Timing

[garion]

Ah yeah, that makes sense... My bad.

[toplessexpat]

@toplessexpat: yes, tdc #4. I'm considering making my own timing indicator and losing the cover. But I'm positive the tdc mark is right on. You also think I should go from 60 to 47 on the idle jet (change of 13) or 50 to 47 (drop by 3, which in my case means 57)??

Thanks guys. I really appreciate you all helping me figure this out!

Yep - I'd change the jetting....

Actually - the timing is pretty easy to do once you've highlighted the markings with some white-out

No worries on advice... Some is good, some is bad, all is helpful

[Fi8spider]

60 primary idle jet is a fair enough size for the engine you have.

I went back to your original post and you mention hesitation under 2500prm, a hesitation when tuning a carb relates to running too lean. So, either more fuel or less air is required in the atomisation of the mixture.
What contradicts this is that you have soot developing on the spark plugs.

A couple things: When you check plugs to see how they are running it's best is to give them a good run and then check them, don't let the car idle before you switch it off to check plugs.

What size primary and secondary main jets you have in the carb? Actually, using the Weber diagram you posted earlier as a guide are you able to get some sizes down on paper of all the brass to see what the comparison is between yours and a stock unit?

Getting this type of fine tuning spot on is considered an art form now days, very far removed from plugging your lap top and playing around with setting.

Also do not discount the possibility of it not being a carb problem yet, best get all your sizes down first and take it from there.

Cheers

[digitech]

As per Brad, a 60 Pri Idle Jet is too large - order a 47 and a 50 and see which you like the best. Quick and painless.

[vandor]

> I verified TDC is correct. I'm using the stock cover, I'd assume that the marks are accurate, maybe not??

In this case assuming is not good enough

> How advance should I be seeing per 1000 rpms?

You should see a fairly steady increase to max advance by ~3500 rpm.

> If I tune by ear, I end up with tons of advance timing and hard starting, but it still doesn't ping at high RPM's, and I can't see >how that's possible. Timed at 10btdc I'm missing on the low end, but she still loooooves the top end.

If it has the stock 8:1 compression ratio then this makes sense. With such a low CR it will not ping even if it is way advanced.
With the stock ignition timing of 0 degrees at idle it's a dog a lower rpm, but advancing the timing cures this.
For good performance one needs a distributor with ~22-26 degrees of centrifugal advance, like some of the later electronic distributors. There is too much centrifugal advance in the point distributor, so it's impossible to set it up for ideal advance at both low and high rpm.

[vandor]

Could the cams be swapped? Is that even possible? WOuld the car run if they were swapped?

Intake and exhaust cam profiles are identical. The only difference in the cams is that the exhaust has the distributor drive gear on it.

[Fi8spider]

The intake and exhaust cams have differing dowel position for the cam wheels.

[toplessexpat]

You have got the cam wheels on the right way around? Don't be insulted.. just checking... every now and then a brain fart creeps in! (Yes - I've done it...)

[majicwrench]

Less than 1 turn out on idle mix screw no big deal, assuming it idles well there. Too small of an idle jet will make the transition to full throttle stumble. Seldom will idle mix make plugs black, unless you are sitting letting it idle for long time then pulling plugs. And if it is too rich at idle screw shoud tell you, do you have screw set for smoothest idle?? IF you screw screw (sounds odd doesn't it) in does idle improve or degrade?? Folks mess too much w jets. That carb came from the factory w jets that would work well in 99% of situations that carb could be in, so if you have stock jets and it isn't working, odds are something else is wrong. Carb are built to compensate for engine size, as more air flows thru carb more fuel gets sucked thru as well. THus you do not need to change jets for larger engine. You DO need to change jets on wild build because of low vacuum, which will not allow the fuel to vaporze as well, thus some fuel always hanging on cylinder walls etc. You need a richer mixture just so enough fuel gets vaporized to support combustion.
Factory timing marks are seldom right on, but are close enough for everythig but acturatly setting cam timing. I see something about total advance "30-35" that is kinda a broad range. Total timing should be 36deg give or take a degree or two, and should be all in before 35oorpm. Have you tried stuffing a stock dist in??
And you can time ignition off of either #1 or #4, they are both TDC at some time.

