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Location:
Nelson NZ
Registered:
August 2003
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Raising Compression
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Tue, 26 August 2003 02:10
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Ok guys
I've got a 18rgeu which is getting a full rebuild soon when i do this i want to raise the compression ratio. They are orginally 8.3:1 i think. Do i just plain the block and head when i'm rebuilding it.
p.s wot other mods are resnobally cheap and easy that get good results on these engines.
p.p.s Should i dump the the efi and go for twin 50 sidedraft webbers.
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Location:
Brisbane
Registered:
May 2002
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Re: Raising Compression
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Tue, 26 August 2003 02:47
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1. The only proper way to do it is with new pistons which have a higher dome. You can shave the head but this is a bit dodgy as it interferes with the cam timing; remember it's an OHC engine, so if you effectively lower the height of the cylinder head, you're making the path for the timing chain shorter.
2. Cheap and easy? Not much apart from the usual extractors and exhaust. For worthwhile gains you can either spend a small fortune building a high-rpm atmo engine, or you can spend a modest amount on a turbo setup. You already have the perfect compression ratio for forced induction, so I know which way I'd go!
3. Definitely not! Replacing EFI with carbs is a serious backwards step. 50mm sidedraughts on anything less than a full-house race engine would be just silly. However if you like spending lots of money on fuel, go for it. 
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Location:
South Australia
Registered:
July 2002
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Re: Raising Compression
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Wed, 27 August 2003 00:31
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You could probably just get some adjustable cam gears if you wanted to plane the head, that way you can get higher compression and tune the cams to be pretty close to perfect. But I don't know how expensive that would be - probably not cheap.
p.s. For an EFI engine that old, make sure you either get the injectors replaced, or at least cleaned/checked out by a 'specialist' (ie a dude with a flow testing/cleaning maching).
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