Carburetor Issue 32ADF

[SteinOnkel]

China carb has arrived. Looks very good, only minimal flashing needed to be removed, nothing crazy. I noticed that the manufacturer's stamp has been ground down. Wonder who actually makes this thing, might be Weber for all I know.

One o-ring wasn't installed correctly, but the carb is clean as a whistle on the inside. I'll put it onto the engine tomorrow and see how she does.

I noticed that the primary throttle has a noticeable gap even though the idle speed screw is not touching the linkage. Thought it was supposed to be fully closed? Hmm.

[18Fiatsandcounting]

I noticed that the primary throttle has a noticeable gap even though the idle speed screw is not touching the linkage. Thought it was supposed to be fully closed? Hmm.

Steiny, sometimes it helps to loosen the two screws on the primary throttle plate, just slightly, and then work the throttle spindle and butterfly valve until the latter fully closes, then retighten the screws.

I've also run across carbs that had the nut on the end of the throttle shaft too tight, and this resulted in the throttle plates not closing all the way. Solution: Loosen the nut, but make sure that the locking washer-tab-thingie is in place to keep the nut from vibrating off (been there, done that).

-Bryan

[SteinOnkel]

Thanks for the tips Bryan!

Herp derp the gap is because the choke is closed and the lever is resting on the fist step of the cam. All working as it should.

Float was way off. Choke was spot on though, hmmm.

Only thing that sucks about this carburetor is the stop screw for the secondary throttle plate. It's not contacting and the screw refuses to move in any direction. But there is a small gap around the throttle plate, so I'm just going to leave it alone.

[18Fiatsandcounting]

Only thing that sucks about this carburetor is the stop screw for the secondary throttle plate. It's not contacting and the screw refuses to move in any direction. But there is a small gap around the throttle plate, so I'm just going to leave it alone.

Steiny, my guess is that this stop screw is just severely corroded, as it should turn and allow you to set the secondary butterfly valve so that the valve is just barely cracked open when "at rest". If I recall, 0.002" should be the gap between the edge of the valve and the secondary bore walls, at least for the carbs I'm familiar with.

But, since one of the last things you want to do is break off that screw or bend the throttle shaft or various levers, I agree with you that leaving it alone might be prudent.

-Bryan

[SteinOnkel]

Okay, China carb is installed...and...drumroll please...it runs exactly as crappy as before

You gotta love old cars.

Immediately it started sputtering through the main venturi like crazy. In order to get anything that could be called an idle on this thing, I messed a bunch with the adjustment screws. Well I set the mixture screw to 1.5 and left that alone for now, let's talk about the idle speed screw. This one - just like with the old carburetor - has a minimal effect on engine rpm. As you back it out (engine was idling at a hefty 1500 rpm with gas spewing out of the main venturi) there comes a point where the idle speed tanks. It then barely stays running at 300 rpm...and...doesn't drip.

So I thought about that for a second. If I need to push that screw so far in that it exposes a progression hole on the carburetor, that would explain the spewing. Now why would I need to do that...maybe because when I installed my new distributor and wires, I completely botched the job?

In order to test this, I manually sucked on the hose going to the dizzy's advance pod and to my surprise it did actually run a lot better. Then I tried to set the timing by rotating the dizzy ever so slightly - forget it. Engine died, could not get it restarted. And I can't read a timing light and crank the and rotate the dizzy all at the same time. So I need to tackle this with a helper.

I want to go back to basics on this one. Who knows, maybe the pulley is misaligned. So I've got some questions:

1) Which one is cylinder number 1? The one in the very front of the car?
2) To determine my TDC mark is correct I would take out the spark plug of cylinder 1, stick a pencil inside and slowly rotate the engine until the pencil reaches its highest point. Sound good?
3) Which cylinder do you use to time these engines? 1 or 4? I seem to read conflicting statements on this.
4) Is the firing order 1-3-4-2?
4) What should I set static timing to? As I understand it the marks on the timing belt cover are 0, 5 and 10 degrees BTDC?

Thanks
Steiny

[blazingspider]

1) Which one is cylinder number 1? The one in the very front of the car?

