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My first New Guy Question (there will be more): As I said in my other post, I have a 1600 Spider from 1985/6 sort of. I don't know much of the history of this particular spider, but I'm pretty sure its been altered significantly from the original. Its got duel Webers :D and a Bosch points-style (single set of points/small rotor/centrifical advance) distributor :( .

Question 1: It backfires rather annoyingly during deceleration. I've set the dwell and timing (58 degrees [close enough] and on the M line at 5100 rpm) but still get the backfiring. Any suggestions on how to tweek this out?

a. would one of those electronic ignition kits (i.e. Performance Ignition or Ricambi) solve the problem (I've been trying to justify one anyway). Anybody with experience in these kits and recommendations on good ones/suppliers?

b. On my engine there is a hose that runs from the valve cover to the air filter box which I assume is Alfa's version of a PCV. There is also a thinner, roughly 1 foot long hose that comes out ot the same fitting on the valve cover and dangles into nothingness. Anyone know where this is supposed to go? I've plugged up the end because, well, it seemed like the right thing to do. Could it have anything to do with the backfiring (there is no vacume disc/attachment on the distributor)?
 

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My '76 Spider (SPICA) has the Performance Ignition system and I've been happy with it. The car still backfires occasionally, though.

The hose you describe as dangling into nothingness is supposed to do just that. I don't think plugging it is a good move.
 

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word of warning: mate of mine spent 6 months renovating an Alfeta saloon, it was back firing, it sent fuel air mix back up the intake chamber & promptly exploded, setting the engine bay on fire & eventually setting fire to the whole car.
 

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I had the same problem when I had my Webers on my 78' SPider. I couldn't get my Webers set correctly and I spent 2 years, 3 shops and tons of $$$ and still had te same backfiring issues. I sold the Webers and went back to Spica and took care of that problem. I went to Webers in the first place because my Spica went dead and I had a lead to a complete set of Webers for 1/4 of the price from new. I am not telling you to ditch your Webers, but something to think about before you spend a whole bunch of time and money like I did.

Keep us here at BB posted on your progress.
 

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In everyone would notice, Spider Ken is from Germany and obviously has some Euro version that's been modified by a previous owner (1985 model 1600cc?).

As for SPICA systems going dead . . . . it's interresting to note that almost all of the pumps sent back to Alfa in the early days as "inop" had nothing wrong with them.

Webers or FI, the issue is knowledge and methodical troubleshooting.
 

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My first thought on the backfiring is that the carbs aren't in sync and/or the throttle plates are not fully closing. Does the engine return to normal idle speed after revving or does it 'hang up' around 1200-1500 rpm?
The small vacuum hose goes on a fitting in the intake manifold for the #1 cylinder. The fitting is just above the distributor and points toward the radiator.
 

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I think my list to trouble shoot this one would be to ensure that on decel the throttle plates are closed, no tension in the throttle cable, center linkage not binding, carbs are in sync and no holes in either air filter, and no lean cylinders.

Best Regards,
John M
 

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Discussion Starter #8
Ken is from Germany and obviously has some Euro version that's been modified by a previous owner (1985 model 1600cc?).

If that isn't bad enough, it takes leaded gas - which isn't sold here anymore either, so that means lead substitute with every tank. Thanks for the suggestions, now I just have to go out and play around.
 

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Ken, don't worry about the leaded gas, actually, don't worry about running unleaded gas. These engines have been capable for years of running unleaded.

I'm not a carb expert, but is the Weber supposed to cut fuel at all during a decel?

Eric
 

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Our 69 1750 with FI did the same till i actually started lifting my foot off the throttle during decelleration.

next time it pops just make a mental note of whether your foot is actually resting on the pedal or not. I'll bet it is.

jf
 

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Discussion Starter #12 (Edited)
We have a tie for winner of the bragging rights (cue drumroll):

no holes in either air filter
John M.

The small vacuum hose goes on a fitting in the intake manifold for the #1 cylinder. The fitting is just above the distributor and points toward the radiator.
papajam

By sheer coincidence, my latest order from Spider Point was waiting for me when I got home yesterday. Included was a new air filter - original Italian with a sort of metal frame over the paper folds - much better than the one that was on there which looked like a cheap Fram knockoff which, by the way, happened to have a large rip between the paper folds. (One 40 cm cylindrical filter, not 2 like some of the others I've seen).

This morning with a cool engine I felt around and, buried in greasy crud and cleverly hidden behind and under the thermostat above the distributor and pointed toward the radiator, was the long sought after vacuum fitting. I would have never have found it on my own until I had to change the thermostat. I had pretty much given up the hose as a vestigal reminent of some earlier distributor or fuel system.

As a result of one, the other, but probably both of the above, the difference is astounding:cool: . I was even downshifting like crazy, I could't get the thing to backfire. I am so glad this worked because I would really like to avoid tinkering with the carbs (I believe it was Pat Bradon who said the best way to tune up carbs is to leave your hands off of them).

Thanks for the help!
 

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That's great news SpiderKen. Thanks for letting us know!
 

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turbolarespider said:
......but is the Weber supposed to cut fuel at all during a decel?
Eric
No, it doesn't. They will still provide fuel thru the idle circuit. Just one of the reasons that fuel injection is more fuel effiecient than carbs.
 

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I had a backfiring problem on steep hills, in downshifted gears, until I installed Bosch platinum +4 plugs. Backfiring completely disappeared. Yes, although webers are pretty much just jet\venturi properly and go, make sure your throttle plates are aligned, which you can do visually by taking the plugs out and looking down into the hole whilst pressing down on the throttle linkage (engine off of course) to make sure the plates appear simultaneously. Secondly make sure your needle and seats are in good shape and your floats properly setup. Then it's basically "forget about it." Try the plugs and keep a fire extinguisher in your car. Before I learned about keeping the needle and seats in good shape, I had gasoline pouring out one of my carbs, but luckily never caught on fire. It's really easy to do.
 

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Hey 69 1750 Spider,

that was a great tip about taking foot completely off petal. I back fire far less now! However my backfiring started after I supposedly fixed my timing. It appears maybe my TDC isn't true Top Dead Center any more... sheesh... cars... But thanks! the tip made an improvement for me!

Sarah.
 
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