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 Post subject: More 998 Questions
PostPosted: Sat Feb 14, 2009 9:55 am 
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998cc
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Joined: Sun Dec 18, 2005 10:54 am
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Location: Adelaide, SA
O.k building a 998 just to get one of my cars back on the road whilst i build the twin cam ..

It was just going to be a rings and bearings build ... but as always it's getting out of hand

First thing i want to know is how big i was thinking .100 or .120 tho is there any point ... i have had a quick read through GR's 998 build and Visards Build and they both go to .40 tho at .120tho do i need to offset bore it ???

Im thinking of putting a spare STD 1275 head on i know a well ported 202 will work just as well if not better but i don't have a ported 202 .. and the 940 is alreadt unleaded and complete ..

Cam wise kent MD 276 ???? or i have to get another one ground... a have a spare 286 but even i know this is to big :D

Thanks for any help
Beanie

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 Post subject:
PostPosted: Sat Feb 14, 2009 11:02 am 
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998cc
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Joined: Tue Nov 06, 2007 9:38 am
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Location: Dorrigo, NSW
I know there is no offset boring required for small blocks at +100 so I am sure the same would be for the +120, that is required only for big blocks I think....

Speak to Doc about throwing big bore heads on small blocks....he is a big fan of it...and would have all the pros/cons of doing it, I am not sure what mods are required though....

Not sure about the Kents, I decided on going an RE13 for my small bore, though the valves will be lengthened at GRs advice so to greatly reduce the chances of binding....


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PostPosted: Sat Feb 14, 2009 11:14 am 
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1360cc
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Joined: Mon Jul 26, 2004 7:23 am
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Location: Sunny Shine Coast, Qld Australia
Talk to GR - He has +100 pistons in his range and bored my 1100 block (same as the 998) to +100 and fitted his flat top pistons to give me the required compression with a 295 head. It has an RE13 cam fitted as well.

Hope you're going to fit a duplex timing chain as well :wink:

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PostPosted: Sat Feb 14, 2009 3:42 pm 
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religious status
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Joined: Fri Mar 19, 2004 6:19 pm
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Location: near Baulkham Hills, NSW
12G940 or 12G1316 heads off a 1275 work OK on a smallbore, IF you notch the block to clear the exhaust valves. They might give less low down torque than a well worked 202 or 295 head but you don't have to shell out big $$$ to pay for the porting. One is going on my 1132 Moke.
A bit of a cleanup inside in the valve bowl areas is all the 1275 ones need for a smallbore.
You do NOT want or need dirty big ports, particularly on a 998.

Yes some people get away without notching the block, IF the valves are worn into the seats and IF the cam isn't high lift and IF using stock rockers. I don't recommend this though, bounce the valves once and you will bend em. :cry:

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 Post subject:
PostPosted: Sat Feb 14, 2009 11:42 pm 
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998cc
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Joined: Sun Dec 18, 2005 10:54 am
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Location: Adelaide, SA
Cheers guys i was defanatly going to notch the block anyways so thats not a problem .. so is there much gain in going to .100 tho or is it better to stay smaller?

Beanie

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 Post subject:
PostPosted: Sat Feb 14, 2009 11:44 pm 
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Bimmer Twinky
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Location: Brisbane
No substitue for cubes Bean

I`ve bored heaps of em out to 120thou

go for it mate :-)

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