Weber Set-Up and Tune Discussion - Page 16 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep CJ Forum > Weber Set-Up and Tune Discussion

Introducing MONSTALINERô UV Permanent DIY Roll On Bed LinePoison Spyder JK Evap SkidRockridge 4WD IS Taking Zone Offroad Suspension Lift Kits

Reply
Unread 10-12-2011, 02:29 PM   #226
uptillnow
Member
 
uptillnow's Avatar
 
Join Date: Mar 2009
Location: Placentia, California
Posts: 481
Quote:
Originally Posted by swatson454 View Post
I've spoken at length with David and had the opportunity to study with him last month. The information that's bottled up in his brain is staggering. Here's a short clip of him discussing emulsion tube tuning that I thought you may enjoy.

http://www.youtube.com/watch?v=1pkFSA_rRFI


Shawn
Hey Shawn,
I can't see look at or listen to You-Tube at work so I sent this home and forgot to watch it. Duuhhh
After listening to it, the screen didn't show anything other than the original picture. I was able to somewhat follow what he was saying but got lost after we turn the carburetor upside down and look at the e-tubes, look at the dyno results and add or plug holes to adjust rich low RPM main circuit or drill holes for leaner low RPM main circuit.
Do you have more on this, I am interested in what he has to say.
UPTILLNOW

uptillnow is offline   Reply With Quote
Unread 10-12-2011, 04:56 PM   #227
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,731
Quote:
Originally Posted by uptillnow View Post
Hey Shawn,
I can't see look at or listen to You-Tube at work so I sent this home and forgot to watch it. Duuhhh
After listening to it, the screen didn't show anything other than the original picture. I was able to somewhat follow what he was saying but got lost after we turn the carburetor upside down and look at the e-tubes, look at the dyno results and add or plug holes to adjust rich low RPM main circuit or drill holes for leaner low RPM main circuit.
Do you have more on this, I am interested in what he has to say.
UPTILLNOW
You're right, it's just an audio file that someone attached a pic to.

What he's basically saying is that if you came off the dyno and had your rpm and air/fuel numbers at hand, something like this, for example:

6,000 rpm 13.1
5,500 rpm 13.1
5,000 rpm 12.9
4,500 rpm 12.9
4,000 rpm 12.8
3,500 rpm 12.5
3,000 rpm 12.4

What you would do is take your emulsion tube out, turn it upside down and lay it next to your chart. The bottom of your inverted emulsion tube is responsible for the air/fuel ratio at the bottom of your chart.

In the above example, it's a little fat on the bottom third of the rpm range so you would add a hole or two on the bottom third of your inverted emulsion tube.


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 10-12-2011, 07:13 PM   #228
John Strenk
Moderator
 
John Strenk's Avatar
1976 CJ5 
 
Join Date: Feb 2005
Location: Shalersville Ohio
Posts: 12,971
Quote:
Originally Posted by swatson454 View Post
I've spoken at length with David and had the opportunity to study with him last month. The information that's bottled up in his brain is staggering. Here's a short clip of him discussing emulsion tube tuning that I thought you may enjoy.

http://www.youtube.com/watch?v=1pkFSA_rRFI


Shawn
You should listen to him talk about air cleaner filters. He's proved the Can Am filters work the best. "Tuning BL A series engines".
John Strenk is offline   Reply With Quote
Unread 11-09-2011, 09:14 PM   #229
mulliflier
Registered User
1984 CJ7 
 
