C'mon guys walk me through this step by step. Krochus'es Carb tuning thread O doom
#43
The problem with that is bleeds have a press in brass part to size the restriction. If you try to drill it larger the bit can catch the press in and pull it out. One guy on the web said he used a drywall screw to remove his restictors.
#44
Drilling the brass ones is a lot easier if you chuck the set screw in a variable speed drill and set it to rotate slowly then hold the bit stationary in a pin vice. You have much better control over the pressure that way, the brass drills pretty easy.
#46
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Interesting. Might have to try those.
Drilling the brass ones is a lot easier if you chuck the set screw in a variable speed drill and set it to rotate slowly then hold the bit stationary in a pin vice. You have much better control over the pressure that way, the brass drills pretty easy.
Drilling the brass ones is a lot easier if you chuck the set screw in a variable speed drill and set it to rotate slowly then hold the bit stationary in a pin vice. You have much better control over the pressure that way, the brass drills pretty easy.
#48
UPDATE:
even though the carb is still slightly rich fuel economy is VASTLY improved. Before I was barely getting 12 today I filled and then refilled after making my 60mile round trip commute not hypermiling but not driving like a hoon and I got 16mpg out if this loop.
It's nice not watching the gas gauge drop like it's been drinking popov.
even though the carb is still slightly rich fuel economy is VASTLY improved. Before I was barely getting 12 today I filled and then refilled after making my 60mile round trip commute not hypermiling but not driving like a hoon and I got 16mpg out if this loop.
It's nice not watching the gas gauge drop like it's been drinking popov.
#49
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I just filled up and went to the track after jetting down primary from 72 to 67 and 78 rear to 76. The. Stepped down the idle to get 14.5ish but after starting again it didn't want to fuel and I had to get it to 13.5. Driving has gotten allot better, but I still can tell when I'm in the low speed circuits off idle, before it cracks to use the primary jets, it's still rich, but not in the 11.0-11.3 like it was. So next step is using the wires from my new brush. Not sure how any to use but I may just see what 2 does.
The track trip and tuning will go against the mileage but it was 12ish before.
The track trip and tuning will go against the mileage but it was 12ish before.
#50
Got the quick fuel in today and slapped her on.
Seems like it's gonna be a pretty good carb. Out of the box the AF ratios are pretty good. I think it needs to loose the power valve though as it goes pig rich at any throttle that causes much of a vacuum drop.
Also the idle mixture screws are hypersensitive and my wideband seems to fluctuate a great deal even cruising steady.
Bigger idle air bleeds perhaps?
Seems like it's gonna be a pretty good carb. Out of the box the AF ratios are pretty good. I think it needs to loose the power valve though as it goes pig rich at any throttle that causes much of a vacuum drop.
Also the idle mixture screws are hypersensitive and my wideband seems to fluctuate a great deal even cruising steady.
Bigger idle air bleeds perhaps?
#51
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I wouldnt ditch the power valve unless your going drag only. Theres replaceable bleeds in the powervalve that can adjust how much fuel it adds when it opens. Make sure its not the acc pump adding too much fuel with throttle changes tho
#52
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Got the quick fuel in today and slapped her on.
Seems like it's gonna be a pretty good carb. Out of the box the AF ratios are pretty good. I think it needs to loose the power valve though as it goes pig rich at any throttle that causes much of a vacuum drop.
Also the idle mixture screws are hypersensitive and my wideband seems to fluctuate a great deal even cruising steady.
Bigger idle air bleeds perhaps?
Seems like it's gonna be a pretty good carb. Out of the box the AF ratios are pretty good. I think it needs to loose the power valve though as it goes pig rich at any throttle that causes much of a vacuum drop.
Also the idle mixture screws are hypersensitive and my wideband seems to fluctuate a great deal even cruising steady.
Bigger idle air bleeds perhaps?
if i lean up the idle to 14.5ish, it goes EXTREME lean 20+AFR at very light cruise, then richens up to 14.0 if i give it a little more throttle. i richened it up to 13.2ish idle and it cruises good now. a couple rich spots at light cruise but i'm getting tired of smelling it. WOT is dead on around 12.8-13.0.
i hope that watching your thread will help me learn to fine tune mine. keep the updates coming.
