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Dellorto DHLA and Triple Talk


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#21 RebekahsZ

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Posted 13 November 2012 - 05:11 PM

Feel free to paste my PMs into your thread. When I sold my Dells, I tried to send the buyer all my jets, etc. That lucky mustard got a great deal! I looked around tonight and only found some 60 and 70 low-speed jets and (2) 175 Air Correctors for the main jets. But - you are in luck-I didn't send him my book. It is called The Dellorto Superformance Tech Book with New Calibration Guide written by Bob Tomlinson. Since I don't need it anymore, send me an address and I'll pack this stuff up and send it to you. Are you familiar with this book? It has a chart to help pick venturis and some recommendations on jets selection. One big problem with the Dells is jet part numbers. It would make sense that to get more rich, you would move from a 1 to a 2 to a 3 and so on. Not so. A 9 may be richer than a 4 which may be richer than a 6. It was like the manufacturer was on drugs when making part numbers. I have a sheet of paper that shows one of my configurations, but I don't know where all my other notes are. Tucked into the book is the names of a couple of my Dellorto suppliers. One is Pro-Tech Enterprises in San Diego which serves the Harley Davidson crowd with Dellorto Parts. There was also somebody named Dave Bean who I ordered stuff from, but I'm not finding his number or address. I spent most of my time trying to get the little intermittent backfire out of the low-speed side of the car's operation. Dellorto controls the Low-speed part of the circuit with the Idle Jets. Idle jets increase logically: I think I settled on a 60. However, the Idle Jet Holder part numbers were just crazy and non-logical. According to Pro-Tech, from rich to lean, they progressed as 8,2,7,6,3,1,9,10,5. According to Dave Bean, they progressed from rich to lean as 7,9,5,4,1,6,2,3. So whats up with that? The idle jet holders were $9 each, times 6, so it was $54 to make a change, argh! I spent a fortune and still had that pesky little pop from time to time. I think my carbs had 36 venturis when I got them. I finally settled on 32s, and I tried some 28s, but it didn't really seem to matter. The reason I think you don't see much on Dellortos is that they are pretty rare, so parts is a real PITA, and there is a lot of trial and error (and multipy the cost of each trial by 6). CB Performance had some stuff too, I think I got my accellerator pump rebuild kits from them. In today's times, if I wanted triple sidedrafts, I'd go with Mikunis for parts availablility, choke mechanism and less leakage. Plus they are Japanese instead of Italian like Weber and Dellorto (am I correct)? Oh one other thing. On my intake manifolds, only the front and back manifolds had a tower to support the shared linkage shaft. The shaft therefore bent or deflected some in the middle which made the center carb hard to synch. If all three manifolds had a tower, I think it would have been easier to synch more accurately, but it would have allowed more of a tendency for the linkage to bind if there was any misalignment of the manifolds. Funny, I still had those dam n carbs from 1997 to 2011! Everybody was always very impressed when I opened the hood.

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Edited by RebekahsZ, 13 November 2012 - 05:25 PM.

1972 240z, purchased in 1991 for $900. Stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. PCM tuner: Lane Culver, Laceys Spring, AL. Best 1/8 mile 6.96, best 1/4-mile 11.0, best 60' 1.43. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!


#22 Heroez

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Posted 14 November 2012 - 06:32 PM

Thanks Blue. Blue has uploaded the tuning guide for Dellortos at http://www.classiczc...hread47297.html
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#23 Heroez

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Posted 15 November 2012 - 10:36 AM

I am considering using a 280zx type distributor and adjusting the spring tension so that I get 30-32 degree timing at 5,000 rpm. It will take a little bit of trial with a timing light. Any thoughts or opinions on this?
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#24 NorwegianZED

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Posted 18 November 2012 - 10:44 AM

Well then :)

I found my back ups of the files who died with the previous laptop, they have been sent to Heroez for uploading :) Des hamil book in pictures, not low quality scans :) Dellorto carb manual and some weber stuff....

