Fiat 850 Coupe Engine Query

DJD176

DJD176

Low Mileage
Hi there,

Newbie here, I have some questions about my Fiat 850 coupe (series 1 - 1965).

It looks like the engine has been changed from the original at some point in its history. The current bottom end/block has the same model number (100GC000) so it is the same type. However the cylinder head from what I can gather is from an A112 Abarth 70HP.

I'm just wondering if anyone knows if this represents an issue for instance:

Is this a good/bad thing i.e. good upgrade or not / wont make much difference?

Should this give more power?

I'm running the standard DIC1 carburettor, does this need to be changed for the Abarth one for optimum performance?

Anyone else running a similar setup?

Many Thanks.
 
JD, the cylinder spacing on the 843 cc (your block) is different from the 903/ A112. How do you know what you have is the A112? Photos would be helpful.
Good Luck
 
Hi, I'm only going off the numbers on the cylinder head below where the exhaust manifold fits.

As far as i can tell it says A112AB.2C0 / 4388297

When i did a search online i found a site that had rebuilt an A112 Abarth and the cylinder head numbers matched?


Attached image is of that engine not mine!

Thanks.
 

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DJD176 said:
Hi, I'm only going off the numbers on the cylinder head below where the exhaust manifold fits.

As far as i can tell it says A112AB.2C0 / 4388297

When i did a search online i found a site that had rebuilt an A112 Abarth and the cylinder head numbers matched?


Attached image is of that engine not mine!

Thanks.
Click to expand...
People can say whatever they want in an advert to try and bring in a buyer ... but that block isn't an A112 70hp 1049cc engine ... the A112 also came as a basic 903cc engine too

the 1050 "abarth" head is this number
www.ebay.it

Testata Motore A112 Abarth 70 HP COD. Fiat A112BB.1C.0 4467173 | eBay

Le migliori offerte per Testata Motore A112 Abarth 70 HP COD. Fiat A112BB.1C.0 4467173 sono su eBay ✓ Confronta prezzi e caratteristiche di prodotti nuovi e usati ✓ Molti articoli con consegna gratis!
www.ebay.it
and has this combustion chamber shape when fitted to a 67.2mm bore

looks like you have a later model 903 head ontop of your 843

SteveC
 
Hi, Sorry these are the only ones i have to hand at the moment, not sure if they're any help? first one shows engine when i first got the car a few years back, second once i'd done quite a bit of work sorting stuff out, last two of engine and cylinder head numbers.
 

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fiatfactory said:
People can say whatever they want in an advert to try and bring in a buyer ... but that block isn't an A112 70hp 1049cc engine ... the A112 also came as a basic 903cc engine too

looks like you have a later model 903 head ontop of your 843
Click to expand...
Don't forget there's also the Series 1 Abarth A112 engine that also used the "100GL" cast block, It had a 65mm bore & 74mm stroke. I don't recall the head casting number on that one. A lot of people get this engine confused with the 1050, they just assume "Abarth A112" equals the 1049cc engine. Best way to verify is to look at the ID numbers that are STAMPED into the front face of the block.
 
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I'm back home now so could try and take some better photos of anything specific if needed? Attached one of car itself if anyone's interested?
 

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dnudelman said:
check if the water pump has 3 bolts or 4 where it meets the block. 3 = 843, 4 = 903
Click to expand...
He already stated his engine block has the "100GC000" stamping on it, indicating it's an 843cc Coupe block. The photos he provided show this, as well it having the correct "100G" casting on the exhaust side of the block.

Screenshot_20230928-013857~3.png

Screenshot_20230928-041532~2.png
 
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DJD176 said:
I'm running the standard DIC1 carburettor, does this need to be changed for the Abarth one for optimum performance?
Click to expand...
The carb shown in your top 2 engine photos is not the standard 2-barrel Weber 30DIC for an 850 Coupe, it's a 1-barrel Weber 30ICF. This carb, along with the intake manifold & air filter housing shown are for an 850 Sedan engine, not a Coupe. If you're wanting better performance, you'll want to use a 30DIC, along with its matching intake manifold & air filter housing.
 
Thanks everyone for your help / comments much appreciated.

Jeff, the car originally came with a Dell'orto FRD30 carb fitted (photo attached from way back!) attached to the air cleaner with electrical tape! this is whats shown on the first engine bay photo. I replaced this with a rebuilt Weber DIC1 carb and inlet manifold shown in engine bay photo 2 but you cant see it properly as it is covered by the large air filter.

With regards to the air filter i always thought this was the correct original setup? I've attached a photo that i took before i shot blasted and painted it showing it has the correct mounting for the double barrel carb? I've also seen other coupes using this cleaner in the UK?

Thanks.
 

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DJD176 said:
With regards to the air filter i always thought this was the correct original setup? I've attached a photo that i took before i shot blasted and painted it showing it has the correct mounting for the double barrel carb? I've also seen other coupes using this cleaner in the UK?
Click to expand...
The air cleaner you have is from an 850 Special (Sedan), which shared the 30DIC. The Coupe/Spider unit is similar, but does not have the warm air intake on the side & does not attach to the exhaust manifold studs..
 
Ah right! Thanks for the info, not surprising its incorrect tbh, the car was a bit of a mish mash of all sorts of parts!
 
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So going back to the cylinder head, from what fiatfactory / SteveC says we can determine it's not a 70hp Abarth one as I thought! I've checked and the number doesn't seem to match the earlier 58hp Abarth one either, so just looks like its a standard later head that's been put on at some point as fiatfactory / SteveC said. Should of known it was too good to be true! :rolleyes: 😅

Would there be any advantage of going back to the head as supplied originally if I can find one or would that be just in effect swapping like for like and a waste of time? The reason I ask is I think the engine / head is going to need some work in the not to distant future so that could be a good time to swap over to something else if necessary.

Sorry for all the questions, this is my first 'classic' car and my knowledge is only basic.

Many Thanks.
 
You photos show a car in pretty decent cosmetic shape. Does it run and drive in its current condition? If so, and if it was my car, I would move on to evaluating the brakes, the suspension and deal with engine mods when everything else is sorted out. You are missing the floor pans under the engine. The A112 Abarth motors have a different displacement, cam profile, compression and carburation than what you have. Adding a few bits, like a cylinder head is not going to add anything to your package.

As to engine work, why? Have you done a compression test? Does it appear to burn oil?
 
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