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| Dellorto Choke sizes | Rating: 
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| Posted: 07-16-2006 05:11 pm |
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1st Post |
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Dan Eiland Member
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I was under the impression that the smallest choke size you could fit into a DHLA 45 was a size 36 choke. There is a set of DHLA 45's for sale and the owner says they have size 35 chokes. I asked him to confirm this and he says they are in fact size 35. I looked on the JHPS site and found where it lists the choke sizes for the DHLA 45 as starting at size 36. Could someone clear this up for me. Thanks
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| Posted: 07-16-2006 08:47 pm |
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2nd Post |
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Jensen Healey Super Moderator 
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Hi Dan, The Des Hammill book lists 34mm as the smallest recommended choke for the 45s so it seems likely the seller is correct. http://www.dellorto.com lists 31mm through 40mm chokes for the 45s. Kurt JH 13148 (no power above 6000 rpm with 33mm chokes and stock cams.)
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| Posted: 07-16-2006 09:29 pm |
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3rd Post |
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Judson Manning Member 
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You can actually get down to 28mm chokes in a DHLA45 and up to 36mm in a DHLA40. Choke size determines maximum amount of flow (assuming the head is breathing to its maximum capability). For a 2.0L engine you need the following choke sizes to produce maximum flow at the designated RPM: 5000rpm = 32mm 6000rpm = 35mm 7000rpm = 41mm 8000rpm = 46mm SCCA E-prod rules mandate the 34mm chokes, and I can confirm even with a ported head, free-flow exhaust and high-lift cams, the 907 doesn't produce any power over 5500rpm. Stock JH chokes are 35mm and 37mm for the 2.2 variant. For street use, I was happy with 34mm in the 2.0 and currently like the 36mm in my 2.2. Top end suffers a little, but low-end throttle response is fantastic.
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| Posted: 07-17-2006 12:13 am |
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4th Post |
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Dan Eiland Member
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Thanks guys, for the information. This clears things up some. I can always depend on the message board when all else fails (like my brain). Dan
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| Posted: 07-17-2006 12:37 am |
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5th Post |
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Jensen Healey Super Moderator
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Hi Judson, The book says the 40s should have a maximum 34mm choke and even though 35mm and 36mm will fit, they will flow better in the 45s. Thus it makes sense that Dan should find 35mm chokes in a pair of 45s. What's your current theory on the soft mounts? Bolt them down tight, or use the factory specs? Mine are tight and I haven't detected any problems that might be caused by not having any flexibility. Kurt
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| Posted: 07-17-2006 02:44 am |
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6th Post |
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Judson Manning Member
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It would be better to get a set of 45s if you can, but the 40 can be made to work....just a lot more testing and tuning. There won't be a 'book' solution. The DHLA45s I got from Dave Bean years ago (Spec 9 variant), spit and popped like mad. I had the black plastic soft-mount which had a total of 8 o-rings, thackery washers and those solid rubber mounts as well. All 'by the book'. My spitting actually stopped when I abandoned the Spec 9 jetting (160 mains), and adopted closer to stock jetting (135 mains). Every 'spit' or 'pop' blew-out an o-ring and/or upset the linkage unbalancing the carbs. After years of frustration, I did a hard-mount and never looked back.
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| Posted: 07-17-2006 05:05 am |
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7th Post |
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Dan Eiland Member
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Judson, are you saying I can make the DHLA 40's work with a 2.2L with some light head work and 104 cams? Keep in mind I really don't need to go over 6000 rpm since I will have a Ford T5 5 speed with the 0.73 overdrive. I would think this combination would give me better response in the lower rpm range and the rest of the package should keep it pulling up to 6000 rpm. This could be wishfull thinking on my part. What are your thoughts. My experience with my Sunbeam Tiger was that most people over carburated the engines. I had all the Shelby options on my car and I stayed with the OE Holley 465 cfm 4 bbl. I did some modifications to fine tune it but once I did, ba ba ba boom. I suspect my JH will be like my old Tiger, just handle better and ride better with more creature comforts. Judson tell me more about using the DHLA 40's with a 2.2L. What would I need to do to make this work for a street car?
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| Posted: 07-17-2006 12:03 pm |
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8th Post |
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Judson Manning Member
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I'm sorry for the confusion Dan. I agree with Kurt that while you could get a 36mm choke to fit in a DHLA40, it would not be the best solution for a 2.2L equipped car. Alternatively, if you were doing a 'stock' 2.0L rebuild, you could make the DHLA40s work just fine. If top-end flow is not as important to you as low-end throttle response, consider using a set of re-jetted Strombergs.
