engine and drivetrain Carb decisions....keep the 38/38 or dive into the DCOE 40s?

[jrhone]

So I am cleaning up some leaks in the engine bay...I think the last 2 were pretty much dealt with...Dipstick hose, and fuel pump not tightened down.  Now I am seeing evidence of a leaky Weber 38 carb.  Seems to de dripping "stuff" all over the intake manifold then down the side of the block.  The carb is about 5 years old and was bought new.  Its probably time for a rebuild.  I have a pair of used DCOE 40s on my shelf with Ti manifolds.  Should I just rebuild those guys instead and proceed with slapping them on?  Or should I rebuild the 38?  Or ???  My hesitance in the DCOEs is that I have been told that I should have some hotter spark and an electric fuel pump so its not just rebuilding the carbs its diving into ignition upgrades and then dealing with linkage.  The car has piano tops, headers, Tii distributor, and a 292 cam so it would make good use of the DCOEs, but its been nice and peppy with the Weber 38. 

[LimeySteve]

John, get them side drafts on you will love it, with your set up you will get the most out of your engine with the DCOE's & the sound is hypnotic .as is the performance.

[KFunk]

I always say DCOE 40s.  Best upgrade I've ever done, by far.  Points are fine, ran them with a blue coil for around 5 or 6 years with DCOE 40s.  Switching to electronic just made it a bit smoother at high RPM.  

I've heard most mechanical fuel pumps are fine, but never tried one.  Try it and see.

If you've got the Ti linkage, use it.  Otherwise, the IE/Redline universal top mount linkage is great.  I wasted too much time with others.

 

If you're the kind that has to tune things to perfection, then they might just overwhelm your temptation to tinker with them.  If you can handle some sloppy power, then they're awesome and keep on working great.

[zinz]

I can't believe this thread hasn't blown up yet....   Side drafts, hands down... You don't need any extra upgrades to fuel pump or ignition, unless you just want to (except, the carbs won't fit under the standard fuel pump, so you'd need the 90 degree/Bavaria pump)  and you'll need the hot water bypass pipe. 

 

Rebuild and cleanup the DCOEs, read all the installation threads, go over your parts lists and jump on in.

 

Nothing sweeter than hearing that, brrrrrraaappp...brrrrraaaaaapppp...brrraaaaapppp!!!

 

Ed Z

[KFunk]

If you could call it a downside, one of my problems is that it encourages me to be a bigger jackass in driving around town.  Lots of fun torque and oversteer whenever and however I want it is a bit hard to resist in a town with brick streets.  I tend to have the rear end sideways in about every turn, just going about my day.  I might finally put in some bigger venturis to shift my powerband higher, and sacrifice some of that bottom end power.  

[nomalt]

I know everyone has chimed in favor of the sidedrafts, but John, this is your DD, right?

 

I wonder if people are taking that into consideration.

 

(I am not suggesting you to go either way, as I am curious to everyones replies also)

[fresh_TD]

Convert to fuel injection :-)

Sent from my Samsung Note 4

[zinz]

hahaha... yep.  After a long day and crappy commute, once I see some open road it's hard to resist giving it the reins...

 

You will never say to yourself, "I wish this car had some low-end grunt... "

 

Will a properly-tuned 38/38 with synch-link run harder?  I don't know...some will say yes.

 

For me? It's the symphony of the velocity stacks' staccato with the brash exhaust note when you roll into the throttle... You can't replicate it with a downdraft. The "burble, burble" as it idles to the lump of that 292 cam....

 

It's the sex-appeal of lifting the hood and have the bystanders go "ooooohhh, ahhhhh..." and the looks from a 32/36 user that says..." wow.. I coulda had a sidedraft setup..."

 

It's the satisfaction of knowing that not everyone has them because they think it takes some kind of witchery to tune them.

 

It's the tinkering with the ignition advance, or the carb synch, or some new jetting to balance some AFR # in the midrange...not because you need to, it's because you want to. 

 

As a daily driver?  My setup runs so nicely these days...25 mpg on the highway, idles great, cruises great, plenty of power whenever I need it...  I wouldn't hesitate one second to run my setup every day.  I've put 14,000 miles in 2 years on this car and have a 35 mile roundtrip commute. In nice weather, I may drive it 3 days a week to work, then more on the weekend. My Solex DDHs run great.  I like them so much I bought another pair from Vintage Autobahn. Almost every single time I thought I had carb troubles, it was something in the ignition ...the ol' 90% rule, right? 

 

Don't do this half-heartedly and educate yourself well in advance.  Don't use a cheap linkage. Properly rebuild the DCOEs you have, and match them as closely as possible while you have them on the bench.  Read a Weber tuning manual, then re-read it again.  Use a known-good distributer and set timing accordingly ( with a little more advance than you would for a downdraft).  All the while, reach out to the FAQ group... (Just ask Beach Bum about how he struggled, only to find his problem and solve it.)

 

Go for it.

