I love my Weber 38 DGES. Here's my 38 DGES install:

[KlassicMotion]

**This is a condensed re-telling of my install.  It has taken me a few weeks to work everything out, including the time waiting on parts, and finding out I had a bad head gasket and to fix that.**

 

 

My application:

1971 2dr 510

1980 L20B w/ W58 peanut head, other wise stock except for Top-End performance header shorty header.

280zx 5spd

Stock rear gears

 

I bought my carb from: http://www.webercarbsdirect.com/

 

I used http://www.redlineweber.com/  to help make my decision. 

 

Reason's why I chose the 38 DGES:

 

I've not been happy in the past with my 32/36 style carbs, They always seem to feel... a little mundane.  No frills.  That said, I haven't tried the Weber 32/36... If I need a carb for my 620, I will try the 32/36 DGEV.

 

At the time I had a set of Hitachi dual SU's from from an L18 being rebuilt, but that ended up taking 8.5 months, so in the mean time I needed to buy something.  After some research, I found the Hitachi SU's are 38mm and 38mm, and the SU's work synchronously same as the Weber 38 DGES.  After reading many posts, I found there are many on here that love the SU's, but there doesn't seem to much experience with the 38 DGES.  In fact there is are mixed reviews on the Downdraft Webers.  Those that have them seem to like them.  Those that don't... don't.

 

Here's a picture of my current setup:

 

 

 

My install:

First I compared the intake manifolds from my stock L16 with the W58 intake.  There is a huge difference in port size.  The obvious choice was the W58.  In fact, I'd be skeptical whether the 38 DGES would be a good carb for the stock L16 intake.  The port size would probably choke the performance of the 38.

 

After deciding on my intake, I took a look at the carb plate on the manifold.  It has two different sized round holes for the stock progressive carb.  The adapter plate of the 38 is one large oval opening that tapers down from the large openings on the 38 to about the size of the two holes on the manifold.  My first step was to cut the intake carb plate out and make the two round openings into one large opening that is port matched to the adapter plate.  Next I realized that the adapter plates were horribly warped and when bolted together, there were large gaps.  The gaskets that Weber provides are pretty flimsy to begin with.  I surfaced both adapter plates on both sides and made new gaskets out of my preferred material.  No chance of vacuum leaks.  Vacuum leaks seem to be the biggest problem with most carbs not running well... in my experience.   Next I bolted the plates and carb on.

 

 

With the carb on, I looked at hooking up the throttle linkage.... No go.  With the increased 1" height of the L20B, the throttle rod was one inch too low.  After some research, with the only suggested options being cable linkage or just hooking up the rod at an awkward angle, I decided to make a new mount for the stock rod on the firewall.  I took my original mount, traced the base shape on to a piece of 16 gauge metal plate, and cut it out (the pictures tell a better story).  I then bolted the new plate in the stock location and positioned the original mount on top of it with magnets as I got the rod into the correct horizontal position to the carb.  I trimmed off the necessary metal to get the stock mount to fit, then I welded the two together, cleaned them up and painted them.  The only difference I notice is the throttle pedal is a tad notchy just as you start to depress the pedal. The rest of the pedal movement feels unobstructed. 

 

 

The next task was to hook up the fuel vapor system and PCV system.  I had already cut my crankcase breather tube coming out of the block a little shorter than I would have liked, but no problem.  I also cut down the stock rubber elbow that hooks up to the crankcase tube.  I needed to use this elbow because it tappers from something like 1" to 5/8" (I don't remember for sure the sizes).  Off the elbow, I ran a "T" adapter I found at O'Reilly's that runs 5/8" straight through and 3/8" "T" off it.  From the 3/8" "T", I got a brass reducer from the hardware store that allowed me to hook up the 1/4" hose from the bottom nipple on the fuel vapor valve on the driver's side strut tower.  The 5/8" hose then needed to go to a PCV valve on the intake.  Since I removed the air pump system from the engine, I also had the need to plug the 3 holes just below the carb on the intake.  My first task was to drill and tap the two diagonal holes leading into the intake runners to accept some plugs.  Next I drilled and tapped the top center hole slightly lower and larger to accept the original PCV valve.  Side note:  I ordered a new "Import Direct" brand PCV valve from O'Reilly's, which turned out to be absolute junk.  I tested the valve with suction and 9 out of 10 times it wouldn't seal up.  The original PCV valve still worked perfectly.  I hooked up the hose coming from the crankcase breather to the PCV valve. 