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| Posted: 07-17-2006 12:50 pm |
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9th Post |
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Brett Gibson JH5 20497 Member
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Dan, could you tell me what size all your jets are that you are using in your 40's, I purchased what Greg had recommended, 33 chokes, from 35's, 145 mains, from 130's, 190 air correctors, from 160's, etc etc, I'm trying to keep a list of what other people are using on there 40's so that I can have a referance point. Last year I tried to run them and had nothing but trouble, so switched back to the Strom's, but since then I purchase a couple more items that may help me get them back on the car, probably give it another go in a couple of weeks. So if you could let me know I'd appreciate it, Thanks Brett
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| Posted: 07-17-2006 02:56 pm |
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10th Post |
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Dan Eiland Member
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Brett, I only know that my DHLA 40's have 35mm chokes. I have not pulled them apart to find out how it is set up. Sorry I could not be of more help. Dan
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| Posted: 07-17-2006 04:12 pm |
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11th Post |
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Judson Manning Member
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Brett, You seem to be at least in the right ball-park with jetting. Exactly what kind of trouble did you have?
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| Posted: 07-17-2006 04:58 pm |
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12th Post |
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Brett Gibson JH5 20497 Member
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Hey Judson, Well just to hit the high points, I had a lot of spit back, and the mixture screw didn't seem to have much effect, so after I took them off the last time, I stripped them down again and soaked them for a month or so in cleaner, purchased the Lotus anti-spit back flanges plus the springs inside the pump jets, (mine didn't have them), I also picked up and studied the "Del Slavens book". So right now they are all back together with all new o-rings and gaskets etc; bolted to the manifold waiting for me to get the nerve to install, I have a 4 gauge vacuum setup that I use on my motorcycle to try and tweak them in, but have been considering getting the "Carb Tune Nanometer" because this seem's the area that I'm falling short in "the tuning". Any suggestion's that you have Judson would be greatly appreciated, I did get some good feedback when I fought this loosing battle last year. Thanks Brett.
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| Posted: 07-17-2006 06:53 pm |
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13th Post |
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Judson Manning Member
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Everyone has different experience and what I've found is every engine seems to like a different jetting. The spitting comes from fuel dropplets dripping on the hot intake valve and exploding when it is closed. There are a number of things that can cause this problem including a leaking pump-jet, incorrectly set float, or fuel condensing on the intake manifold. The latter can happen on start-up when the runners are cold. It can also happen when the mixture is way too rich. If your carbs leak or have wrong jettings, the answer is not to add another accessory. The Lotus Spec 9 calls out for 160mains and 57idle jets, compare that to the stock JH 130mains and 55idle jets. The correct answer is somewhere in between. My 2.0 ran great on 135s and my 2.2 runs great on 140s. Are 145s or 160s for you? who's to say, but the best thing to do is get several jets and iterate to a solution that's best for you. BTW an EGT and/or O2 sensor makes this soooooo much easier.
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| Posted: 07-17-2006 07:03 pm |
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14th Post |
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Brett Gibson JH5 20497 Member
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Thanks Judson, I'll keep you posted Brett.
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| Posted: 07-17-2006 09:27 pm |
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15th Post |
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Jensen Healey Super Moderator
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I thought spit back was caused by a too lean condition. As I have repeatedly posted, the smooth running of Dellortos is directly related to the idle circuit. The idea is to get the idle jet into the correct range and then find the correct idle jet air corrector ( idle jet holder) for optimum performance. The original JH jetting had a lean corrector. If you use this your car will never run right. Try a 7850.7. The Des Hammill book explains this in detail but takes several readings to understand. The cheaters way to adjust air correctors is to drill them out to the next size using machinist's bits using the guess and check method. If your car runs well to 3500 rpm and then has issues, it's time to focus on the main jets and air correctors. The mains have no effect at low rpms. The adjustment screws are more for micro adjustments and will not make a lousy jetting job run better. Good luck, Kurt
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| Posted: 07-18-2006 06:53 pm |
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16th Post |
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Brett Gibson JH5 20497 Member
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Kurt, thanks for the reply, I did change the idle jets holders to what was recommended, but still had my problems, the best thing I did was get the Del Slavens book, that's why I took them apart again and made sure I did a thorough cleaning, and now have a better understanding of were things go and how they operate. Sure hope they work out better this time. just for your info here's a list of what I'm using. Mine / New Mine / Old Carburetor Size (mm) 40 Choke Size (mm) 33 / NEW 35 / OLD Venturi 7848.1 Main Jet 145 / NEW 130 / OLD Main Jet Emulsion Tube 7772.5 Main Jet Air Correction Jet 190 / NEW 160 / OLD Idle Jet 55 Idle Jet Holder 7850.7 / NEW 7850.5 / OLD Pump Jet 45 Cold Start Jet 70 Cold Start Emulsion Tube 7482.1 Needle Valve ? Float Assembly 7298.2 Butter Flys 7481.2 Brett
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