I got the chance to swap my new carb for the old one that i rebuilt about a year ago. It was time for an upgrade because i simply was not getting enough fuel to my engine. I have been running it for a few days now and have gotten it tuned pretty well. i think i might need some timing work done as well to perfect it though. Maybe even a slightly larger jet kit as well. Only time will tell.

Anyways, i figured i would do a short little write up for those looking to do the swap. Note that the intake and other things have already been modified. See Signature for details.

Here is what i had.


This is what i got.


New and old.


Remove the 4 bolts holding the air filter frame.


Old carb removed. (4 more nuts on the intake studs)


This is the adapter plate that i have. What is it? Seals well, but seems handmade? is it a really old Weber adapter? Why is there a W? Came with the Offenhauser intake.


Carburnation.com forgot to send one of the 2 gaskets i ordered, so i i had to make one out of some gasket material i had leftover. I also used Edelbrock Gaskcasinch to ensure a good seal.HJad to work fast, os i could not get pictures of this step. After looking at my adapter plate, if i have any issues i will just order the LCE spiral adapter. (anybody have any credible info on this with the dual plane intake?)

After i got it installed.


New throttle linkage did not match up so i had to put the old piece back on. Where can i get a new throttle linkage set from the pedal to the carb?


Old linkage i used.


Reinstall new air filter frame with gasket underneath.


Attach electric choke, snap air filter in to place.


Start the truck up and see how she runs. I am not sure of any proper carb break in procedure, but i just start it up and let it idle then i did a bit of light driving, then checked the nuts on the carb once warm. Anybody know the proper torque for the carb to the intake manifold.

Hope this helps.

 

Spent about an hour after tuning this. The Weber came with the mixture screws 2 full turns out. Mine seemed happy between 1.5 and 2 turns out. Perhaps i might need a jet kit down the road?

Should i do a full tune up? (plugs, wires, dist. cap and rotor, etc) Or will it be just fine? I was thinking i might want to do a better plug to get more spark?

 

The torque specs should be in the instructions
rejetting might help

 

1. You have an Offy intake, therefore you do not need adaptors. What you have are carb spacers, not adaptors.


2. Pull the old throttle linkage off of your 32/36 and bolt it on in place of what is on your 38/38. Or call carbs unlimited. Take care not to overtighten the throttle-shaft nut on reinstall as you can pull the throttle shaft clean out of the carb body.


3. You need to look online for Weber tuning procedures, or get them from carbs unlimited. You will need to do some basic idle speed/jetting from the sound of it.

 

A search would find this
https://www.yotatech.com/forums/f115...b-info-241818/

 

Torque specs were not in the instructions sent.

1. Why is there a spacer then? It appears that it it was made for a 32/36 since the openings are different sized, but so are the ones on my Offy intake. Should i remove the spacer and just mount to the off intake directly? Would the LCE plate make a difference?

2. I simply swapped the piece that hooks to the throttle linkage. no need to pull the whole thing apart.

3. I have read just about everything Weber has printed on the 32/36 and 38. It helps, but its not a definitive guide.

I have read a few times. The tuning guide is for the 32/36 not the 38, but they sent me a paper copy of that stuff and the 38 tuning guide as well.

 

1. Sometimes spacers are used to keep the carb at a specific height for throttle linkages or clearance issues. Offenhauser intakes come with a square 2bbl-bore. You can bolt any 2bbl Weber I am aware of direcly to it. There are also those who believe carb spacers add power. I have never seen dyno results on these engines at their low performance levels to confirm that they do or do not. I would not use one if I were using an Offy intake. I prefer to minimize gaskets.

2. I missed in your first post how you had already swapped the throttle control lever from the 32/36 to the 38/38. See this link: http://www.carburetion.com/sitesearc...%20Carburetors

When changing throttle control levers take care not to over-tighten the throttle control lever nut. You can pull the throttle shaft clean out of the carb body if it's over-tightened.

3. Their tuning guidelines are quite clear in my literature. Further explore the Carbs Unlimited website for Weber tuning guides or be more specific about what exactly it is you're having trouble understanding, that way the folks here can better assist you.

With your idle mixture screws at under 2 turns out, that means your idle jets are too big. I assume you have 45's in? If so, you need 40's. Also available at Carbs Unlimited.

If you do not have an extensive background in automotive repair or modification that's ok, but you should try to use the resources available through searches and factory literature. Don't over-think it, like a test.
You'll most likely be experimenting with your carb for a while. My truck is my daily driver, I have in the center console a Weber 38/38 jet kit and a small screwdriver for side-of-the-road or parking lot adjustments. I've been set up for some time, so it's not really needed for me at this point, but for you to do the same would be a good idea. You're not going to ruin your engine by experimenting with jet sizes.

I am not affiliated with Carbs Unlimited. They sell genuine Weber parts, not knock-offs and as such I recommend them for everyone to use as a Weber part source.

 

Pardon me, check this link, it will help you: https://www.yotatech.com/forums/f114...tuning-261129/

The only real difference in setting up the two carbs is the amount of turns used to judge whether or not your settings are correct. In general with the idle circuit, if your jets aren't far enough out, they're too big. If they're too far out, they're too small.

I'll add in that, when setting idle SPEED, not MIXTURE, the reason for not setting the speed screw too high is that it opens the throttle plate causing potential dieseling issues and possibly supplying vacuum to your vacuum advance port. You do not want your vacuum advance engaging at idle.

The Weber mixture tuning is two elements; the idle circuit and the main circuit. The transition or middle circuit is when both the idle and main jets are supplying fuel in tandem. If the idle screws are too far in or out they may hurt your mid-range performance. It is important to try to keep your adjustments within the Weber guidelines for this reason, and to tune your circuits in the order Weber suggests. The correct way to adjust a Weber is through jetting, not by manually setting the screws above or below the Weber guidelines.

That isn't to say the engine won't work if the screws aren't perfect. Everything can be fudged.

 

Also, you really don't need torque specs for a carb. The only things I ever torque on these engines are critical parts that will cause catastrophic failure like the flywheel, head, mains, camshaft, snout bolts, etc...

Manifolds/exterior stuff is not that precision. Just be careful with steel bolts into aluminum. Easy to strip. A carb would have to be tightened pretty hard to have a problem, especially with through-bolts or studs. My bet is the spec is probably in the neighborhood of 10lbs, give or take a couple.

Just get it snug, then add a little in an even pattern. And use lock washers.