[highdesertexplorer]

@Fi8spider: my carb is exactly like the diagram I posted

@vandor: I have high compression pistons. I don't know the actual ratio. I am using the stock distributor with an optical pickup installed. I will readjust my curve, and see about limiting the amount of advance. From what I've seen, any distributor upgrade will mean moving it to the block, and I don't want to do that. If there is one that will run off the cam, I'll see about getting one. But limiting max advance wouldn't really be that difficult.

@toplessexpat: no, they are not switched...I've verified more than once.

@majicwrench: according to weber, if it's less than 1.5 turns, the jet needs changed. Since I'm half of that, I'm definitely going to follow the manufacturers recommendation and change it. I am set to smoothest idle per the manual. I agree with you in that the carb is essentially able to compensate for engine size. But if a jet is too big, less air flow will not necessarily mean less fuel flow, especially after a certain point. Also the consensus seems to be that the idle circuit plays a big role in fuel delivery up to 3500rpm. If that's the case, my rich idle condition will have a profound impact on the low end...which is where I'm having all my problems. As mentioned above, it is the stock distributor, with an optical pickup. Ignition can be timed off 1 or 4, but when all marks line up, it should be firing #4...and that's how I'm set up.

Thanks again everybody. I'm getting some conflicting advice, but it's making me think and giving me different views to explore!

[phaetn]

Hi,

Sorry to glom-on, but I've a similar problem...

Me three. I've added to this post (I hope you don't mind!) so we're all on the same page.

In my case there's a stumble/miss/roughness under load at speed with gentle acceleration into the secondary, 3-4,000, full throttle acceleration either masks the issue or eliminates it.

I have similar symptoms, also on an 1800 with a 32/36 DFEV and Mark Allison's CompuTronix distributorless ignition. I can hold gentle throttle and it seems okay, but if I go close to 1/2 way (assuming when the mechanical secondary is coming in), also between 3-4000, I get a real stumble/miss/roughness, just like you, and the exhaust note really changes. If I mash the throttle I can sometimes get through it, other times not. I've only had the car a week so am still figuring out its characteristics.

I decided to dig into the carb and clean it out a bit and see what's what before fooling around with timing and checking valves.

I wrote down the various jet/air corrector sizes I found (second number) and how they vary from Weber specs (first number):

Primary Idle jet: .60mm .55 installed
Secondary Idle: .50mm .50 installed

Primary Air Corrector Jet: 1.65mm 180 installed
Secondary Air Corrector: 1.60mm 165 installed Edited for accuracy - see post below. Originally I had incorrectly indicated a 185 was intalled.

Primary Main Jet: 1.37mm 137 installed
Secondary Main: 1.40mm 140 installed

Soooo.... I looks like my Primary idle is a bit less than stock, but Brad and others have suggested this is actually preferred on an 1800. I'm wondering about the air correctors as mine seem way higher than stock. I wonder if that means I'm lean and fuel starving...

Plugs looked more brown than white, but it's always hard to tell with pics on the Interwebs...

This pic shows an old plug on the right with mixture settings the way they were when I bought the car, and where I'm at now with new plugs and adjusted mixture on the left.

The electric choke was not connected so the butterfly valves were fully open. I started the car and I manually moved the plates to see if they helped on a cold start and it just ran rough so I decided I don't really need them functioning. The PO probably only used the car in warmer weather and just didn't need the choke. It made me wonder, though, if my acceleration issues might be because the choke plates are somehow moving when they're not supposed to and restricting airflow. To test this, I threw on a nylock nut and some lock washers on the butterfly valve to secure it open. Tomorrow I'll take it for a test drive and see if it helped. My hopes aren't too high, given the similarity of symptoms with others here, but you never know.

Cheers,
phaetn

[Fi8spider]

Hi phaetn, jet sizes look fair enough, maybe swap the air correctors around though I wouldn't expect too much of a difference.

