Technical 500L Engine build parts recommendations

[cdatte]

Rebuilding my 550L which has the 126 73.5 mm X 70mm engine
wanted to get some recommendations for some upgrades to replacement parts for pistons, valves, cam.

Been online and can get oversized stock pistons but haven't seen anything else like higher compression pistons.

There seems to be either a stock cam or the 40/80 cam but that's all I've been able to find and 40/80 recommends a 10:1 compression but haven't found those pistons yet.

I have seen a couple of valve variants with friends engines but haven't seen them online other than stock ones

with a 2 main bearing crank, I didn't want to do too much

thanks

 

[the hobbler]

My advice would be to contact 'Mr Fiat'. they are the main supplier for (classic) Fiat 500 parts in the USofA. They are based in Atlanta and have a fairly comprehensive catalogue of parts. They should be able to advise you, sell you the parts you require and possibly put you in contact with other 500 owners in California. The other way is to work your way through the European suppliers who have a massive array of parts available. My own engine is a Fiat 126 (652cc, same as yours) engine with bigger inlet valves, a ported head (and exhaust elbows), a 35/75/75/35 cam, a sports exhaust, 500 flywheel (4-1/2lbs lighter), copper head-gasket, re-jetted carb, 3-1/2litre alloy sump (essential if you are tuning the engine) all carefully put together. The result is a strong engine that will cruise at 60 and pull a shade under 80mph wack-out. But, before you start throwing parts at the engine, try and meet a couple of owners, share a pint with them and get a feel for the project; alternatively, just keep asking questions on the Forum. All the best with whatever you do and welcome to the forum.

 

[cdatte]

doing a similar build, done several engines but usually 4's & 8's

mine has the 73.5 mm bore
what size intakes do you have ?
I've seen the stainless abarth valves, what kind of valves did you use ?

was curious on the flywheel as I didn't want to make it too light.

yep, I did get run over with euro parts houses, trying to stay away from Chinese parts as I have a few mg's and they didn't hold up and had to do them all over again

thanks

 

[the hobbler]

Your engine is an early '595cc' engine, with almost identical dimensions to the 'Abarth 595' specs. It has 31mm inlet valves and 28mm exhaust valves. I would not fit any larger than 34mm inlet valves and leave the exhaust at 28mm. The optimum ratio between inlet and exhaust valves is between .78% and .82%---so if your inlet valves are 34mm the ratio of .82% gives you an exhaust size of 27.88mm! Middle Barton Garage (in England) sell 34mm inlet valves. Their gear is good (bought my car off them) and they know what they are talking about when it comes to tuning. make sure you get new valve collets with the valves!
If you cannot get hold of a '500' flywheel, I would lighten the '126' flywheel by no more than about 2kg (4-1/2lb). If you CAN get hold of a '500' flywheel, just have it VERY LIGHTLY skimmed to ensure a fair, flat surface. If you are using the car as a 'daily runner' you want smoothness rather that absolute (relatively!) power. If you can get the complete crank assembly--crank/rods/pistons/flywheel/oil thrower/front pulley balanced, so much the better.
If you want to contact me direct, feel free to do so.