Lotus Elan

34mm chokes?

PostPost by: webbslinger » Fri Sep 02, 2016 11:40 pm

I've got a motor built to Bean's Stage lll specs. In Bean's catalog they spec their carb jetting based on 34mm chokes. I'm wondering if any of you have tried this set up or something similar, and how you liked 34mm chokes in a street car. I use the full rev range and want the power the engine was built to deliver, but I'm wondering if it can be tuned to get away cleanly on a hill if the need arises, or to be able to get up to speed from stopped to cross oncoming lanes or to merge confidentiality. I'd like to see how many were happy or unhappy with 34's. Also, how close did your final jetting wind up being compared to the suggestions in Bean's catalog? Did anyone change back to smaller chokes?
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PostPost by: rgh0 » Sat Sep 03, 2016 1:25 am

I have run various size chokes in similar specification engines up to 36 mm without drivability problems on the road. The details of compression ratio, cams and cam timing, exhaust system and carb tuning all need to be right however when you get up to 35 or 36 mm sizes. 34mm should generally not be an issue.

I would start with the Dave Bean jetting recommendation but do a rolling road dyno session with someone who knows what they are doing to get it dialed in right

cheers
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PostPost by: seniorchristo » Sat Sep 03, 2016 1:57 am

Hi Webbslinger
I have a stage ll engine running 33mm chokes with jetting similar to that recommended by QED for their Q360 camshafts. For their Q420 camshaft (stage lll) they suggest:
34mm chokes:
140 main
155 air corrector
F16 Emulsion tube
45F8 idle jet

Where in Bean's catalog are there recommendations for specific jets? I can't find them.
Thanks,
Chris :)
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PostPost by: webbslinger » Sat Sep 03, 2016 2:19 am

Thanks Rohan. The cams, springs, etc were about $1000 and I want to get my money's worth out of them which probably wouldn't happen with smaller chokes. I've never talked to anyone who has used 34s, but I'm going to give them a try.
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PostPost by: elancoupe » Sat Sep 03, 2016 2:21 am

seniorchristo wrote:

Where in Bean's catalog are there recommendations for specific jets? I can't find them.
Thanks,
Chris :)



Hi Chris,
The jets specs are in the carb section, page L19.

Mike
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PostPost by: webbslinger » Sat Sep 03, 2016 3:48 am

Thanks Chris. I've decided to give the 34s a try. Bean stage lll with 34s is: main - 125, air cor - 175, E tube - F16, idle - 45F.9, pump - 45.
Thanks for QEDs suggestions, it might give me some ideas on which way to go.
Victor
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PostPost by: webbslinger » Sat Sep 03, 2016 4:06 am

...and my apologies to you all for the multitude postings. I was trying to do it on my phone while going in and out of service and had better results than I thought.
Victor
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PostPost by: bitsobrits » Sat Sep 03, 2016 5:27 pm

I don't think the size of the chokes is as important as having all pieces work together properly.

I'm running a street car with fully ported 165hp spec head (.410 lift cams, 1.625 intake, 1.375 exhaust valves) on a 1750cc bottom end with 45 Dellortos on 35mm chokes. All very tractable and smooth throughout the rev range. Took many hours and many jet/bleed/tube changes ($$!) to get there, but it was worth it.

Cycle Racing Developments in California (don't know if they're still around) got the cams and porting right, so having a pro involved there was most helpful. Sorting the carbs was just my time and the aforementioned many brass tuning parts.
Steve

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Elan S3 1967 FHC pre airflow

Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
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Esprit S2 1979
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