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40/45 DelOrtto's  Rating:  Rating
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 Posted: 02-13-2013 11:09 pm
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roverman
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Is there a simple visual check, say a carb body # ? Thanks, roverman.

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 Posted: 02-13-2013 11:45 pm
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Jim Ketcham
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On the top of each carb body there is casting identifying the carb. it should read DHLA45 or 40. Immediately after should be a stamped letter. As far as I know, all Lotus 907 Dellortos should be stamped E. The letter designates features such as emission versions, etc. The only way to determine the jetting is to disassemble and check each number.

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 Posted: 02-13-2013 11:56 pm
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roverman
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Owning a machine shop, is it practicle/possible to bore-out 40's to 45mm , and install larger throttle plates ? Thanks, roverman.

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 Posted: 02-14-2013 12:34 am
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Jim Ketcham
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It's been done. I do not know how well they work. There are a pair of converted 40 to 45s on eBay. Here's the link:http://www.ebay.com/itm/LOTUS-907-DELLORTO-45-DHLA-CARBURETORS-/290826274153?pt=Motors_Car_Truck_Parts_Accessories&hash=item43b698c569&vxp=mtr

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 Posted: 02-14-2013 12:54 am
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roverman
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$715 ea. I would go injection- first. Thanks, roverman.

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 Posted: 02-14-2013 04:14 am
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Jensen Healey
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Since those carbs are jetted for a Lotus "Escalat" all bets are off!

For the modifications you've discussed FI seems like the way to go. Tuning Dellortos from scratch is a task that Lotus took years to get right.

The tuning of the original Dellorto 40's on the euro JH is far from perfect. Some of the "book" assumptions don't work for the pent roof 4 valve engine.

Thankfully, the Dellortos are infinitely tunable if you get the choke size right for the expected use of the engine.

Cheers,

Kurt

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 Posted: 02-25-2013 07:16 pm
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subwoofer
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Back in the seventies wideband O2 sensors and data logging systems were not readily available. No one had those analytics capabilities back then, so no wonder it took them ages to get it fairly right. Add the lack of reliable spark due to points to the mix and it gets even worse to tune.

Today, if you have the inclination, an LM2 and a full tuning kit you should be able to get it right fairly quickly - even from scratch, given that you understand how the emulsion tube works.

But don't ask me how to tune the mid range, I only have a cloudy idea of how it works - EFI is much easier to grasp and does not have to be a compromise for any part of the operating range.

--
Joachim

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