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Old 14-08-2011   #1
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Fiat 850 Project

Hi all,

after reading the story of Ditchdigger's project 850 sedan on retrorides, it's got me enthusiastic about getting my 850 up to scratch again. It's been sitting idle in the garage for the last 18 months, mainly due to a very crunchy second gear which makes very ugly grinding noises when changing down.

There's quite a bit of scope for making it more enjoyable to drive, most of the suspension rubbers are perished, ride is pretty harsh, and a lot of bump steer.

Things done over the past 20 years of owning the car (OMG it's been a long time!)

Engine: Rebuilt when first got the car. Std Fiat 850 sport pistons, Total Seal gapless rings. 25/65 reground camshaft. Weber 28/36 DCD carburettor. Std extractor header with straight through muffler.
Suspension: Reversed front main spring - too low!
Body: Repainted 10 years ago.
Interior: Roof lining and rear parcel tray retrimmed.

Cheers.
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Old 14-08-2011   #2
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Re: Fiat 850 Project

Before fixing the gearbox issue, needed to get the car mobile. Symptoms were extremely hard starting, and running rough between 2000 and 5000 rpm.

Pulled the Ducellier distributor apart, and reshimmed the shaft as it had several millimetres of up and down play, thinking that it was causing issues for the electronic ignition sensor. Probably 8mm worth of shims in total. Put in a couple of copper washers too, thinking they may wear instead of the aluminium distributor housing. Also changed over the distributor cap and rotor as they were showing signs of wear. I have a preference for the Ducellier distributor over the Marelli one, it seems to have less slop in the
bearings. The cap also seems to have a more positive engagement when locked down.

Built a test jig with spark plugs, coil and mount for distributor. After hooking up power and spinning the distributor shaft with a drill, found one of spark plugs was sparking erratically - ah ha! Replaced the dodgy plug, and put everything back on the car.

That did not fix the problem with bad running. Hmmmm, on to next step.

Pulled the carburettor apart checking for blockages, and reassembled. All nice and clean again.

Nope - still no good. Running out of ideas. After some head scratching and reading through a few articles, thought it could be a vacuum leak. But I'd already replaced the manifold gasket as well as carburettor gasket. Where else could there be a leak? Finally figured out that the port which I'd taken as a EGR port, was actually a take off for a vacuum advance distributor.

Doh! It was connected to the air cleaner, providing ready access for air to bypass the primary barrel in the carburettor. Weird thing is that the car has been running OK in this configuration for several years. Quick scrummage around in the garage for a bit of rubber to block the port.

Finally, with the battery charger switched to maximum boost, leads connected to the car, looking like a garage version of Dr Frankenstein Lab - THERE WAS LIFE. Albeit farting,spluttering and popping, there was the familiar 850 sound missing for so long. While the car was starting at least, it was still misfiring, with nice flames shooting out of the exhaust. Back to the drawing board.

Last roll of the dice. The car has been sitting around for more than a year, maybe the petrol is off? Is this just a urban myth? According to some articles on the web, petrol can oxidize in the tank over time, and volatiles evaporate off. Jacked up the car, unscrewed the tank drain hole and dumped the petrol. Ran the electric pump, to check the tank was empty, and noticed petrol kept circulating through, with nothing coming out of the bottom drain hole. WTF? There must be a pot or baffled area which the pickup sits in. Took off the return line and pumped the tank empty. Also removed the main jets to empty the bowl in the carburettor. Out with the old, in with the new - some of Mrs Shell's best brew. Unfortunately it was also 11:30pm, so thinking of the neighbours had to wait till the next morning.

Woo hoo - problem solved. Starts nicely, and the misfire is gone!

Next job, do some tuning of the jets to stop the plugs sooting up, eradicate a little hestitation when flooring the throttle, and maybe some better economy as a side effect.
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Old 30-08-2011   #3
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Re: Fiat 850 Project

Glad to hear you got your 850 sorted out. Does your car have the 843 or the 903 engine in it?

I have a 71 Sport Spider with the 903 that I have been working on. I am almost ready to start the rebuilding process on the engine.
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Old 31-08-2011   #4
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Re: Fiat 850 Project

Hi,

All 903 goodness, standard for the sport coupe. By far the most popular version of the 850 here in Aus. Unfortunately we did not get the spider here in Aus.

Cheers.
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Old 26-12-2011   #5
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Re: Fiat 850 Project

Hi All
Just joined fiat forum
I have a 1970 s2 sport coupe been unde tarp 15years
Can anyone supply a basic wiring diagram just to turn engine over bypassing everthing else fear many gremlins and earth problems
Many Thanks In advance
Peter
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Old 23-01-2012   #6
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Re: Fiat 850 Project

Quote Originally Posted by Peter Tigani View Post
Hi All
Just joined fiat forum
I have a 1970 s2 sport coupe been unde tarp 15years
Can anyone supply a basic wiring diagram just to turn engine over bypassing everthing else fear many gremlins and earth problems
Many Thanks In advance
Peter
No diagram needed. Simply disconnect the coil from the wiring harness and wire it to your battery. All of the other wires are on the engine. This will isolate the engine from any harness issues. You can jump the starter solenoid directly, no key needed.

