Having wanted a Fiat 500 for more years than I care to think, and having hired one from Cotswold 500 earlier this year, I now definitely want to go ahead and get one. I want to use it as a daily driver (much to the shock and bemusement of my friends and relatives, especially as I have a Jag as my daily driver at the moment!) so I'd like to have an engine which can keep up with modern traffic, as well as giving me some fun if I find myself on a country lane. To this end I recently bought the engine Abarth 695 had for sale and I've decided to completely strip it down and rebuild it; partly to see if any parts need renewing/replacing, and partly because I've never done a full engine rebuild before and thought a small, 2 cylinder engine would be a good place to start. I mean, really, how hard can it be?

I've read, re-read, and then read again Bambino's thread on his 695 engine build which has given me a lot of enthusiasm and knowledge. It's a sticky - I recommend reading it if you're thinking of undertaking a similar engine build.

I'm going into this with very little mechanical experience, so I've got a couple of manuals and, most importantly, my dad to hand just in case... I'm hoping it's going to be a great learning experience (providing nothing goes catastrophically wrong!)

I realise I'm putting the cart before the horse, but as my garage has been temporarily taken over by my Dad's MGB, and because I don't have the cash at the moment, I've bought an engine and gearbox, but don't actually own a 500 (yet) to put them in! All in good time.

When I told my dad I'd bought the engine and gearbox he was concerned he wouldn't have enough room to work on his car (my garage is a slightly larger-than-normal single garage) until he saw it. He commented that he'd worked on larger motorcycle engines!

We managed to get most of the engine stripped down in an afternoon. It took a little longer we'd hoped, mainly because the sump plugs were well and truly stuck in place, and I was a bit reluctant to go at them with my impact wrench. To drain the oil out I had to remove the dipstick and then very slowly tip the engine onto its side to remove all the oil. The rest of the engine came apart without too much hassle. I spent a lot of time sorting all the parts into various containers, labelling everything, and photographing every stage, so at least I'll have a fighting chance when I come to rebuild it.

My plan is to rebuild the engine with some slight alterations. The engine crankcase has already been rebored and had larger cylinders and pistons fitted. Unfortunately I don't have a micrometer or a pair of vernier callipers to accurately measure the bore of the cylinders. I *think* they are 79.5mm, but I might take them along to a local engineering firm to have them accurately measured (or buy a set of digital callipers). Abarth 695 measured the stroke of the pistons (something I should have done before I dismantled the engine - you live and learn) and got a measurement of around 70-71mm. Looking at the manuals, the engine has a stock stroke of 70mm, so I assume that's what it still is.

Having taken the sump off the crankcase, it seems to be a 3.5 litre sump. I filled it to the level with water, and it took 3.5 litres. I was working in London last week so I called into R Proietti (if nothing else just to ogle the bambinis) and bought an engine gasket set. They mentioned that if you have an alloy sump that, instead of fitting the sump gasket, you should refit the sump with silicon seal. I noticed my sump has silicon in place of a sump when I removed it and wondered if that is how it should be fitted? Anyone else have experience of this, or should I use the gasket?

Abarth 695 fitted the engine with a petronix magnetic electronic ignition system and coil, so this will definitely be staying on the engine.

One thing I'm not sure of is what cam is fitted. I found some markings on the cam, but as I've no idea who originally machined it, I don't think I'm going to work out what they mean. I'll take it, along with the other parts, to the engineering firm to see if they can work out what it is. I'm hoping it's something like a 43/73 or a 40/80.

The head is a twin port Panda 30 head, with a Weber 30 DIC carburettor. Before buying the engine I'd already sourced a Dellorto FZD 32/28 carb from Italy, so I plan to replace the head and carb with a standard 126 head (with 35mm intake valves fitted) and the Dellorto carb. I'll need to source some original tinware (fan and thermostat housing), as the tinware on the engine has been modified to accomodate the Panda head. As the tinware can be bought in the UK from a number of suppliers as either new, reconditioned, or 2nd hand, this shouldn't be too much of an issue.

I'm selling the Panda head if anyone is interested. It comes with 35mm inlet valves already fitted.

One thing I didn't know until this week was how the displacement of an engine is calculated. I'll probably be teaching grandma how to suck eggs by posting this here, but someone may find it useful.
The following was copied from Wikipedia:

Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre (TDC) to bottom dead centre (BDC). It is commonly specified in cubic centimetres (cc).

