Dual Weber IDF 40s, Carb Rookie question... Options

[930cabman]

I run 12+mm on my 40IDF Weber floats. I prefer to have the fuel level a bit lower as opposed to higher. Is your fuel pressure in the 1 - 3 psi range? I run around 1.5 and seems to work just fine.

That is my next recommendation.... As I started doing test drives around the hood, it was suggested to run at 3.5 psi.

Recently, it was recommended to drop to 2.5, so once I get the carbs back on and the idle adjusted and sync'd, I will drop the pressure.

Whole thing started when I noticed the pressure was 1.5 not sure what happened with that, but since then, I have made enough changes to pretty much start from scratch.

So here I go...

For me 1.5 works great (on the street), a track machine might be different and I have never ran the float bowls empty with 1.5 psi. Staying on the low side makes sense for me.

[porschetub]

I run 12+mm on my 40IDF Weber floats. I prefer to have the fuel level a bit lower as opposed to higher. Is your fuel pressure in the 1 - 3 psi range? I run around 1.5 and seems to work just fine.

That is my next recommendation.... As I started doing test drives around the hood, it was suggested to run at 3.5 psi.

Recently, it was recommended to drop to 2.5, so once I get the carbs back on and the idle adjusted and sync'd, I will drop the pressure.

Whole thing started when I noticed the pressure was 1.5 not sure what happened with that, but since then, I have made enough changes to pretty much start from scratch.

So here I go...

Not really sure about that ,1.5psi is very low,specs are around are 2.5-3.0 normally for your carbs.
Are you running a quality fuel specific gauge rated to just above your pump output ? ,I have found if you run a say a 10 or 15 psi gauge for a max fuel pressure of 3.5 psi the gauge may be off due to the range of the gauge.
I suggest you check your gauge,cheers.


For me 1.5 works great (on the street), a track machine might be different and I have never ran the float bowls empty with 1.5 psi. Staying on the low side makes sense for me.

[malcolm2]

Found some time last nite and I re-assembled the carbs and set the screws as recommended in the Weber set up document. One thing I did notice is that the AIR BLEED SCREWS, marked red below, were NOT SEATED.

They were 2 maybe 3 turns OUT. all 4 were that way. I don't remember doing that, but I am sure I did.

Wouldn't more air call for more fuel? So maybe this had something to do with my Super Rich situation?

[malcolm2]

[Superhawk996]

Good find. Usually you’ll only have 1 air bleed screw adjusted per carb and even then only slightly.

Keep going - you’re on the right path!

Also make sure if your carbs are equipped with vacuum ports - they should be sealed. I’ve seen Weber IDF’s with no ports, 1 port per pair of carbs, and 1 port on each barrel. Not sure what dictated the port configurations. Regardless, they need to be sealed, either with plugs or by being connected to the distributor vacuum canister (without leakage) if you’re using vacuum advance.

[malcolm2]

I do have a vacuum can on the disty. Both carbs have a Vac. Advance Port as noted above. They came plugged. I removed 1 plug and attached a hose to the vac can. I also have a 1 way valve on that hose or something similar. IIRC AC.net recommended the device to help smooth out erratic pulses.

[rhodyguy]

Tomlinsons Weber book p.22 ….’pre-set your air by-pass screws. Set them 1/2 turn off the bottom’. Beg, borrow or steal a Tomlinsons.. Start at the beginning and go thru the set-up procedure again. It’s only a few screws and settings. Should take about 10-15 minutes. Start fresh.

[nditiz1]

ACN recommends using the port over cyl 4. I use the anti pulse when running dual carbs as well.

I haven't cracked my Tomlinsons in awhile, but I set my air bypass the same as Richard from PMO sets his. All closed, whichever chamber is the lowest, open to bring it up. Should only need a few turns. Anything excessive and you might have a vac leak. I think you were able to sync all 4 chambers so that's probably not a problem.

Now that you have them back together, turn your car on to fill the fuel bowls. Then turn off the car and manually operate the throttles to see the squirt volume. Both sides/all 4 should have the same shot.

