38 Weber / fuel pressure question

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There is an extremely specific way to measure these floats or you'll get it wrong - use this picture to clamp the top like this in a vise (protected with padding, of course) -


dgvplasfloat.gif


Those dimensions are metric of course ,
Dropped - 2.007
Closed - 1.614 (brass) 1.377 (plastic)

The idea here is to allow the float to rest against the internal damper spring without compressing it so the measurements can be set correctly . Most people miss this setting and have fuel height problems . Be gentle about bending those tabs and keep them straight as possible .


Does your inlet head where the fuel line attaches have both ports tapped , or is one just cast and not threaded ?
Sarge
 
Hey Sarge,

My carb only has one port tapped.

I installed the fuel filter with the return today. I fixed the vacuum leaks under the carb this past weekend. Tomorrow, I'll adjust the floats as per your suggestion. Thanks for the diagrams... That makes it easy!

Wish me luck on the test drive tomorrow... :hmm:

Much more of this $#!+ and I'm buying a Trollhole!!!
 
The whole issue boils down to a crappy design to fit the Cruiser - I've set them up on a whole lot of other vehicles and other than the Heeps they all work excellent and perform better than anything else . The adapter plates , air cleaner (another whole subject ) and linkage setup for the throttle are all a joke . I'd prefer to run that carb reversed with the bowl in the rear , modify the vent like I used to do here and make it run nearly upside down . Then again , the Cruisers are so top heavy that doesn't really become an issue .
Now , a lightweight Sami with wider axles , is another story ...
Sarge
 
After adjusting the floats, re routing fuel lines to keep them cooler, and installing the fuel filter with a return... I NERVOUSLY went for 20 minute drive.

The 40 did great! Right up to the time I turned onto the road where I live. She flooded and died... Took awhile to start. She backfired twice! Just two days ago, I set the timing at 10 BTDC, and the idle at 700.

Once I got her home, I checked the timing again. There was no bb to be seen. The idle was at 1100. I could not turn dizzy by hand. This is the 2nd time this has happened.

While setting the timing, it would fluctuate! How does this happen? How do I fix it?

Anyone with a solution, please chime in.

THANKS!
 
Most likely , either a broken advance spring or the advance plate is sticking . Time to rebuild it or get the side cover/disty from a 60 series engine and do the swap . Or , could go with Trollhole's electronic non-USA reproduction unit ....works great on mine . If it's trying to flood , probably dirt in the float - common any time you swap fuel lines around .
Sarge
 
I'll replace the advance this evening.

For what it's worth... when I block off the vacuum advance, to set the timing, the rpm does not change. Will this result in fluctuation?

I let the 40 idle for 30 minutes this afternoon... she gained 50 rpm while idling. :bang:

I'll check the float again. It was clean earlier.

If I go with a 60 dizzy.. Where can I ship it to be rebuilt?

Thanks again for all the help!
 
It's all a matter of making certain the carb is not pulling vacuum at idle . The gain in rpm could be heat saturation if you don't have an insulator under the carb . You can take the distributor apart and clean up the bearing plate and check the springs . I think JimC and a few others offer rebuild and recurve services , just do a simple search .
Sarge
 
A number of years ago I swapped a motor in my 67 Datsun Roadster. After getting the "new" motor running it would randomly die. What I finally found was when that motor was pulled from the original vehicle the person was not careful. Where the wire to the points goes through the dizzy body a small machine screw, inside an insulating block, had been used to hold the coil wire. On the inside of the dizzy that machine screw was held in with a nut. When that wire had been removed the nut had fallen off and, unknown to me, it had been allowed to drop down into the bottom of the dizzy, where it rattled around with the advance mechanism. Occasionally the nut would jam between the dizzy housing and the advance weights and turn the dizzy.

Check your dizzy to make sure nothing is down around the advance mechanism that can jam between the weight and the dizzy body.

Don
 
handcannon, Thanks for the input.

This evening I installed a new vacuum advance... everything in the dizzy looked good. I rebuilt this HEI dizzy last year with AC Delco parts. It's been working great until the last week or so. Though I have researched a significant amount, I still don't understand how the timing can advance so significantly without the dizzy moving. In a 20 minute drive today, the timing advanced 5-6 degrees...

