Re: Large valves for Austin 7 Block

From:
Date: 26/11/97
Time: 9:49:06
Remote Name: 194.168.65.8

Comments

Mini Cooper inlets , but turned down at both ends will fit I believe. I have used these in a friends engine, but he was not sure where they came from. Standard A7 inlets were used. My own engine has Hillman Imp and Austin Maxi valves and springs, but these need the tappet guides in the block machined flat with it. The valves are 1.2 inlet and 1.05 exhaust and they touch when they pass each other! So an unleaded block with hardened inserts is out of the question as there is hardly any gap between the seats. I also use a cam with 5/16" lift. With big valves and a 7:1 head, the valves hit the head. So if you do fit big valves, check for this and grind it away, mine broke through, so I had to repair it- old heads corrode badly inside. Most important, but off the subject, is to ditch the top water branch gasket if using a late Ruby type head. It is ok with the standard 5.8:1 comp, but above 7 will blow the head gasket here as the fibre gasket will move and the two head studs will never tighten down. The answer is to use a solid copper gasket here and preferably one for the head gasket too. I blew two head gaskets in under 1000 miles with a 7.6:1 compression ratio. A 16 gauge gasket is best, it also lowers the comp to about 7:1 in my case. With those big valves, extensive porting is desirable too, but best left to an expert or someone with good supply of blocks. I can send you a picture of my block if you like.

Hope this is helpful, Barry Lovelock.


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