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Carburettor project advice needed


Crownin_Round

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Update question time Anyone know if a choke for a dhla will wit a drla?

looking at some carbs for a project and I dont know squat about brands, ive had a browse on google and just as many people have opinions on either product I have re searched so I thought fuck it ill make a post and abuse some band width,

Now bearing in mind this is a "maori" project these are what I have come across

http://www.trademe.co.nz/Browse/Listing ... ermanent=0

and

http://www.trademe.co.nz/motors/car-par ... 552321.htm

From what I could find out the webbers are better for top end fueling and they are simpler and better parts availability and that the dellortos have better fueling across the rev range but also are not to dificult to rebuild.

The engine I plan to use these on is my 5mge and I will be running 3, the user also has listings for 40mm items but I didnt really wanna go to large will 3 36mm be enough after I re jet them? manifolds are not a problem at this stage

any input greatly appreciatted

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any of those carbs will be sweet if tuned/rejetted to suit. any reason you wanting downdrafts instead of side drafts? got enuf bonnet cleareance etc? always wanted to carb a 5mge, will be a mean upgrade over the shitty factory injection i reckon.

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the DRLA are supposed to have better progression than the IDF's are pretty prone to have a bit of a flat spot alledgedly, nothing that would matter for a budget setup though.

have you worked out what size chokes you need agains the factory weber sizing graphs? i.e. workout airflow per cylinder and you can determine choke size for an assumed VE once you know that you can work out if 36's or 40's will be the go (better to have a smaller choke in a bigger carb than the choke very close to the carb size - within reason)

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any of those carbs will be sweet if tuned/rejetted to suit. any reason you wanting downdrafts instead of side drafts? got enuf bonnet cleareance etc? always wanted to carb a 5mge, will be a mean upgrade over the shitty factory injection i reckon.

Just price and ease of use atm who cares about bonnet clearance ae lol

the DRLA are supposed to have better progression than the IDF's are pretty prone to have a bit of a flat spot alledgedly, nothing that would matter for a budget setup though.

have you worked out what size chokes you need agains the factory weber sizing graphs? i.e. workout airflow per cylinder and you can determine choke size for an assumed VE once you know that you can work out if 36's or 40's will be the go (better to have a smaller choke in a bigger carb than the choke very close to the carb size - within reason)

From what I can ascertain from google'ing 36mm will be enough for the 5mg rev range I will just get re jetted to suit, I dont know about bike carbs havent looked into the science of that but I can only guess it will be a cunt to make a hi revving carb work on a low revving engine but yeah sooner stick to car carbs although I was looking at something like these http://www.trademe.co.nz/motors/motorbi ... 456725.htm but they look rubbish but there are similar ones that look better

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bike carbs are good on 4cyls being as most bikes that have them are four cyl, but would be a bit of a cunt to set up on a 6 , unless you maybe got two sets of triples off a triumph or similar? but yeah, if budget is the key you really want to get some weber/delortos off something with a similar sized capacity per cyl to help reduce the amount of fucking round with jets. by the time you have bought jets for 6 barrels it gets expensive.

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no carb is inherently "high revving" all a carb does is meter fuel to air +/- a few other factors depending on the carb to make for smooth running through speed/rev/throttle transitions. a big engine turning slow and a small engine turning fast can have the same airflow requirements and would just need different idle/transition settings.

whether it is a bike carb or a car carb or a boat carb or whatever. for bike carbs you could get two sets of four and just split one set to get six - depending on the throttle synchronisation arrangement.

BUT

the original question was about twin throat equal opening weber/dellorto downdraft carbs.

chart I was refering to is something like this one below. although not sure what VE this chart is assuming but 85% is the usual guess for 2 valve engines (i think the 5mg is 2 valve?) and 2.8L yes? so ~467cc cylinders

8192.jpg

so according to that chart you should be looking for about 36mm Venturis - so those 36DRLA or 36IDF carbs will unfortunately be too small and will probably strangle power above 5000rpm, and thats presuming you get max size chokes for a 36mm carb (probably 32mm chokes).

Thats not saying it wont work at all but it will be alot of money and work for a much less than ideal setup. really 40's with 34mm chokes or 44 or 45 carbs with 34mm or 36mm chokes would be best.

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ask the seller? or if you are looking at them in the metal look down the carb and it will usually be stamped/cast into the edge of the choke itself. final straw would be to use to inside calipers to physically measure it.

su's non existant?

http://www.trademe.co.nz/motors/car-par ... 653557.htm

or look at pick a part. might have to search around/buy a couple of pairs if you want to run triples like they do on jag motors sometimes (you wouldnt run 6x SU's, just 2x or 3x)

also I doubt there are manifolds available for SU's to a 5mg. or IDF's to 5MG for that matter. you could probably find DCOE's to 5mg with some searching I would guess as they are the most common performance webers to use on anything.

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if you have patience a tig a mill and $50 i have some carbs for you,

they're off a v6 220hp johnson i believe

sdc12056t.jpg

sdc12057i.jpg

as you can see they run a main ali body that would need parting and a central shaft that would need disecting, all six carbs are present

oh yeah they be sidedraft though

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Dude, I got triple 48mm Dellortos on me Charger, the key is not the carb, its havin a really good analogue vacuum gauge to balance them. I pull nearly 1200 cfm at full welly boot and it eats Skylines for lunch. Port match yer head to exhaust and inlet then bench flow it, then choose the carbs. You will have the ugliest but coolest Wagon in the world. Any Reconnditioner or head specialist can do this for not much, love the idea.

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Port match yer head to exhaust and inlet then bench flow it, then choose the carbs. You will have the ugliest but coolest Wagon in the world. Any Reconnditioner or head specialist can do this for not much

yes port matching is worthwhile, if you have the head off and probably wouldnt cost too much or is easy enough to do yourself if you feel inclined. but getting a head flowbench ported is not cheap at all! and alot of reconditioners would not have a flow bench - and often (unless you "know the guy") those would be shops doing race engines and charge an arm and a leg because its "race engine work"

thats my first hand experience at least.

knowing the flowrate would be useful and can help you optimize choke size a bit - although you could figure the same thing out in practice once the engine is running including other factors such as exhaust setup which are not accounted for on the flow bench.

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I know a bloke who has quite a few SU's. If you were interested exploring the SU route, go see Daryl at Economy Auto repairs. He's dismantled quite a few triumphs. So he has a good collection of SU's and strombergs. I've often fantasized about running three 1.75's on a chrysler slant 6.

Daryl is pretty good at making them run right too. He gave my old datto a tickle up and it sang.

I'd expect youd be able to buy a trio of carbs, and get them on and running cheaper than just buying the carbs if you went for the weber option.

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