ok, so, the seller said i got 44 webers with my motor but it seems like the carbs are too big.
no vacuum to speak of once you're off the idle. we haven't measured the venturis yet, that's next on the list.
so we look at the stamping and here's what it reads (on both):

40 IDF 48 2B

so, what do i have?
40s?
48s?
44s?

i'm lost (again) ...
Andy

Looks like 40IDF's to me. Pull the chokes out measure and get the number stamped on 'em.

Where is he *trying* to measure vaccuum ?


B

you have 40IDFs. I would just remove the air cleaners and look down in the throught of the carb and see what number is cast into the top edge of the venturi. It will be pretty hard to see, you may have to clean the venturi to see it.

Andy,

Have Bill run the valves. I'm betting they are tight and causing this vaccuum issue he is seeing.



B

actually, he did that the other night, they were all way tight ...

we fired it up today, idles fine but has a complete dead spot right after you come off the idle jets, at that point zero vaccum (around 3k rpm), if you floor it, it'll catch and run fine on high rpm.

seems like the venturis are to big (not enough air-speed).

Andy

stupid question ....

could my 1.8 SSI exhaust be too restrictive for the engine (too much back-pressure) ???
Andy

Nope. Same size tubing as 2.0.

You are on the right track with the venturi's sizing. You may also need to step up on the idle jets or step down on the mains.

I love carbs.


B

mains are 155 right now ...

too big?
Andy

What size engine are we talking about? What size air corrections and idle jets are you running? It sounds like you need a bigger idle jet. What is the timing set at? What dizzy? 90% of all carb problems can be found in the dizzy.

He slapped an 009 on in place of a 050 that wouldnt keep its cap on.



B

I am sure that is not helping the problem. Been down that road before. Duct tape the cap on the 050 if necessary but heave that POS 009 and the car should automatically start running better.

He will have to wait until he can get by the shop. I have a specific 1.8 dizzy pulled for him that works well with carbs.

This engine had the flat spot with the 050. a BAD flat spot. Like scary.. cars dies flat spot..

Float level may need to be checked.



B

Yeah, if that is the same 205 ___ ____ dizzy that I am running he should be really happy. If you are working on it I am sure it will be right in short order.

actually, i think i mixed that up earlier.
it's still a 050 but it now has a cap that actually fits!

here's the rundown as far as i know by now:

40 IDF weber with unknown venturi size
55 idle
155 main
F11 emulsion
200 air corrector

2056cc with aggressive euro race "H" grind cam, 9/1 compression, KB Pistons, dual valve springs, ported & polished heads. Pertronix ignition.
don't know valve sizes (didn't take heads off)

bill set the timing today but i wasn't around so i don't know what he set it too.
but he knows T4s very well, i'm sure he didn't mess that one up.
Andy

I'm not working on it. He took it to a place closer to his house while I was out of town. They will get it figured out.


B

155 mains are gigantic. This is tied to venturi size, not throttle plate size (that's what the 40 in 40IDF means). Either the mains are way too big, or the venturis are 36mm, which is the limit on what will fit in a 40IDF. 30mm, maybe 32mm, is about the venturi I'd say would work on that engine unless the cam is way wild.

The typical formula is to run mains a 4 or 4.1 x the venturi size in mm. So, for 30mm venturies, 120 or 125 mains are right. For 32mm, 125 to 130.

I presume from the cam this is supposed to be a race engine, so the fact that the idles are probably a bit big isn't likely to be an issue. I'd worry a bit about the engine leaning out on the top end with 200 airs in it. I'd have some 180s on hand to test with once you're ready to put some actual revs on the engine.

It's very odd to have 40s on a wild-cammed 2.0. Most people go with 44s on an engine like that.

that's what i thought was on the engine when i bought it ...

Andy

The "H" grind cam is far from wild. I ran the cam years ago in 1911 street engines. It has less than .500 lift.


B

OK, so if this is a street engine, then 30mm venturies are very probably the way to go. Any more, and you'll have a hard time getting it jetted right for low end. Drop to 52 idles, leave the 200 airs in there, and drop to 120 mains. You might need 125 mains, depending exactly on that cam (which I obviously know diddley about).

The venturi size should be stamped or cast into the side, which you can't see unless you take them out.

ok, is that good or bad for what i want to do with the car ???
easier to tune? easier to convert to FI down the road??


should i give the engine back to zois and cut my losses?
~about $1500 in parts and labour so far (that's *without* what i paid for the engine )
Andy

doesn't somebody down there have a spare set of carbs you can install? this is the same engine runing the same carbs that died due to a fuel starvation issue?

kevin

Slap a 60 idle in there and see what happens. Check and see what the adjustment is on the accelerator pump linkage. maybe you need a little more gas on the pump shooter. Do not drop the idle size it will get worse

What do the plugs look like? 150 maybe a little big on the mains but with a 200 it may work well. I ran a 135 on my 2056 with 36mm Vents in 44IDFs with a 190 air. never had any problems.

Venturi size is not best selected with a formula, it is best selected through experimentation. My 2056 wouldn't pull a noodle out of a cat's ass with the 40IDFs on it so I slapped a set of 44s on there and it was a night and day difference. I ran the car everyday got 21+mpg with my foot in it all the time.

You don't have to take the venturies out. It is stamped on the inside top edge of the venturi at the most you will have to remove the air cleaner mounting plate.

No need to take the engine back. just have a little patience.,

Andy, Have you figured out the venturi size yet?

On my 2.0 with mild cam and ported heads I ran 40 IDF's with 28mm vents, 50 idles, 120 mains, 210 air correction, f11 emulsion tubes. This set-up worked well for me, very smooth and flexible, no flat spots, although many people think 32 vents are the way to go. Just a suggestion if you find you have 28mm vents.

ok guys, get this. bill pulled the venturis this moring and they're 45mm !!!

now what? does that mean the carbs are actually 48s ???
how could one fit a 45 venturi in a 40 IDF ?

ahhh, will this ever end?
Andy

The H grind will work fine with what you are doing. It is a good cam.

45's ? HUH ?

Get down there and take some digital pics.

Oh.. they are not 48's.. the 48's are totally different carbs than what you have. It is very easy to mix up a 40 with a 44. The carb bodies look identical.


B

Andy,

Just FYI, on my 2056 with 40IDFs here are the settings:

Main Jets 130
Emulsion Tubes F11
Idle Jets 50
Air Correction Jet 160
Venturi 32mm

Even with the linkage problems (which was quite badly setup it turns out), it seemed to run and pull strongly with no bad flatspots.

I don't know what cam I have though.

Richard

Nobody is talking about accelerator pump jets. Seems like the carbs are pretty weirdly setup, but everyone seems to forget about the accelerator pump jet. It's in the bottom of the fuel bowl and controls how much fuel bypasses the accelerator pump when you step on the pedal. A smaller jet will give you a fatter shot of fuel. This might be a good path to go down.

It is possible that you have 48IDF carbs. Don't know much about them. If that is the case no wonder you have a flat spot, the mixture probably stops in the intake and has lunch before traveling SLOWLY into the chamber.