 

 

Next the PCV port off the valve cover needed to go to the air cleaner.  Yes, this port off the valve cover needs to go to the air cleaner for the Datsun PCV system to work properly.  You may have a different way to hook it up, but I just drilled a hole in the bottom of the air cleaner base and put in a 90* elbow to attach to the hose going to the valve cover.  If you do this, measure twice drill once.  You will notice it is a tight fit between the air filter on top, and the top of the carb on the bottom.  Next, is the hose coming from the top port on the fuel vapor valve.  There are two options here.  I opted to drill another hole in the bottom of the air cleaner base plate and used a brass 90* elbow and something to screw on the top to keep it in place.  The other option on the Weber 38 is to drill the port on the carburetor top plate and hook it up like the 32/36 does from the factory.

 

 

You can opt to drill out this port and tap it with a hose barb instead of drilling another hole in the air cleaner base plate.

 

 

Weber has warning signs all over the instructions that say this carb must not run more than 2.5-3psi fuel pressure. I tested the stock fuel pump and found it pushing over 4psi.   I first tried the cheap Mr. Gasket unit sold at most parts stores.  I hooked up a gauge to it and I was not able to get it down to 3psi.  So I then opted to buy the recommended Weber fuel pressure regulator.  It is worth the money.  I decided to run it off the front of the engine.  I didn't like my initial install with the fuel inlet on the carb being in the stock location of the driver's side (left side).  I also wanted to install a permanent fuel pressure gauge.  So I drilled and tapped both fuel inlet ports on the carb top plate to accept the fuel gauge in the stock left side inlet position and relocated the fuel inlet to the right side. 

 

This is my original setup with the cheap Mr. Gasket regulator and fuel inlet towards the left side of the car.

 

This is my current Weber fuel pressure regulator and fuel inlet setup (part number 31800.063).  http://www.carburetion.com/Products/ProductDetails.aspx?Part=31800.063

 

 

 

Another note:  When I installed the air cleaner top plate on, and tried to snap on the retaining clips, the two clips on the backside towards the firewall would not fully clip on.  I just cut a little material off the bottom tap on the clip so it wouldn't hit the carb when it went on, and that fixed it.

 

Adjusting the carb:

Floats:

The carb ran pretty well out of the box, once I got the fuel pressure sorted out.  But it still had issues.  I tried setting the float levels as per the instructions on the Weber website for the 38 DGEV.  They say to set the float at 40mm from the gasket to the bottom of the float... ( They showed a different style float), and the max float travel was said to be 50mm.  The instructions for the 32/36 DFEV, showed the float that I have, but the measurements were 38.5 and 46.5mm.  I tried both.  Neither worked all that well.  I then refereed to instructions that came with the Weber Jet kit I bought.  Those instructions had the words "set the float level to 18mm from TOP of float, DO NOT depress the ball and spring in the needle valve".  After doing exactly this, I found the measurement to be 38.5mm to 46.5mm measuring from the gasket on the top plate, with out depressing the ball spring.  Runs great.

 

Idle mixture screws:

Weber says to screw in the mixture screws until they lightly seat, then back them out 1.25 turns for your initial start up.

