Try to locate a Renault 5 (1985 onwards), 9 or 11 with a C2J engine, that's the 68/72 bhp version you're looking for. Depending on car model (R5 vs. R9/11), the newer 68 bhp can wear code "C2J-768" or "C2J-700", the older 72 bhp is code "C2J-717". These codes are from Renault Finland's lists and might differ for other countries. But as long as the prefix is C2J (and the carburettor a 2-bbl Weber) you should have at least 68 bhp.
The C2J is basically the same engine as your C1J, the only internal difference is the camshaft. Crankshaft, pistons, valve gear, cylinder head etc are identical.
To perform the "upgrade" you'll need the following parts from a C2J engine:
- Weber 32 (DRTM?) carburettor
- alloy intake manifold + cast iron exhaust manifold (watch out for cracked ones)
- air filter box
- distributor
- ignition ECU
- flywheel
- crankshaft position magnetic sensor (aka TDC sensor)
- camshaft + followers
That should do it. Make sure you take all related vacuum hoses, carburettor linkages etc. that differ from your C1J engine. Taking these from a donor car are usually included in the price of the other parts (unless the scrapyard proprietor's incredibly greedy...), but getting them new afterwards from Renault can cost a hell of a lot money.
Actually you might want (/need) to buy the entire engine, but in my experience these old engines shouldn't be too expensive, even if you only need it for the abovementioned parts.
Taking the camshaft from a used engine is only recommended if it's not excessively worn (get someone experienced in engine rebuilds to have a look if you can't tell). Provided it's OK, you should use the cam followers from the same engine and not mix their places. Camshaft and followers wear in pairs, and mixing them in wrong positions can promote accelerated wear.
If the camshaft is worn, I guess it's somewhere in the region of 170 euros new from Renault, plus new followers. Not too bad I think if you're doing a full rebuild and want a reliable engine for a long time.
Hope this helped!
