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Stumble @WOT

rebootej

rebootej

Well-Known Member
Local time
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Feb 2, 2012
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Hey guys I decided to switch over to a Quick Fuel Slayer 600VS on my mild 318. Really happy with it so for but its taking some adjusting to get it dialed in to my engine. But thats why i got it because it is so adjustable. Ive changed the air bleeds already and that helped the idle. But right now I've got a stumble almost die if from idle when going to WOT then it catches up. I have an O2 sensor on it and it is going very lean when it almost dies. But if its an easy acceleration engine runs just fine.

They guy on the tech line said I should increase my squirter size from a .31 to a .33 or .35 and to get the vacuum spring set and try adjusting those with a stiffer spring. What do you guys think? Im tying to learn carbs, his advice makes sense because of the leaning out. But is there something else I should look at first? Should i jump straight to a .35 or should I try the .33 first?
 
I think I'd just go to a .035 nozzle right off the bat. The tech has you going in the direction,especially the secondaries may be opening too soon and that's a big "lean" right there.
 
Is this a brand new carb? Even so, it might be useful to take a close look at the accelerator pump circuit and make sure it's timed correctly to where it activates at the slightest throttle movement.
 
Thanks! Yes this is a new carb. It appears to start activating right as you crack the throttle. It has a pink cam and it looks like its in the #1 slot the upper one correct?

So a .035 will give me a faster shot of fuel right?
 
AR67GTX said:
Is this a brand new carb? Even so, it might be useful to take a close look at the accelerator pump circuit and make sure it's timed correctly to where it activates at the slightest throttle movement.
Click to expand...
I agree with this. Does it backfire through the carb as well?
 
It sounds like a carb issue from the lean condition your 02 sensor is showing. But you might try cranking in about 4 degrees more timing and see what that does. I could not completely get rid of off-idle issues with my 440 until I re-worked the distributor to allow me to put more initial timing in.
 
My timing is already at 15 deg btdc. I had it at 20 once with the old carb and it was pinging but I haven't tried with this carb. Still haven't nailed down what timing this engine likes best
 
When you say you changed the air bleeds, did you change just the idle air bleed, or did you also change the main air bleeds. Changing these can affect where the transition occurs and can impact how much you need to cover up with the pump shot. My guess is that the pump shot with the squirter and possibly the cam is putting you in the right direction. One other thing that can happen is that the adjustment of the lever on the cam can result in a spot where the cam is not operating. It really does need to respond as soon as the throttle to is touched. I am assuming the air fuel at wide open throttle is in a good range 12.5 +/-. All the circuits run together, so a leaner idle or cruise will also have an effect.
 
Oh AR69 you put more timing in your distributor?? Recurbbed it?

Update I upped my total timing to 17-18 degrees. Not hearing any detonation/pinging. The engine vacuum kept increasing up to about 25-28 degrees but I was sure I would have detonation at that point when underload, but dang was it snappy on the rev. Increased the squirter size and changed the spring To a stiffer one. The stutter at WOT is basicly gone still goes a bit lean for a second then catches up.

Jcharger yes I only changed the idle air went up three sizes it helped a lot but I think I still need to go a little bigger on the idle circuit. Engine is still rich at idle and lean at partial throttle. And yes your right it runs about 12.8-13.3 on acceleration.
 
Nice! looks interesting! Ill have to check that out eventually!

My exhaust now sounds slightly muddled, not as crisp. Is this a sign my timing is advanced to far?
 
rebootej said:
Nice! looks interesting! Ill have to check that out eventually!

My exhaust now sounds slightly muddled, not as crisp. Is this a sign my timing is advanced to far?
Click to expand...
Rich usually sounds more in exhaust, lean through carburetor. Follow the link below and practice up on patience and note taking for each change and the result it produces. I'm proof that any fool can do this, I'm sure you will excel.
http://www.4secondsflat.com/Spark_plug_reading.html
 
Wow this is very detailed! Awesome! Ill give this a try. I didn't know the plug could tell me so much. Ill try and pull a plug tonight or tomorrow.

I got scared by the exaust sound a backed my timing off to 15-16.. the studder is back. I get a small rev, vra..splat (lean 16.8-+17) then..vraaaaaaaa

should i go back to 18?? it seams like a lot of advance?? Thoughts?
 
Reboot change the squirter first & then see. Also a Holley cab book is never a bad idea, you'll learn so much.
 
oldbee said:
Reboot change the squirter first & then see. Also a Holley cab book is never a bad idea, you'll learn so much.
Click to expand...
Reboot it to what? I upped it from the 31 to a 35. Do you mean go further or go back to the 31?
 
I didn't see post that you changed squirter, sorry. You MAY have to change pump cam also, you have many choices on the cams.
 
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