If when you are adjusting the screws, you find they run best screwed in more than 3/4 turns out, then the idle jet is too rich (too large).  If the idle mixture screw is out more than 1.5 turns, then your idle jet is too lean (too small).  I hooked up a vacuum gauge to the intake manifold to get the best reading for setting these.  both my idle jets seem to bee happy right at or just past 1.5 turns, so my task tomorrow is to try one size larger idle jets.  But right now, it runs great!  I don't have any complaints at all, but if I can put the carb into better specs, then I will try.  We will see what happens tomorrow. 

[KELMO]

Just bought 2 webers my self.  1 for the 1200 and 1 for the 510. Installed the one on the 1200 and at start up it ran between 4K and 5K at idle...adjusted idle and mix screws to no avail.....then I thought hey, that 510 carb is the same, lets try it.  Bolted it on, started it, idle is fine.....gotta do a little looking at the one for the 1200 and see whats up.

 

Nice how to BTW

[Farmer Joe]

hows the driveability with it now?

 

does it feel like it too much for the engine, or no?

 

ive got a 38 on a KA24 and it gets it. even with points ignition, and no vacuum advance...

 

i enjoyed the writeup! thanks for all the good oics!

[datzenmike]

Kudos on the intake. This is one of the disadvantages of a weber carb swap...it goes to an adapter that pinches it down to fit a smaller intake. Looks great.

[tr8er]

Sweet!  Great writeup.  I've been running a 38 for a few years on my L20B and I love it.  But I'm taking your que on a few things that I didn't do.  That pressure gauge is pimp.  Perhaps not necessary, but I'm doing it.  And the port matching is happening.  

[KlassicMotion]

hows the driveability with it now?

 

does it feel like it too much for the engine, or no?

 

ive got a 38 on a KA24 and it gets it. even with points ignition, and no vacuum advance...

 

i enjoyed the writeup! thanks for all the good oics!

 

It's definitely not too much carb for this engine.  Drive-ability is great.  I have absolutely no issues.  It pulls hard from a stop, clear on up the Revs with no hesitation.  I haven't seen just how far up the Revs it will go, but once I feel like I "know" the engine better, I will play with it more.  At first I was getting a little dismayed with the performance of the L20B, and was thinking about more performance mods or a swap, but now that the carb is tuned in better, it's fun.  I've tried to bog the engine down by putting my foot in it while under 2000 RPMs in 4th and it still pulls from there.

[banzai510(hainz)]

I ran a 38/38 on a slighly modded L16

I like them. can go back to a 32/36 if gas gets to pricey

Ez to maintain and I think be best bolt on for a L motor esp for a L20.

 

Only thig I notice is taking off on a hill it could drop the vaccum and stall out

 

Like the write up. Very good.

Clean set up you go there

[KlassicMotion]

So I've been playing with the idle air jets today.  Since the factory jets of 50 were causing me to have to screw the idle mixture screws out more than 1.5 tuns, I put in #55 jets on both sides.  It sitll runs great, but now I have the right side (valve cover side) idle mixture screw out 1 turn.  So that one is within specs.  The Left side is right at 3/4 turns out.  This is the minimum spec, so it is still within specs, but right on the line.  I think I will leave it for now.

 

So to sum up my adjustments:

 

Putting on a good fuel pressure regulator and adjusting the float to the proper setting made a huge difference in performance.

 

Bumping up the idle air jets one size larger from 50 to 55 put the idle mixture screws within specs. 

[tr8er]

Gotta ask cause I've been looking into it.  I'm assuming you made the decision to install a fuel pressure regulator in place of a return line.  I've read that pressure regulators can put undue stress on mechanical fuel pumps.  Do you think there is anything to that?  

[KlassicMotion]

Gotta ask cause I've been looking into it.  I'm assuming you made the decision to install a fuel pressure regulator in place of a return line.  I've read that pressure regulators can put undue stress on mechanical fuel pumps.  Do you think there is anything to that?  

 

I never thought about it.

 

I put the regulator on, because Weber said it's a must.

 

The return line wouldn't be a bad idea, just some time and effort.