In this previous thread
http://www.fiatspider.com/f08/viewtopic ... 60#p206968
you had low compression in one of your cylinders, how did that all go? Did you sort that out?

Sorry to say but I feel that trying a fine tune on an engine down on compression in one pot maybe a waste of time. You gave the car a compression test yourself though I feel that taking up Marks suggestion of a leak down test as a good step forward.

[phaetn]

Thanks for the reply.

Haven't touched cylinder #1 and haven't tested compression myself, just had the mech do it. I am going to get a leak down tester though they are surprisingly hard to find around here, despite a lot of large automotive stores.

I agree that I'm always going to be chasing ghosts if one cylinder is low. That said, lots of people seem to be having the same acceleration issue with 32/36 DFEVs in about the same throttle range so I'm inclined to think it is about carb setup. lm48 seemed to have some success by forcing the second barrel to open earlier... <shrug>

Thanks again and cheers,
phaetn

UPDATE: 2014-04-19
Keeping the choke butterfly valves open didn't help. No surprise there.

What did help was going out on an expressway. For the first time since I've owned it, I took the car over about 55mph. Most of the driving I do is tooling around between 35 and 50. I'm thinking of taking a short trip to the country tomorrow (not far -- 15 mins away) so I wanted to see what it was like at speed but only for 4 or 5 minutes so as to not overheat or stress anything. If it's lean I definitely don't want to hole piston!!

While it did hesitate a bit when in third and merging, it was generally quite happy in fourth and fifth. Took it to 60, then 70, then cruised for a while between 75 and 80. Pushed it up to 90 mph indicated. There definitely were some flat spots at times with hesitation, but I just had to get it to the right zone and it was happy and in full song.

Right after getting off the freeway I decided to goose the throttle a few times at stoplights. It pulled cleanly and with more power than ever before. It would just surge in a way it hasn't for a week of city driving. After five minutes of slower driving, the hesitation came back.

Temps were always good (it's a cold day here at about 41F). Driving around it wouldn't go over 190, and was a bit cooler at freeway speed.

I wonder how it will react as we get to warmer temps... Maybe I just have to keep the car at higher revs more often. The thing is that it pulls with a nice growl, especially in fourth, when doing 40-50mph at somewhere around 3500rpm. If I'm in first or second at 3500 I tend to have my foot on the throttle more and that's when it stumbles...

Cheers,
phaetn

[phaetn]

Hi phaetn, jet sizes look fair enough, maybe swap the air correctors around though I wouldn't expect too much of a difference.

In this previous thread
http://www.fiatspider.com/f08/viewtopic ... 60#p206968
you had low compression in one of your cylinders, how did that all go? Did you sort that out?

Sorry to say but I feel that trying a fine tune on an engine down on compression in one pot maybe a waste of time. You gave the car a compression test yourself though I feel that taking up Marks suggestion of a leak down test as a good step forward.

I hope I'm not hijacking this thread -- it's all 32/36 DFEV related... I'll get to compression in a bit...

Today I swapped the air correctors around. Turns out I could see the engraved numbers better on a sunny day than I could previously in the dark of the garage with a hanging shop lamp. Initially it was a 180 air corrector on the primary circuit and a 165 on the secondary, not a 185 as I had indicated previously. This is actually somewhat consistent with the stock Weber spec where the primary is larger than the secondary (165 and 160, respectively), though not with as large a difference.

I swapped them around, thinking why not put the correct # on the primary and then see what happens. I had been getting some spit back through the carb (especially visible on the primary butterfly valve, it seemed) so I thought why not put on a smaller air corrector in case it was running lean, though I know this also affects the draw of fuel.

A test run initially seemed really positive. There wasn't the hesitation that there had been previously in any throttle position. It just pulled cleanly. Wow! So far so good! After about 10 minutes, and playing around in different gears, rpms, and throttle positions, pulling from stopped, mashing it at speed, etc. I stopped in a parking lot by the National Aviation Museum to check the idle mixture screw in case it needed adjusting with the new air correctors since I hadn't changed its position when I initially swapped them around (as the engine wasn't at full running temp yet). A couple of old gents that were volunteers came for a chat and one regaled me with his story of being on the German Autobahn in a Fiat 124 with a buddy in the 70s when he was stationed over there.