I am reading the word document shared in this thread and i can't help to notice that the graph seems to sugest that dhla40 is too small for L24 never mind the L28? I am building my l28 and i am slightly worried? but not so moch as it seems the 40 are more than enough for the l24 by far. any thoughts or experiences?
Best regards
Arnulf

1973 240Z being rebuildt

#25 Tony D

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Posted 19 November 2012 - 07:15 PM

" One big problem with the Dells is jet part numbers. It would make sense that to get more rich, you would move from a 1 to a 2 to a 3 and so on. Not so. A 9 may be richer than a 4 which may be richer than a 6. It was like the manufacturer was on drugs when making part numbers."
They are Italian, this negates logic when dealing with part numbers. If they were German (Solex/nee Mikuni) the part numbers would be constipatingly logical....

Tomlinson's book is great, it was sold through CB and VW vendors for years.
Misanthropic Anthroparion Class 5 Hoarder, aspiring to posthumous fame as my containers are cut open and the market floods with crap I've squirrelled away over the years! I endeavour to persevere...

#26 Heroez

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Posted 21 November 2012 - 06:47 PM

It is easier to memorize the Enochian alphabet than to find a logic in the Dellorto emulsion tubes and idle jets. Des Hamill seems to be confused as well on page 67 of the PDF file "How to Build and Power Tune Weber and Dellorto..." In a paragraph he lists the idle jets in lean to rich, then the next column in a different paragraph states the leanest as the richest. Maybe it is just me. Does anyone else notice that? You former Dellorto owners, please give me some information you know please. Something to go on that you know! Tony, is my zx distributor idea good?
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#27 Heroez

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Posted 21 November 2012 - 07:07 PM

Well then :)

I found my back ups of the files who died with the previous laptop, they have been sent to Heroez for uploading :) Des hamil book in pictures, not low quality scans :) Dellorto carb manual and some weber stuff....

I am reading the word document shared in this thread and i can't help to notice that the graph seems to sugest that dhla40 is too small for L24 never mind the L28? I am building my l28 and i am slightly worried? but not so moch as it seems the 40 are more than enough for the l24 by far. any thoughts or experiences?

Take a look at the update at datsunzgarage.com/weber for may 2012. His L28 is using 40s with 30mm chokes. Where highly modified strokers I see 45s with 38mm chokes selected for maximum high rpm loading power. I think we are on the right track for our engines Arnulf, in what we have selected for basic equipment. Maybe we can compare jet sizes when we get down to tuning them in.
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#28 NorwegianZED

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Posted 22 November 2012 - 01:50 AM

hmm, maybe the graph is for each cylinder?
Best regards
Arnulf

1973 240Z being rebuildt

#29 Heroez

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Posted 22 November 2012 - 05:05 AM

Most of the tables are for 4 cylinder engines. Some are for cylinder size. However all of them seem to be for maximum power, which means not the best match for driveability. For easy start ups, smooth off idle throttle transitions, we have to size down the results given in the graphs and charts. That is why I found the datsunzgarage write up so helpful. It more closely matched my engine and goal. If you look at the picture, he has the rubber fuel line with 3 Tee fittings supplying fuel. What do you guys think about that? Is it less prone to heat problems? Should there be a restriction at the fuel return line?
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#30 Tony D

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Posted 23 November 2012 - 12:58 AM

Back pressure regulation. FPR after the "load" (carbs) - the pressure is controlled by restricting flow back to the tank. This allows full pump output to be put to the carbs during WOT when the floats drop.

Most charts are for street cars, not racing vehicles. Be sure you know what you are looking at in this regard. Almost any 40 mm Carb Guide will be for street use.
Misanthropic Anthroparion Class 5 Hoarder, aspiring to posthumous fame as my containers are cut open and the market floods with crap I've squirrelled away over the years! I endeavour to persevere...