 

I could buy into the theory that regulator may put some extra back pressure on the pump, but I wonder how much damage it could really do.  We are only talking less than 2psi that the regulator is stopping.  You know, are we talking years before you notice the pump is going out, or months??  I don't know.  Regulators have been in use for decades, I personally have not heard any bad things from running one.  I'm not worried about it enough to change what I've got.....  And I would put one on my next setup.

[Farmer Joe]

what did you set the the floats to? 

 

was in in inches or MM?

[nerdistmonk]

I dont have a reg or a return on mine, the max weber calls for was 3.5 psi, my pump is at 4 and you will find that the entire weber community across all brands of vehicle is divided on what pressure works, all i know is im not the only one to let it run unrestricted and i havent seen anyone speak of actual failure because of it so when i get my 38 it will be the same, no return and no regulator, i can see a fuel injection 22psi pump causing damage but a 4 psi pump on a 3.5psi carb? im not seeing it.

 

and that racetep site goes even farther, they run their 38 webers with no reg and a 6psi 90gph (turbo chug!) pump, no ill effects, so i finally just said meh to all the pressure discussions and said 'what the hey!'. My truck was so lean, the spark plugs were orange...so it certainly couldnt hurt to do all i could to get more fuel to it (its not the pressure, but that regulator and return line also hurt your fuel flow which is really important and a 30gph pump is right on the line for what a z24 needs so if you divert flow your starving it)

 

but in the end as long as your vehicle runs good, the plugs arnt funny colors and you get the power you want when you stomp the pedal, then meh who cares, there comes a point where i just put the book down and wing it. Fuel system setup is one of those things thats an art not a science, it all looks good in black and white till you implement it and it doesnt work for beans.

 

Good luck with your vehicle, also another question, are you happy with your electric choke?, i couldnt stand mine, it kept revving the engine too high for my comfort so i converted it to manual control with a pull/push rod on the dash.

 

Also man that engine is so clean, to quote ferris bueller's day off: "he never drives it, he just wipes it with a diaper" hehe ;)

[KlassicMotion]

what did you set the the floats to? 

 

was in in inches or MM?

 

""Adjusting the carb:

Floats:

The carb ran pretty well out of the box, once I got the fuel pressure sorted out.  But it still had issues.  I tried setting the float levels as per the instructions on the Weber website for the 38 DGES.  They say to set the float at 40mm from the gasket to the bottom of the float... ( They showed a different style float), and the max float travel was said to be 50mm.  The instructions for the 32/36 DGEV, showed the float that I have, but the measurements were 38.5 and 46.5mm.  I tried both.  Neither worked all that well.  I then refereed to instructions that came with the Weber Jet kit I bought.  Those instructions had the words "set the float level to 18mm from TOP of float, DO NOT depress the ball and spring in the needle valve".  After doing exactly this, I found the measurement to be 38.5mm to 46.5mm measuring from the gasket on the top plate, with out depressing the ball spring.  Runs great.""

[KlassicMotion]

I dont have a reg or a return on mine, the max weber calls for was 3.5 psi, my pump is at 4 and you will find that the entire weber community across all brands of vehicle is divided on what pressure works, all i know is im not the only one to let it run unrestricted and i havent seen anyone speak of actual failure because of it so when i get my 38 it will be the same, no return and no regulator, i can see a fuel injection 22psi pump causing damage but a 4 psi pump on a 3.5psi carb? im not seeing it.

 

and that racetep site goes even farther, they run their 38 webers with no reg and a 6psi 90gph (turbo chug!) pump, no ill effects, so i finally just said meh to all the pressure discussions and said 'what the hey!'. My truck was so lean, the spark plugs were orange...so it certainly couldnt hurt to do all i could to get more fuel to it (its not the pressure, but that regulator and return line also hurt your fuel flow which is really important and a 30gph pump is right on the line for what a z24 needs so if you divert flow your starving it)

 

but in the end as long as your vehicle runs good, the plugs arnt funny colors and you get the power you want when you stomp the pedal, then meh who cares, there comes a point where i just put the book down and wing it. Fuel system setup is one of those things thats an art not a science, it all looks good in black and white till you implement it and it doesnt work for beans.

