Re-jetting (or not) the DFEV

[18Fiatsandcounting]

question fro Bryan, even if the timing didn 't advance properly, wouldn't it still rev past what he has, but just not really have any power. I accident;y was driving around with the vac advance disconnected and it was not that noticeable. I know the mech part is more significant.

Geo

Geo, yes, you are right, but I'm kinda grasping at straws here. I can only recall a couple of instances decades ago where I ran across Fiats that wouldn't rev past 2000 or 3000 rpm or so, and both times the issue was ignition and not carbs. I recall one instance was when the mechanical ignition advance was stuck and so the engine was always at 10 BTDC no matter the rpm, and once where it was a dual point car and I had gotten the "cold start" points set right but was hopelessly messed up on the "run-warm" set of points. The car would start and idle OK, but wouldn't rev.

-Bryan

[wetminkey]

Goodness, I've got some catching up to do!
Let's see,...I've got an entirely new distributor now, ENTIRELY. No significant changes,...probably a better idle. I'm using my pencil marks as TDC and guessing approximately an inch for advance,...might need a 'tich' more,...
I think that my old distributor advance was sloppy and provided advance immediately, with little left to add.
I've made no changes to the DFEV (only assessed what was inside and reassembled).
TDC was established at #4 TDC and cams at their pointers. TDC does occur for a couple of degrees and I think everything is set to the end of TDC. Do these engines run if they're off a crankshaft cog?
Hard to mix the plug wires, since the cap has each numbered,...but I guess that I could see someone doing it.
Float is properly set to 35 mm and 51 mm, per: https://www.piercemanifolds.com/category_s/317.htm
Plugs don't look too bad after idling to warmup several times,...not sooty, smell OK. Chambers look 'clean' and 'dry' from what I can visualize. Compression test #1 - #4: First run: 140 150 145 145 Second run: 153 152 143 148
It's within 10% overall, and in adjacent chambers. I would consider 145 - 150 reasonable compression.
I still wanna see what is going on under the cam covers,...I want ensure that I set the valves CORRECTLY 20 years ago! If I'm happy, then I'll get my near-deaf buddy, racer-Mike, to give me a hand with jetting the DFEV's mains. He's raced Weber carbs for about fifty years,...it would be child's-play for him!
Valve clearance checks tomorrow.
Thanks guys. Todd.

[SteinOnkel]

You need a timing light. Don't buy the innova ones, they are junk. If two plug wires are mixed up, it will sound like a can of marbles. If three are mixed up, it won't start.

Set it to 10*BTDC and leave the vacuum advance disconnected. I don't see why everyone is saying to connect it to manifold, they are supposed to be connected to ported vacuum, which these carbs don't have. I've had it disconnected on many many engines and I can tell you it makes zero difference. The trick is to set your initial advance a tad higher. So if stock is 5 w/ vac advance you go to 10.

Also just for funsies I went to the VW and set it to 20* static timing. Revs up just fine past 3000 rpm. I don't think that's your issue.

What I would do is take off your air cleaner, rev it to 3000 by hand (might want to wear hearing protection for this), then back it off slightly and jab the throttle while looking down the throat. If you don't see a squirt of gas from the accel pump when you jab, your bowl is dry and you're running out of juice.

[18Fiatsandcounting]

Todd, I'm running out of ideas here, but a couple quick thoughts:

1) On the timing belt, I don't think being off one tooth would cause your problems. I played with this in my younger more foolish days, and while the engine performance didn't get any better, it was only marginally worse.

2) Are you still using ignition points with your new distributor? If the point gap (or dwell measurement) is way off, you could get a very weak spark that would be OK for idle but not sufficient once the engine starts to rev.

-Bryan

[wetminkey]

'79 is electronic. And I set my gap prior to installation, too. The rest of the ignition is pretty new (MSD coil, and, Accel module). Worked just fine previously, and not something I would question.
I want to see valve clearances and observe TDC. My old notes are in the shop manual, but I want to check them. That way I'll KNOW,...I'm sure you understand! One less possibility,...
And rejetting the DFEV would be no huge deal,...I've recorded it's jet sizes and I think the old ADHA jetting might be able to guide me some,...
It's not rocket science.
Manyana.

[18Fiatsandcounting]

As I mentioned, I'm pretty close to being out of ideas, but here's one more: For your DFEV, I assume you were using the DGV float diagram on the Pierce Manifolds website to set your float specs. Am I missing something, or perhaps the DGV specs aren't right for the DFEV?

