Increase engine displacement with a rebore.

obi_waynne

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You can increase the power of an engine by increasing its capacity. This is a fairly involved process and requires a good deal of research and preparation. Unless you want to have to retrace your steps and go a different route midway in to the job. Some of TorqueCars.com members have had their engines rebored ,and this does seem a good way to increase power. However there are a few things we should take into account.

Continue reading... or post your comments below on this article.
 
You never bore a motor to increase it's displacement, you stroke them. Bores can only be increased thousands, stroke inches.

Bore x stroke, which gets you a bigger motor faster?
 
I'm afraid I must disagree with the word never
For a start boring an engine increases capacity as well but at a much lesser cost . So often it is done on turbo engines as every cc helps the spool up.
On the engine I know rb26
Standard is 86.0 MM bore and 73.7 MM stroke. Stock they can be bored to 87.5 by just changing Pistons and this is a widely used mod.
The much used HKS 2.8 kit is 87.0 MM bore and 77.7 MM stroke so definately bored and stroked and this is by the manufacturer.
Probably the ultimate RB engine is the giken 3 litre which does increase the stroke but this means a new crank ,rods,pistons and block so very costly. This means 86mm square so the stroke is hardly inches . Also it's common to bore the giken motor to 87mm as well - again it is bored and stroked.
Increasing any stroke by an inch would mean a completed change in characteristics as the piston speed is often the limiting factor on high revving engines.
 
I have a 4G63 4 cyl that has been bored out by 1mm and the stroke increased by 12mm taking the original 1998cc to 2323cc the factory stroke is 88mm and there are 92mm,94mm,100mm and even a 105mm IMMSMC.

There are so many options with a 4G motors including destrokers and long and stock rod combinations.

FYI Brian over here we use a 3 litre RB30 bottom end from a VL Commodre with RB25 OR 26 TC heads that is far less costly than the OSGIKEN 3 litre.
 
True especially when using rb30 stock bottom ends. But when you start to increase the power they need to be forged which narrows the gap.
The giken is actually an RB motor specifically built from scratch to be a high power 3 litre engine so comes that way and will run 1000bhp no problem as every part has been built with that in mind. Details like a custom flywheel with eight not six bolts rather than six . Im told they generally rev better than an rb30 with the same spec.
hope so as Im having one built at the moment
 
We have built single cam RB30's running 8's and a registered VL Commodore with unopened NA RB30with bolt ons doing an 11 flat &128 mph.

Brian I am sure you will love all the single and twin cams in this video|B:)
 
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great vid
In oz you can fall over rb30s so parts are cheap and developement easy so they are an obvious choice. That then encourages companies like RIPS to take things to the limit .
We cant do that in the UK because there are no commodores or rb30s .
Thats probably why the giken was built over here .
 
Ya, I should be careful in choosing my words. My point was also maybe based upon American V8's and not the motors we are talking about here.

In that world you can stroke the motor an inch easily, but the bore is limited to at most .125 inches.

Never was way too strong for sure. You're examples seemed to make that point. I've never had a 4 cylinder, not since that 1971 Pinto I had. I'm here to learn.
 
Enlarging an American v8 and a much smaller straight six turbo is certainly completely different even though they may produce similar power.
I'm sure your comments are perfectly valid on the former
 
Thanks for throwing me a bone :) It is a different world. But you can still stroke centimeters, and only bore millimeters. That was what I was trying to state. You can get more from stroking than you can from boring, in displacement increase.

I never considered availability of parts...oops.
 
of course thats right but the two ways have different end results. Boring any motor is pretty safe assuming the block can take it
increasing the stroke increases piston speed (at the same rpm ) . I doubt this makes a difference to a relatively low revving 5 or 6 litre v8 but it can to a smaller turbo'd straight six thats made to rev to close to 9000 to acheive similar and sometimes more power.
 

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