12G295 instead of 12A1456
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Mini4Ever
- 998 Cooper
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12G295 instead of 12A1456
I am trying to work out whether or not it is needed to skim a 12G295 head when fitting it to a pre-A+ 998cc engine which originally had a 12A1456 head. The engine itself would get the high-compression flat top pistons instead of the dished ones (so no D-tops). Does anybody know whether the disappearance of the dish in the piston compensates sufficiently for the larger combustion chamber (about 3.8cc) of the 12G295 head?
Too many cars...
Re: 12G295 instead of 12A1456
You'll have slightly over 9:1 with that set up, fit a MG cam and you'll have a nice engine.
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Vegard
- 1275 Cooper S
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Mini4Ever
- 998 Cooper
- Posts: 664
- Joined: Fri Jun 25, 2010 7:46 pm
- Location: Netherlands
Re: 12G295 instead of 12A1456
Which MG cam are you guys referring to? I was considering an 997 Cooper cam (2A948) or 998 Cooper cam (AEA630) myself.
Too many cars...
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Vegard
- 1275 Cooper S
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814CWE
- 998 Cooper
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Re: 12G295 instead of 12A1456
the mg 1100 cam is very good
id be tempted to take another 20 thou off the head for best results,,you know you want to
id be tempted to take another 20 thou off the head for best results,,you know you want to
for my sins,i own a 1957 wolsleley 1500
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ianh1968
- 1275 Cooper S
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Re: 12G295 instead of 12A1456
The 997 Cooper cam was the best standard/road cam from Leyland and wasMini4Ever wrote:Which MG cam are you guys referring to? I was considering an 997 Cooper cam (2A948) or 998 Cooper cam (AEA630) myself.
first used as a tuning aid on lesser models during the '60's for that reason.
With In/Ex duration of 252/252, it was longer than the 998 cam and the 'S' cam.
The old 731 cam which was once considered to be "half-race" was previously
the next one up on the factory scale and was 268/268.
When the MG Metro came out, the cam was a sort-of hybrid of the 997 cam
and the 731 in that it was 252/268 degrees. Having more exhaust period
than inlet on 'A' Series engines has been shown to be beneficial, said to be
something to do with the siamese exhaust porting...
With a sensible road engine the MG Metro cam would be a good choice for
many engine builders. I have used it in a 998cc engine equipped with a
12G295 head with 1.312" inlets and 1.0625" exhausts and offset bushes and
it went quite well. The same head and cam spec also got fitted to a 1242cc
Hillman Imp/1098 cranked engine and this was a nice engine as well.
The conclusion to be had here is that the 252/268 cam is a good all-round
"one-size-fits-all" cam and would be one up from a 997 cam.
Ian