The bore (not me, the engine bore!) is the diameter of one of the cylinders.
The stroke is the distance one of the pistons travels from BDC to TDC.

Displacement (in cc): pi/4 x bore x bore x stroke x no. of cylinders (if you want to calculate the displacement in cubic inches, rather than cubic centimetres, simply convert your measurements from metric to imperial)

To calculate the displacement of a Fiat 500/126 engine, the following is true:

Stroke: 70mm (7cm)
Number of cylinders: 2
Bore: for a standard 500 engine it's 67.4mm (6.74cm). For a standard 126 (650cc) engine it's 73.5mm (7.35cm). For my engine it's 79.5mm (7.95cm). By plugging these figures into the formula above we get:

Displacement: 10.9958 x bore x bore

500 engine: 499.5
126 engine: 594.0
My engine: 694.9

You should see the way my wife's face lights up with enthusiasm and interest when I explain stuff like this to her

So based on the measurements, the engine should definitely be, on paper at least, a 695. If I bolt on some parts with Abarth stamped on them, surely this makes it an Abarth 695?

If you're planning on dismantling a 500/126 engine, definitely make sure you've got a 13mm spanner and socket to hand. Almost everything on the engine seems to be held in place with 13mm bolts or nuts!

As I don't have a car yet to bolt the engine and gearbox into once it's complete, I'd like to build a dolly to set the engine up on and run it in a bit. I've just been on a welding course and bought myself a MIG welder, so I can see a bit of an A-Team project coming on. I saw this on youtube


I then found an abandoned shopping trolley close to my house which I've *acquired*. I love it when a plan comes together. There are many bambinos, a few frankenbinis, but I think this will be the World's first and only... shoppingbini! An Abarth 695 shoppingbini no less

Hi Matt,

Great thread, lovely to see my old parts being looked after so well

Keep us posted as I am as much curious as you are about the cam.

P.S. I found the engine mount spring, it had rolled underneath the car ( I am on my way up this Friday to Newcastle to watch Brazil at the Olympics so could meet up on the m1 to drop it off). Pm me if you can meet me on the way.

Again great start to a thread keep us posted.

Alain

Great work Matt - and so neat to boot.

I'm glad you enjoyed the engine rebuild thread - I had a great time playing with that little motor - and I'll be watching with great interest as your engine comes together.

I also may be interested in the Panda head, tin ware +/- DIC if they are up for sale, though I think that the postage would cripple me.

Kind regards,
Chris

PS: Regarding the silicone treatment on the sump. I've heard about this also but when I assembled my alloy sump to the alloy crankcase I used a standard cork gasket and was just very careful torquing up the bolts. One of my other cars is an old Alfa (alloy sump, crankcase and just about everything else) and it uses a standard cork gasket with no leakage problems. I'd be interested in other opinions as well.

Thanks for the support guys!

I've been asking around as to which parts should be renewed/replaced as standard when rebuilding the engine. So far the list is:

- all gaskets
- both crank bearings
- valve guides
- piston rings
- big end shells
- cam followers
- oil pump
- timing chain

I also thought I'd renew the rubbers for the push rod tubes. Bambino, I notice you replaced your push rod tubes with the aluminium push rod tubes on the Fiat 500 Ricambi site. I was wondering if I need these too?

Are there any parts which I've missed from my list, or are there any parts on the list which don't need replacing?

I'll also probably replace a lot of the bolts and washers just be on the safe side.

Having done some more research on fitting Panda 30 heads to 126 engines, I found out that two of the cylinder head studs are shorter than standard studs to accommodate the head (which can be seen in the photo of the crankcase). This means I'll need to replace those two studs with the normal length studs. Not sure where to source these from, so I'll have to do some more digging. I also found that the push rod tubes fitted to my engine are shorter than the standard push rod tubes, so these will need to be ordered as well. I'll keep hold of the existing studs and push rod tubes so I can bundle them in with the head if someone buys it. Hopefully everything else in the engine is standard, so I don't end up with a huge parts list to order! I assume the push rods are a standard length - does anyone know the length of the push rods from a 126 engine?

Matt,

To answer both of your questions -

My old pushrod tubes were dented, bent and one was split and clumsily repaired. The top and bottom seals were also shot and had been sealed with what looked like some sort of mastik. The tubes on the 126 engine that I bought were not much better so I replaced them all with a nice set of spring-loaded alloy ones.