I'm at my wits end...:bang:
 
Honestly , and I know some folks like them , but I'd stick with a Toyota distributor . Trollhole's electronic unit works excellent and never wanders - curve is nice and steady every time I've checked it and rock solid return to baseline setting . I've never cared for how GM distributors fit into these engines , just my opinion but risking the cam gear isn't worth the effort .
Sarge
 
Weber Sarge said:
Go find a CJ series fuel filter or similar - it has a bypass built in that will bleed off pressure if your tank has a return line . Generally , over fueled Webers will die at idle or at least chug pretty bad and clear right up when the throttle is opened . It doesn't make sense to run good cold but that could be the pump being sluggish .
Sarge
Click to expand...


Learn something new every day. Thanks
 
Anvil said:
handcannon, Thanks for the input.

This evening I installed a new vacuum advance... everything in the dizzy looked good. I rebuilt this HEI dizzy last year with AC Delco parts. It's been working great until the last week or so. Though I have researched a significant amount, I still don't understand how the timing can advance so significantly without the dizzy moving. In a 20 minute drive today, the timing advanced 5-6 degrees...

I'm at my wits end...:bang:
Click to expand...


Might want to pull the dizzy and inspect the cam gear. Could it be rotating on the camshaft? Also check and make sure the cam isn't walking back and forth.
 
It's a trick the Sami guys been using for years - that's a cheap build crowd and not always a bad thing . I spent enough years on Zuhwarrie and OffRoad.com boards teaching them all how to properly set up their Weber carb kits and built a lot of modified units to pull crazy cfm's for high-end engines . Some of the blower guys were running over 200hp from a 1.3L on the street/trail . Years ago it wasn't an issue until Purlator and others starting outsourcing the fuel pressure regulators - they are all crap now unless you buy an expensive one that has a bypass return and those are north of $400 to build . The CJ filter just bleeds off the pressure , even from the most aggressive stock pumps - most psi you get is around 2.5 at the carb . The Weber doesn't have a high-leverage angle against the float valve , like your Toyota carb version has - hence the issue with pressure control . Best way to to tap the casting and make a return at the carb , but doing that requires a specially ground tap and a lot of care/prior experience - I destroyed a couple castings before I figured it out .
The carbs that were tapped - mainly original older Italian castings had both ports tapped and the factory used a metric straight thread with an aluminum seal washer - I actually have a drawer of those outlets here left , very rare part .
Sarge
 
Trollhole,

I pulled the dizzy (please see below). Only a third of the gear has been meshing
cam. Thinking of drilling a hole in my spare... 3/8" down from existing hole.

Does anyone know the Toyota measurement from bottom of gear to bottom of shaft?


IMG_0248.webp
with the
 
Bought a brand new Trollhole dizzy today, as well as a mechanical fuel pump.

Now if I can just figure out this Weber carb... :bang: Tried the bypass filter and fuel regulator... no worky.

At least I no longer have vacuum leaks! :)
This afternoon I had the 40 idling in the driveway and it flooded :deadhorse:.
 
just throwing a few things out there.....

by flooded what exactly is it doing? stumbling after awhile and dying?

did you pull the plugs and see it was flooding out plugs are wet?

I didnt see you post what jets are in it? idle/main

is this a new carb or something thats been on for awhile?

ball linkage or did you replace with cable? check for binding keeping idle up throttle not going to idle position fully
 
Thanks for chiming in Johnny C!

The carb makes a gargling/boiling sound and a cloud of white vapor comes out of the hood louvers, and then the engine dies. This only happens after the engine is warm. I can smell fuel. Occasionally it will have a significant backfire.

I'll check the plugs today.

Not sure of the jet size... I'll need to check that as well. The carb has been running well for that last two years. I ordered a rebuild kit and jet pack...

The carb was installed in 2009.


No binding in the linkage.

Thanks again!
 
look down the carb with a flashlight.... throttle open... look to see if your intake manifold has a crack
 
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