Shouldn't need a 35, I'd put the 31 back in it and try a more aggressive pump cam, shoot for an earlier longer shot.
Start from square one on jetting 70 primary 74 secondary
My engine sure seems to want more jetting
- Thread starter Lil Demon
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Start from square one on jetting 70 primary 74 secondary
Intake, single or dual plane?
Lil Demon
Well-Known Member
Dual RPM Air Gap, As far as the pump cam, you suggesting something like the green or orange cams? What do you suggest for PV?
TT5.9mag
Two atmospheres are better than one
Wow that’s ugly. I bet once you get the fuel cleaned up a bit you’re cruise vacuum and idle vacuum will show much higher. Best piece of advice at this point is to go back to factory settings. Everywhere. And if you have clear sight plugs on the bowls set the float level in the middle of the glass. Start there.
try the green, I believe that's mid range and a step lower than orange.
Lil Demon
Well-Known Member
I've actually always ran the floats at mid level. Lowering them two days ago was my first step in my new strategy. It sure idles a whole lot nicer with the lower float settings and without a jet change at that point it improved the bucking by a lot, That's actually when I decided to start jetting up
TT5.9mag
Two atmospheres are better than one
So your theory there is backwards. Lowering the float level reduces head pressure on the jet, leans it. Raising it increases head pressure, richens it. You’re saying it drives much better with more jet, (rich) but lower float level (lean). I’m saying go back to stock on ALL settings and set float level to the middle and start tuning there. That will be your baseline. You can use small changes in float level to affect the afr slightly but it really doesn’t do much.
I'd stick the 6.5 back in it for now.
Lil Demon
Well-Known Member
I will try it, but it drove like dog Sh in that setup. So I must have gone in the wrong direction but that was not a good setup.
At that point I had
Floats - mid
Pri jet 73
Sec jet 76
Pri Noz 31
Trans slot .030
PV 6.5
Initial timing 22
I had to rev it past 2k and pumping the pedal to keep it from being embarassing as I left traffic lights
Fishmans 67 is helping you tune through this: "and pumping the pedal to keep it from being embarrassing as I left traffic lights" with the accelerator pump cam duration and nozzle diameter he is recommending. I don't believe your gears are tall enough to cause an excessive load, especial at your elevation (INMO).
Getting your car to transition from the accelerator pump "crutch" to your main jet circuit would seem to be the logical item to address first.
That excessive fuel is ending up in your motor oil...
Lil Demon
Well-Known Member
I appreciate all the feedback trust me. I am just saying that with the default carb setting that I just listed it ran significantly worse. That's why I am at a loss. Since the suggestions I am getting are to go back to my original settings in which it didn't perform and had a lot less power and even idled like crap. Now it seems to idle so much better since I lowered the floats. Again that's why I reached out. I am perplexed LOL
since I began to increase jet size I don't have to pedal out of the hole. Now it just rolls out but the plugs are black vs just dark brown like they were before
Hit up Fishmens 67 and have him help you with idle bypass air. He runs a naturally asperated set up. Once your idle is clean then you can tune transition/accelerator pump. Once that's covered tune the primary main circuit and ... you get it.
I had similar issues 25 years ago with a fat cam'd 340 4spd and 3.34:1 axle turning 275/60/15's in a D100 @ 3440#. In the end I went to a Holley spreadbore atop of an LD340 intake. "Crutched the combination."
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MobileCustoms
You can twist perceptions, reality won't budge
I'd go back to the suggested starting point of 70/74 jets and a bigger power valve. Then start again with the basic tuning steps of:
-Replace your spark plugs or at least clean them thoroughly. Double-check firing order is correct.
-Remove carb & make sure both the front and rear transfer slots are not too far opened. The opening should look like a square, not a rectangle. Set float levels to middle of site glass.
-Set all 4 idle mixture srews evenly to about 3/4 of a turn out.
-Make sure there are no vacuum leaks anywhere and that the pcv valve is working. Maybe even plug it off for this stage of tuning to see if that helps at all. It could be defective.
-Verify timing then warm it up real good.
-Adjust idle mixture screws to achieve the highest vacuum readings then adjust idle speed & repeat to further tweak those things.
-Write down your findings and readings.
-Test drive with vacuum gauge inside car and make note of readings at various speeds. -Check plugs and AFR readings also.
Then come back with your results for further tips from the other guys who really know their stuff (that ain't me!)
-Replace your spark plugs or at least clean them thoroughly. Double-check firing order is correct.
-Remove carb & make sure both the front and rear transfer slots are not too far opened. The opening should look like a square, not a rectangle. Set float levels to middle of site glass.
-Set all 4 idle mixture srews evenly to about 3/4 of a turn out.
