Just while harrisonati is online - always wondered whether the 30DGS Weber from GS Citroens wouldn't suit 203/403s, both being around 1200cc ...manifold ( suitably configured - will sketch it later ) and all.
peugeot manifolds,etc.
- Thread starter Steven King
- Start date
The best indicator for carburettor choke size is your target power output. All things being equal (which they seldom are!), power will depend on the volume of air fuel mixture passing per unit time. Thus, if you're targeting about 60bhp+ from your 203 or 403, then the GS carby should be OK. Remember that GS power outputs were Net while 203 & 403s were Gross. Also, in my experience, sub-optimal choke size/s can still yield significant power increases. SOLEX published choke sizing fomulas many years ago, but I haven't seen any for Webers.
Just as another alternative, and as you're already talking Italian and not French carburettors.
The small staged 2 barrel Hitachi carburettors are a fine little unit. These came out on Datsun 1200s, 120Ys, Sunnys etc. Subaru also used them on their early flat fours. A 120Y is rated at 69 BHP and they have very good fuel consumption. Different stud pattern to the other 2 carbys mentioned, but anyone half handy can knock up an adaptor plate. I usually make my adaptors out of thick plastic cutting board. Easy to work with but tough as, and you get the added bonus that it serves double duty as a heat insulator as well.
I've bought a few of the replica Hitachi carburettors off EBay and they run sweet straiģht out of the box. Manual choke, no emissions gear. I had a quick look and they can still be found for under $100 delivered (from within Australia).
Just my 2 cents worth, always found they were a much better option than some flogged out 50 year old unit. This one's $91 delivered.
The small staged 2 barrel Hitachi carburettors are a fine little unit. These came out on Datsun 1200s, 120Ys, Sunnys etc. Subaru also used them on their early flat fours. A 120Y is rated at 69 BHP and they have very good fuel consumption. Different stud pattern to the other 2 carbys mentioned, but anyone half handy can knock up an adaptor plate. I usually make my adaptors out of thick plastic cutting board. Easy to work with but tough as, and you get the added bonus that it serves double duty as a heat insulator as well.
I've bought a few of the replica Hitachi carburettors off EBay and they run sweet straiģht out of the box. Manual choke, no emissions gear. I had a quick look and they can still be found for under $100 delivered (from within Australia).
Just my 2 cents worth, always found they were a much better option than some flogged out 50 year old unit. This one's $91 delivered.
That's a good idea, however:Just as another alternative, and as you're already talking Italian and not French carburettors.
The small staged 2 barrel Hitachi carburettors are a fine little unit. These came out on Datsun 1200s, 120Ys, Sunnys etc. Subaru also used them on their early flat fours. A 120Y is rated at 69 BHP and they have very good fuel consumption. Different stud pattern to the other 2 carbys mentioned, but anyone half handy can knock up an adaptor plate. I usually make my adaptors out of thick plastic cutting board. Easy to work with but tough as, and you get the added bonus that it serves double duty as a heat insulator as well.
I've bought a few of the replica Hitachi carburettors off EBay and they run sweet straiģht out of the box. Manual choke, no emissions gear. I had a quick look and they can still be found for under $100 delivered (from within Australia).
Just my 2 cents worth, always found they were a much better option than some flogged out 50 year old unit. This one's $91 delivered.
View attachment 221006
Is the replica true to the original?
Some caution should be taken over the power claimed by some Japanese manufacturers in that era - some claims would seem to be optimistic by a significant margin.
I've no idea if the factory Nissan claim is accurate or not? Nissan did supply engine dyno charts to road testers of the time indicating it made what they claimed it did.
I guess if we decided the 48 bhp claim for a 5 port iron head Morris 1100 is fair enough, then upgraded this engine to a 1200, added an 8 port alloy head, increased the compression ratio, added some cam timing, replaced the single small SU carb with a modern staged 2 barrel one and a freerer flowing exhaust manifold, what would a reasonable bhp estimate be?
The A series Datsun engine is a development of the A series BMC engine after all.
I've had a repro carby and a genuine 120Y one apart at the same time, they both had the same 26/30mm butterflies and 20/26mm venturies.
I fitted one to an A15 Datsun motor in place of the emissions swamped original, it ran great. I've also fitted one to an aircooled 1300 Beetle and a 1200cc Corolla. I also had one on the supercharged Reliant, it ran fine driving normaliy, but couldnt supply enough fuel, quickly enough, if you nailed it down low. Roots blowers need a lot of fuel real fast at rapid full throttle application. I went with a large SU instead. I still have that Hitachi clone boxed up in the shed, I've been thinking about fitting it on the Suzuki Carry van.
