Are there any drawbacks to overboring?

A D series?

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In general.

Depends alot really, I am not a fan of doing it on honda engines in general as they are balanced very good from the factory and I am not a fan of it on boosted engines unless you are running sleeves. A all motor H22 or something I can see it but on like a D series I would not do it, the B16's are a perfectly square engine as is so I do not like the idea of throwing it off for a few more cc's of displacement. The B18's on the other hand take to it fairly well if you plan good with it. Say you have a B18C1 and bore it out to displace 2.0 liters then you have a very good example of a b20 vtec or cr/vtec done the right way.

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Why not a D? It seems to suffer most of honda engines from small bore.

Basically, I don't know what happens inside a block. Overboring obviously has limits because at some point you'll bore one clyinder wall into another, or into an oil passage or something, but I was wondering if there are any other limitations to it I might be unaware of.

The main thing with the D series is that they tend to overheat being their a open deck block.

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There, that's the kind of info I'm looking for. Can you elaborate on how that works? (Why exactly it overheats.)

Ok the cyl wall sit in a "pool" of coolant that is why it is called a "open deck" because the top of the deck is....well.......open. The top of the deck does not meet the cyl wall at any point, say you take the head off your D series you will see the coolant sitting around the cyl wall. On a closed deck the top of the cyl wall and the block meet together.



^ open deck



^ closed deck

Being the open deck all but supports itself and the pressures from the combustion process it needs to stay as thick as it can to keep it from warping, cracking. The over heating comes from the lack of ability to get rid of the head simply because it moves through the cyl. walls faster being they are thinner. That translates to hotter coolant temps, and a all around hotter running engine. Also the cyl wall has a chance to actually move around a bit putting wear on the headgasket and letting coolant seep into the cyl producing higher temps

Closed deck designs do not have as much of a problem with the movement, warping, or cracking of the walls and can get rid of the heating problems because the cyl walls do not move and are alot more stable. Aside from actually sleeving a block the closed deck design is a good way to go. Honda engines like the H23 use this design.

Anything else?

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Could you explain the process of sleeving?

Excellent, excellent information thus far, by the way.

They wedge these in to make a really strong closed deck design

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