that Peter Klutt talks about in this recent video has made starting my MK-4 easy peasy.

https://youtu.be/AzcRYlJDv9s

I now follow this old forgotten practice and I'm having NO ISSUES starting my car.
The Redbone Roadster now starts every time and I haven't flooded it since.