Join Date: May 2009
Location: Colorado Springs, CO
Posts: 144
Ok, so I finally got around to cleaning up the whole carburetor situation, after fixing some other trail damage and whatnot. Iíll walk through this at the most basic level, since 1) Iím not far from it and 2) hopefully it will help someone later if they are silly enough to go with the 34/34 DGEC. If you are an experienced carb fella, please be patient if I go into too much detail. The intended audience is the first-timer doing their initial carb work.
How I will structure this post:
1) Describe my basic setup, and post some pictures of the engine bay to make sure we are looking at the same things.
2) Describe the process I went through to initially setup the carburetor.
3) Describe the tuning process and the results I have found thus far.
4) List the remaining questions I have.
Basic Setup:
I have a 1984 CJ-7 which I am finishing a frame-off rebuild on. The engine is not original, since the PO destroyed that one Ė this one was a direct replacement and I verified the numbers a while back. The 258 had a scored cylinder, so I had it rebuilt by Columbus Engine and Crank (in Mississippi) back in 2004. The engine now has about 640 miles on it (yes, it took me that long to get it runningÖ) and quite a bit of idling time on it since it also took me that long to learn about carburetors. Regardless, the 258 is now a 261 c.i. motor, with the following:
1) stock intake
2) Borla headers and high-flow catalytic converter
3) DUI HEI (Blue) with Livewires and Bosch two-point plugs (which I am considering swapping back to coppers)
4) Holley Fuel Pressure Regulator (FPR) set to 3.5 psi
5) Weber 34/34 DGEC (this means it has two barrels, both of which have a 34 mm venturi and are vertically oriented. It also has an electric choke.)
6) Transmission is an SM 465 from Novak, which has the following gearing:
a. 6.55, 3.58, 1.57, 1.0
7) Transfer case is a twin-sticked Dana 300, with a high range of 1:1 and a low range of 2.62:1 (this information is readily accessible on Novakís website, which has a phenomenal knowledge bank.)
8) AMC 20 rearend with 4.56 gearing and a powertrax lunchbox locker, front is a Dana 30 with 4.56 gearing, open diff.
Initial Setup:
First thing I did was pull the carb off the intake manifold. This was a simple task which entailed removing the throttle linkage, the PCV and the vacumn advance hoses, and the 4 nuts which hold the carb to the adapter plates.
I documented all of the jets I was currently using, and screw positions (keep your mind out of the gutter). I will post these in a table so they are easy to read.

Pulled the air filter adapter plate off, then the top cover. For those that are new to the 34/34, the top cover requires 5 small bolts (5/16Ē), and then the one bolt on the side that attached the electric choke bracket to the base of the carb (ironically I think this is a 9mm). After that, she lifts right off. Be careful with the gasket and with the float.
After that, you can see all the necessary bits and pieces. She has two venturiís, or throats, which are 34 mm in diameter (hence the 34/34). Again, Iím walking through this from the view of a noob so it can be followed. This carb has two circuits, the idle and the run circuit, and has both a primary and secondary side. The idle jets are on the side of the carb, with the primary side being on the same side as the electric choke (which should be the drivers side). The run jets are in the base of the float bowl. Each jet is a tiny brass screw looking thing that has a hole drilled in it.
I set myself back to the original jets, which were a 65/47.5 idle jet (pri/sec) and a 150/147 run jet (pri/sec). Jet selection is something McMud pointed out, but bears repeating to help folks find a starting point Ė take your venture size in mm, x 4, and that should be the average of your run jet. So for a 34/34, something like 4 times your venturi is 136 mm, which is approximately the average size (between the two) of your run jets. With a 150/147 pri/sec, Iím a little high, but wait until you see my final results to judge for yourself if they are too small. The idle jets can be found by taking your displacement divided by 10 (4.2 liters/10) x (the size of your run jet), so you end up with (.42 x 136) = 57.12.

Jet setup
Idle Run Air Correctors
Primary 65 150 175
Secondary 47.5 147 174

For the Idle Speed Screw
Turns Where it put the throttle plate
2 Just cracking into the 1st progression hole
3 all of the 1st PH exposed, starting to expose 2nd
3.5 1st and 2nd PH's exposed
4 spark port (vacumn) exposed


(tune table is attached as a pic.)

I first went and sanded the adapter plates. For those of you new to carbs, I was shocked at how un-flat they were. I even put a straight-edge against it, and it LOOKED straight, but the eyes apparently canít tell the small differences. To be sure, I had about a 70-rpm swing in my idle before this largely due to small vacumn leaks, so believe me when I say that this step is crucial. Sand your adapter plates flat. To do this, find yourself a flat surface like your workbench, and some 400, 800, and 2000 grit metalsand.

Sandpaper vs. emory cloth: as was pointed out in another post, sandpaper is formulated for wood and will shed particles, whereas emory cloth is designed for machinists and will not shed sand or grit into your work. For this, sandpaper is fine Ė you will have a chance to wipe down your work before it does back onto the engine. Walmart or Home Depot carries a fine selection of metalsand. Just find a flat surface, add a little WD-40 for lubrication, and run it back and forth (Again, minds out of the gutter.) After a bit on the 400 grit, youíll start to see the high points, and youíll realize how uneven the surfaces actually were. Keep it up until itís all shiny, then run to the 800 and 2000 for final finish.

