engine and drivetrain Dcoe Tuning On New Engine -

[Guest_anonymous]

Fuel reversion

[TobyB]

 

Today was painfully slow and unproductive. I feel like I'm going backwards.

 

Ahhh, welcome to the 'pre science' or 'amateur's mind' phase of DCOEs.  They will thwart you for days,

and then suddenly, the sun will come out, Budda will smile upon you, Jesus will annoint you, and

it will start to make sense.  The worst part is that it happens so gradually, you hardly realize it's happened.

But the carbs start responding like they should.

So don't lose heart, grasshopper- you'll get it sorted out.  And you'll have a real skill AND art when you do.

 

I actually DID go back and look at that (excellent) pic before I posted- we were talking about

something else at that point, and I wasn't sure that was an on- car at- idle pic.  In my scribbles below, IF the throttle opens in

the direction of the white arrow AND the thing I've red- arrowed is the edge of the throttle plate, you SHOULD

be running on just the idle jets.  Unless something mechanical is really boogered in there.

So I'm gonna assume (arrgh) that the plates are right, the bearing supports aren't oblong, the side seals are in,

and everything else is ok in the bore.  That's a big leap of faith- there is SO MUCH that can be wrong in there...

 

Put some thread sealant on that regulator.  Tapered threads are not what they used to be.

I would REALLY feed these beasts at 2 psi for troubleshooting purposes.  It just rules out

a couple of dynamic issues that you may be having.  As in, the rocking engine and the

high pressure may very well be conspiring to drive you nuts and run off with your wife...

 

That fuel puddling, though, as you've said, is wrong.  Regulate it, drop float levels artificially, feed the carbs from

a fuel can on the roof (yes, it actually works!) but get them to stop doing that!  (and yeah,

I know, that's not necssarily gonna be easy)

 

One last thing off the top of my head- when you set baseline timing, can you confirm that, when you

rev the car, the advance works, and really advances the timing?

I know it's a dumb, basic thing, but since there are reverse- revolution dizzies kicking around,

it's not impossible that your dizzy advance curve ALSO wants a chance at your sanity.

And yes, all these things can work together to really confuse things....

 

Tryin' to help,

 

t

Edited September 19, 2014 by TobyB

[felix_666]

Thanks Toby, I really appreciate the ongoing help, without the support of the board I think I would of put these suckers in the neighbours pool some time ago.

 

The throttle plates are orientated as you said. The carbs were re-built by a fella that solely works on carbs since my old man was my age, not saying he doesn't make the odd mistake, but when ever I drop in I'm always amazed at the cars he is working on - I say this to give hope to your large assumption that everything else regarding the plates is right.

 

I'll have another crack at the regulator, its brand new so I was kinda bummed about it not working, speaking with the seller presently.

 

I'm unsure about your last point regarding the dizzy, "when you rev the car, the advance works, and really advances the timing?"

When I rev the car (since giving it a little more advance yesterday) the engine was much more responsive than on previous occasions. I can only assume the advance works because as I 'advance' (rotate the dizzy counterclockwise) the rpm increases, to a point, before turning to crap, and coversely, if I retard the dizzy (clockwise) it runs terriably. I actually can't retard the timing as it won't run. The highlight yesterday was adding 1-2* of advance and smoothing out the the idle. 

 

Does that answer your question?

 

Lastly, I'm still unsure about the floats. Literature doesn't say much about anything aside from the 8.5/15mm setting. I was thinking of increasing the stop height, to say 9mm, to see if this would lower the fuel level in the bowl/well. I'm guessing you're going to say sort out the regulator first, huh?

 

Grazie mille

[Chris_B]

I am reluctant to give you more advice, given the amount you have already received, but here it is.

 

1. Set your timing to 02 stand specs. Presuming your ignition system and motor are basically sound (have you run a compression check?), your complaints are likely related to the intake side. You can go back and optimize ignition timing after you get your carbs sorted out. However, the most common scenario for an 02 that won't rev over mid-range RPMs is incorrect timing, which can be caused by poorly adjusted points or other ignition problems (what kind of ignition system do you have?).

 

2. Intake leaks will mostly affect your performance at idle, unless they are really gross. Your hunting idle may be due to an intake leak, or a too lean idle mixture setting. What do you mean by "hunting" (for example, how many RPMs does it hunt; at what idle speed, etc,) Backfiring indicates excessively lean conditions or exhaust leaks.  Older DCOEs like yours can leak a significant amount of air at idle through the throttle shafts. You might want to have a look at the seals on the shafts.

