Kadron idle to main fuel transition

[HBRag]

Anybody know at what RPM the Kadrons transition from the idle jet to the main? I've been looking for diagram, but have been able to find one yet. If seems like it's around 3000 RPM...

HB

[oc63rag]

From Aircooled.net:
Idle jets operate from idle to 2500-3000rpms or so. Main jets are primarily from 2500-4500rpms, and Air jets affect the engine from 3500/4000 on up.
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Designed for four soldiers and a machine gun...also for family use.

My food baby is crowning.

[HBRag]

Thanks, I've read the same article and I have a chart for the Dellorto's. I just don't know if the Kadrons are the same.

I've got the jetting setup so that I'm get an AF of 12.6 to 13.4 on acceleration, and 14.0 on cruse at 3500. The problem is its loading up down low (<1500). It really likes the next size down on the idle jet (60), but it goes lean at 3000 to around 15.3 or so. It seems like it's just starting to transition on to the main jet, but increasing the main only make is fat up top. Next step would be to ream the idle jet to a 62.5 or so, and see how that does.

I'm getting a slight exhaust pop on deceleration, 23 MPH and runs fairly well.

HB

[oc63rag]

Could that pop be timing related?
_________________
Designed for four soldiers and a machine gun...also for family use.

My food baby is crowning.

[[email protected]]

you can be on the idle jets ONLY at 7k RPM, or primarily on the mains at 2K, depending on throttle position.

Most folks are too rich on the idle jets.

John
Aircooled.Net Inc

[HBRag]

It a possibility that the pop is timing related. I'll be hooking up an EGT to it this weekend. With that I should be able to really dial it in. I'm using and LM-1 and with the Auxbox, and it has an option to record timing advance as well. It requires building a small sensor and circuit, but it's pretty straight forward. I think I'll go ahead and include the wiring in the harness. I've got a few different distributors and is would allow me to map and graph the curve an all three. I was hoping to get the carbs as close a possible before going into ignition. I may need to address the ignition and then go back and fine tune the carbs.

HB

[HBRag]

It's at cruise on the freeway that it goes lean if I go down a size on the idle jets. It's more responsive with the smaller jets. The way I got the carbs they had 67.5 idles and 165 mains, and it's way more responsive with 60s if I can figure out the cruise at 3000 RPM. WOT is no problem it works fine, and the AF is right around 13.0. Right now I've got 65 idles and 167.5 mains in it. If I go to 60 idles then the AF above 3500 in cruise creeps up to 14.5. Which I'd live with if the 3000 to 3500 range didn't end up and 15.3. I've got 34mm venturies, Web 122 cam on 105 lobe center, 8.1 CR in a 2017cc.

I think the timing is next stop. I bought the Mallory Unlite (Vacuum Advance) from Aircooled, but broke it. I dropped a German 009 that had been curved and bushed in. But the vacuum makes a huge difference. I've got a SVDA I'll put in tomorrow, until I get the Mallory fixed. It's bench time for the Mallory, the mechanical advance isn't working at all.

I sure if I bump up the compression to 8.6-9.0 it would also be a lot easier to tune. This engine is an experiement for me. If I take it back apart to change the CR, it will go back together with the 45 DRLAs on my shelf.

HB

[[email protected]]

65 idles? There is no way in #%@ you need bigger then 55 idles.

15.3:1 A/F is fine under a light load. The key is making sure that as you increase the throttle, it pulls down towards 12.5-12.75:1

John
Aircooled.Net Inc.

[HBRag]

That's what I love about this industry, everybody has and opinion. Not everyone agrees with your stance John. But then again most haven't spent the money or time to get the real numbers. I'm going to have to agree with you on this one John. It runs much better on 55 than anything else. I was concerned about the AF number in the low fifteens at cruise. With 55 idles and WOT the AF was around 14.2-14.5, so maybe 55 idles and 170 mains

The engine is in an early car and is running a bit on the warm side. The vacuum advance should help that, but I didn't want to add to it with a lean condition. One things for sure - the MPG should get better.

Thanks for the input.

HB

[[email protected]]

most "experts" regurgitate a bunch of BS they read from a book or on the Internet somewhere. They do not know, they are just parrots.

You are not supposed to have 12.5:1 A/F all the time folks. If you do, you are pissing away 35% of your MPG. The 009 will kill you for another 10%, you need vac advance for MPG and drivability! Even 55 idles are too big for almost all applications.

