Head Swaps

Cylinder heads are a complicated and simple at the same time!

All 1300 and 1500 heads are interchangeable in that they will all bolt on, and all manifolds fit as the inlet/exhaust port arrangement is always the same. However it is vital to get the compression ratio correct for the fuel available. 

515573 13/60 Heraldsmall inlet valvefigure 8 valve retainers8.5:1
515973 Spit Mk3small inlet valvetwin collet retainers9:1
218139 1500 forwardbiggest inlet valve8:1 (on 1500)
218140 1500 forwardbiggest inlet valve9:1
218141 1300 Toledobig valves8.5:1
218142 1300 Spitfire IV(not US market)big valves9:1
TKC1156 Dolomite 1300slightly smaller inlet valvesno water outlet in RH rear corner8.5:1
TKC1155 Spitfire/Dolomite/Midget 1500 (not US market)slightly smaller inlet valves9:1 on 1500
There is a variety of USA heads with/without valve seat inserts, with/without air injection, and some at 7.5:1 with dished pistons or 9:1 (1976) with flat. Physically they will all bolt on.

Problems occur with 1300 heads on 1500 engines as the compression is too high, but a 1300 head at 8.5:1 is fine with the 1500 dished pistons (low compression pistions)! Torque of an engine is really related to its capacity, the BHP can be increased by making the gasses get in and out easier and faster but this is always at the top end. The most important thing normally is to get what is there working correctly.