[malcolm2]

Tomlinsons Weber book p.22 ….’pre-set your air by-pass screws. Set them 1/2 turn off the bottom’. Beg, borrow or steal a Tomlinsons.. Start at the beginning and go thru the set-up procedure again. It’s only a few screws and settings. Should take about 10-15 minutes. Start fresh.

Maybe you would send it to me..... ??

I will pay the freight to and from and get it back to you ASAP. (IMG:style_emoticons/default/chowtime.gif)

[rhodyguy]

PM sent.

[Jack Standz]

This float setting does not seem to be accurate. I see videos with the dude hold the plate vertically, the floats bounce back and forth and he sticks a mic on it and says it is not right.

Sorry, but I don't see the exact second when he is measuring a moving float.

ACN says they set mine at 12mm.... I can move the plate around and say BOOM... 12 mm. is that right? (IMG:style_emoticons/default/barf.gif) THis guy suggests 10mm. i can't tell.



https://www.youtube.com/watch?v=54uPwTZ3DJw

The current standard specification is 12mm to 14mm (and with the float flipped the other way, it's 34mm).

Something about fuel now being part alcohol (10%). This makes the float sink a little more because current fuel is lower specific gravity. So, unless you're running 100% gasoline in the motor, you should be good.

[nditiz1]

Tomlinsons Weber book p.22 ….’pre-set your air by-pass screws. Set them 1/2 turn off the bottom’. Beg, borrow or steal a Tomlinsons.. Start at the beginning and go thru the set-up procedure again. It’s only a few screws and settings. Should take about 10-15 minutes. Start fresh.

Maybe you would send it to me..... ??

I will pay the freight to and from and get it back to you ASAP. (IMG:style_emoticons/default/chowtime.gif)

I think I have an extra one for Weber, or an extra for Dells, but yeah I can send it.

[malcolm2]

Tomlinsons Weber book p.22 ….’pre-set your air by-pass screws. Set them 1/2 turn off the bottom’. Beg, borrow or steal a Tomlinsons.. Start at the beginning and go thru the set-up procedure again. It’s only a few screws and settings. Should take about 10-15 minutes. Start fresh.

Maybe you would send it to me..... ??

I will pay the freight to and from and get it back to you ASAP. (IMG:style_emoticons/default/chowtime.gif)

I think I have an extra one for Weber, or an extra for Dells, but yeah I can send it.

Thanks. I bought a weber one on ebay. And i have borrowed the supertech book. I will read it and return it. No need for copies or pdfs. Wink wink.

[malcolm2]

I go back and forth on ethanol or pure. Nice to know why we were getting 10 and 12 from different folks.

[malcolm2]

OK.... engine started. Had to give the idle screws a full turn to get it to idle.... but it is running on it's own this morning.

The first thing i wanted to do was adjust the fuel pressure. it is just slightly above 3 this morning.

I did get some comments that the gauge could be troublesome. But I attempted to adjust the QFT low pressure regulator and the gauge did not move... threaded it in and out and got no change in the gauge. Did not notice any engine changes either.

EDIT::: I turned the engine off, and let the pressure bleed off and restarted and was able to ADJUST to 1.5.


But which way do i adjust the regulator? I would have thought IN would block the fuel and lower the pressure??

Jegs QFT 793-30-804 (the one I purchased)

[930cabman]

Keep us in the loop as you get her purring.

[r_towle]

Synced ?

I’m hoping you nail it!

Rich

[malcolm2]

I may have..... Flow matches on all barrels, idle is set, linkage is back on and the flow #s and RPM stayed the same.

I took a video of the end and will add it here later. I am happy, but my FP gauge is still acting strange. I can't really adjust it up, but I can adjust it down.

This morning it was on 3, i took it to 1.5 and every now and then I see it drop to about zero.

[malcolm2]

youtube won't let me rotate..... but you can still watch. Hey, is there a way to add a DOCUMENT to a post?


https://www.youtube.com/watch?v=ofShSBhPMSo

[r_towle]

I’m still hearing sumpin wrong.
Still sounds like one cylinder is not performing the same as the other three.
I forget what venturis you have, but you may want to get smaller ones
It seems sluggish at lower idle.
Maybe get a new fuel pressure unit?