#53
I just got back from a quick "test n tune" (gotta love living in the country) and losing the powervalve just like with the Holley was a good move. The float level was also a little high so that got adjusted down too.
It cruises out real real well now. With part throttle AFRs staying well above 13.5 the whole time accelerating normally as in traffic up till the mains start to come on then it leans out further into the low 15range.
It's no longer going pig rich if I dig into the throttle a bit now. Sans powervalve it hovers around ideal up till I really dig in towards 1/2 throttle then it leans out a bit up towards 16. This however isn't an especial concern to me as if you're like me anything past 1/4 throttle is merely on the way to WOT anyhow!!
Speaking of WOT there's even more WIN! I'm up a total of 17 jet sizes over the 670 Holley and it's slightly leaner now than before around 13 screaming pretty hard. That's gotta mean that motor is sucking down enough extra air to make use if that much more jet! And that my friends are how little baby horsepowers are made
It cruises out real real well now. With part throttle AFRs staying well above 13.5 the whole time accelerating normally as in traffic up till the mains start to come on then it leans out further into the low 15range.
It's no longer going pig rich if I dig into the throttle a bit now. Sans powervalve it hovers around ideal up till I really dig in towards 1/2 throttle then it leans out a bit up towards 16. This however isn't an especial concern to me as if you're like me anything past 1/4 throttle is merely on the way to WOT anyhow!!
Speaking of WOT there's even more WIN! I'm up a total of 17 jet sizes over the 670 Holley and it's slightly leaner now than before around 13 screaming pretty hard. That's gotta mean that motor is sucking down enough extra air to make use if that much more jet! And that my friends are how little baby horsepowers are made
#54
Yes technically I can tune the amount of fuel it adds, but that amount would be pretty darn small Since getting rid of the thing completely has been getting me pretty close to ideal.
#56
After a few days with the quick fuel it looks like two things need to happen.
1 I need a bigger accelerator pump shot as I have a slight bog on the bottom in conjunction with rapid throttle change
2 and I'm not sure how best to address this (bleed or ifr) I'd like to take a little fuel from the idle low speed circuit. I'm slightly rich under the main jets and the idle mixture screws are super sensitive and closed pretty far.
1 I need a bigger accelerator pump shot as I have a slight bog on the bottom in conjunction with rapid throttle change
2 and I'm not sure how best to address this (bleed or ifr) I'd like to take a little fuel from the idle low speed circuit. I'm slightly rich under the main jets and the idle mixture screws are super sensitive and closed pretty far.
#57
I went ahead and drilled the idle bleeds out to .077 from .070 this brought the part throttle a/f ratios into the mid 15's which is good yet surprisingly the mixture screws remain hyper sensitive and are out less than 1/2 a turn.
I also closed the secondary baseline slightly opening and compensated slightly on the primary. This was very productive in restoring chrispness to the throttle response. The tip in stumble was also reduced as a result.
I think I can now look into adding the powervalve back but it only needs a FRACTION of the fuel the factory .055" restrictions are providing
I also closed the secondary baseline slightly opening and compensated slightly on the primary. This was very productive in restoring chrispness to the throttle response. The tip in stumble was also reduced as a result.
I think I can now look into adding the powervalve back but it only needs a FRACTION of the fuel the factory .055" restrictions are providing
#58
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What is your WOT A/F ratio? And, what jets do you have in the front and rear?
#59
This is pretty typical for a 4 corner idle carburetor on a small block.
I is very surprising to me that you can get anywhere near the WOT A/F ratio you need and still get clean part throttle A/F ratio with the power valve block.
What is your WOT A/F ratio? And, what jets do you have in the front and rear?
I is very surprising to me that you can get anywhere near the WOT A/F ratio you need and still get clean part throttle A/F ratio with the power valve block.
What is your WOT A/F ratio? And, what jets do you have in the front and rear?
WOT AF starts mid 11's and cleans up to 13 or so at extreme high rpm.
With the power valve it was <11 at all rpm @wot and at any throttle that caused the PV to open the AF would shoot straight to pig rich and the car would fall on its face
The kicker with the mixture screws is this is just a two corner carb