#31 RebekahsZ

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Posted 23 November 2012 - 05:48 AM

I haven't made sending you that Dellorto book a priority. I'll try to get it done after the holiday. The Des Hamil book is worthless, as most of the books by that publisher are: pretty, glossy cover with nothing inside. How about you post the part numbers of your current venturis, main and idle jets? When I got my carbs from the junkyard (I got them in trade for the old Anson slotted mags that were original to my car), I replaced all the parts that had melted in the engine fire (which started in the aircleaner) , simply making all the part numbers the same for all three carbs. Then I cleaned and rebuilt them using new gaskets, accellerator pump kits and o-rings. If you look in any of the books I've found, all the calibrated part numbers that were in my carbs were wrong. Well, would you believe the darn thing started right up? But, it had that pesky little backfire. So, then I spent thousands of dollars on parts to find the "right" combination. Honestly, it was never really any better than it was on that initial start up. Why don't you just install them and see if you can get what you have to run? If it doesn't run, screw your idle jet adjustment all the way in and back out 2.5 turns counter-clockwise. With the new updated hybridz format I can't seem to put my youtube link in a post. To see my Dellortos running from a cold-start (not in the winter mind you-cause then you would see me cussing and having to jumpstart the car off my truck because in the winter trying to get the car started usually took more cranking than one battery could supply), go to youtube and search RebekahsZ + 240z + Dellortos and it should come up. I ran a stock distributor with the vacuum plate delete modification. The car had the little backfire before and after the vacuum plate delete. I think you can run any old distributor just to get it running. PS-once you have the carbs running, be sure to remove the venturis every couple of months and clean the corrosion off that builds between the venturi and the carb body - getting those venturis out can be a real bugger if they corrode in. But, boy, do those carbs look and sound sweet at full throttle! In this day and age where other alternatives exist (like fuel injection), triple sidedrafts are so much like porn (so I've heard): they look and sound good, but they burn up a lot of time are hard to live with.

Edited by RebekahsZ, 23 November 2012 - 05:57 AM.

1972 240z, purchased in 1991 for $900. Stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. PCM tuner: Lane Culver, Laceys Spring, AL. Best 1/8 mile 6.96, best 1/4-mile 11.0, best 60' 1.43. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!


#32 Heroez

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Posted 23 November 2012 - 06:52 AM

Back pressure regulation. FPR after the "load" (carbs) - the pressure is controlled by restricting flow back to the tank. This allows full pump output to be put to the carbs during WOT when the floats drop.

Most charts are for street cars, not racing vehicles. Be sure you know what you are looking at in this regard. Almost any 40 mm Carb Guide will be for street use.


That makes sense Tony. Its crazy how much logic I can overlook when thinking about a concept as a whole, and not looking at seperate functions individually. This leads me to think that no fuel return would cause the float bowls to overflow. So, does anyone have a recommendation for a type/brand of presrure regulator to be used after the carburettors? Should I just Tee off my existing S30 fuel rail at the rear outlet and use the restrictor that is already used on the return line?

Edited by Heroez, 23 November 2012 - 09:36 AM.

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#33 Heroez

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Posted 23 November 2012 - 07:06 AM

RebekahsZ, you got it. The plan is to plug them in and see if they work. I just have to work out a couple set up changes like fuel feed and initial timing changes. Good tip on the corrosion! I appreciate your support. That is very big of you. It is very helpful to have your advice. It is ok to take your time sending the resources. Let me know what I owe you for that stuff. I will post the jet/emulsion tube sizes as soon as I am able. I have been meaning to send you a PM about that anyway. Talk to you later. Thank you, everyone, for your posts in here! I am learning!
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#34 Tony D

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Posted 23 November 2012 - 05:37 PM

I have seen the stock rail feeding front and rear carbs using the stock mechanical pump and restrict or.
Never tested it myself other than for an informal transport or farting around car...but it seems to work fine.

Put a "T" in there and monitor fuel pressure. If it stays where its supposed to be...you're done.

Experimentation and documentation are recommended!
Misanthropic Anthroparion Class 5 Hoarder, aspiring to posthumous fame as my containers are cut open and the market floods with crap I've squirrelled away over the years! I endeavour to persevere...

#35 Heroez

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Posted 24 November 2012 - 05:25 PM

10-4. Good use for that fuel pressure gauge now that it is no longer in use on a certain turbo ZX. ;)
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#36 RebekahsZ

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Posted 24 November 2012 - 07:49 PM

Finally figured out how to insert video. Dellorto DHLA40. Stock (Autozone) fuel pump, Holley bypass fuel pressure regulator to allow return line to tank set at 3psi on gauge, stock distributor with vacuum plate delete mod, dirty gas tank:( Sold on ebay about a 6 months ago for $1500 (I think). Wish I could remember who I sold them to so we could see what parts I had in them.


