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  #1  
Old 01-04-2007, 04:06 AM
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What Compression should I grind my engine to.

I have been taking to Mike about his stage 2 and I would like to do up my spare engine with Cams, Stage 2 & shave the heads. The big question what do you guys think I can take the compression to?
Tony
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  #2  
Old 01-04-2007, 05:03 AM
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oooooo...good question, I'd like to know as well!
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  #3  
Old 01-04-2007, 07:23 AM
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Well from what I'm told by our engine builder you need to do the compression first then cams later to get the optimium result. The real question is what are you willing to live with in terms or reliablity and longevity, also, how much of the internals do you want to strenthen to handle the extra power.
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  #4  
Old 01-04-2007, 07:46 AM
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I thought you had gotten the stage 3 s/c??

Tom
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  #5  
Old 01-04-2007, 03:47 PM
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Tony,

If you reduce the gasket thickness by .010, you will gain .3 points.

I believe the factory piston to head clearance is .040-.042", perhaps intended to be 1mm exactly. Clearances must be confirmed.

How much, depends on cams, what does Mike think is appropriate?

Quote:
Originally Posted by Dessertrunner
I have been taking to Mike about his stage 2 and I would like to do up my spare engine with Cams, Stage 2 & shave the heads. The big question what do you guys think I can take the compression to?
Tony
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  #6  
Old 01-04-2007, 04:04 PM
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Quote:
Originally Posted by Dessertrunner
I have been taking to Mike about his stage 2 and I would like to do up my spare engine with Cams, Stage 2 & shave the heads. The big question what do you guys think I can take the compression to?
Tony
The first denominator to fix within the equation is a decision regarding the octane rating of the fuel you will be running. No figure can be logically suggested without such information. There are many reasons for restrictions in this area and if there where not you could go sky high. Provided you accept valve clearance problems.
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Old 01-04-2007, 04:24 PM
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Trevor,

What octane is commonly available in NZ and AU fuel?

Quote:
Originally Posted by Trevor
The first denominator to fix within the equation is a decision regarding the octane rating of the fuel you will be running. No figure can be logically suggested without such information. There are many reasons for restrictions in this area and if there where not you could go sky high. Provided you accept valve clearance problems.
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  #8  
Old 01-04-2007, 05:22 PM
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Quote:
Originally Posted by NeedForSpeed
Trevor,

What octane is commonly available in NZ and AU fuel?
Don't know about NZ but I think AU still offers leaded gas with octanes above 100 for street use.
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  #9  
Old 01-04-2007, 05:37 PM
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Aussie gas.

No leaded is out now, we get 92,95,98 octane ULP. 98 will support 11.5:1 in a good combustion chamber.

Harvey.
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  #10  
Old 01-04-2007, 05:56 PM
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Quote:
Originally Posted by NeedForSpeed
Trevor,

What octane is commonly available in NZ and AU fuel?
98 unleaded is available in N.Z. as premium fuel at all outlets. Higher, I think 104, is on sale at some gas stations.

The point in my post was that Tony may, or may, not be restricted to pump, fuel.
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  #11  
Old 01-04-2007, 06:27 PM
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Thanks Trevor,

I did catch your point clearly, but did wish to know what was available commonly.

Quote:
Originally Posted by Trevor
98 unleaded is available in N.Z. as premium fuel at all outlets. Higher, I think 104, is on sale at some gas stations.

The point in my post was that Tony may, or may, not be restricted to pump, fuel.
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  #12  
Old 01-04-2007, 07:19 PM
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I can normally get 95 or 98 and Tom yes I have a SC kit to install but I will do that when I can afford to get a 3rd SVX. The reason I want to shave the heads is that I did it to a Subaru back in the 80's and the thing had wings we all talk about the possiablities and how tough the SVX engine is but we never try some of these things. Take for example removing the dust shield on the front breaks simple job and yet it changes the performance of the brakes. Matt did it and then drove the car in a Rally and never once lost breaks.
We do cams ECU injectors and every thing we can think off but never shave the heads so it is time to give it a go. So guys how much are we going for and I only want the engine to last 50,000 K but a fun 50.
Tony
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1995 - SVX 700,000 K Mine, DMS Struts to lift car 2in. Tyres Wrangler Silent Armor 235/70R16, PBR Radiator. 6 speed with DCCD and R180 rer diff, Heavy duty top strut mounts front and rear. Speedo correction box fitted. New stero (gave up on the old one). Back seat removed and 2 spare tyres fitted for desert driving. ECUTune SC sitting in the box for the next SVX.
1992 - SVX 255 K Wife (Want to stay Married so not allowed to fit SC)
1992 - SVX Pearl with black roof race car roll cauge etc ready to race. Ex Tasman Targa car.
1995 - SVX Green low k mint condiation.
1995 - SVX Rally car, ex Matts car. Now to be used on track.
1992 - SVX red & Black being converted to Mid Engine.
1995 - SVX Red 143,000 bit rough.
Owned 5 others Subaru back to a 1974 1400 GSR.
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  #13  
Old 01-04-2007, 08:30 PM
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Quote:
Originally Posted by Dessertrunner
I can normally get 95 or 98 and Tom yes I have a SC kit to install but I will do that when I can afford to get a 3rd SVX. The reason I want to shave the heads is that I did it to a Subaru back in the 80's and the thing had wings we all talk about the possiablities and how tough the SVX engine is but we never try some of these things. Take for example removing the dust shield on the front breaks simple job and yet it changes the performance of the brakes. Matt did it and then drove the car in a Rally and never once lost breaks.
We do cams ECU injectors and every thing we can think off but never shave the heads so it is time to give it a go. So guys how much are we going for and I only want the engine to last 50,000 K but a fun 50.
Tony
Tony,

My SVX is quote happy running on our standard fuel which is 91 octane. The car was introduced when lower ratings where the norm. I think you need not be too conservative. A cross section of late models would be a yardstick which would help.

You have the right idea in seeking opinions and figures as nothing finite will be available. The more dope you are able to put together the better. Trouble is what comes off can't be put back, so good luck.
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  #14  
Old 01-04-2007, 09:34 PM
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why not go to different pistons?? it is easier and I think a better option, if you shave the heads too much you will need a custom intake...timing belt...etc

Tom
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  #15  
Old 01-04-2007, 10:32 PM
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I'm with Tom regarding watching how much you work the heads due to the interaction with the intake, etc. Without having done all the math, I'm guessing you could go to 10.5:1, possibly 11:1 without any "ripple" effect...
-Bill
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