It is 100% correct that if you have the proper sized idle jets the engine will act "lazier" at part throttle. This is not bad, you are not supposed to be tuning the idle and progression circuits for max power, but unfortunately that's what people do, they put the smallest jet that is "crisp", which is why their MPG is in the toilet! 12.5:1 is what your main circuit is for! This is why my engines easily attain 35mpg, while others struggle to get 25 (or even 20 LMAO). It's also the source of arguments as to "how in the hell can a 2332 get 30mpg?". Engine size DOES NOT AFFECT MPG. Tuning does, engine size does not.

if I posted what carbs I had, and what jetting, most folks would yell "liar" or "it's not tuned", or something like that. Watch; I have 47 idles on my 48 IDFs, and have bigger then 44mm venturis.

My carbs are tuned 10X better then every set out there except for one set (Mark Harney's) I know of. I've spent months tuning them, a lot of that time was in learning mode, but I got it down now!

John
Aircooled.Net Inc.

[HBRag]

Well that's where I'm at now...the learning mode.

Seemingly small changes make a huge difference. I'll bet I'm getting 25% more power, than when first assembled. I paid to have the carbs and ignition setup to keep tuning efforts to a minimum. At this point I'm of the option that every engine needs to be put on a Dyno to really get them right.

Small changes make a huge difference. If you go with ballpark numbers for jetting and timing, you are leaving a lot of performance and drive ability on the table. What I have found is that it takes instrumentation to get it right. The more I tune, the more information is required. One thing affects another. Most of the "ready to go" parts and ballpark settings were on the safe side, but the engine was/is a pig IMO.

It's been a great learning experience so far...we will see where I'm at in 2 months. It's a good thing it's a weekend car.

Thanks for the help John.

HB

[Dogo]

Thread revival, sorry...

I have a new set of Kadrons that can’t quite tune them right. I didn’t really want to mess with them any more than the mixture screw, because really, I just don’t know what I’m doing, just learning.
It stumbles and sputters at lowish rpm. Starts and idles fine. It seems to do the sputter and stumbles under load only, but if I stab it she goes pretty good. If I go easy on the throttle is when she stumbles most. There’s no smoke, and pretty sure she’s not rich.
The stamping on the jets of the new carbs has been filed off, so I have no baseline reference. Yesterday I realized I still had my old Kadron carbs lying around, so I switched the idle jets. ln with the old carb idle jets (55) and out with the new carb idle jets (unknown size). Runs MUCH better and a lot less stumble, but still some present. The idle rpm has gone considerably lower with the 55s.
My main jets in the new carb have also been filed off, but haven’t touch them yet. I have the pair from the old carbs marked “130”
My question(s) is:
-Since I have no baseline reference, in which direction did I just go (bigger/smaller) with the 55 idle jets (rpm slowed down with these)?
-What do I do from here to gradually get me where I want to be and in which order? Tweak timing? Adjust mixture? Go some more in the direction I headed with the replaced idle jet (bigger/smaller)? Install the 130 mains that I have?

In layman’s terms if possible, please

Engine is otherwise stock (as far as I can tell) carbs are new. Electronic svda. New cables and spark plugs. New tank, fuel lines and filter. Fuel pressure hovering at 1.75-2 psi.

Not expecting anyone to completely diagnose my issue, but just a little guidance and enlightenment so I can maybe steer in the right direction.
Thanks in advance

[Frank Bassman]

Dogs, did you adjust your idle mix screw after the jet change?

-Frank

[Dogo]

[Dogo]

I kind of started over to see if I could isolate (in my ignorant mind) which jet was the issue... i put the unknown size idle jet back in and replaced the unmarked main for the 130, although it really didn’t look like it was different (measured by toothpick depth), unless increment are are minuscule they are hard to detect(?). However, it did run better and with less stumble but still some there. I then also removed the unknown idle jet for the 55 adjusted mixture... stumble was gone. I figured I was done and solved it...
A little back story before I go on... before my first post, I took it to a mechanic. I figured I was doing something wrong with either timing or mixture adjustment etc. All was good and he narrowed it down to “an issue in the carbs”. He said he tuned as best as possible but didn’t want to fiddle with the carbs. At least that eliminated me being the problem.
Onwards... although it now had no hesitation it didn’t feel like it had a lot of power. I checked the timing with vac removed and it was 40* at idle and about 60* advanced (!?!). First I took it back down to about 30* advanced, and stumble came back. Not terrible but it’s there. Brought up to 34 and it about the same stumble. Does this tell anything about fuel supply? The fact that it will get rid of stumble (although less power) with such a high degree of advance?
Thanks.