Max displacement on a 2.5 block
05-20-2003, 05:53 PM
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Three Wheelin'
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Max displacement on a 2.5 block
I have been dreaming up my new motor, and I was wondering what the maximum safe displacement you can get out of a 2.5 liter block, in terms of bore and stroke as well as liters. Not to say that would be my goal, I just want to know what limitations I am working under.
Also, I have available to me a good condition NA block out of my parts car, anyone have any experience building a high HP turbo motor off of a NA block? I seem to recall there is an oil line that needs to be drilled?
Lastly, are the S2 and 968 cranks the same?
TIA guys.
Also, I have available to me a good condition NA block out of my parts car, anyone have any experience building a high HP turbo motor off of a NA block? I seem to recall there is an oil line that needs to be drilled?
Lastly, are the S2 and 968 cranks the same?
TIA guys.
05-20-2003, 07:15 PM
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Define safe displacement 
Max would be around 3.2 ltr (2.5 bored and stroked)
<img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" /> <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
Max would be around 3.2 ltr (2.5 bored and stroked)
<img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" /> <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
05-20-2003, 09:29 PM
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nope...but i know the bore cant be that much over stock.My advice would be go with a stroker kit.The most common use the 968 crank,rods,and pistons...i also here JE makes some pretty good pistons and can set compression to whatever you want.I think the 968 bottom end on a 8v 951 head is about 2.7-2.8 liters.I know people that run this setup with lager turbo and produce big numbers with great reliablity.If you are looking for a 100k engine this might be your best bet.
05-20-2003, 09:39 PM
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A 2.8L stroker uses the 3.0L crank with stock 100mm bore. It uses custom pistons from Andial for stock alusil block, or aftermarket pistons (JE, ROSS,..) if the block is sleeved.
102mm bore with 2.5L crank = 2.6L
104mm bore with 2.5L crank = 2.7L
106mm bore with 2.5L crank = 2.8L
100mm bore with 3.0L crank = 2.8L (Stroker)
104mm bore with 3.0L crank = 3.0L
106mm bore with 3.0L crank = 3.1L
To go from 100mm bore to anything larger you'll have to sleeve the block, or NICOM it (it'll become Nickasil vs Alusil) and you'll have to use aftermarket pistons...
102mm bore with 2.5L crank = 2.6L
104mm bore with 2.5L crank = 2.7L
106mm bore with 2.5L crank = 2.8L
100mm bore with 3.0L crank = 2.8L (Stroker)
104mm bore with 3.0L crank = 3.0L
106mm bore with 3.0L crank = 3.1L
To go from 100mm bore to anything larger you'll have to sleeve the block, or NICOM it (it'll become Nickasil vs Alusil) and you'll have to use aftermarket pistons...
05-20-2003, 09:42 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> nope...but i know the bore cant be that much over stock </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I know the bore can go out to 106mm, not sure if thst is max size.
3ltr block is the way to start a dream engine.
3ltr block is the way to start a dream engine.
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05-20-2003, 10:11 PM
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I am looking at increasing the bore and the stroke, and the 106mm bore looks pretty good. I seem to remember someone on here having a 108mm bore, although that may be a bit much for me.
So I am guessing that sleeves are required for a 106mm bore because the open decked block doesnt leave much room for boring.
So I am guessing that sleeves are required for a 106mm bore because the open decked block doesnt leave much room for boring.
05-20-2003, 10:29 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> So I am guessing that sleeves are required for a 106mm bore because the open decked block doesnt leave much room for boring.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Yes,
The reason I said to start with a 3 ltr block for a dream engine, it is a much stronger base and you could always sleeve it to.... maybe 110mm ?
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Yes,
The reason I said to start with a 3 ltr block for a dream engine, it is a much stronger base and you could always sleeve it to.... maybe 110mm ?
05-20-2003, 10:53 PM
#10
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Due to the 1mm thinner cylinder walls on the 3.0L blocks, I wouldn't go beyond a 108mm bore. This comes out to 3.4L with the 3.0L crank.
Only problem is the darn size and weight of the pistons. Weight goes up to the 3rd-power of size. You'll be swinging around a massive piston, thus requiring a massive rod; both of which means weight.
Perhaps an even bigger problem is sucking in all that air through the same tiny little valves. VE-volumetric efficiency will go down unless you do extensive valvetrain upgrades as well.
Only problem is the darn size and weight of the pistons. Weight goes up to the 3rd-power of size. You'll be swinging around a massive piston, thus requiring a massive rod; both of which means weight.
Perhaps an even bigger problem is sucking in all that air through the same tiny little valves. VE-volumetric efficiency will go down unless you do extensive valvetrain upgrades as well.
05-20-2003, 11:44 PM
#11
Three Wheelin'
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Well, I don't exactly have the Cash for the 3 liter block. 
Dream engine, yes you are right!
I do, however have a free 2.5 block, so I will see what I can do with that.
Dream engine, yes you are right!I do, however have a free 2.5 block, so I will see what I can do with that.
05-21-2003, 02:34 AM
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I'm building a 3.2475L from a 2.5L block with 106mm bore. I'll keep you posted on how it turns out... just heard today that my rods will be coming in 6 weeks later than expected... doh!
