Needle Modification for L20b SU's

[Just Joel]

Conclusive results! I love it :p I'd say we're well within a decent margin of error. Now, if you don't mind, plot our most recent modified sets over the base line z therapy m66

[Just Joel]

I also have a set of m43 needles that I can profile and add to the list ;)

[mtngoat]

Now for the mods...

 

3D

[Just Joel]

I love graphs :)

[mtngoat]

Conclusive results! I love it :P I'd say we're well within a decent margin of error. Now, if you don't mind, plot our most recent modified sets over the base line z therapy m66

Here you go, I used your measurements for the 'stock' ZT M66

[mtngoat]

Hey Joel, what's your 'central oregon' location? I can see we may need to compare notes in person!

[Just Joel]

Bend :)

 

Have you done any wot runs yet? How are the numbers so far?

[bonvo]

so much info lol for the most part i hate to say it but im going to be copying joels stuff for the most part when i get my su's on the car since we live in the same area but if im honest after watching him fight these things just in the 2 years ive been here i might just sell off my su's and buy a single weber side draft

[mtngoat]

Sigh....i need to do this at some point too. But first i need to learn more about the su‘s to feel smart enough to take this on. Do either of you have a blown up schematic of the su carbs? Ive sesrched around and cant seem to find one. Im still in the process of identifying everything that has already been done to my car (previous owner was a tool that just parked the car in his driveway and let it sit for years.)

It's way easy, and a relatively cheap risk. Just go slow and take a lot of measurements, don't sweat it. At first I was meticulous and agonizing over each placement of the calipers. For the initial and final measurements, still am.

 

But when I'm sanding, I started off that way...and by the end, I was just slapping 'em down close to the mark and counting on repetition and decent method to cancel random errors. And if you just relax and don't try to remove too much at once, you'll get a feel for it pretty quick. After some rough out passes, start at the lowest station and start working down. when you get within .001, move on down again.

 

Each station grinds those on either side a bit at the same time, so leaving a teensy bit extra as you go will work itself out. you can always do one more pass on the whole works to clean up 0.001. I had to do that on one...5 passes top to bottom of 2 secs each smoothed and finished that one. 

 

when chucking up the needle, you don't need much tightness at all. as soon as I felt the chuck grab i'd quit, and I had no problems with needles spinning in the chuck. after all, you're just barely pinching the paper to them with light pressure...important to use both fingers to trap the needle with one as you pinch the paper with the other..no bending it!

 

IMPORTANT: IMO, a wideband O2 gauge is *crucial* for this work. I personally think you risk a motor without one if you're screwing with the needles. With it...gravy. Over lean shows up instantly. 

[mtngoat]

so much info lol for the most part i hate to say it but im going to be copying joels stuff for the most part when i get my su's on the car since we live in the same area but if im honest after watching him fight these things just in the 2 years ive been here i might just sell off my su's and buy a single weber side draft

My weakness has always been the lousy fit of needles for a 2L, which I believe cost me my last motor. With them much closer to right for a L18, I had them dialed in perfect. If you do little things like intentionally cross hatching the adjustment screws with a notch so they don't back out (or in), mine have always stayed in tune. Well, other than topping up carb fluid, lol. People freak when they see you doing that. funny. 

 

La Pine, huh? I went through there in about '06 or so on the way to Lakeview. 

[Just Joel]

I will admit that I have struggled over the last couple years making these carbs perform as well as I think they should and to be honest they almost drove to me *cogh* swap to a modern motor. But, I do believe I'm getting close. People need to understand this is a little harder than just throwing paper to needle and making your dream carbs. Every adjustment and every potential variable between the two sides needs to be considered and synced to the other down to simple float adjustments, dome drop rates and even choke linkage. If they don't work and adjust identical to one another, you'll never get them "just right" An awesome resource for learning and understanding Hitachi su's is Ztherapy's video. The production values suck and I don't see %100 eye to eye with some of their parts/services and tuning techniques but the video is a valuable resource for understanding if your just starting out. These carbs cant be bought new off the shelf (believe me, I tried) Were dealing with 40+ year old technology and parts so knowing and understanding when something is warn out is also important. Don't let this discourage you... instead, think of it as a pep talk to make sure your truly giving yourself your best shot of tuning your carbs rather than only focusing on one aspect then giving up when it doesn't fix all your problems. I have basically modified or replaced every part in my cabs since starting this endeavor and it seems to be paying off. Weather some of us like it or not, these carbs are just as much of the history and class of our little cars as GL plastic grills and tail light garnishes so I feel they are certainly worth the time and preservation. Go slow, take your time and have fun with it... that is why we own and drive these cars after all :)

