So basically it does'nt matter either 40 or 45 DCOE weber because either one would get jetted or set to my car. Its harder to find 40 DCOE weber so its sounds like it might be a 45.

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Morgs

Im building a very similar setup; overbored 1098, absolute monster cam for a smallbore (298 deg duration, 88 deg overlap) and a heavily ported 12G940 with RimFlo valves.

With a setup like this or similar, I think its smack bang in the middle between a 40 or a 45. I went and bought a 42...

If I knew your cam spec I would be able to give you a better opinion. I would go the 45 if your going to be HEAVILY working it as you'll get more top end. If its just a mild/semi-race build, I'd stick with the 40 as it will give better low end torque and higher low-rpm air speed. I've heard 45's can have a bit of a screwy idle coz of low air speed on small bores.. anyone care to confirm?

This is just MHO so anyone feel free to correct me if I'm wrong

Cheers, hope all goes well!

This will help what weber size to choose 40 or 45. Engineering info - 1100, rebore and hone, deck block .200, cambearings, guides, seats, cleen head and block, machine fly wheel, crankgrind, shot peen rods, close hone rods, balenced, surface grind and more bearings seats and guides. Cam Lift 260 Thou, Tappet Clearance 15 Thou, Duration IN 301 DEG Ex 298 DEG. Extractors and exhaust. I hope all this helps.

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Morgs

Ok you have a very similar cam to mine, I just have a little more lift (.295") If your using just a modified 202 or 295 head IMHO I would go for the 40. If its a 'big block' head like a 940 then I would say either a 42 or a 45. A 42mm for a bit better low end running with good up top as well, or a 45 to get every last bit of hp out of the cam at the top end of the RPM scale.. hope that helps...

oh just thought I'd add, its better to undercarburate your car then overestimate and get a bigger carb than you need...

Thanks everyone for their help its much appreciated.

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Morgs

Chong's 1152 motor with 266? Kent cam, 295 head and 45DHLA carb ran fine with 34mm chokes. But I wouldn't go bigger, really 32 or 33mm chokes would be better for midrange response.
Same deal with a Weber.
The choke size is more important than whether it's a 40 or 45 carb.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yeah thats what I was trying to remember from good ol' Mr Vizard. I think there was a certain cross-over point where if you had to go over 'x'mm chokes then you should go for the 45... I cant seem to find it tho..

34 is the crossover size. The biggest you can run in a 40mm carb is a 35.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.