In the 60's L Y N X (can't spell that one properly here or the forum hangs up for some reason) engineering was doing a 1426 engine conversion as well so 1380 isn't the biggest you can go , but pistions are harder to come bby for the really big sizes . I'm assuming Matts is stroked as well (????) for that capacity but it is a mini engine .

David , that is correct but then you also get into the physics as well as just the 2 dimensional area where a single larger diameter pipe will flow more air/water/whatever at a faster rate than two smaller ones equaling the same size . that's where the air velocity affecting the carb piston comes into it but if it's properly setup then you're right . You may well still lose out a little on low revs but top end will want to keep going , definitely suited to a high revving motor of larger(1275 and up) capacity .

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... and you can't just add the area of twin carbs together and compare area to a big single. A single sees airflow all the time, the twins get breathed through alternately for 1/2 the time. eg whilst cylinders 3 and 4 are sucking on one carb the other gets no flow- apart from a meagre amount that goes through the balance tube.

Vizard explains this but I don't have chapter and verse handy.

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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.

What sort of air filter did you run (if any)?

THATS A HUGE BITCH!!! (Deuce Bigalo style)

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61 850
65 DELUXE
69 DELUXE

MY MINI PICS: http://www.flickr.com/photos/morrie850/

Yeah, Kev sort of has it right,,, on a twin carb set up, basically each piston/cylinder sees only the one carby anyway,,, so if you have twin 1" & 1/4 carbs then each cyl is only using one carb (1"&1/4), even tho there is a small balance pipe between the two carbs, there isn`t much "Usable" air being drawn thru it.

With A single 2" SU , each piston is drawing ait thru a 2" hole, simple as that.

it`s the single manifold that is more of a restriction than the carb, twin carbs utilise a far less restrictive manifold & also help distribute the mixture more evenly across all 4 cyls than a single manifold does.

& yes my 1510cc donk is Bored & stroked , like i`ve said (160thou over bored & approx 120thou longer stroke)

Dam good "Little" road motor

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

What do you use for a head gasket Matt? I have an aquantaince who keeps blowing head gaskest due to too big a rebore.

Tim

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1951 Morris Commercial J Type Van
1955 BSA C11G
1961 Morris Mini Traveller
1969 Triumph TR6R
1977 Leyland Moke Californian

Payen BK450 haven`t had a blown head gasket on any of my minis or any of my customers engines since the silver shiney gasket was produced & then they changed them to black ones & they`ve now been black for years & years, so if he blows a BK450 then he has more trouble than the gasket. simple as that.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.