 

Ed Z

[LimeySteve]

My car is my daily driver , 26 mpg unless I get heavy footed, same on the freeway as it's a 4 speed & 4500 RPM so mpg stays the same. I am well happy with it & I'm on 2 45DHLA Dellortos . Stock fuel pump & a Filter King fuel regulator .

[jrhone]

Yup…thats what I wanted to hear…now do I do the rebuild or send them out?

[KFunk]

It's my daily driver as well.  Some days now I drive the Datsun truck when I need to haul things, or the Yamaha if its warm and I want easy parking on campus or uptown, the Miata if there's salt on the road.

Most days are still the 02 though.  It's just easier to take off and get to work/class easier with it than the others.  Around town being a jackass I tend to get 20 to 23MPG or so, on the highway I get 28MPG (5-speed/3.90).  This is with never really tuning the carbs much more than just mixture screw and fuel level.

My wife also doesn't like the fuel smell I leave behind in the garage when I start it up cold.  I'm just hoping she'll get used to that eventually, heh.

[mike472]

It's looking IKE I'm the only one here who will tell you this but the 38/38 has more punch off the line if it's setup correctly. For a DD that would be my choice. You're not going to "slap" dual carbs on like you're changing an oil filter. It's much more complicated then you or others are making it sound. Lots of compromises involved, like having good air filters that fit, linkages that work right, constant gas fumes, leaking manifold gaskets among others. Just getting these jetted correctly is a task in itself. I have a cam and 38/38 and have had side drafts setup properly and I can tell you the 38 is more fun on a DD. also I can't believe the mileage some people say they are getting with the duals. Almost impossible to get into the twenties unless you drive them like you have an egg you don't want to break under your foot.

By the way, this is not a progressive carb so there is no "quick link" for it as both barrels open simultaneously. Each cylinder has two barrels feeding it versus one with the duals. Much better fuel distribution with the stock manifold. This really helps the low end. If all you want is bragging rights, gasoline smell, and exotics looks and noise, go for the duals. If you want an all around fun to drive car, stick with the 38/38. A lot simpler to make jetting changes and get this dialed in exactly. Some people will call this heresy but I'm telling it like it was. The only place duals really come into their own is on the track. My two cents.

[M3M3]

It's looking IKE I'm the only one here who will tell you this but the 38/38 has more punch off the line if it's setup correctly. For a DD that would be my choice. You're not going to "slap" dual carbs on like you're changing an oil filter. It's much more complicated then you or others are making it sound. Lots of compromises involved, like having good air filters that fit, linkages that work right, constant gas fumes, leaking manifold gaskets among others. Just getting these jetted correctly is a task in itself. I have a cam and 38/38 and have had side drafts setup properly and I can tell you the 38 is more fun on a DD. also I can't believe the mileage some people say they are getting with the duals. Almost impossible to get into the twenties unless you drive them like you have an egg you don't want to break under your foot.

By the way, this is not a progressive carb so there is no "quick link" for it as both barrels open simultaneously. Each cylinder has two barrels feeding it versus one with the duals. Much better fuel distribution with the stock manifold. This really helps the low end. If all you want is bragging rights, gasoline smell, and exotics looks and noise, go for the duals. If you want an all around fun to drive car, stick with the 38/38. A lot simpler to make jetting changes and get this dialed in exactly. Some people will call this heresy but I'm telling it like it was. The only place duals really come into their own is on the track. My two cents.

this.  all of it.  especially for a daily driver that you already have dialed in.

[LimeySteve]

I could not disagree more with Mike 472 , I have no gas smell as the floats are set up correctly & 3 psi from the filter king makes a big difference, I have monitored gas consumption with a gps speedo set up for mileage & a gas station for fuel intake . I don't drive lightly but when I go nuts the gas consumption does get worse obviously. I have small main jets but my wide band 02 sensor is what I used for the tune & that don't lie.I have fun at the track & fun/reliability around town , it never loads up & starts dead easy. My 02  . They are not for everyone but I love them , I have for 35 + years on various cars in England & here.

[KFunk]

Yup…thats what I wanted to hear…now do I do the rebuild or send them out?

 

 

Oh, about that, how well were they stored and how long have they been sitting?  The guy I bought mine from had stored them pretty well, and there wasn't much to do to them.  Just clean out the all the jets and maybe replace needle valves with an off the shelf kit.  It's not much different than other carbs, there's just a lot more jets.  Make sure the little o-rings around the pump jets are soft and sealing well.  Mine were crusty from storage and failed quickly.  Setting exact fuel level is most essential thing I've found.  

I feel sorry for you guys that have had such bad experiences, but what can I say?  neener neener.

I'm not lying, I did just slap them on my daily driver with a couple different engine set-ups and have never re-jetted or really read the book.  I've just used a few tips here and there.  My odometer has the right W number for the diff, and I do the math.  I have dipped down into 17-18MPG range when I'm just making short trips around town while being an idiot and/or autocross.  Most of my driving now is a 10 mile curvy backroad commute to work, combined with lots of short trips from my lab to main campus.  It's usually to mid to low 20s most of the time.  Again though, I'm usually spinning the tires and oversteering, a lot.

Edited April 22, 2015 by KFunk