This is the 2 piece split adaptor for the blower. I had to do it this way as the blower stud pattern clashed with the carby one. The bottom plate bolts to the blower, the carby studs go through both plates. Doing it this way provided a nice flat plate for the carb to sit on without any countersunk bolts interfering with carburettor gasket's sealing surface
The Hitachi stud pattern is 62 x 35 mm and uses 6mm studs.
.
you really did mean cutting board!
Hadn’t realised it was so comprehensive - received wisdom at the time was Datsun had just reinforced the bits that could be made to brake.
Funny, just read Wheels and Motor had morris major ( 998cc ? ) at 50 bhp and mini ( 848cc? ) at 34 bhp respectively, before oxenford conversions.
Hadn’t realised it was so comprehensive - received wisdom at the time was Datsun had just reinforced the bits that could be made to brake.
Funny, just read Wheels and Motor had morris major ( 998cc ? ) at 50 bhp and mini ( 848cc? ) at 34 bhp respectively, before oxenford conversions.
The cutting board in the photo I had to buy unfortunately. When I worked at the abattoir they used green HDPE material for cutting boards about 1" thick. When they were due for replacement I'd get a couple and take them down to the the maintenance department. They'd mill both sides for me and I'd end up with dead flat material 3/4" thick. I'd use them up over several years making 4 barrel carburettor and supercharger adaptors. It is bloody good stuff, rigid, machines beautifully, petrol resistant. I've also made adaptors out of a good quality piece of timber on more than one occasion.
Same deal as the plastic: easy to work with and great insulating properties against perculation and vapour lock.
The Morris Major had BMC 'B' engine of 1489cc. My reason for questioning the power claimed for some engine related to the venturi size Vs power calculation. I didn't want to start WW3!
i would love to see any photos; having been unable to find diagrams of heads post-403, i cannot imagine the arrangement as cast and machined. it's still a plenum more than internal manifold? seems to be a few more welsh plugs, at least on the exhaust side ...
i dont know how much truth there is in it, but my dad used to say that a lot of British cars were long stroke because the stoke was a factor in the calks for HP and cars were taxed by HP so the lower the rated horsepower the cheaper it was for rego , so i suspect that horsepower rating could possibly have been down rated to make it more marketable for budget orientated buyers ,34 HP for a mini seems awfully low but spose it isnt lugging a heavy body around !
Me either (WW3) and I apologise if you read my post as argumentative, that certainly wasn't my intent.
That's why I said "if we decided the Morris's 48 bhp is accurate". A 40%ish increase in power wouldn't be considered unreasonable based on the differences between the 2 engines.
But if the Morris was in reality nearer 40 bhp, then the Datsun would really be in the mid 50s.
There are 2 sizes in the Hitachi carburettors the EBay ones are a copy of the early 1200/120Y Datsun. There is a slightly bigger one, but I'd be making the measurements up if I stated them, but IIRC each measurement is around 2mm bigger than the smaller version. I've only ever seen one of these. The earlier Datsun 1000 Hitachi looks quite similar to the 1200 version, but is more primitive in its fuel metering circuits.
I only mentioned the Hitachi as a brand new repro carby is about the price of a good quality rebuild kit for an old carby, of any brand (before you start doing throttle bushes etc) and from my experience, the EBay carbies are just set and forget.
BTW I had an 850cc Mini panel van around 35 years ago. Ran sweet as a nut, my Dad was still alive then and he was an ex BMC mechanic, so I got him to tune it.
It is still the slowest "modern" vehicle I've ever owned and Dad said "that's what they go like".
To put it in perspective the 650cc 2 cylinder Niki I owned was rated at 26 bhp, was a similar weight, yet had a slightly higher top speed and significantly better hill climbing ability than the Mini did.
The Niki was probably a net rating, but even so that would only put them at roughly the same claimed bhp (if both were measured at a gross rating). So is even the 850 Morris's 34 bhp an overestimate?
I thought the position was that cars were taxed in Britain based on the RAC power calculation which took bore into account, but not stroke - so you could make a bigger more powerful engine without increasing the tax rating if you only increased the stroke. Hence lots of long stroke British engine designs. The RAC power was quite separate to what was advertised by marketing departments. I thought the advertised claims from that time were generally overstated - eg, Jaguar claimed 265hp for an e-type but is it generally accepted that a standard e-type produces nothing like 265hp?
The old (British) RAC system of taxable HP was calculated on the bore diameter of the engine.