After that, I set the studs into the adapter plates. Now, I had some terrible studs, and ended up switching studs, which jacked up the original threads, so I ended up using some Permatex Thread Repair (this is meant for intake manifolds.) If you end up using this product, make sure 1) you have a fresh batch, and 2) take your time. It works just fine, but donít try to clean up all 8 threads at the same time like I did. Enough said.
Because I used the thread repair, I could not use Loctite, because it was no longer a metal-to-metal connection, it was metal-to-thread repair compound. Never fear Ė use some permatex high-tack (a compound usually used for sealing radiator hoses). It is just like a glue, and a little on the threads will lock the studs in place just fine. I confirmed this with a call to Permatex.
Alright, so set the studs, wait overnight (if youíre paranoid like me) and then set the carb down on top of your freshly sanded stack. Now, youíve also set your primary throttle plate to where it is just barely cracked into your first progression hole, vis-ŗ-vis the throttle set screw. Record how many turns it takes to get from the screw contacting the landing pad to where the first progression hole is. (With this setting, you will have some vacuum at the S port, but itís a good place to start).

Once this is all set, ASSUMING YOU HAVE COVERED ANY OTHER VACUMN LEAK ISSUES, the jeep should start right up.
From this point, run through the ĎLean-best Idleí procedure on p. 2 as illustrated by Swatson. As a ballpark, your timing should run between 10 and 12 DBTDC, mine is currently set to 10.2 (this is from the timing light, which is an ACTRON, with the digital display and the advance function.)

I kept trying to run the screw to rich to see if it would stumble and die, but it didnít, it just kept idling higherÖso, I ran it back and found lean-best idle at about 3.25 turns in on the mix screw. Idle ended up at 525 or so, so once I set the mix I up-ped the idle speed screw until I had 650. The reason for this is the voltage regulator on the alternator kept cutting out; it needed to be over 600 to allow the alternator to supply voltage, and also because it ran slightly rough at 550. At 650, I had about 1 in Hg of vacuum at the S port.


Questions remaining:
1) What do the stamped numbers on the throttle plates stand for?
2) Does the 34/34 have emulsion tubes hidden beneath a brass plug (i.e. you would have to find the plug and drill it out to remove and replace the emulsion tubes?)
3) The fact that it idles down to 550 and lower with 0 in Hg vacuum is great, but when I go through lean-best idle I am a little afraid to set the advance above 10-12 degrees with no vacuum advance Ė what does detonation sound like?
4) I know that you are looking for something around 14.5:1 or 15:1 fuel/air ratio. Is there a way to rent the sensor equipment to test for this?
5) If you do not have a sighting glass with which to view the float without the top cover off, how do you set the float?
carb-tune-table.jpg   main-progression-holes.jpg   mostly-unsanded.jpg   starting-see-high-points.jpg   carb-bowl.jpg  


Last edited by mulliflier; 11-13-2011 at 02:25 PM.. Reason: second try
mulliflier is offline   Reply With Quote
Unread 11-09-2011, 09:18 PM   #230
mulliflier
Registered User
1984 CJ7 
 
Join Date: May 2009
Location: Colorado Springs, CO
Posts: 144
deleted

Last edited by mulliflier; 11-13-2011 at 02:27 PM.. Reason: no longer necessary
mulliflier is offline   Reply With Quote
Unread 02-06-2012, 12:12 PM   #231
jeeprider1
Registered User
1987 YJ Wrangler 
 
Join Date: Nov 2011
Location: Westbury, NY
Posts: 8
Shawn - I have to go to a different place here - my 38/38 ran great and was very easy to tune. Felt like I had fuel injection. Suddenly it won't idle. It only occurs when the engine warms up and comes off the chokle/cold idle. At that point it just slows down and won't run. If I close the choke butterfly with my hand, it will idle. If I turn teh idle mix screws in or out, it makes no difference (unlike before).