1972 240z, purchased in 1991 for $900. Stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. PCM tuner: Lane Culver, Laceys Spring, AL. Best 1/8 mile 6.96, best 1/4-mile 11.0, best 60' 1.43. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!


#37 Heroez

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Posted 25 December 2012 - 06:58 AM

Now through the holidays I had time to read, study, search and ask questions. I got up the courage to take some parts out to examine the numbers. This is what I found- Main Air Correction is 180, Main Emulsion tube is 7772.5, Main Jet is 132, Idle Jet is 50. Idle Air Corrector/Jet Holder was marked 7850.1 (0 looked like C). This is in the middle of the range from weak-rich according to CB performance. From what I have read the Main Air Correction is good. Main Jet to Venturi size is a bit big. 30 x 4 = 120 so 132 Main jet is a bit rich but way better than too lean. Idle jet may be a litte small at 50. Main Emulsion tube... Umm, still unsure. Anyway, how do these numbers look to you folks?

Edited by Heroez, 25 December 2012 - 10:08 AM.

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#38 Heroez

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Posted 25 December 2012 - 06:59 AM

Im also still researching spark control. Mallory unilite seems to have mixed reviews. Megajolt seems cool but I would like to keep it simple and mechanical. Decisions! Ugh.

Edited by Heroez, 25 December 2012 - 07:05 AM.

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#39 RebekahsZ

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Posted 25 December 2012 - 09:14 AM

I had either 125 or 135 mains. Best i could figure, the main jets only really matter at foot-on-the-floor wide-ppen throttle. Homestly, how often does that occur? And for how long? That is why the mains are selected pretty much based on venturi size. Most of your pain will be spent tuning the low-speed or idle corcuit. I think I ran 60s on the low speed circuit. I bought 55s and 50s-no real chang in how the car ran. Car ran rich with 60s, 55s, and 50s. Went down to 45s and it popped. Tried dropping venturis to 28s and it didnt help. Went back to 30 venturis. I think a pretty easy way to tell if you are in the ballpark on idle jets is this: if you can't make it stumble by screwing the bleed air screws in all the way, your jet is too rich. If it back fires you are too lean. Unfortunately, the "idle jets" control not only idle but they also control part-throttle operation. Think of this as everything between start up and full-wide-open throttle. You will spend most of your time selecting idle jets and messing with the bleed air screws. In order to not backfire regularly, I ran 60s and adjusted the air bleeds for fastest idle on each throat. The result was a car that drove smooth but was always a little on the rich side with a black tailpipe and pretty bad gas mileage. We chose between the main jets by using a stop watch to determine which jet gave us the fastest time full-throttle between two highway mile markers with a rolling start from a specified speed. My favorite: trial and error with a hillbilly dyno! Funny-my auto correct changes dyno to dunno-how appropriate!.

1972 240z, purchased in 1991 for $900. Stock LS2/T56/DBW from 2006 GTO, swap completed in 2011. 400rwhp/435 rwtq. 2400# minus driver. JCI swap, Mantic ER2 clutch kit, JTR headers, single exhaust, Borla muffler, MGW shifter, M2 Differentials shortened Z31 CV axles, Chequered Flag Racing billet stubs and companion flanges. MSD 2-step, Hurst roll control, both operated from switches on clutch pedal. 9" Hoosier drag slicks on Weld Draglites, 245/45/16 Hoosier A6/R6 on 16X8+10 Rota RBR. 225/250 sectioned coilovers, Koni 8610-1437RACE shocks, DP and EMI camber plates, MM shortened rear control arms, TTT front control arms, poly and aluminum bushings. PCM tuner: Lane Culver, Laceys Spring, AL. Best 1/8 mile 6.96, best 1/4-mile 11.0, best 60' 1.43. Home Track-Jake's Dragway, Moulton, AL. SCCA autocross club - TVR, Huntsville, AL. Lets race!


#40 Heroez

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Posted 25 December 2012 - 09:51 AM

Maybe a different emulsion tube choice would have corrected the rich idle if the idle and low speed operation are closely related? Or is my theory flawed?
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