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Information On Cylinder Heads.

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#1 Ado1379


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Posted 01 February 2020 - 12:00 PM

I’ve managed to pick up a 12G295 head for £15!

I’m looking at building it from the ground up and I’m looking for advice on valves, stems and the like. I’m not interested in porting as I know when I’m out of my depth 😂 all valve seats will be re cut and head will be skimmed by the local pro so I’m just wondering what bits to get. I have removed and refitted head before but that’s about it so I’m a total novice when it comes things like this.

I will be reading up in the mean time but where better to find knowledge than the famous TMF page right?

#2 DeadSquare


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Posted 01 February 2020 - 12:08 PM

If you are not going to reprofile the ports and chambers, "The Local Pro" will fit you up with standard valves, guides and tougher springs.

#3 blacktulip


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Posted 01 February 2020 - 02:51 PM

Do you know what spec the rest of your engine will be yet? As you need to think about this before working on the head. You need to think about the cam profile and the compression ratio you wish to run to determine what cc the chambers need to be to achieve this.

#4 Moke Spider

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Posted 01 February 2020 - 05:05 PM

First thing you will want to do before spending any money on it is have it crack tested. These heads were not prone to cracking, but it's not out of the question.


You'll almost certainly find the valve guides will be worn, and so you'll want to have them replaced. There's Cast Iron and also one of the various Bronze types generally available. For your use, I'd steer you towards Cast Iron, just make sure they have the groove in them for the Umbrella type seals.


In regards to valves, just standard valves will be fine, however, before buying them, I would suggest you go see your machine shop guy as you may need oversized valves if the seats in the head are worn beyond what a basic clean up will do.


I'd also suggest having hardened seats fitted for unleaded fuels. I'd also suggest using the latest 'brown' coloured valve stem seals. Also, have the By-pass Adaptor removed and fit a plug.


While these did have double valve springs fitted originally, you may want to think about what Cam you'll be running with and the upper RPMs that you might be running to and fit spring(s) to suit.

#5 Ado1379


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Posted 01 February 2020 - 08:50 PM

Thanks for the input guys. The engine in the car was already built by one of the previous owners. All I know is it’s not ‘stock’ and I have no idea what’s in it as of yet. Having already replaced the head gasket and having the old valves replaced on the head I already have, I was told that if the valves go again it cannot be repaired. So basically I’m trying to preempt a replaced. Having not had anyone look inside the engine all I know at the minute is the pistons are domed? There is minimag article on the car I believe but I’m not entirely sure what year it is so it’ll take some digging. As you can imagine.... I’m out of my depth at the minute 😂

Thanks for the input though guys I’ll update anything I find!

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