How do I tell if it is dirty and needs cleaning? Or do you just pull it apart and clean it? Would the choke require work? Thanks!
jeeprider1 is offline   Reply With Quote
Unread 02-06-2012, 04:43 PM   #232
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,731
Quote:
Originally Posted by jeeprider1 View Post
Shawn - I have to go to a different place here - my 38/38 ran great and was very easy to tune. Felt like I had fuel injection. Suddenly it won't idle. It only occurs when the engine warms up and comes off the chokle/cold idle. At that point it just slows down and won't run. If I close the choke butterfly with my hand, it will idle. If I turn teh idle mix screws in or out, it makes no difference (unlike before).

How do I tell if it is dirty and needs cleaning? Or do you just pull it apart and clean it? Would the choke require work? Thanks!
Those are definitely the classic characteristics of a plugged idle/progression circuit. Luckily, the passages are fairly large and the idle jet itself is tiny and often catches the offending particle.

What I would do is pull the idle jets out of the carb and separate them from the jet holders. Actually, give them a real thorough inspection before yanking them out of the holders.



When this has happened to me, the orifice at the nose of the jet has usually captured the particle and is easily either wiped away with a q-tip or blown out.

They can be sneaky little buggers though so be sure you can blow through the jet each direction and get a really close visual each time you blow through it.

I had one last year that managed to stick itself to the orifice like a flap. I could blow through it backwards and it appeared clear. When I blew through it in the direction of fuel travel, however, it felt clear with my tongue-manometer but upon really close inspection, I could see the little "flap" of material hanging out into the orifice. As soon as I saw that, I simply wiped it away and the problem was solved.

Mine was an intermitten deal and I knew what was going on so I waited until it started acting up again (luckily I was right near the house!) and pulled the jets. Sure enough, my offending particle was still captured in the jet.

Hopefully that helps!
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 02-07-2012, 08:14 AM   #233
jeeprider1
Registered User
1987 YJ Wrangler 
 
Join Date: Nov 2011
Location: Westbury, NY
Posts: 8
OK Ill give it a shot here and se if I can clean it out - that and the fuel bowl. I guess it had some gunge in it - dirt or something. Thanks!
jeeprider1 is offline   Reply With Quote
Unread 02-13-2012, 06:45 AM   #234
jeeprider1
Registered User
1987 YJ Wrangler 
 
Join Date: Nov 2011
Location: Westbury, NY
Posts: 8
Worked great, Shawn! I took the opportunity to clean out everything while I had the carb off the Jeep. Blew out passageways, etc, mains, air correctors, all of it. Used lots of carb cleaner. While I had it off, I took the opportunity to go up one size on both the idle jets and the main jets since, based on my tuning efforts, I felt it was ever so slightly lean across the board. Not overtly, just felt like I was doing a bit too much screw twisting to get it right.

When I put it back on, it feels like a fuel injected engine. Took no more than 1/4 turn from baseline on anything to get it running perfectly. During my test driving over the weekend, it felt like a new Jeep.

Thanks for your help and advice!
jeeprider1 is offline   Reply With Quote
Unread 02-13-2012, 07:12 AM   #235
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,731
Excellent work man! I'm glad you got 'er straightened out


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 02-13-2012, 10:58 PM   #236
twoscooterz
Registered User
1986 CJ7 
 
Join Date: Oct 2010
Location: Eastsound, WA
Posts: 90
I hope this isn't hijacking or too far off-topic. After reading through the thread, I'm wondering if a Weber Synchro DGES38 is a better choice than the Holley 8007 390cfm I recently purchased? I was going to install it on an Offy dual plane.

Are the clogged jets/orfices I read about just symptoms of poor fuel filtering and/or dirty air filters? I hear the Webers are more reliable off-road & in heavy vibration. If true, should I scrap the Holley & go w/ a Weber 38 on the stock manifold? Is the Offenhauser unneeded w/ the Weber?

Thanks for your input.
__________________
'86 CJ7 Laredo, 258, Weber 38, DUI, T5 w/Hurst shifter, 4.56 Dana 30, AMC 20, Detroit TruTrac, Moser axles & Blue Torch truss, Dana 300, stock YJ springs SUA, 33" MTR's, Poison Spyder sliders, NewGen tank cover, Warn 9.5ti w/synthetic rope
twoscooterz is offline   Reply With Quote
Unread 02-15-2012, 01:30 PM   #237
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,731
That's going to be a judgement call on your part. You're likely to get the same number of opinions for either combo and there are pitfalls and plusses with both.