As to your second question, if you are using the standard heads, the 652cc 126 tubes and pushrods are the same length as the 499cc 500 ones and they all the same length.

You should be able to get crankcase studs from most Fiat parts dealers.

Chris

Interesting project and I hope that you get the car to fit the engine. I have not seen a crankcase with that boss above the oil light switch to take a pressure sender before. I looked to see if I could see the engine number but it looks as if that area has been ground away. The timing chain looks more like a 126 Bis as it has no automatic tensioners like the aircooled engines. Also no locking tab washers on the camshaft sprocket hex screws. Are there countersunk shakeproof washers on those two front main bearing csk screws ?

There are a few odd things about that engine - I must admit, I hadn't looked that closely until now.

I've posted a couple of photos of mine complete with an installed and tested, but as yet unconnected, oil pressure gauge sensor.

Toshi is correct -

There should be shakeproof washers under the Phillips-head countersunk bolts and hefty spring washers under the hex-head bolts. It's also not a bad idea to loctite the threads as well.

The camshaft sprocket bolts should be secured with lock tabs - as should the flywheel at the other end of the crankshaft and the hollow bolt on the front pulley. From memory, the other places that there are lock tabs are on the big end bearing caps.

The self tensioners can be seen on the timing chain.

Chris

Also the fine timing gradations are missing from the crankcase cover, though I'm not sure how important this is.

Chris

Thanks for all the info guys. I'm going to order a new timing chain as part of the bits I'll get to refresh the engine. Do you know if the shake proof washers and spring washers are available to order?
I'll get a photo of the engine number - I definitely remember seeing it.

The Hobbler (Tom) showed me these pushrod tubes which look pretty nifty:

http://www.megabug.co.uk/vw-empi-adjustable-pushrod-tubes-set-of-8-up-to-1600cc-1093-p.asp

They can be seen in this engine build:



Cheers,
Matt

Matt,
You should be able to get the washers pretty much anywhere.
I like the you tube videos - particularly the next one in the series where they run the engine in the car on a dyno. Like my motor, it is possible to get them balanced so that they don't try to jump out of the engine bay when they are running.
Chris

Chris,

I plan on getting the engine balanced by my local engineering firm. Is there any benefit in having the flywheel lightened, or should I just stick to having it balanced?

I know you can't get a manifold to bolt the Dellorto to the Panda head. I was considering producing a technical drawing and getting a company to machine a manifold from billet aluminium. Can anyone see a benefit from this, or should I just use a 126 head? As I already have the Panda head and it's fitted with 35mm intake valves, it seems to make sense to keep it.

Matt

Hi Matt;

The main advantage of lightening the flywheel is that a lighter flywheel allows the engine to 'pick-up' quicker--the downside is that you do have to make sure it's balanced properly as the flywheel then lacks some dampening mass--as you are going to use it as an 'everyday' car, I would be tempted to weigh your flywheel as-is, and then have it lightened to 1/2 way between yours and the 2.7 kilo f/wheel. Whatever you do, have it done by a reliable tuning/engine building firm and all the best.

Thanks for the advice Tom. There's a local engine building firm which has a very good reputation so I'll see what they can do.

Matt,

I didn't change the weight of my flywheel as I wasn't building a racing engine, though I agree with the hobbling one (?Tom) in that a little lightening wouldn't do any harm as long as it is done correctly and the flywheel is properly balanced when finished.

My reasoning was that since flywheels act as a store of rotational energy, a relatively heavy one does take some energy to get it moving but once rotating, the angular momentum will act to smooth the inherent lumpiness of a two cylinder engine.

Either way, my engine starts, revs and runs smoothly. You could say a gold medal performance (that would be Australia's 3rd ) - gotta be happy with that.

As to the carby, my advice was that the Dellorto FZD is the best carby for these motors and that there is little advantage for a mildy tuned engine in going for a twin port head. Get the 126 inlet port machined to match the carby, fit slightly larger intake valves and your most of the way there.

For some extra opinion, have a read here

http://club126uk.co.uk/smf/index.php?topic=4472.0

and here

http://club126uk.co.uk/smf/index.php?topic=5656.0

Chris

Thanks Chris. My thought was I could utilise the Panda head rather than trying to sell it and source a 126 head. If I won't see any advantage in using the Panda head with the Dellorto carb, I'll sell the head.

Matt