 

Good luck with your vehicle, also another question, are you happy with your electric choke?, i couldnt stand mine, it kept revving the engine too high for my comfort so i converted it to manual control with a pull/push rod on the dash.

 

Also man that engine is so clean, to quote ferris bueller's day off: "he never drives it, he just wipes it with a diaper" hehe ;)

 

Running extra fuel pressure is just going to push fuel past the needle and seat.  I don't see it doing and "damage".  Just flood the carburetor.  I suppose you could just compensate for it by adjusting the float level.

 

You also put in another post that you had your idle mixture screws out past the 1.5 turns which is why your engine is running lean.  The mixture screws on these Webers are opposite what other carbs are on adjusting the mixture screws.

 

I only run electric chokes when I can.  They are very easy to adjust the high idle on.  I've never had any issues.

[nerdistmonk]

Out is richer, in is leaner man, even my instructions that came with show that in the illustrations, maybe your model of 38 is different? (im looking at my original manual to the 32/36 its out for richer, in for leaner)

[KlassicMotion]

So I've been playing with the idle air jets today.  Since the factory jets of 50 were causing me to have to screw the idle mixture screws out more than 1.5 tuns, I put in #55 jets on both sides.  It sitll runs great, but now I have the right side (valve cover side) idle mixture screw out 1 turn.  So that one is within specs.  The Left side is right at 3/4 turns out.  This is the minimum spec, so it is still within specs, but right on the line.  I think I will leave it for now.

 

So to sum up my adjustments:

 

Putting on a good fuel pressure regulator and adjusting the float to the proper setting made a huge difference in performance.

 

Bumping up the idle air jets one size larger from 50 to 55 put the idle mixture screws within specs. 

 

So I've been running around town doing errands in the 510 this afternoon. When I came home I re-checked the adjustment on the idle mixture screws.  The Left side preferred 1 turn out this time.  I will try that for now.

 

I also had the engine diesel once on me while I was out...  I have on hand the idle cut off switch from the 32/36.  I want check on one thing first, then I will look into putting the switch on and seeing what happens.

[KlassicMotion]

Out is richer, in is leaner man, even my instructions that came with show that in the illustrations, maybe your model of 38 is different? (im looking at my original manual to the 32/36 its out for richer, in for leaner)

 

Interesting.   Then the 38 is different, because my instructions say out for lean.

[nerdistmonk]

Thats what i was saying that its different, the 38 has more than one screw also doesnt it? i think it has at least 2 mix screws (one for each barrel?)

 

Also i had mine diesel at first, but i was able to fix it:

 

Three things on these cause dieseling>

 

*Too far advanced timing

*Idle speed too high, mix too low

*Vacuum leak

[KlassicMotion]

I'm with you on the mixture screws now.  The 38 does have one for each barrel.

 

My timing is perfectly on 10* btc as per the factory manual.

 

Idle is set to 800 rpms. 750 recommended. 

 

Checking for vacuum leaks is next on the list.

 

The instructions also state if your idle screw is in more than 1/2 turn you could have problems, I'm going to re-check that.

[nerdistmonk]

My opinion ignore weber's paperwork, just set it to what sounds best, carbs are tuned by ear, not by a instructional help packet. Turn those idle screws equally till it sounds better (they have to in sync obviously same amount of turns for each mix screw)

 

Also when tuning it you normally want the idle speed screw at 1.5 or 1.0 turns no more than that, the mix screws on the other hand, dial them in equal turns each till the engine is running its fastest, then once turning them richer doesnt do anything go back just a smidge, thats how i tune mine.

