To make a long story short a friend took his engine on a shop to rebuild it. The mechanic there supposed to overhaul it, put it on the car, did 500 meters or so and then a strange noises came!! Engine is opened and here we are. It is 126A5 from 500R, I took a look of it and I have a few questions since I want to help him locate all the needed spare parts he has to buy for proper repair. Is the Crankshaft same with the fiat 500 and fiat 126 or we have to find exactly the same type from a fiat 500R? We are looking for a good used one. Camshaft is also worn along with the crankcase which is going to be repaired with a new bushing, do you know the profile of this particular cam and since we are going to replace it can you suggest a faster profile for daily use since this is going to be pretty stock but if we can take a couple of horses why not? I noticed that the carburetor is 24 mm is this stock fiat 500R? I guess things will be much better with a 28 mm. The gearbox has the starter on the side as you can see on the picture, is this stock 500R gearbox or they have changed it with 126? Did the R had synchro gear box?
Technical Resurrecting a 594cc engine
- Thread starter gordinir8
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Technical Resurrecting a 594cc engine
Taking your questions in reverse order that is the correct place for the starter, same as the 126. As to wether the gearbox is synchro or not is an ongoing debate here and still no firm conclusion. The single biggest improvement in performance will be gained by switching to a 28IMB carb inline with the 594cc 126. This may require the inlet port on the head being opened up to 30mm diameter if it is still 26mm like the 499cc. Also what carb base does it have, photo? If you uprate the camshaft I would look for a 35/75 spec. Crankshafts are the same throughout the range of air cooled engines so a 500 or 126 will do the job. You need a specialist engine machine shop to examine the crank journals to see if they are within tolerances or will need a regrind. Guess you will need new bearings to suit also.
smart51
Established member
I'm not certain on the crank shaft. They're all the same stroke, so they could all be the same. Someone else will confirm. All the parts are readily available, including the crank and bearings. New parts are not much more expensive than good used ones.
The cam in the 500 is fairly mild. There are lots of options for you. I'd go for a 30/70 cam. It is an improvement over stock but still very tractable. It is often called a 540cc cam. There are 35/75 and 40/80 cams that give you a lot more top end at the expense of loosing power at "normal" engine speeds. I'd leave those to people who permanently drive like they're on fire.
The 24IMB carburettor was fitted to deliberately strangle the engine. Fitting the 28IMB releases the 5 BHP that was stolen from you. Be careful though. Almost all 28IMBs are jetted for a 652cc engine. You'll need to change the main jet, air corrector jet and probably the idle jet. They're a couple of quid each, so no problem.
My 500R doesn't have a synchro box. Some say theirs does. Whether a previous owner swapped theirs is up for debate.
The cam in the 500 is fairly mild. There are lots of options for you. I'd go for a 30/70 cam. It is an improvement over stock but still very tractable. It is often called a 540cc cam. There are 35/75 and 40/80 cams that give you a lot more top end at the expense of loosing power at "normal" engine speeds. I'd leave those to people who permanently drive like they're on fire.
The 24IMB carburettor was fitted to deliberately strangle the engine. Fitting the 28IMB releases the 5 BHP that was stolen from you. Be careful though. Almost all 28IMBs are jetted for a 652cc engine. You'll need to change the main jet, air corrector jet and probably the idle jet. They're a couple of quid each, so no problem.
My 500R doesn't have a synchro box. Some say theirs does. Whether a previous owner swapped theirs is up for debate.
Took a look around and found that I can put oversized crank bearings up to 04 so maybe we can keep the crank, it just had to go to a machine shops and clear it to see what is left, then we will take from there. I wonder if the cam can also be repaired, I guess I have to talk with the machine shop also. Cool about the carburettor although I don't want to mess with carburettor adjustments since this is not my engine. The carburettor inlet looked small to my eyes so I guess in a case of 28 rework has to be done first.
Thomas
Thomas
You can go to 0.8mm undersize on the crank journals if you need to. Would be interested to know the inlet port diameter on the head.