Replaced Hitachi with new Weber-Suggestions Needed

[620Turbo4X4]

Not sure what you mean by 5 deg. past 20 mark? 15 deg, or 25? 15 would be fine, 25 is going to cause a loss in power and cause spark knock. Its when the magnetic pickup and reluctor points are lined up is when plug fires. The rotor might not be 100% lined up with terminal on cap. There is quite a bit of slop in the dist. drive so best to do with timing light. You'll notice under the rotor, opposite of the black mag pickup is rub block mounted to a spring that looks like a set of points without the contacts. This is there to reduce slop and prevents spark scatter by providing some resistance on dist. shaft while engine is running.

 

12 BTDC is what you want.

 

The stumbling and bogging your having sounds more like a lean condition (vac. leak) to me. I've never had to increase the idle jet size or turn mix screw more than 1-1/2 out on a DGV. In fact my new (mildly modified) engine is running one size smaller pilot jet (55), and only 1 turn out on mix screw. Mains were increased to 165 and 170 though.

[650savag]

Thanks, Turbo! I can see where trying to time it like that could be inconsistent with too many variables. I will wait until tomorrow and set it with the timing light and then maybe tinker with the carb after I get that set to 12 degrees. It's possible that I still have a small vacuum leak that I can't detect with carb cleaner. I have it completely desmogged and everything plugged and the egr blocked with platecand gasket. It runs so much better than it was with the old stock carb on it that I'm content to put up with the very small lag. It really romps and stomps all the way through the throttle range especially when the second throttle plate starts coming in. It never ran that strong with the Hitachi so I'm not going back. The hard starting when hot seemed to be much better today after I smugged up on the carb nuts. That seemed to have eliminated the tiny vacuum leak. I took it for a test down the highway and was running it up through the gears (not pushing it to the 2d throttle plate but close). When I started to go to 5th, I looked at the speedo and it was up to almost 70! I bwas shocked because it never ran like that with the old carb. I will update tomorrow after I check the timing!

[Lockleaf]

Tuning. That's all that needs.

 

The only time I've ever had a prolem with a DGV was when I had one on my first rock crawler. It flooded over.

 

I love the tunability of the DGV. And modifications are endless with a DGV too. Custom auxilliary venturis, remove seconday choke plate and shaft, larger needle and seat, shave the power valve...lots of things you can do to them.

I'm glad someone mentioned this. It's no different than bolting an Edelbrock to an SBC or installing aftermarket efi. They come at a very baseline setup and require fine tuning to altitude, displacement and power curve. They can be dialed in to perfection, just takes some research and effort. I followed the suggestions in this book and I've been pretty happy with my 32/36 in my 4x4 720.

 

http://www.amazon.com/gp/aw/d/0895863774/ref=pd_aw_sbs_263_of_30?refRID=1M5B537G1VV7R6TN10VX

[650savag]

Thanks Lockleaf! I will check out that book on Amazon. I was surprised to find it was not set up at all out of the box! The first thing I checked was the mixture screw and it was set 9 1/2 turns out. I knew that wasn't going to work. The auto choke would not close at all so I had to set the tension on the spring and also both idle screws. The only thing I haven't done is change out any jets.

[Doctor510]

You are headed in the right direction.  If you will take a look at the magnetic pick up in the distributor, the pick up looks kinda like the letter "P".  In the rounded part, facing inward, you'll see a vertical metal piece.  If you line up one of the "spikes" on the reluctor, the spinney one, with that metal protrusion, check the timing mark on the pulley, that is where your timing is set.  The rotor should be pointing towards the contact in the cap. 

[datzenmike]

The '78 used an EI dizzy called a remote igniter. The '78 also used a water cooled intake and it was not bolted to the exhaust. Only the '75-'77s had this. Excessively retarded ignition will allow too much heat to be absorbed into the cooling system so be sure you are timed at about 12 degrees.

 

The L20Bs used a fuel return line because they ran so hot. You should not be running fuel directly from the pump to the carb without one. Run the shortest line from the return to the carb. The fuel return line constantly flows fresh cool fuel from the tank past the carb. This will reduce the chance of vapor lock and fuel boil over after shut down.

 

The stock L20B air filter has a cold air inlet, I doubt your weber does. This means it is sucking hot under hood air. Cut the stock air filter housing so it fits the weber carb. Run heater hose from the air snorkel to in front of the rad.

 

 

 

With the engine off try turning the plastic fan blades by hand. There should be firm resistance. If excessively loose it will not move enough air at low speeds.

 

If you don't have a coolant recovery can make one up. You need a special rad cap and a container. Run the rad over flow hose into the container and be sure that the liquid level in the container is above the hose. Upon expansion or boil over after shut down the coolant is forced into the recovery can. When the engine cools the coolant siphons back into the rad. This save you constantly re filling the rad in hot weather and risking over heating.

 

I see your rad shroud is still on which is good. Inspect the rad cooling fins for debris like leaves, pine needles and crap that blocks air flow.

 

Watch the lower rad hose while revving the engine. Suction from the water pump will collapse a soft hose and restrict flow.

 

Are your heater hoses connected properly to the heater core? If you have had a problem and just looped the heater hose from head back to the lower rad hose you are not helping the cooling system any.

[650savag]

Thanks King Rat and Doc for all the great help.  I think I have the stumble issue solved and hopefully the "hard starting when hot issue" also.  The bogging issue turned out to be the primary idle jet just like several of the great comments suggested.  After I got my timing set right, I pulled the primary idle jet out and it was a #60  If I understand correctly, that indicates that the hole through the center is .6mm.  Instead of ordering the next size jet, I chose to employ some "Ratsun engineering".  I will post a pic, but what I did was grab one of my tip cleaning sets (I have about a dozen of them lying around the shop), and took it apart and measured the sizes with my Starrett dial calipers.  The tip cleaners have a smaller, smooth diameter for the first 3/8ths of an inch and then the serrated diameter starts which is a tiny bit larger od (like a tiny round file). The third from the smallest measured .021 and .023 respectively, and the 4th from the smallest measured .023 on the smooth end and .025 on the serrated od.  So, according to my calculations, .6 mm is .0234 which is what the hole in the #60 jet measured.  to go up to the next jet size, I needed to open it up to .025 or maybe a tad larger.  .7 mm = .0273 so I didn't want to jump a whole size just yet. So I took the tip cleaner that measured .021/.023 and reamed the hole out until the next size tip cleaner (.023/.025) would barely slide through the hole.  I reinstalled the jet, set my idle to the slowest idle that the truck would run at.  I was then able to adjust the mixture screw and got a real smooth, slightly faster idle at about 1 1/4 turn off bottom. PERFECT!  I raised the idle up to 700 rpm, closed the hood on my truck and took it for a spin!  Absolutely no more hesitation, bog or stumble and it honks!!  I am stoked!!!  I will know more about the hard starting issue after I drive it some more  Thanks for all the help that I have gotten on here!  

 

[Doctor510]

#60 idle jet is perfect, get the idle speed up to 850-900 and the timing 12* BTDC.  Good job!

[650savag]

I reamed out the #60 to a #65 size .025 and that little difference let me adjust my mixture screw down from 3 turns out to 1 1/4 turns off bottom and that small amount of increase took out all of the stumble! Thanks again to everyone!

 

Dan

[Stoffregen Motorsports]

I love a happy ending.