 

If you have a vac leak it makes tuning them oh so much fun since they can have multiple personalities lol

 

If your engine has the shakes thats a telling sign, it should sit fairly still when running, if its acting like it needs a bathroom break then either its not getting enough fuel and too much air or it has a vac leak which is leaning your mix out unmetered.

 

edit: if you find yourself venturing past weber's max turns for the mix screws you got a vac leak then somewhere since your compensating for that unmetered air by giving it extra fuel.

also make sure its nice and warm and the electric choke has disengaged or you'll be starting all over again when it does warm up.

[KlassicMotion]

Concur.

 

It idles smooth, no shakes.

 

I'm tuning it with a vacuum gauge.  I don't trust my ears.

 

I could see the argument made that not everything is going to be perfectly the same from one side of the carb to the other, so I personally would allow the mixture screws to be 1/8, maybe up to 1/4 turn different.

[KlassicMotion]

Just in case I wasn't clear on how the fuel vapor valve (flow guide valve as Datsun calls it) hooks up:

 

The crankcase goes into the intake PCV valve.

 

The valve cover goes into the air cleaner.

 

Then the fuel vapor valve is on the strut tower.

 

There are three lines on the fuel vapor valve. 

 

The one pointing towards the fire wall goes to the fuel tank.

 

The other two lines pointing towards the engine:

 

   The top line goes into the air cleaner.

 

   The bottom line needs to "T" into the crankcase.

 

To test the valve to see if it's working:

   

   The line towards the firewall should allow you to suck and blow through it freely.

  

   The line on the bottom should allow you to suck on air through it, but not blow air back.

 

   The line on the top should allow air to be blown through it, but not suck the air back.

[Sealik]

I dont have a reg or a return on mine, the max weber calls for was 3.5 psi, my pump is at 4 and you will find that the entire weber community across all brands of vehicle is divided on what pressure works, all i know is im not the only one to let it run unrestricted and i havent seen anyone speak of actual failure because of it so when i get my 38 it will be the same, no return and no regulator, i can see a fuel injection 22psi pump causing damage but a 4 psi pump on a 3.5psi carb? im not seeing it.

 

and that racetep site goes even farther, they run their 38 webers with no reg and a 6psi 90gph (turbo chug!) pump, no ill effects, so i finally just said meh to all the pressure discussions and said 'what the hey!'. My truck was so lean, the spark plugs were orange...so it certainly couldnt hurt to do all i could to get more fuel to it (its not the pressure, but that regulator and return line also hurt your fuel flow which is really important and a 30gph pump is right on the line for what a z24 needs so if you divert flow your starving it)

 

 

 

I've ran my Z24 and LZ23 with a mechanical and or an elec pump (32/36 and 38 Webers)...with and without reg....no difference...no issues.

Never touched the factory float settings.

 

Obviously the pumps 'produce' more fuel than most carbed engines can use....so why not return the hot unused fuel back to the tank????

None of my engines are starved running return lines...low 12s at WOT suggest a pretty good  A/F ratio

 

I've used a wideband... and sometimes a vacuum gauge to tune Webers....and SUs

 

http://www.youtube.com/watch?v=CU55Z6yvQNo

[KlassicMotion]

^^Yeah, a return line would relieve the excess pressure.

 

My float was out of spec, and once I set it correctly, it ran much better. 

 

Of course each carburetor could be set up differently from the factory for various reasons.   In addition, no two engines are a like, thus each engine will need different tuning.  It's possible yours just happened to be setup correctly for your car.

[Sealik]

^^Yeah, a return line would relieve the excess pressure.

 

My float was out of spec, and once I set it correctly, it ran much better. 

 

Of course each carburetor could be set up differently from the factory for various reasons.   In addition, no two engines are a like, thus each engine will need different tuning.  It's possible yours just happened to be setup correctly for your car.

 

 

Correct....

 

Found my other 38/38 vid

 

http://www.youtube.com/watch?v=TCorrBZ7Nd0