The consequences of having a small bore is you end up with a longer stroke to maintain a reasonable engine capacity. Most of the old British cars had numbers like 9/20 or something similar after their name, the first number was the taxable HP and the second was the engine's BHP.
I've attached a Wikipedia link, it's quite interesting how different countries came up with their taxable HP systems "back in the day".
Tax horsepower - Wikipedia
In my misspent youth doing something for minimal expenditure meant quite a lot. At the time, running a succession of Standard 8's & 10's for transport, I discovered that one could just about put any carby you liked on the input side. I ran a twin choke Stromberg from a Ford v8 flathead for quite some time, that's a carb meant to feed a 221 cub in donk on a teensy 1L or less outfit.
It drove better with more ooph, that's techno for 'go', and, surprisingly, gave me better overall economy win win...
With the help of the accelerator pump it didn't need any choke either !
Back then, you could fill the Standard's tank from empty to full for less than a quid [$2] !!
Bob
It drove better with more ooph, that's techno for 'go', and, surprisingly, gave me better overall economy win win...
With the help of the accelerator pump it didn't need any choke either !
Back then, you could fill the Standard's tank from empty to full for less than a quid [$2] !!
Bob
Oooh thanks Greenpeace,my mazda1000 has two of these on as standard,handy to know as a couple of carby places I contacted a couple of years ago gave me the not interested not available response..jimJust as another alternative, and as you're already talking Italian and not French carburettors.
The small staged 2 barrel Hitachi carburettors are a fine little unit. These came out on Datsun 1200s, 120Ys, Sunnys etc. Subaru also used them on their early flat fours. A 120Y is rated at 69 BHP and they have very good fuel consumption. Different stud pattern to the other 2 carbys mentioned, but anyone half handy can knock up an adaptor plate. I usually make my adaptors out of thick plastic cutting board. Easy to work with but tough as, and you get the added bonus that it serves double duty as a heat insulator as well.
I've bought a few of the replica Hitachi carburettors off EBay and they run sweet straiģht out of the box. Manual choke, no emissions gear. I had a quick look and they can still be found for under $100 delivered (from within Australia).
Just my 2 cents worth, always found they were a much better option than some flogged out 50 year old unit. This one's $91 delivered.
View attachment 221006
always good to work with what one has / knows
but in my case presently, that's just google;
and an old 403 head - and SketchUp
but in my case presently, that's just google;
and an old 403 head - and SketchUp
Last edited:
I remember when older Subaru 4WDs (Brumbys etc) were "traditionally" modified (ie: before everyone just chucked a FI turbo in them) fitting a 500 cfm 2 barrel Holley was a very popular mod.In my misspent youth doing something for minimal expenditure meant quite a lot. At the time, running a succession of Standard 8's & 10's for transport, I discovered that one could just about put any carby you liked on the input side. I ran a twin choke Stromberg from a Ford v8 flathead for quite some time, that's a carb meant to feed a 221 cub in donk on a teensy 1L or less outfit.
It drove better with more ooph, that's techno for 'go', and, surprisingly, gave me better overall economy win win...
With the help of the accelerator pump it didn't need any choke either !
Back then, you could fill the Standard's tank from empty to full for less than a quid [$2] !!
Bob
Even though one of the carbs can comfortably fuel a 6L V8, for some reason on a sub 2L engine they "just worked".
yes Steven , the main problem installing side daft manifolds on 03s is the position of the distributor as you are aware
Aliexpress does have a 504 dissy with and extended shaft for $100 last i looked , which may help .
i have seen Pinto and cross flow Cortina manifolds and carby used effectively on 03 heads , require dissy mods
Aliexpress does have a 504 dissy with and extended shaft for $100 last i looked , which may help .
i have seen Pinto and cross flow Cortina manifolds and carby used effectively on 03 heads , require dissy mods
think there might be a nice old Bosch from a beetle with applicability, at least in part
I've got a good Beetle distributor here off a 1600 twin port. IIRC it has vacuum advance?
I think I might have replaced it with a Bosch 009 dissy with mechanical only advance as the engine had a few mods.
You can have it for the cost of postage if it's of any use.
PS I just went had look at it. It is vacuum advance, it's like new, but it is a repro, can't see any part numbers on it at all.
I think I might have replaced it with a Bosch 009 dissy with mechanical only advance as the engine had a few mods.
You can have it for the cost of postage if it's of any use.
PS I just went had look at it. It is vacuum advance, it's like new, but it is a repro, can't see any part numbers on it at all.