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oranngetang

Tuning this 3.0 on SUs...

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Comparing the SM against the SS and RB needles (what seems to be popular stock), using mintylamb's charting has got me wondering. Both needles seem to decrease radius at about the same point mine do and continue to do so, just slightly less aggressively.

 

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A pair of SS needles jumped in the mail from APT this morning. From the chart I posted, looks like a richer needle with cruise efficiency considered. SUmidel never got back to me, and with current events in CA going on this week I doubt I'll hear from zTherapy until Friday or the following Monday.

Placed some nuts in pistons around the damper reservoir to limit overall piston rise around for an experiment. Greatly leaning out the AFR at WOT and cruise, but with obvious flow restrictions. Interesting to see how this balance can be manipulated.

Quite interested to see how stock and SS grinds will behave.

Edited by oranngetang

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Some stuff from the '72 engine manual (also available elsewhere on site):

1. 1/2 turn of idle adjust nut stroke = 0.5 mm (0.0191") Fig. EF-48

2. Jet needle: N-54 (and in the emission section,jet dia. = 2.5mm(0.100") needle N-58)

Got early (4-screw) nozzles and N-27's (for my 3-screws)from MSA in 2013. N-27 is only stock needle for 4-screws as far as I know. According to MSA, per phone call and this: http://www.thezstore.com/page/TZS/PROD/classic17a04/11-2532, '72 (3-screw) nozzles are NLA, and you can't use early needles with the later nozzles.

I wonder why. Could it have something to do with why I have to run it with the mix nuts 5 turns down (even with SM's and modified N-27's), when FSM says 2.5 turns for my altitude and temperature?

Edited by Stanley

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I did a couple of hours of reading yesterday as to what the difference would be. Honestly, everyone is quick to point out the 70-71 needle and the 72 needle (s). I can't find any evidence that the jets or needle diameters/lengths are any different. ZTherapy even seems to say all nozzles are 0.100" as are the needle bases, and the nozzles are are a one size fits, though they offer plus or minus sizes.

APT emailed me today in reply to my needle questions to state that only k&n air filters are interchangeable between SU, nothing else.

Seems to be some confusion between various sources.

I ordered those needles prior to the reply, so if they fit, I'll have to let them know.

Edited by oranngetang

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APT's SS needles showed up today, they're about 1/8" shorter than the needles that I have in there but fit like a glove so far. Engine fired right up and idle mixture works well with them, as did prelim 4K RPM without load in the garage. Snowing out... I'll attempt some go-pro/AFR and whatnot someday when it's dry out.

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Agreed. Stanley, did you try a thicker oil or what? From what you've described, it should help with your WOT transition.

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It does not seem these engines require nearly an aggressive needle as what these SS are. I still havn't heard back from zTherapy, but I'm thinking a stock needle might actually perform better than SS or Rebello at this point, seeing as I also need to lean out the mixture screws to the point of idle problems in order to get an acceptable cruising fuel ratio.

 

Currently I'm able to idle ~20-23 AFR, cruise at ~15, accel at ~14, but as soon as I'm close to WOT, ~11, 10, 9... 

 

I was ambitious enough to set up a GoPro to review some data this afternoon, but upon reviewing my footage I see the camera was not at all happy with the AFR gauge LCD refresh time. I'll have to play with some FPS settings to see if I can get a reading on that gauge while recording, rather than 1/4 of the display randomly flashing.

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I think that's where I'm going to end up. Hopefully I can get my hands on 3 or 4 pairs, and work my way to something that works well. 

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I changed dashpot oil to 30 wt. a few months ago and it helped reduce the miss at transition to WOT, but didn't eliminate it entirely. I had the N27's polished, and that made a further improvement, but still not 100%. Installed the SM's a few weeks ago. I like the peppy low end they're providing but I still can't get on it unless I make it too rich at idle. Got the N-27's polished some more last week, will reinstall them in a few days, and see. When I put them back in I'll take the SM's in for polishing, and see what's better.