Given your recent posts about the ignition, I'm kinda back to a fuel starvation issue as Steiny has suggested. You could try adjusting the float level so that the gas level in the float bowl is higher, even if not to spec. See how that runs. In the distance past, I've also removed the top float cover, pinched off the fuel inlet hose (or held the needle valve closed with a rubber band around the float and top cover), filled the float bowl about 1/2 to 3/4 with gas, and then started the car. It should run long enough to observe the behavior of the fuel level, and if you're quick, you can rev it while observing the fuel level. If you still have plenty of fuel in the bowl when the engine runs out of steam over 2000 rpm, then your problem is not fuel starvation. Might need an assistant for this test, to start the car while you stand ready over the carb/throttle.

Use caution when working with gas, of course.

-Bryan

[geospider]

Setting the float was a bit trickier than I had thought. First time I had it way too high and was dumping fuel into the engine; enough to get into the oil and had to change that.

then reset and was too low and would bog down by 3rd gear; or even revving a lot when in the garage.

thought I was being particular the first time. then was more attentive (I guess) and got it right, one morning before driving to the Alameda car show. glad it worked that time, since wife was with me.

lesson was that these are a bit trickier than I thought. Was also my first time in years to do one. Have also heard that the floats can get stuck, so being careful making sure it "swings" free when going together.

Geo

[wetminkey]

So,...how did you go about setting the float level in the DFEV?! And what level did you set it to?
Thanks, Geo!

[geospider]

Todd,
Well, after 2 failures in opposite directions, I stared ;looking at several sites for help. Basically used the Pierce #s for the plastic float that I have. Same ones you have been using. I'm guessing I paid more attention to the tab at the needle valve. The part that stops the float a it goes down. From what I have read, there should be 2 mm of travel for the float.
so basically, I used the 35 mm measurement , then using thee small tab in the back, make sure the float travels 2 mm off the ball at the needle valve. on the Pierce diagram , the tab is marked with an A.

It all finally worked for me.

As I had said, runs great, but now idles high: 1400, and idle set screw is all the way out. ???

Good luck If this were last Oct, it would be right in the front of my brain.

Geo

[18Fiatsandcounting]

Geo, perhaps a new thread is needed so as not to hijack Todd's, but a few thoughts on your high idle. Ideally, when you back the idle speed screw all the way out, the primary throttle butterfly should close all the way and the engine should die. If it doesn't, either the primary butterfly (or the secondary) is still partially open and letting in air and fuel.

Check to see that, with the engine off and the idle speed screw all the way out, both the primary and secondary butterflies are closed all the way and there isn't a linkage somewhere that is holding them slightly open. If you have a long thin piece of very thin but sturdy wire (nichrome?), try to gently poke it past the butterfly valves at the perpendicular points to the throttle shafts. If you can get a wire through there, the butterfly valve is not all the way closed. With the carb top cover removed and the "wing-shaped" venturi in the throttle bore removed, you might also be able to check with a very thin feeler gauge.

The butterfly could also be held open because it or the throttle shaft is bent. Here's hoping that's not the case.

-Bryan

[geospider]

No hijack intended. Todd and I tend to bounce things back and forth.
Thanks for the ideas. Will check out tomorrow.
Where in Bay area are you again? I am Concord.

Back to Todd: what have you found?

Geo

[18Fiatsandcounting]

Where in Bay area are you again? I am Concord.

Livermore. Still waiting for you to buy me a free beer!!! Or vice-versa.

-Bryan

[wetminkey]

Before any fall weather hits, I've been under the house, on a furnace venting repair, for a couple of days.
I found my old valve shim diagram from 11/31/00 with all of my shim sizes and gaps. Now it's time to compare them with the present measurements. If all is good, then the only possible problem could be the DFEV's jetting.
Still adding thin layers to the driver's rear fender upper to complete the contour,...all other bodywork is finished and primed.
Sure would be nice to find out why this car is not driveable,...

[focodave]

Todd,

With your recent intake manifold swap, is it possible that there is a leak between it and the head?
That would also account for you having to make the idle mixture screw so rich.

Just a thought...

Dave

[SteinOnkel]

Ahoi.

I suspect you are idling on your mains and they run out of steam at 3000 rpm.

It needs to idle at 1.5 turns out and ~800 RPM, otherwise your jetting is off.