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Shorrock Tech...

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#1 Dr s

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Posted 30 August 2019 - 06:21 PM

So I have a moderately tuned 998 cooper engine.
It’s 1050cc, 12g295 head with 32*28mm valves.
10.2:1 CR.
Makes about 70ish bhp.

I’ve got my myself a shorrock C75b. It should be able to make 7psi on the stock pulleys.

Do I need a de-com plate? Or will it be ok? Do boosted engines need less or more advance?

My Alfa Romeo is 9.75:1 and runs 26psi... but that’s a modern engine...

#2 hazpalmer14


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Posted 31 August 2019 - 08:21 AM

You could enlarge the Chambers in the head to lower the compression ratio.

There is many varying factors as to what boost you can run with what compression ratio. If you're are using a carb and a dizzy then you can't fuel and time everything as accurately as fuel injection and an ecu. And then there is the 5 port thing as you'll need to run on the richer sides so the outer cylinders are fuelled enough on boost

#3 mini13


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Posted 31 August 2019 - 09:27 AM

I really dislike decomp plates as the screw the squish up, I'd say with the charger which will be old tech and not terribly efficient and that your not be running an intercooler ( I assume) you'll want to err on the side of caution, I'd be looking for about 8.5:1 compression, also in terms of advance you want less as boost increases, your probably up around 30 deg total advance, I'd guess you'll end up needing about 24-25 deg

#4 Steve220


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Posted 31 August 2019 - 11:41 AM

However you do it, get to set up on a rolling road and make sure the operator uses det cans. I was so shocked at how easily the outer cylinders detonate on boosted set ups.

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