Head swap for 1275 engine?

[nathandarby67]

Looking through my shop manual, it shows the 12V series 1275 engines such as in my 73 Midget as having 8.0:1 compression ratios, while earlier 1275 engines have 8.8:1 ratios, and you guessed it, more power. Is this difference in compression due to diffenret cylinder head designs, or are there other differences such as pistons, etc? When all is said and done, what would be the easiest way to increase compression in my engine? If I could find a head from an earlier model, is it a direct bolt-on swap or are there other modifications that have to be made?

 

[aeronca65t]

The compression difference is mostly pistons (more "dished" on the low-comp 1275).

 

[nathandarby67]

So are earlier heads more or less identical to later ones, save for the air injection ports?

 

[aeronca65t]

All 1275 heads will interchange (including heads from the low-performance 1300 Austin sedan). Biggest problem with these heads is exhaust seat cracking.....I saw three cracked 1275 heads for sale in the last year (and I've had several fail myself).
The best heads are the Mini-Cooper 1293 heads...and I think there are aluminum heads available now too (check minimania.com for these)

[ 06-02-2003: Message edited by: aeronca65t ]</p>

 

[Bugeye58]

If you are looking for performance, and are willing to do a little port work, the 12G1316 castings are the ones to work with. They are the ones with the smog ports, which are easily plugge using #4 AN or SAE steel plugs. They are less prone to cracking than most of the 12G940 castings.The best one to use is the Cooper "S" casting, #AFG163, but those are getting harder to find.
Jeff