Yeah, it was easy to hot wire old cars. Power the coil, jump the starter and go.
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Old 23-01-2012   #7
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Re: Fiat 850 Project

I LOVE this thread! My 850 Sport coupe was my favorite 850 variant. I owned the Sedan and spider as well. The coupe wasn't that popular in the states, it's hard to find one now. It was the best proportioned of all the old Fiats in my opinion.
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Old 13-02-2012   #8
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Re: Fiat 850 Project

How time flies - already February again, and have not had time to work on the car. Fortunately it was Autobella concourse run by the Fiat Car Club of Victoria last weekend, which prompted getting the car presentable with a big wash and polish session

Since the last post have been re-organizing the garage so can do some spraying and work on the car without falling over old furniture and kids toys cluttering up the garage. Unfortunately during the cleanup one of the old tables hanging up in the roof fell on the fender, causing a 10 centimeter dent - think of one of Bruce Lees best karate chops with the edge of his hand on that lovely curve near the 850's head lights. Was. Not. Happy.

Anyway, prior to washing, knocked out the worst of the dent with a hammer and dolly, and apart from cracks in the paint at the end of the dent, it came up reasonably well.

Tips for the day: make sure that the surface of the hammer and dolly are as smooth as possible. I used a orbital palm sander to make sure that the surface and edges were as flat and smooth as possible. Ideally use a buffing machine to get a mirror finish. In this case no paint was knocked off, even though pounded during the repair.

On the day of the concourse folded the kids into the back seat (and they are not short), wife and picnic lunch, and headed off. Amazing that such a small car fits four, and great to be back on the road, albeit with a fair amount of gear crunching and grinding with the dodgy second gear syncro.

Good turn up of 850's at Autobella, more so than the previous couple of years, they must be breeding. Two sedans and four s2 coupes, but no spiders. At this rate there will be more 850's turning up than 124's in a couple of years!
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Old 13-02-2012   #9
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Re: Fiat 850 Project

Quote Originally Posted by Peter Tigani View Post
Hi All
Just joined fiat forum
I have a 1970 s2 sport coupe been unde tarp 15years
Can anyone supply a basic wiring diagram just to turn engine over bypassing everthing else fear many gremlins and earth problems
Many Thanks In advance
Peter
Hi Peter,
please PM should you require additional details regarding the wiring diagrams.

If I can make a suggestion:
Check the fuel lines, and the rubber sleeve connecting the petrol filling pipe to the tank (about 2 inch diameter). Good candidates for starting an engine fire after a long layup.

Cheers, John
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Old 13-02-2012   #10
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Re: Fiat 850 Project

Quote Originally Posted by stanz View Post
I LOVE this thread! My 850 Sport coupe was my favorite 850 variant. I owned the Sedan and spider as well. The coupe wasn't that popular in the states, it's hard to find one now. It was the best proportioned of all the old Fiats in my opinion.
good 850's are getting harder to find here too. Used to see some old folk pottering around in the wee cars, heading off to the shops and the lawn bowling greens. Reckon that about 10 years ago a lot of 850's were sent to the metal recyclers, or dismembered for parts due to propensity for rusting. The ones which are left are probably in the hands of enthusiasts.

Only had one sedan in my hands, but it had been brutalized by a past owner. One of the fenders had been roughly replaced with sheet metal. Alas it had to be consigned to the bin.

Fiat had the styling spot on with their coupes in the late sixties, with 850 and 124. Reckon a 850 s2 coupe and 124 AC coupe would make a great pair in anyone's garage. Shame the spider never made it to Aus.
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Old 24-02-2012   #11
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Re: Fiat 850 Project

Jayarr,

I'm trying to figure out how much tire I can stuff into my Coupe and I noticed you are running a large tire(tyre) in the rear. Can you tell me what you are running front and rear?

Thanks,
Stan in MA
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Old 24-02-2012   #12
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Re: Fiat 850 Project

Hi,
Assuming standard offset wheels, and no flares
185x60x13 on 5.5 = great on the track or fanging around on suburban streets (all round) doing a lot of revs at 60 mph. More than enough tyre to irritate other people in exotics through the twisties.
175x70x13 on 5.5 = good compromise between highway running and suburbs.

Have seen people running 205x13 on rear. I suspect that this is probably over tyred.

Think that finding good quality tyres on 14 inch rim is going to be difficult. Paradoxically seems to be better tyre choices with 13's. May not be as much of as issue in the US.

Cheers, John

175 width is about the most you can fit in a standard spare wheel well at the front.
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Old 24-02-2012   #13
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Re: Fiat 850 Project

So, you are running 175/70 in the front?

I'm hoping to fit 185/75 in the rear to cut down the revs at highway speeds.

thanks for the info, these are the wheels I will be running. They're from a Lancia Beta:

http://imageshack.us/photo/my-images...50coupe99.jpg/


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Last edited by stanz; 24-02-2012 at 12:57. Reason: more info
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Old 25-02-2012   #14
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Re: Fiat 850 Project

Sorry, did not really answer your question

Have had 185x60 all round, and separately run 175x70 all round. No issues with clearance.

Reckon 185x75 a comparatively big tyre. Really don't know how you would go.

Think the Lancia rims are 14" inch. Friend had them on a 124, and had to machine the centre bore in order to get them on the hubs. Given they are or a front wheel drive, they may have too much offset, and may rub on the front inner wheel arch approaching full lock.

cheers, John
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Old 25-02-2012   #15
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Re: Fiat 850 Project

The wheels have 12mm more offset I figure I'll need to run spacers up front to stop them from rubbing.

I've been using the following two websites to go over all the tire/spacer options:
http://www.1010tires.com/TireSizeCal...?action=submit

http://www.willtheyfit.com/

Thanks for the information, every little bit helps me. The 185/75 14 may be too much of a difference for my clutch to handle on launches, around 12% over the stock 145/80 13.

Quote Originally Posted by Jayarr View Post
Think the Lancia rims are 14" inch. Friend had them on a 124, and had to machine the centre bore in order to get them on the hubs. Given they are or a front wheel drive, they may have too much offset, and may rub on the front inner wheel arch approaching full lock.

cheers, John
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