I am not a fan of the Offy intakes. It just goes against everything I am to have the charge from the carburetor slam into a shallow plenum floor right out of the gate. Some may say "the Offy has provisions for water heat." While true, I have to wonder how much of that heat makes it to the level of plenum division. It's also far better to have a manifold that doesn't slam the fuel into it to begin with than one that makes an attempt to deal with it because it does. I don't know but I don't like it. *Opinion*

What I do like about that combo is the 390. When just cruising around, 90% of your time will be spent on the primary side of the carb, well, at least for most or some of us . That equates to a little over half of the throttle area presented by the 38. We could assume that that would make for a pretty reactive and responsive ride. You can change pump squirters and cams pretty easily and you can adjust the rate at which the secondaries open with a spring kit. You also have a lot more air filter options than with a Weber.

What I don't like about that combo is also the 390. I don't know how well the low-speed circuit is set up for a 258 on an out-of-the-box 390. If it's good, you're in luck! If it isn't, however, you either have to deal with it or break out the drill and tap and die kit to correct it. It isn't like a Weber where you can swap out idle jets without removing the air cleaner. You have to drill and tap the idle-feed restrictors and low-speed air bleeds, tap them and start testing different tiny, brass plugs that you've drilled out with various size bits. Tiny bits in .002 increments. That's time consuming!

The 38 is an awesome carb but they can be finicky and the adaptor plates and linkage can be a real PITA. The adaptor plates can be radiused into the manifold for a little better entry but it's still an adapted carb so it isn't perfect. Whatever is.

With the Weber, you have access to all kinds of tuning that you don't have with a Holley. The idle jets are swapped out in 5 minutes flat. You can get to the mains without trying to catch all of the fuel as it dumps onto your engine and you have a wide range of tuning options with emulsion tubes and air correctors.

If you have a performance cam, the Holley may have a slight edge because of how precise you have to be on the throttle plate position on a Weber. The transition slot on a Holley isn't as much of a "go, no-go" as the enrichment holes of a Weber are. The Holley will also allow you to cheat a little bit with the throttle plate position of the secondary.

As far as which one is better off road or not, I couldn't tell you but there are guys on here who can. You can upgrade the needle and seat in a Weber to a viton-tipped unit which will eliminate the need for any fuel pressure regulators when used with the oem, bypass filter. The Weber needle valve also has a spring-loaded ball on the end of it to dampen any pulses or bouncing of the floats. Both of those are good things for off-roading!

I know I didn't help you much but like I said, it's a judgement call with pros and cons on both sides.

Good Luck!


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 02-15-2012, 02:22 PM   #238
uptillnow
Member
 
uptillnow's Avatar
 
Join Date: Mar 2009
Location: Placentia, California
Posts: 481
Good post Shawn,
I agree, I don't use my engine much above 3000 RPM. This is when the Clifford and the Offy manifolds seem to start working best due to their larger plenum and larger than stock ports to the cylinder head.
I have had very good performance from the stock Jeep manifold, and I use and recommend the 38-DGES on a stock manifold. Works great and lasts a long time, (if you get the adapter plates flat and radiuses blended for smooth entry) as Shawn claims in his above post. Tuning can be easier with the Weber, although there are many who have tuned and perfected their Holley also. Good Luck with your decision, either way could get some power from your Jeep.
UPTILLNOW
uptillnow is offline   Reply With Quote
Unread 02-15-2012, 02:45 PM   #239
swatson454
Mall-crawlin' Hot Rodder
 
swatson454's Avatar
1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,731
Thanks uptillnow.

Personally, I think in a stock or slightly modified 258 with an rpm range below the occasional 3,500 rpm (which is beyond the range of the stock cam and head anyways), the 38 and stock, 2-barrel intake would be damn hard to beat, especially with an emulsion tube/air corrector jet combo that worked with the 258's torque peak rpm.

Damn hard to beat!


Shawn
__________________
Live in a way that those who know you but don't know God will come to know God because they know you.
swatson454 is online now   Reply With Quote
Unread 02-15-2012, 05:00 PM   #240
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert, CO
Posts: 9,899
Hey Shawn,

After keeping up with this thread for a while now, I'm wishing I had given the 38 more consideration when I purchased my 32/36.

What performances differences would I realistically see between the two?

BTW, I hope you're feeling better.

Matt
Matt1981CJ7 is offline   Reply With Quote
Reply
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.