 

Also bought a high-flow fuel filter (for 400+ HP engines) to install by the tank, instead of WIX can there now, below the level of the outlet (doesn't make it easier) as the manufacturer recommends. Overkill probably, but it might provide more flow. I saw fuel pressure go up about 0.1 to 0.2 psi when I tossed the glass fuel filter. Sometimes there's a combination of problems.

 

A good digital micrometer might make it easier to keep track of the needle mods. Wonder if my $10 Harbor Freight micrometer would be up to it. The ones from Japan look OK.

 

If carbs are modified to flow more air, stock needles might be too lean. Don't give back too much of that 285 HP just for drivability.

Edited by Stanley

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I've been in the Kootneys sitting in hot springs and canoeing, thanks for the link. I'll catch up on some reading. There seems to be opposing opinions on even the SM needle being 'fat' on that first page.

In other news, still havnt heard from the folks in Salem, so this evening I reluctantly spent another $100 bucks on two pairs of needles to work with from elsewhere.

I have zero luck with US based businesses.

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On a side not and until I return home, I've been encountering a starting issue with this engine and have somewhat assumed it's just a sympton of a higher compression engine.

The car will crank endlessly without issue when cold, however once it's being driven and either stalls or is turned off it can barely crank. The pinion engages and the engine will rotate but gets stuck on a compression stroke and often takes several attempts before it kicks and I'm on my way again.

Would installing a new or 'gear reduction' starter possibly help?

I should note that for some reason immediately after this occurs, the ammeter shows nearly a full 55 amp deflection for a short period of time and then returns to a normal 5-8 amp indocated draw.

I have a 60 A bosch alternator with internal regulator, most wiring between battery/starter/tach/coil, etc. is new. Battery is a fresh yellow top.

$200 CAD shipped for a gear reduction starter on ebay from the normal vendors.

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Using a gear reduction starter from a 280 made a huge difference on my car.  I haven't tried it with the new engine but I think i paid around $40 at my local parts store

 

 

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Thanks Kurby. I see Rockauto has them for very cheap; cheap enough I'll just order one. They tend to send via Purolator, who just leaves stuff at my door, and/or has their depot across from where I work.

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Working on it... I'm finding it hard to believe that the only place I'm successfully having stuff put in a box and mailed to me is from the people that say the needles won't fit the carbs. The guys that rebuilt my carbs can't seem to be bothered to take an order or reply. I've pretty well wasted $200 bucks and a couple of weeks of driving the best highways in BC in the luckiest weather break ever, because someone can't get an envelope in the mail.

 

I'm curious how yours runs on your stock needles, or did Dave grind yours aswell?

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I'm starting this thread to keep track of my findings, but please chime in if you have any thoughts, suggestions or critisisms on the matter.

 

The engine is a fresh 3.0L Rebello "Full-on" package, which have my zTherapy 4 screw round tops bolted to it, on a smoothed balance tube, and a 6-2-1 header. Compression is said to be 10.1:1, I noticed the head is slightly ported, and the valvetrain noise is overly aggressive even with a fresh lash adjustment. Cam is a '99DI', IIRC, which Dave himself said runs very loud. Rebello Racing bored these to 48 mm, and as it appears did some crazy grinds on the needles to put down 282 HP on my dyno sheet.

 

That said, my experience with the tune has a been a little frustrating.

 

For starters, this engine will not idle. With suspicions of the car running overly rich, I purchased an Innovate DLG-1 dual wideband gauge to monitor with banks of my header at the 3-2 collectors. The gauge has told me a lot, but most importantly that the engine IS running rich. How rich?

 

With the float levels at 20mm from top of bowl, at 3 turns down (2.96 mm by caliper), I'm putting down 9.1-10.1 AFR at WOT, through the rev range, and >20 AFR at an idle of 800 RPM.

