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998 More Power


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#1 germini30

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Posted 12 August 2019 - 11:59 AM

My 998 drove 300 miles to the imm and back great, used no oil or water. It'll whizz along nicely at 80mph and the gearing is good but I would like a little more poke. Its a stock 1989 998 cc with a stage one kit and megajolt. I have a 1275 unleaded spi head here doing nothing and was thinking of fitting that. Also have a hif44 doing nothing too. Was thinking of a cam maybe too. Which is the best way to go

#2 unburntfuelinthemorning

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Posted 12 August 2019 - 12:21 PM

I'd say go for a modified small bore head to keep the port sizes sensible and not have to worry about pocketing the block.  You'll get a nice increase in mid and top end without loosing out at the low end.

 

A large bore head will develop more power at the top end but if you're on the standard gearing for an '89 model that isn't going to help too much.  You may sacrifice some fuel efficiency too.



#3 germini30

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Posted 12 August 2019 - 12:59 PM

OK so a decent small bore head and it'll be good.

#4 unburntfuelinthemorning

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Posted 12 August 2019 - 01:18 PM

The cylinder head's the key to increasing performance.  Get that right and any other mods will be far more effective. 

 

You'll need to rolling road it afterwards to get the right needle in the carb and tweak the ignition timing to fully reap the benefits. 

 

That HIF 44 is too large for the state of tune of your engine.  You only really need one this size when they're very highly tuned.

 

A cam change would make a difference too but that's really an engine out job.  A fairly mild cam would be best with the high gearing you have.



#5 germini30

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Posted 12 August 2019 - 03:07 PM

Yeah may sell the 1275 I have and use the cash to get a bit more out of the 998

#6 Cooperman

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Posted 12 August 2019 - 03:15 PM

Apart from the cylinder head limitations, with a 998 of that age the high final drive ratio is what kills the acceleration.
The ideal FDR for a 998 with some modifications is a 3.44:1 FDR. Then a better cam will work well when combined with a well gas-flowed head.

#7 andyapanel

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Posted 15 August 2019 - 10:33 AM

A lightened flywheel will not provide any more power, but it will allow you to accelerate more quickly.






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