 

3. to really tune your carbs, you will need to install a wide-band 02 sensor in your exhaust; but, you can get to a point of reasonable driveability without it

 

4. Fuel level and needle valve integrity is very important. If you can see fuel dripping into any of the carb barrels when you shut your motor down, you likely have a weak needle valve, poorly adjusted float or excessive fuel pressure. 4 PSI doesn't seem excessive in this context. Check the fuel level in the main jet cavity with something that will allow you to measure from the carb deck.  If you want to be conservative, go with 25 MM from that point to the fuel. 23MM will make things too rich, but that condition doesn't seen consistent with your other symptoms.  It is best to measure either with the motor running or shortly after shutdown. When are you checking the condition of your plugs? To get a good reading on overall carb performance, you need to drive at street or freeway speeds for a while, then engage your clutch, coast to a stop to a safe spot on the side of the road where you can pull a couple of plugs to have a look, without letting your motor idle for more than a few secs. Your wonky throttle plates will have less and less effect as your RPMs increase

 

5. Idle mixture adjustment has no real effect on performance, except at idle. These carbs are designed to idle at 900-1000 RPMs. Adjust the idle speed to that level before you check idle mixture and balance between the carbs. Note that the so-called "best lean idle" setting is not the correct way to set idle mixture, which should be 11-12 AFR (meaning, you should turn your idle mixture screws out a bit after you set to best lean idle (number of turns depends on the vintage of carbs and design of idle mixture screws).

 

6. You should be able to use your synchrometer to determine how badly your back carb butterflies are out of whack (which it looks like they are from your pics). Balance between the carbs is critically important at mid-range speeds (e.g,3-4K RPMs). What kind of linkage between the carbs do you have? You should be checking balance above idle, at least at 1.5-2K RPMs.

 

7. 32 chokes seem mighty small for a motor with a 292 cam and 9.5:1 pistons, but this shouldn't really affect your low to mid speed running. My guess is that this is due to a lean condition in your idle/transition range. You may want to try F9/60 idle jets. Don't worry about all of the other calibrated parts at this point (like pump jets) - they will not affect your basic, light load running and acceleration.

[TobyB]

Yup, sort out the regulator-

 

but don't be afraid at all to lower the float level.  It's a good diagnostic tool,

and many of us who race these things fart with it with some regularity to

try to fine- tune WOT mixtures.

And on the street, you can use it to compensate for transition problems.

 

As to advance, all spark systems advance the spark somewhat as RPMs increase.

The standard 2002 way is with weights in the base of the unit.  As revs increase, the

weights fly outward against springs, and they move the point cam and the rotor

forwards.  They can add anywhere from 8 to 22 degrees as revs increase from idle

to 4500. 

This is completely separate from the vacuum advance.

In the 318, the distributor was made to rotate the opposite way as the 2002.

I have no idea why.

But since those parts exist, and look very similar to 2002 parts, it's possible

(I've done it myself, before I knew better)

to put them into a 2002 distributor, and they will make the car run like crap.

You'd swear your engine needs a rebuild.

 

The way to check it is to get the timing light shooting something recognizable,

and then rev the engine.  The mark should advance quite a few degrees, and then

return to the baseline as revs drop back to idle. Ideally, it's a very smooth progression

forward and backwards.  Often, you'll need to shoot the front pulley, and have some

marks on it.  It doesn't have to be super- scientific- if you can see that it moves significantly

and smoothly and repeatably, you're 90% of the way there.

 

Hope this helps.

 

t

Edited September 20, 2014 by TobyB

[felix_666]

I seem to be going backwards again. Things were best a couple months ago when I hadn't touched a thing, no shaking, no stumbling, and it seemed to idle ok. 

 

Fuel pressure: 2.5 psi

 

Wet float test: 26-27mm - this is with the shut of height set to 9mm, drop 15mm

 

Problem: engine won't idle, shakes like crazy.

 

I'm questioning the ignition, timing and crane. Everything is new except the cap, i think. I don't understand what could of changed from when it was good, given I haven't touched anything ignition related except adding a little advance.

 

What else makes the engine shake? Lack of fuel?

 

To top it off I lost a progression cover, cutting my day short. I think I'll give it a couple more goes, then tow it to carb guy as the engine needs to be run in and this isn't good for it.
 

[Chris_B]

Recheck your carb-to-carb balance. Poor balance is a prime suspect for the symptom you describe.

[TobyB]

Yeah, I agree, balance.  Then try fussing with the idle adjust screws a bit- this time, tune each one

for smoothest running.  That might help.

Also, dick with the timing as you do this.  A degree or 2 can make a difference...

 

All just by way of experimentation.

 

Also, I'm convinced fuel slosh can make them shake themselves worse-

the fuel in the bowl sloshes, the engine shakes, the fuel sloshes more,

the  engine shakes worse.

Because if it sloshes badly enough, it can slosh right over the top into the

bores...

 

Historically, most DCOE installations have the engine strapped down pretty tightly...

 

And yes, at some point, there's absolutely nothing wrong in calling in the experts.

 

t

[felix_666]

Had some spare time and got things going again.

 

Balanced the carbs, they are even stevens, but were pretty close to begin with.

 

Checked over the ignition system, nothing major there, except the coil gets damn hot after running for 15 min or more, can't remember if this is normal, but the Crane is tepid to touch, so I think its all good.