 

With the float levels at 20mm from top of bowl, at 1.5 turns down (1.48 mm by caliper), I'm putting down 10.8 - 12.4 AFR at WOT, through the rev range, and the engine is much snappier above 2000 RPM, but below it has no power and will idle for only a few seconds with the idle screws generously opened up.

 

I suspect these fancy looking needles may have some, if not ALL to do with these problems. Thanks goes to Blue for walking me through uncovering them.

 

attachicon.gifneedles.jpg

 

With the amount of material removed, it seems to be that I need to set the mixture to be excessively lean to compensate, leaving no fuel for the engine to idle on.

 

I'm going to try playing with these a bit, and am pondering the idea of spinning some SM or stock needles a little to see how it effects my specific engine.

 

In the mean time, I'm kind of wondering if setting these needles set higher into the piston, or filing off a tidbit of material at an idle/low end position may assist with the idle issue.

 

Better drop those needles in the trash and buy some decent ones...

My god looks like a hamster has been eating on those needles..

 

You could ask Ztherapy for a right set of needles for your application.

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I did get the "big bore" adjustment done, but i have not seen the needles in person yet.  Perhaps you can post a link to the conversation you had with blue to extract the needles from the carbs.

 

Without too much of a threadjack my motor is in.  I probably need another 3-4 hours of hook up and plumbing to get it running.  Kids baseball is killing me..

Edited by Kurbycar32

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1. You need to unscrew and remove the black damper caps, they're thumb tight and slide out with a damper-plunger on the end, they may be wet with oil, FYI.

2. Unscrew the 3 or 4 screws that hold the dome down and lift it straight up. this will uncover the piston and piston return spring.

3. Remove the spring (it just lifts out)

4. Very carefully lift the piston straight up, the needle is attached to the bottom, so lift straight up until it is free. The centre of the piston where the damper came out of may be FULL OF OIL, so be careful not to tip it by accident. There may also be a plastic washer that sits below the spring, so don't lose that.

 

Those are your needles. If you decide to remove them, note that there is a shoulder at the thick end that isn't beveled. That shoulder must be flush with the lower area of the piston, not the notched out groove it's mounted in.

 

For example, when re-seating this needle it would be wise to turn your jet adjustment nut all the way up so the top of the jet nozzle is flush with the jet sleeve. Slide the needle into the piston, but not all the way, tighten the needle screw enough you can still move the needle into the piston without much force, hold the bottom of the jet asembly UP and lower the piston into the chamber. This would seat that needle at the same height as the nozzle sits, in each carb.

 

If anyone has anything to add or remove, please speak up as I'm new to these things.

Edited by oranngetang
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I would try a different starter first or just try the reduction starter. Definitely check all connections .

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Still using the SS needles? From the chart posted, looks like they have an interesting profile, like custom needles, going richer at top end (where it needs more gas, and bottom (for when you suddenly floor it from cruise and the piston drops due to reduced vacuum). 

 

Can't find data on stock N27's. Measured them with my $10 micrometer, but would like to compare with the official numbers.

 

Recently installed a vacuum gauge under the dash, it's interesting to watch what is does while driving. Makes it easier to understand what the SU experts are talking about (Blue's SU mod thread, for example). Since the SU piston and needle position depends on vacuum, watching the gauge allows me accelerate without the engine missing or popping. When I see the vacuum drop to about 5 in/hg (with SM needles) I back off the throttle a little, since that's where it happens. When the revs are high, the vac stays high, and throttle position has less effect on vacuum. Obviously, this isn't what most drivers get from a vacuum gauge (hope to eventually learn that stuff too). Since 5 in/hg is lower than the vac at idle (about 15) maybe I can figure where that is on the needle (probably very close to the base) and polish that down, to tune out the miss and still not be too rich at cruise and idle.

 

Regarding the hard starting, maybe more friction in engine in the first half of break-in period?

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