-Make sure there are no vacuum leaks anywhere and that the pcv valve is working. Maybe even plug it off for this stage of tuning to see if that helps at all. It could be defective.
-Verify timing then warm it up real good.
-Adjust idle mixture screws to achieve the highest vacuum readings then adjust idle speed & repeat to further tweak those things.
-Write down your findings and readings.
-Test drive with vacuum gauge inside car and make note of readings at various speeds. -Check plugs and AFR readings also.
Then come back with your results for further tips from the other guys who really know their stuff (that ain't me!)
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TT5.9mag
Two atmospheres are better than one
I don’t know what else to tell ya. But looking at that plug your tune up is so far in the weeds I can’t imagine it running at all. Are you 100% sure you didn’t have a vacuum leak or some other drivability issues? Or a choke stuck closed? Post the model (list) number of the QF650 you’re using. I want to see what the emulsion stack is. It might have 5 open emulsion blocks in it.
MobileCustoms
You can twist perceptions, reality won't budge
Agreed. Might also be a good idea to open the choke all the way for now, to make sure that's not interfering with things. You can warm it up with your foot to get it ready for tuning.
So what MAB, IAB and how many emulsion holes are open and what size are they?
We also need to know your idle feed restriction is and where that jet is.
Not nearly enough exposed, should start off square, measure and figure out how many turns on the idle speed screw to get that distance for future reference
Lil Demon
Well-Known Member
OK UPDATE:
New setup
Primary 70
Secondary 74
Pwr valve 6.5
Prim Nozzle 33
Green cam
Floats just below sight
No other changes. Not even to my mixture or timing. Like I mentioned before, my idle really cleaned up when I lowered the floats and almost made the transition slots disappear. Idles now at around 900 and clean and smooth.
Drove significantly better and I had to leave very slowly to force it to lean buck. I drove it on the road in 4th to keep it at 3500 rpm with engine vacuum at 15 to just clean up the plugs a bit. Came back and checked plugs did clean up a good amount but will be better with a fresh set and may as well change the oil to address any fuel wash out.
As I deduct where I went wrong, years ago really when I started with the 6.5 PV. and 31 primary nozzle. My guess is that I had the transition slot over exposed and that pink cam wasn't adequate. so at that point I switched to a 4.5 PV obviously a bad move. I left it like that for quite a while just dealing with the lean take off until I began to really dig at it these last few days, albeit in the wrong direction.
Very valuable information from everyone I very much appreciate it. Drinks on ME!!! I am thinking of ordering a 7.5. PV since that's the only one I don't have in my inventory to see what it does. After that I will try a smaller jet to see just how clean I can make it.
Thanks a lot guys. Like I said before. You guys ROCK!
That lean buck is too much timing.
If those pictures of the plugs you posted are what they look like after you did the latest tuning you are still pig fat rich. Very very rich.
MobileCustoms
You can twist perceptions, reality won't budge
If you're pulling 15 inches of vacuum, then I'd go with a 10.5 PV and give it a try. If you already have one in stock. You want the power valve to open sooner on tip-in. There's been quite a bit of discussion here on the 10.5 power valves VS what Holley incorrectly recommends using one that is only half of your vacuum. I just switched to a 10.5 and it really helped the little stumble I was having at tip-in.
Lil Demon
Well-Known Member
I agree those plugs still look like crap but I don’t think they would clean up from the level of fuel they had on after a quick 10 minute drive. It was just a test to see if they would “clean” up. New plugs will be going in tomorrow and oil.
As far as my 15 inches of vacuum. That was forced just cause I was at a higher RPM than usual. With the 3.91’s 28 inch tires and the 6 speed my RPM range is closer to 1200 to 3000 and cruises at 1800 to 2200 depending on gear and speed obviously. I almost never use 6th. So with that being said my cruise vacuum is usually well below 10. I may even try the 8.5 I have there. Max I have is the 9.5 after I put the new plugs in tomorrow and see how it does. I prefer running the smallest jets possible I was just obviously needing direction cause this one has kicked my butt for a while.
You can see a change on the plug in one dyno pull. Or one pass at the track.
It doesn’t take miles and miles to show a change.
You are incredibly rich but it’s probably not a jetting issue.
Lil Demon
Well-Known Member
Thanks for all the great feedback. Given the latest results, would you say I should expose them to square? That’s how I had them when I had the floats halfway, but closed them down when I lowered the floats a then I noticed an improvement in idle and my lean buck. But it’s now working waaay better with your suggestion.
Jeremiah (jd)
Well-Known Member
The spark plugs need to be replaced before any additional tuning takes place. That or clean them off with a 150 shot of n20
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