 

PROBLEMS:

• Idle can be set nice to about 950 RPM, but when driving the engine spits and bogs under acceleration. I thought this meant it was too lean or not enough advance, but it also blows smoke and advance is about 12*, any more and the idle turns to crap.
• RPM will randomly drop and stall the car and restarting when its warm is a real pain, the only way it will start is with wide open throttle.

I adjusted the valves about a month ago and perhaps they are too tight? I have a go-no-go gauge and would of set them cold for 0.25 mm

 

It should be noted than the engine has about 20km on it so I'm expecting it will blow smoke while the rings continue to bed, which makes problem shooting difficult.

 

Spitting can be caused from ignition and valves, anything else?

Edited November 13, 2014 by felix_666

[Chris_B]

At what RPM is the spitting/bogging occuring? This sounds like a too lean condition, and not a timing or valve adjustment problem (unless you are really out of whack). Spitting can also be caused by an exhaust leak at the head.

 

The stalling at idle and hard to start afterward sounds like a flooding condition. Have you looked down the carb throats with a flashlight to see what is going on when the stalling occurs? If you see liquid fuel dripping into one or more of the barrels, you may have a bad needle valve in the affected carb.

[felix_666]

Spitting/bogging occurs when driving it off idle, but when stationary (no load) and I rev it by hand there is not spitting and it freely revs.

 

Pressure is good for the fuel at a steady 2.5 psi, according to my gauge. 

 

I haven't checked the needle valves as you indicated, but have adjusted the floats a few times and the spring and ball are in place, which other parts of the needle valve goes bad?

 

I added a pic for clarity.

Edited November 13, 2014 by felix_666

[Chris_B]

The spitting you are describing is the classic DCOE just-off-idle lean stumble. You might try going up a size in your idle jets. What are you running? Also, sometimes repositioning the throttle flaps by opening the throttle stop a bit can help by (which will make your idle higher of course). You can check this by removing the plug over the transition holes and observing how close the plates are too the first transition hole. What this does is place the flap closer to the first transition hole so that when you accellerate, there is less of a dead spot between the idle and transition circuits.

 

When you measured your fuel pressure, was it with the motor off?

 

What usually goes bad with needle valves is either the needle  itself or the needle seat.

[felix_666]

Idle jets were 55/F9, but I'm currently running 50/F8. It's hard to understand how it can be lean and blowing smoke, I guess it needs a fair bit more bedding in.

 

Check further up the page foe pictures of where the throttle plates are sitting. Can you be more specific about the "first" transitional hole, is that inboard or outboard?

 

Pressure checked whilst running. When the car turns off the pressure is much the same, maybe it drops a little.... was this a leading question regarding the valves?

 

So can the seat and needle be checked physically?

[Hans]

I'd be looking at a few things:

 

-those rubber O ring insulators. They are trouble. My O-rings upon close examination were cracked; they can slip out when being installed, getting equal tension top and bottom while mounted on the car is a royal pain. I went back to paper gasket. In the pics, one of yours appears to be skewed. Mine used a coiled spring washer under the nuts to allow adjusting the tension/gap. Another brand had some sort of rubber washers. You appear to have neither. Check out 

 

https://www.google.ca/search?q=dcoe+soft+mounts&espv=2&biw=2133&bih=1096&tbm=isch&tbo=u&source=univ&sa=X&ei=it1kVO7kCIqRyQTHQQ&ved=0CDIQsAQ&dpr=0.9

 

and Pierce Manifolds if you want to keep those. Or get the solid ti style insulators.

 

-fuel pressure regulator. All I know is that mine runs like crap if I stray too far from 2.5. I used a fuel pressure gauge to fine tune the actual regulator, which wasn't accurate.

 

-float levels. Italian model uses different spec than later Spanish as I recall. In any event, read posts on how to measure and adjust. Somewhere there is a chart with float levels for different models

 

-timing. I spent a lot of time fooling with carbs until I took IE advice on setting full advance to 33 or so. Made a big difference.

 

Also, if memory serves, Italian models take one turn out to start, Spanish 2.5. In any event, different base points. Try starting at one turn out..

Edited November 14, 2014 by Hans

[Chris_B]

You might want to go back to the 55f9 idle jets and see if that helps your lean hole. What color is the smoke?

 

Your throttle plate position looks pretty good. Have you checked all 4 throttle plates? Still, you might want to open them up just a smidge (maybe 50 RPM worth at idle).

 

Yes- your fuel pressure should be stable for quite a while after you shut off your motor If not, that fuel may be leaking into the carbs, which could also be happening at idle. That is why I suggested you look down the carb barrels at idle and immediatly after you shut the motor down, to see if there is any fuel dripping in (surely to cause a flooded condition).

 

Yes, you can eyeball the needle valve and seats. The surface should be smooth with out any pronouced groves. Also, you can simply hold the valve closed and blow gently in the fuel inlet. The valve should not let any air through.

 

How did you check your fuel level? The only accurate way to do it is in the main jet wells, from above (main jets assemblies removed, of course).