Single weber or duel webers for L18

[blueribbon]

I've got a 1973 610 with the L18 and A87 head. I'm in the process of putting a header and new exhaust on it. I want to replace the restrictive Hitachi carb with all the smog accessories on it but I don't know wether to go with a single Weber or the duel setup. Obviously the duels will be quite a bit more expensive but will they be as reliable as a single?  I want more power capabilities but not if I have to tune them constantly. I guess I need to know the pros and cons of the two setups.

I'm sort of on the fence here everyone. Your advice would be of help to me. Thanks!

[metalmonkey47]

Twin 40's will be too much for a stock L18. You'd be better off with a 38/38 downdraft or some SU's. 

[blueribbon]

Here is the car in case anyone is interested.

 

[blueribbon]

What about a 32/36 Weber?

[ggzilla]

Twin 40s will be too small for an L18 - depending on the tuning. I had twin 40s on my stock Datsun 1.2 liter engine and it drove well. However if you select the largest tuning parts the 40s will make excellent power on a L18.

[ggzilla]

Twin Webers do not need "constant tuning". Once tuned, they only need minor adjustment at the Datsun factory scheduled tune-up interval. Get a manifold with quality linkage so it stays in adjustment longer.

 

I will suggest a single 40, because it makes 98% the same power, looks cool, and fits in the LHD engine compartment.

[EastBay521]

weber 38DGES is lovely on the l18.plenty of power for my daily driver

[olderdat620]

Hello I have  both L16 and L20's and they both do very well with the weber 32-36 with offenfenhouser intakes  minimum adjustments and they fly

[datzenmike]

The Hitachi is neither restrictive nor does it have 'smog accessories'. The L18 was used around '74 and the only 'smog equipment' available then was the air injector pump, dual points, PCV system and the newly introduced EGR system, none of which affect the carb.

 

Performance, economy, drive ability... pick one but you loose one or the other two. The Hitachi is the best compromise for all three. There are larger carbs that can add respectable performance at the cost of economy and drive ability. The 32/36 weber is fine for an L18 and is slightly big for it. The 38/38 is a V6 2bbl and is way too big for a stock L18 and it and side drafts will not reach their full potential without a larger cam and less restrictive exhaust.

 

Never never over carb your engine. It's better to have too small and want larger than to have too large and wish you had smaller.

 

 

For about $300 a new weber 32/36 with electric choke and idle cut solenoid is the best bang for the buck. Comes with adapter, air filter and everything needed to fit your stock manifold.

[laotsu]

^ another concise, to the point, and excellent answer from D-Mike

[ggzilla]

Except it is wrong.

 

> The 32/36 weber is fine for an L18 and is slightly big for it.

 

32/36 has a small 26mm primary venturi, excellent for a 1.8 liter engine. And the 27mm secondary is great for L18 at 7000 rpm. 32/36 has more airflow than the stock L18 carb, but less than the stock L20B carb.

 

 

> side drafts will not reach their full potential without a larger cam and less restrictive exhaust.

 

If the sidedrafts are tuned correctly they will be perfect for a stock L18. Never overcarb your engine. With twin sidedrafts you can tune them for small or large airflow. Twin 40s can be tuned for stock 1.2 liter engine or for 2 liter engine.

[laotsu]

must be Islander logic... both your rebuttles agree with the points you refute. In other words you're saying "that's wrong, but technically you're correct".

[smoke]

I feel the appearance and the words 'dual carbs' make many feel that it's over carbing an engine. But, what you need to really look at is this....What you are really doing is running one small carb per cylinder. Think of it as a separate sort of thing, like a single cylinder motor cycle for example. One cylinder on an L18 is around 442 ccs. Now, sticking with that same single scenario, A 450 cc, single cylinder motorcycle often comes from the factory with a 40 to 42mm carb for it's one cylinder. What ggzilla is suggesting is essentially running one, single 26mm carb per cylinder. That is not over carbing it. As a starting point on most individual carb per cylinder set ups, you want the carb venturi to be a few mm smaller than the intake valve. In my opinion, a 26mm choke would be really limiting in upper rpm on one of these. Here is also something....when done just right, not only will you have a smoother engine, quicker throttle response and more power with a single runner per cylinder, you can actually get better mpg at light cruise. It's the reason you see so many small cc, old VW engines with dual carbs (I should add that only a few of those are tuned right) when they are tuned right, they really wake those engines up and make them pull down some respectable mpg for such an old engine. Running well tuned, individual runner carbs is about as close to fuel injection as a carb is going to get, not the same, but as close as you're going to get. 

