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Author Topic: Help! 40dcnf jetting  (Read 3086 times)
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Dynomax
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« on: December 11, 2023, 05:38:08 PM »

I'm looking for a bit of a starting point for the jetting of a 40dcnf on a Volumex. I've fitted the carburetor and got the car running pretty well but it sounds like it's pinking slightly accelerating from lowish revs. It didn't do this on the original carb so I'm thinking that the timing is OK.
I've just installed an AFR gauge so should be able to get the mixture right but don't know what size chokes and jets I should be starting with just to get a head start.
I've seen a post on here that listed the jets that is a good starting point but I'll be dammed if I can find it now I need it.
Can somebody point me in the right direction?
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WestonE
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« Reply #1 on: December 12, 2023, 06:59:24 PM »

This is listed in Guy Crofts first book which I seem to have hidden well in my house move! Hopefully someone who can actually find it will share it with you. You will want to go to a Rolling Road to set it up properly.

Eric 
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Dynomax
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« Reply #2 on: December 12, 2023, 10:28:28 PM »

Thanks Eric, I've been looking for a copy of Guy's book but so far not much look. As you say hopefully someone has a copy and reads this post and let's me know the recommended starting position.
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smithymc
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« Reply #3 on: December 13, 2023, 11:17:27 AM »

You mean this?

Mark


* thumbnail_IMG_8196.jpg (493.85 KB, 1440x1920 - viewed 472 times.)
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Dynomax
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« Reply #4 on: December 13, 2023, 07:55:06 PM »

Hi Mark, yes that's the sort of thing, however I don't see the Volumex on there and it's only 1 40 DCNF not 2.
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smithymc
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« Reply #5 on: December 14, 2023, 11:30:57 AM »

There isn't anything else I can see in my edition of the book that discusses carburation on a vx other than the extracts below.

Hope they help.

Mark


* vol2.jpg (710.42 KB, 1440x1920 - viewed 445 times.)

* Vol1.jpg (735.29 KB, 1440x1920 - viewed 520 times.)
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rossocorsa
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« Reply #6 on: December 14, 2023, 12:24:41 PM »

Are you using the standard inlet cam or have you changed it? Many folk have fitted a standard 2 litre inlet camshaft or a fiat 130tc one, this will in theory make a decent difference. The choke needs to be relatively small, around 28mm, that is what I have on mine but it's yet to be tested in anger but it seems to run well out of the car.

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Dynomax
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« Reply #7 on: December 15, 2023, 09:03:52 PM »

I have a 2.0 ie  camshaft, just waiting for vernier pulleys.
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Dynomax
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« Reply #8 on: December 15, 2023, 09:07:20 PM »

There isn't anything else I can see in my edition of the book that discusses carburation on a vx other than the extracts below.

Hope they help.

Mark
Thanks Mark that's good.
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Dynomax
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« Reply #9 on: November 22, 2024, 07:40:44 AM »

Crikey I can hardly believe it's almost a year since I got most of the bits together to modify my Volumex.
So a bit of an update,  the 2000ie inlet camshaft didn't measure up to what I was expecting so I ordered a Kent cams FT10 which has a lift of 10.54mm. They also came up trumps with a vernier pulley as the one from the Internet had the wrong offset and the belt would not stay centralised.
So the next problem was the shims.  Because the camshaft has a smaller base circle than the standard camshaft the shims required were outside the normal range,  this is when my luck changed,  the gasket between the cam carrier and head measured up to the exact size to the differences in the base circle. So removing the gasket and fastening the carrier straight to the head with the appropriate loctite and the jobs a good un! I even used the original shims, it was a real stroke of luck.
So with the cams dialed in using the 118⁰ as recommended on the forum I set about the jetting.  Using an AFR gauge and a wide band lambda sensor in the exhaust downpipe I started driving around the village taking note of the readings at various throttle positions and engine loads and after a fair bit of tooing and froing I have to say I'm absolutely delighted with the result. The engine has flexibility that I don't think I've ever experienced before and it will still rev with ease when you need it.
It's probably going to be some time before I can get it on the dyno but until then I have a small issue with the rear suspension! To be continued.....
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