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  Author    which carburator for 1380 cc tuned   (currently 2,706 views)
Geert_Vanassche
Posted on: September 6th, 2014, 09:34:07 Quote Report to Moderator
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Location: Belgium
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Hi,
I intend to buy a A engine 1380cc  well tuned , the builder gives 100-110 hp.
I have to choose between several types of carburators .I have read some topics but it's very difficult to make a choice : webers , hif 6 , single or twin , etc.....
Some people say that twins give more problems and higher fuel consumption but much better response , webers are only good for tracks and high rpm's ........
My choice goes more to the simple  single HIF 6 but wil this be ok for 100-110hp , I will use the car  only on the road........ but sportif drived  , but I do not  want to loose to much power or acceleration .
So if anyone can make me more wise in this matter ......
kind regards
geert

Last modified September 6th, 2014, 23:54:57 by Geert_Vanassche
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mike brown
Posted on: September 6th, 2014, 14:20:47 Quote Report to Moderator
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How about throttle body's and fuel injection don't know what or where but could be run with megasquirt.
Mike
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Brian
Posted on: September 6th, 2014, 16:19:51 Quote Report to Moderator
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Do you have a bit of information about what you intend to use the setup for? Street+track days? Street only? Track only? Race? Vintage race? Etc?

If there's any track events at a competitive level, then there will be rules as to what gear you can have in your build.

For carb, I gave my engine builder free reign, I told him that I want a some street, mostly casual track build (where I didn't need to worry too much about restrictions on how original or which vintage). He went with a single weber 45. I have only just gotten the car on the road, so I can't give good feedback there though.

Also, for most of the options you asked about, check out the David Vizard books (I think it's called tuning an series engine). They're old, but cover most of the options still available (other than the fuel injection). He talks extensively about the tradeoffs for each option, in terms of power, torque, economy, longevity, etc.
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Geert_Vanassche
Posted on: September 7th, 2014, 00:02:35 Quote Report to Moderator
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Location: Belgium
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Hi Mike and Brian
Thanks for your reply.
I  will use the car only on the road , but the car  should be fast in acceleration and with good torque at low rpm's.
The specifications are for the moment :
* 1380 cc
* 286 cam
* adapted head + crankshaft
* lighted flyweel
* all balanced
* upgraded oilpump and  clutch and straight gearbox
* diff with pins
* carburator ?????????

geert
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Geert_Vanassche
Posted on: September 7th, 2014, 00:02:42 Quote Report to Moderator
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Location: Belgium
Posts: 13
Hi Mike and Brian
Thanks for your reply.
I  will use the car only on the road , but the car  should be fast in acceleration and with good torque at low rpm's.
The specifications are for the moment :
* 1380 cc
* 286 cam
* adapted head + crankshaft
* lighted flyweel
* all balanced
* upgraded oilpump and  clutch and straight gearbox
* diff with pins
* carburator ?????????

geert
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Steve_Schmidt
Posted on: September 7th, 2014, 02:33:41 Quote Report to Moderator
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Location: Gippsland, Victoria, Australia
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I've just built a similar engine and decided to use a Weber 45DCOE. I already had the manifold and found a good used carby for the right price - when tuned properly they give plenty of torque and are fine for driving around town. One aspect that I really enjoy (some say it's the worst thing!) is the throaty induction growl. The downside is fuel consumption, I've never been able to achieve SU-type economy from a DCOE. Another point in their favour is that you don't need an ugly bonnet bulge to fit one under the bonnet of a Marcos  
However, a HIF6 SU is probably the sensible choice for a road car. It can deliver similar performance to a DCOE (perhaps not quite as good at the top end), it's a lot quieter and more economical.
With a 1380 you'd need twin 1.5" SUs. I've used this set up on a 1330 Cooper S and achieved very good results after modifying them according to Vizard's book. But for simplicity, a HIF6 is probably just as good.
I don't know a thing about injection - too many sensors and wires for my liking  

Steve (MM 7056) Downunder
http://www.mm7056.wordpress.com
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David_Farmer
Posted on: September 7th, 2014, 06:14:37 Quote Report to Moderator
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Steve has outlined your choices correctly, a HIF6 1.75 for good all round simplicity, performance and economy; twin SU 1.5 for performance and economy and a weber if you don't care about exhaust or noise pollution

Regarding reliability, all carbs options will give you no problems if they're in a good state of repair and have been set up correctly. Hope this helps

I myself will be looking for a torquey 90hp motor and hoping that twin SU1.25 will be up to it because I like the look of that set up!

Last modified September 7th, 2014, 06:18:51 by David_Farmer
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Steve_Schmidt
Posted on: September 7th, 2014, 12:01:46 Quote Report to Moderator
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Location: Gippsland, Victoria, Australia
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This what a Marcos with a 1310 Cooper S donk running a 45DCOE and LCB extractors sounds like from inside the car.