[KlassicMotion]

I'm a bit hesitant...  I've got a rebuilt set sitting on my shelf that I have something like $350 in, but I bought a Weber 38 DGES while they were being rebuilt (for 8 months!), and that Weber runs so well and is so easy to adjust that it seem counter productive to swap it out....  I've delt with plenty of SU's on my British cars.  I'm just not sure it's worth the time to set them up...  I suppose I should take the time and at least try them to see the difference.

[Just Joel]

I would like to know how they compare... during my fight with these I bought a brand new 38/38 down draft and restored an edelbrock (sp?) Intake to match. I was on the verge of the swap and backed down. I just can't give up the look of the side drafts under the hood. I'm sure changing to the weber would save time and trouble but I really think I can still make the hitachis work equally as well.

 

Joel

[Just Joel]

Plus I'm stubborn and don't accept defeat well :)

[Eagle_Adam]

been quietly following......

 

 

 

 

good work 

[mtngoat]

Bend :)

 

Have you done any wot runs yet? How are the numbers so far?

I'm hitting 11-12

[Just Joel]

Good... that's not bad... a little rich but it should be good and safe ;) best I can reaserch, 12's are where you want to be for power on a n/a engine but please correct me if I'm wrong :)

[mtngoat]

I've been on a few long trips now and my highway mileage has definitely improved. Easily 2 or 3 miles per gallon, nearly 5 on a trip with long sustained cruise and not many hills. Pretty cool. I think I'll have a go at the other set of needles and tape off stations 5 and above, and then peel everything lower down to the narrow profile I got on my last pass with the current needles.

[Eagle_Adam]

so which one of you geniuses is gunna start offering needle mods to others.......

 

 

Cus im first in line :D 

[Just Joel]

^^^ Been thinking about this ;)

[Sealik]

so which one of you geniuses is gunna start offering needle mods to others.......

 

 

Cus im first in line :D

 

 

^^^ Been thinking about this ;)

 

Unless the engine/car specs are exactly the same...no workie.

Too many variables in the mix.

 

Rebello suggested RA needles for my LZ.......>....very lean conditions through most stages

[Just Joel]

I've been doing some around town driving over the last couple weekends and have found the car is quite a bit more responsive and smoother transitioning from stopped to start. The numbers at low speeds accel and steady state cruse condition range between low 12's to mid 13's... this reads rich to me but after a long consistent run at these numbers, the plugs read perfect. Considering the power increase and smoother operating symptoms I would say the car prefers a richer state at these sample speeds. Out on the hwy at 45 to 60 mph, the numbers are wonderful hovering right around 14.7 and peaking at around 15.5 on transitional acceleration. (Remember, before the numbers were the 16's and 17's at the speeds and conditions) I didn't modify the stations below 10 so my wot stays the same and is more than acceptable in 11 to 12's. All of these test were conducted in cooler operating temperatures where conditions are leanest. Now, I'm think I'll modify a new set of needles and like goat, I'll leave regions 1 through 5 a loan an modify only the regions below exactly as I have already. This might lean out the lower speed numbers and I want to test just for comparison sake.

[Just Joel]

Unless the engine/car specs are exactly the same...no workie.

Too many variables in the mix.

 

Rebello suggested RA needles for my LZ.......>....very lean conditions through most stages

and this is where those thoughts took me :p

[Just Joel]

That being said, most l20b users accept the m66 as a universally correct needle and perhaps a richer needle set can be a better, almost perfect solution regardless of engine spec differences... excluding lz's and other extreme builds of course :)

[KlassicMotion]

I'd buy a set (depending on cost).  Seems the L20B prefers your profile over the M66.  I'd rather buy your needle that has had some R&D than the standard M66.  Safer bet in my book.