[datzenmike]

For about $300 a new weber 32/36 with electric choke and idle cut solenoid is the best bang for the buck. Comes with adapter, air filter and everything needed to fit your stock manifold.

 

Or spend a lot more for side draft(s) that don't need rebuilding and a manifold and an air filter.  Figure out a throttle cable for it and get them tuned and running right. On a stock L18, this is fast becoming spend a dollar for one cent of improvement.

[smoke]

I agree with the dollar assessment in full. Unless you really luck out, you're going to be into a set of side drafts a lot of money, not just including the price to start with, but if you buy different vents, jets and so on, you will be wrapped up in these a lot of bread.

[blueribbon]

Thanks to everyone for the help. Sounds like I should stick with a 32/36 until I upgrade my cam and even then I can get a bigger single. I do love the look of duels but they really are expensive!

[RatVonDude]

Here is the car in case anyone is interested.

 

What a bad ass ride !!!!!!!!!!!!!!!!!!!!

Is it really a major hassle smogging 75 and up Datsuns?  Honestly 

Is it a bitch? eh? or no 

[datzenmike]

Well it will have to have all the emissions equipment on it and in working order and have to pass the emissions rating for that year. Earlier ones don't require testing but technically they have to have all the emissions equipment on it so it could pass a visual inspection if it ever came up.

[RatVonDude]

Ugg,

What a bummer, I wish they would push the smog law to accommodate the King Cab, 610, 710, 810.  

Its such a pet peeve of mine.

 

or just buy a pre 76 duh, I didn't realize they made them

[RatVonDude]

$300.00 on ebay. Manual choke and adapter plate. :thumbup:  

[banzai510(hainz)]

you got a bad ass 610

if your car is running fine a 32/36 isn't going to make a huge difference. just drive it and put money in a electronic ignition. a free flowing exhaust of 1.75 to 2in. If you got the better exhaust 2 to one typemanifold I would keep it. Im not positive on the 610 exhaust manifold set up. I had dual 40s on a L18 put and it worked but once a cam went in it went better.

 

Nice 610 keep it garged. not many 610s left.

[JoeCool]

I am going to do a Weber on my 720 soon. It will be getting emission delete and a full exhaust done as well as redoing the fuel system from front to back. (filters, pump, floats, etc)

I am also going to use a  normal 8 or 10" round open sided air filter as I hate the way that dinky little rectangle filter looks and hate the crappy clips that like to fall off all the time!

 

adapter:                                                                                                                 Filter:

 

 

But before I buy, what is the major difference performance wise and fuel mileage wise between a 32/36 and a 38/38 Weber on an L20B?

Also I am considering switching to a manual choke seeing all the @#$%&! trouble I am having with the POS Hitachi and it's crappy choke right now. (and YES the piece of junk has been rebuilt, it just sucks!) Bad idea or good?

[banzai510(hainz)]

joe cool  whne you put a weber on the adapter plate will raise the carb and the new aircleaner may hit the hood

[JoeCool]

joe cool  whne you put a weber on the adapter plate will raise the carb and the new aircleaner may hit the hood

 

So I get a lower profile filter?

[datzenmike]

But before I buy, what is the major difference performance wise and fuel mileage wise between a 32/36 and a 38/38 Weber on an L20B?

The 38/38, both barrels open together so you will have to step into it slower or will bog. 32/36 is a progressive vacuum operated secondary that opens only when needed. Easier to drive and better mileage. All out the 38/38 will out perform the 32/36 at top end.

 

The 38/38 is a V6, small V8 2 barrel carb. It's too big for a 2 liter motor but like using a 4 bbl., it will work, but the larger it is the more trouble to drive it.

 

If your L20B has a large cam and ported head, larger valves, large exhaust pipe then a larger carb won't hurt as much. If running a stroker 2.2 or big bore 2.3 or even an LZ24 the added motor displacement will help.