The engine was running the whole time; I didn't have to change the mixture screw much more than a 1/4 turn and then I headed home. I now noticed a slightly different sound from the pipe when letting off (a burble that wasn't there before) and even a slight hesitation. Darn it, it seemed so clean just 10 minutes beforehand! So I pulled over to another parking lot to check the screw again to set it back to where it was before and now the engine died as I put the clutch in.

Uh oh! While still coasting I let the clutch back out and it fired back up. Idle was now *very* rough and I had to give it gas and around 2500 rpm just to keep running. I could now hear a definite misfire. I was wondering if it might the electric choke that I had recently hooked up and if the butterfly for that was not fully opening or something. I opened the hood, pulled off the air filter and the choke valve was fine; I tried to play with mixture screw again and set it to where it was before but it remained very rough. Just by coincidence, at this very moment, Spiderdan happened to be driving by (not in his Spider yet) and he popped by to say hello as, seeing a dark blue Fiat round those parts, he thought it might be me. It was a nice to put a face to the name!

After he left I nursed it home, having to keep the throttle up to keep from stalling. There was a definite misfire throughout the lower end. I needed to hold a little gas to keep it at 1000 rpm, and it always wanted to drop to a stall; pulling the throttle knob or adjusting the idle screw so it would stay running run meant too high an RPM and I could still hear the miss. Before any of these changes the idle was always rock solid.

Sooooo. Okay - a misfire: check the plugs -- maybe one of them is fouled. I didn't want to pull the plugs with the block still hot in case I stripped a thread, so I waited a while by putting the air correctors back to the way they were. Still rough.

Once the engine was a bit cooler, but still very warm, I pulled the plugs, one by one, and I could see they were all white and chalky. I mean white. Egads!! Last week they had been a been a nice tan colour. Worried that with the engine so lean I might have overheated a piston (can't imagine I would have holed one as it would still run okayish at higher rpm) I decided to do my own compression check. With my tester, all of them came in at 120psi -- and this is a tester that had once been a little low on my motorbike, so I could see it being a bit higher than than. Most importantly, they were all even, and within an acceptable range. This contradicts what the mechanic told me a couple of weeks ago right before I bought the car about #1 being 20% or so low compared to the others (105 for #1, 130 for the others). shrug I have my own ocular proof that they're all even. I'm happy about that, anyway, as it means I didn't kill a piston and I guess I can hold off on a rebuild that I thought I might have to do sooner than later to change rings on #1.

Started it again and still the misfire and it just wants to die at idle. Disconnected the electric choke in case it or the shared wiring was somehow interfering with the CompuTronix igntion (though it shouldn't). Still rough.

Tomorrow I'll go and buy new plugs to see if that helps (I doubt it). Then I'll open up the carb again. I wonder if a bit of dirt or something somehow got into the primary circuit and is clogging the idle jet and interrupting fuel flow. Or maybe something is going on with the float.

The thing is, the idle was just fine even *after* I switched the air correctors around, was good even after a couple of stops at stop streets and one extended stop in a parking lot as I used the phone, and only became problematic after I went to check on the mixture screw. In fact it ran great, but I know from two strokes that sometimes engine seem the best right before they seize because they're so lean...

It was after the stop that something changed. I'm not sure if the white plugs are from the idling or from the run with switched air correctors. It seemed so much better after I made the intial change, that this is now really disappointing.

I'll take a look see again tomorrow, but it looks like I'm not taking it to work...

[majicwrench]

These things are notorious for pluggin the low speed/idle jet. Find it and clean it. I had one year I cleaned mine every week or more. Last year just cleaned it once. When it plugs, instant ratty/no idle and hesitation.
Don't bother changin your plugs. If a plug fouled, it would still idle, just rough.