Correct #1 is at the front

2) To determine my TDC mark is correct I would take out the spark plug of cylinder 1, stick a pencil inside and slowly rotate the engine until the pencil reaches its highest point. Sound good?

When #1 is at TDC so is #4 as they both ride the crank together as do #2 & #3, so yes you can use either 1 or 4 to determine TDC.

3) Which cylinder do you use to time these engines? 1 or 4? I seem to read conflicting statements on this.

You can use either for ignition timing BUT you must use #4 for valve timing hence the confusion. I always stick with #4 for both. That way you can use your timing light to look at the valve timing too!!

4) Is the firing order 1-3-4-2?

Correct

4) What should I set static timing to? As I understand it the marks on the timing belt cover are 0, 5 and 10 degrees BTDC?

Your understanding of the timing marks is correct. Sounds like you're using a later model electronic distributor for your 78, I'd disconnect the vacuum line to the advance capsule, plug it and set initial static timing to 10 degrees BTDC at about a 900 rpm idle speed. As you know when you advance or retard the ignition timing you will have to re-adjust the idle speed BTW where are you pulling vacuum from for the distributor?

[18Fiatsandcounting]

Blazingspiders covered your answers above and just one other thought from me: If you can get the car running, can you check the ignition timing at 3000 or 4000 rpm? At this rpm, the timing should be fully advanced and should be around 35 to 38 degrees BTDC. My thinking is that the engine is running much more smoothly at high rpm than at idle. I know there aren't marks for 35 BTDC, but if you have a mark for 0 and 10 degrees BTDC, then you can eyeball 3 times that 0 to 10 distance from the 10 degree mark and you should be right around there or a little before. You get the idea.

Then, as you lower the rpms, the timing should fall fairly smoothly from 35 to 38 to around 5 to 10 BTDC. If it doesn't fall smoothly, or arrives at some other value at low rpms, then that is an issue.

-Bryan

[blazingspider]

At risk of preaching to the choir, don't forget that if you use #1 to determine TDC make sure that #4 is on it's compression stroke and not #1. The 0 degree timing mark for the crank will be way off otherwise. Remember, the crank revolves around twice for every single revolution of the cams.

Also, have you disconnected the throttle linkage from the carb to ensure that it is not holding open the butterflies on the primary barrel of the carb? And...have you followed the weber redline procedure for setting the idle mix and idle speed settings. Finally, you're off the choke right and the engine is at operating temp when messing with this stuff, correct?

Keep us posted

[SteinOnkel]

You can use either for ignition timing BUT you must use #4 for valve timing hence the confusion. I always stick with #4 for both. That way you can use your timing light to look at the valve timing too!!

I'll use #4 for simplicity.

Your understanding of the timing marks is correct. Sounds like you're using a later model electronic distributor for your 78, I'd disconnect the vacuum line to the advance capsule, plug it and set initial static timing to 10 degrees BTDC at about a 900 rpm idle speed.

This is exactly right. My initial error I believe is that I took the old distributor out and stuck the new one in without thinking about the valve timing at all. I don't think I even turned the engine to TDC, whoops. Then I timed it to 5* BTDC on cylinder 1.

As vor the vac advance, currently not connected anywhere. I connected it to the vac port on the carb yesterday (not ported, basically manifold) and I was surprised at how little there was. Further proof that I'm not truly at idle.

I'll connect it to that port or drill out the carb for ported vacuum after we get the idle sorted and:

If you can get the car running, can you check the ignition timing at 3000 or 4000 rpm? At this rpm, the timing should be fully advanced and should be around 35 to 38 degrees BTDC.

Yeah I can check with my digital light. I believe the dizzy to be 22* mechanical advance + 14 vac. w/o vac we'll only get to 32*, but that's fine. The vac advance is only for highway cruising mpgs anyways, so not critical at this point.

My thinking is that the engine is running much more smoothly at high rpm than at idle.

Like an absolute dream. At around 3000 rpm it stops sputtering and everything works.

[18Fiatsandcounting]

Like an absolute dream. At around 3000 rpm it stops sputtering and everything works.