Steve (MM 7056) Downunder
http://www.mm7056.wordpress.com
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miniswift
Posted on: September 7th, 2014, 16:13:03 Quote Report to Moderator
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Location: Newton Hall, Durham
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Hi,

Weber will get out of tune quickly.
HS4 Twin carbs is better than weber for not going out of tune.
HIF44 will be good choice but I will go for 2x Bike carbs from big bikes so that you can have almost 450cc x2. This way your carbs will be big enough. Bikes are higher reving than car engines and they revs to 16k rpm and 1380 will be 7.5k rpm-ish.

This is why R1 carbs(250cc/carb) is good enough for 2000cc(500cc.cylinder) car engines.
You can buy bigger jets and so on for bike carbs, too. They are very good for not getting out of tune.

If you want to use DCOE then I would go for Dellorto as this is more '80s technology. Webers hasn't evolved but Dellorto has been improved from Weber.

Cheers
Atchi
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jimnaylor
Posted on: September 7th, 2014, 20:54:31 Quote Report to Moderator
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Location: Bedfordshire
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My half penneth,

HIF6 and Webber 45 flow almost identicaly (at least after doing the simple mods to the HIF6 outlined by Vizard) and so produce almost identical power. The differances are more to do with the different manifolds than the actual cabs. 45's tend to produce a little bit more top end because the manifold is straighter, HIF6's tend to produce a bit better pick up in mid range, but it seems to vary from car to car. Old HS6's and twin HS4's don't flow anything like as well and so don't suit a very high flowing (high hp) engine, even twin HS6's struggle. In theory twin HIF6's should be the dogs ******* but I've never seen any dyno figures.

HIF6's used to be the cheap, but less sexy alternative to a 45, but they are much rarerer now and not much different in cost to a 45.

Most racing mini's use 45's because that's what the regs say e.g. mini miglia or use injection if carburation is free. Be warned if you ever want to race historic, HIF's are too modern and so are not permitted.

But in answer to the original question a single HIF6 is quite capable of supplying enough mixture to a 110hp motor, but it needs to be on a good (gentle bends) manifold.
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jimnaylor
Posted on: September 7th, 2014, 21:26:32 Quote Report to Moderator
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Thinking further, the bottom line is who is going to do the final setup and tuning?

They will almost certainly produce better results both in power and drivability with the type of carb they are more used to.

Rolling roads that stock lots of webber jets and tubes are more common these days than those that have lots of HIF needles. I suggest you ask before making your final decision.
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mike brown
Posted on: September 7th, 2014, 22:04:57 Quote Report to Moderator
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Quoted from jimnaylor, posted September 7th, 2014, 21:26:32 at here
Thinking further, the bottom line is who is going to do the final setup and tuning?

They will almost certainly produce better results both in power and drivability with the type of carb they are more used to.

Rolling roads that stock lots of webber jets and tubes are more common these days than those that have lots of HIF needles. I suggest you ask before making your final decision.


That's the beauty of throttle body's and megasqirt you can tune it with a laptop driving down the road. Not that I have the first clue but a couple of friends in the land rover crowd tell me it's relatively easy and it's the route I was going to use with a swift engine in a Marcos.
Mike

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Nigel_Holmes
Posted on: September 8th, 2014, 20:48:00 Quote Report to Moderator
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This may be a bit off-topic, but can I ask how many of these alternative carb set-ups can be fitted without requiring bulkhead or bonnet surgery?

With my Mk3 I am struggling to fit a single HS4 so that it does not either hit the bulkhead when choke is out or top of dashpot fouling the bonnet. As it is I had to chop a bit off the top of the dashpot to get a little clearance...
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Brian
Posted on: September 8th, 2014, 22:46:29 Quote Report to Moderator
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On my mk6, for a weber 45, I had to cut a hole in the bulkhead and make a box to fit it under the dash. But, in pictures I've seen of the older ones, the bulkhead seems to have room to fit a weber. The mk6 bulkhead is a lot smoother and goes down from the bottom of the windshield at about the same slope as the windshield, whereas the older cars I've seem in pictures seem to have a large flat shelf that goes back to the windshield, then straight up.

Also, my weber is on a longer neck to provide as straight an air path as possible -- shorter intake manifolds would probably reduce the need for a cutout on mine, at the cost of performance.
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admin
Posted on: September 8th, 2014, 23:26:56 Quote Report to Moderator
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Quoted from Nigel_Holmes, posted September 8th, 2014, 20:48:00 at here
This may be a bit off-topic, but can I ask how many of these alternative carb set-ups can be fitted without requiring bulkhead or bonnet surgery?



With the twin-bump bonnet you can only fit twin HS2 or HS4 carbs on the usual "log" manifold, or similar. Don't use a non-standard manifold thet is too steeply inclined. With the later (Mk.V) single bulge bonnet you can use single HIF44 or HIF38 carbs. The flat cylindrical K&N filters with the central mounting holescan be used, but not the conical ones. With HIFs make sure that the base plate doesn't hit the cross member or you are likely to wear it down until it leaks.
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