Sure sounds like it could be an incorrect ignition advance at the lower rpms. When you can, check the ignition advance from idle to 3000-4000 rpm and see what you get. I'd expect 5-10 BTDC at idle (as best you can get), 20 degrees BTDC at 2000 rpm, 30 degrees BTDC at 3000 rpm, up to a max of 36 BTDC or so. These are just rough estimates of course.

Keep in mind that some cars have a vacuum retard (as opposed to vacuum advance), and while I don't recall any Fiat DOHC engines using a vacuum retard, I could be wrong. The overall idea of course (for any engine) is to get the optimal timing advance under all engine conditions, through a combination of static timing, centrifugal advance, and vacuum advance or retard.

-Bryan

[SteinOnkel]

At risk of preaching to the choir, don't forget that if you use #1 to determine TDC make sure that #4 is on it's compression stroke and not #1. The 0 degree timing mark for the crank will be way off otherwise. Remember, the crank revolves around twice for every single revolution of the cams.

Also, have you disconnected the throttle linkage from the carb to ensure that it is not holding open the butterflies on the primary barrel of the carb? And...have you followed the weber redline procedure for setting the idle mix and idle speed settings. Finally, you're off the choke right and the engine is at operating temp when messing with this stuff, correct?

Keep us posted

D'oh! Why didn't I think of that...that's usually the first thing I do after the engine I'm tuning has warmed up - on multi carb setups. Silly of me to not do so on a single.

Yes, engine was fully warmed up. I had messed up the choke setting on the china carb and the choke wouldn't open all the way. One smart twist of the choke spring alleviated that.

As for the procedure, what I would really like to do is use my http://www.gunson.co.uk/tech-torque/Col ... on-chamber, but there is no point to this when the engine is either at 300 or 1500 rpm.

Yep, I'll keep everyone posted. I hate it when you look up threads like this years later and the OP never posts what the solution was. Friday my brother and I are tackling this. We'll figure it out eventually, always do.

[SteinOnkel]

Like an absolute dream. At around 3000 rpm it stops sputtering and everything works.

Sure sounds like it could be an incorrect ignition advance at the lower rpms. When you can, check the ignition advance from idle to 3000-4000 rpm and see what you get. I'd expect 5-10 BTDC at idle (as best you can get), 20 degrees BTDC at 2000 rpm, 30 degrees BTDC at 3000 rpm, up to a max of 36 BTDC or so. These are just rough estimates of course.

Keep in mind that some cars have a vacuum retard (as opposed to vacuum advance), and while I don't recall any Fiat DOHC engines using a vacuum retard, I could be wrong. The overall idea of course (for any engine) is to get the optimal timing advance under all engine conditions, through a combination of static timing, centrifugal advance, and vacuum advance or retard.

-Bryan

This is the dizzy I have installed:

https://autoricambi.us/collections/igni ... carbureted

31* of mechanical advance. Should be plenty with or without the vacuum.

My VW used to have a dizzy that had both vacuum advance and retard. Fun times. Now it has all that electronically with a timing map, even funner

[18Fiatsandcounting]

OK, so now I'm wondering if maybe you have too much advance at idle? But when the engine gets up to 3000 rpms or so, the advance is appropriate at that speed and so it runs fine? A long shot, I know, but I'm perplexed by your issue. As an aside, I once got my ignition timing way too far advanced, and while the engine would start, it ran the engine in reverse. Briefly, of course, with all sorts of stuff backfiring out of the carb...

-Bryan

[SteinOnkel]

I think what we will do is set the timing by ear (within reason of course) to achieve maximum idle speed w/o the drip, then back the idle speed off. Then set the mixture, reset idle speed, done.

That is the theory anyways. Let's see how that will clash with reality.

Yes, after 3000rpm everything is gucci.

[manoa matt]

If you don't already have it, there is a Fiat factory service manual for the carb that goes way above and beyond what is in the factory manual for the car itself. There are several on the bench adjustments that would likely help. Although the manual is for the 32ADFA, the adjustments and settings are good for the 34ADF too.

Send me an email if you need the manual: matt.scarton@gmail.com