hey guys,

ive heard of overboring an engine when rebuilding it, and i gather it increases the capacity for the engine... but what exactly is it??

please explain what exactly is being overbored and how, and why it makes such a difference...

plus i know its a big thing with muscle cars, but havent heard too much about overbores being done on fours... is there a reason for that?? cost too much for too little gain??

what kinda performance gains u looking at?

Cheers

 

it when you bore out the cylinders to a width outside of factory spec. basically, you grind the walls of the cylinders down so that the cylinder gets larger. generally you'll need oversize pistons. overboring the cylinders is a good way to get extra displacement. I'm not sure of the average addition to the displacement, but usually it's just a few hundred CCs at the most. the older american engines could get a lot more since they had more starting displacement. a 10% increase from 5 liters is a lot more than a 10% increase from 1.6 liters :D

that good for ya?

 

I would like to know more on this too, as i plan on rebuilding here real soon. Would like to know if its possible to bore out to something like 1.7 or 1.8 on my d16a6 bottom end, without weakening the walls to much. Thanx.

 

Yeah thats pretty much what i gathered from reading other posts... cool... at least i was on the right track..

What exactly is displacement?? is that the amount of fuel being pumped into the cylinders??

Does overboring increase/decrease compression?? and what does compression do for your car??

Is it possible to overbore too much??

can it shorten the life of the engine??

i take it burns more fuel??

what kind of performance gains we looking at here?? in hp or kw.

is it worth it??

cheers

btw... whats sleeving and why you have to do it on some overbores??

also what would be the MAX SAFE overbore on a d15b?

 

displacement is how "big" your engine is. this is measured by how much volume the cylinders displace when they go through their strokes. this is calculated from bore multiplied by stroke. my engine is a 1.6 liter engine. that means that the combined volume that the cylinders displace is 1.6 liters.

ultimately, compression comes down to the shape of the piston (all other things being equal). if you change the bore of the cylinder you;re going to need new pistons or you'll have issues. at that point you can choose what pistons you want, and you can pretty much select your compression ratio. choose high for NA or low for FI.

yup. the cylinder walls get thinner and thinner. even with a strong sleeve you reach a point where there's just not enough material left. this isn't very common since most shops know better than to allow such a thing. usually overboring is just for a few hundred CCs and doesn't really thin out the walls drastically.

I'm not sure. I wouldn't imagine it would. at least not nearly as much as making the stroke longer (stroking). when you have a wider piston, you just ahve a slightly heavier slug (enless you go with a lighter material). when you have a longer stroke, that slug has to travel faster and that wears on engine components a lot more.

yop

depends on the final CR. again, it all depends on how you do it.

there's no replacement for displacement. all other things being equal, more displacement = more power.

word.

I'm new to Hondas. I'm more experienced with Subarus. Sleeves aren't an issue with Subarus. nobody ever really speaks of them. I think they have permanent sleeves that don't get changed out or replaced. From what I gather, Honda engines have removable sleeves, and "resleeving" is a common thing to do when one gets up there in \NA power or boost. since the sleeves can be removed, I can only assume they'd be removed prior to overboring an engine. certainly they would no longer fit, and you'd have to get a new set since the bore is bigger. I'm not experienced with sleeving so maybe someone else could chime in.

 

The sleeving process is when the STOCK cylinder walls/sleeves are cut to a certain point and a new sleeve is installed.
such as this:


Once the stock walls are cut, the sleeves are pressed in and decked at the top to have a flat surface on the block. here's a sleeved block already done.


For B series, the stock sleeves are 81mm and are usually bored out up to 87mm MAX for most setups. an 84mm bore, will get you a 2.0L in that b18 block.

for D series, the stock sleeves are 75mm, and usually are bored up to 79mm. most common are 78mm, which yield about a 1.7L displacement after boring to 78mm.
Hope that helps.

Wil

 

How much would it cost to have my stock sleeves on my d16a6 block bored out to 1.7l. Whcih is, like you said, 78mm. And when i buy pistons, what size would i buy, same with piston rings. I plan on doing this real soon, so any info is appreciated. I have never really seen anyone do this beofre on a d-series.

 

you cant bore out the stock sleeves to make a 1.7L you would have to RESLEEVE the block to be able to bore out that much to make a 1.7

 

so a resleeve and overbore of 78mm = 1.7l on a d series would cost approximately how much...

$500, $1000, $2000!!??

 

resleeving a block costs $880 + the parts to assemble the block, rods, pistons, etc.

 

Woah, i guess thats outta my price range, i didnt realize you had to resleeve to do it. Oh well, i guess its just plain ole' 1.6 for me. Ill have to make up for it with a turbo.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by suprfast &raquo;</TD></TR><TR><TD CLASS="quote">
CAN I STROKE OR BORE MY RX7?
kris</TD></TR></TABLE>

no way man... you'll throw a rod.

I'm allowed to joke. I gave lots of info :D.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by suprfast &raquo;</TD></TR><TR><TD CLASS="quote">usually the LS is resleeved then bored to 2.0L(84.5mm) which will give you a stronger B20 if you will(if dont right).
</TD></TR></TABLE>

1.8L LS block sleeved 84mm will get you 2.0L

 

you can get a 1.6 up tp 2.0, and stroking it wont wear on it more.....as long as you chaing your oil and make sure **** is straight, ok it will.....but itsnot noticeable

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by carrcarr &raquo;</TD></TR><TR><TD CLASS="quote">you can get a 1.6 up tp 2.0, and stroking it wont wear on it more.....as long as you chaing your oil and make sure **** is straight, ok it will.....but itsnot noticeable</TD></TR></TABLE>
I disagree. Please explain your post..
to get a 2.0L from a B series 1.6L block or even a d series block. it will need a custom Crank and a nice over bore on the block. With both factors involved, it clearly shows that its not your everday setup. This feat is not recommended for EVERYDAY commute. It just isnt practical. Its not a simple motor and its not just watching the oil that would make a difference in its longevity.

 

This is my understanding - correct me if I'm wrong.
If you are stroking an engine the crank is replaced with one that has larger lobes. This allows the piston to be pushed higher up in the cylinder and pulled down lower in the cylinder as the engine is rotated. Shorter rods are used to maintain proper clearance between the pistons and valves. The downside is that the rod/stroke ratio is changed. Consider the crank as it sits at the 90 degree and 270 degree marks (0 degrees is when the crank lobe is straight up and the piston is TDC). It's sitting towards the outer part of the motor more than stock now. This presses the piston against the outer walls of the cylinder more than stock. The rings and cylinder walls will wear faster because of this. Also piston speeds are increased. Figure that 1000 rpm = 1000 rpm no matter what you have in the engine. The piston is going to go up and down just as many times no matter what. With a longer stroke the piston has to rise and fall FURTHER within the cylinder since the lobes on the crank are bigger. More friction = more wear. Civic Type-R engine is basicly a destroked version of the Integra Type-R. The piston speeds are less, but the displacement is less as well. It's not as powerful of an engine, but should last longer internally. Probably a better choice for a road race car or daily commuter car.

The 1.6 D-series blocks are very similar (A6, Z6, Y8) and all share the same horid rod/stroke ratio. The D15 actually has a better rod/stroke ratio than the A6. Unfortunately they are not interchangable. You could pay about $600 and get a custom grind on the A6 crank to make it similar to the stroke found in the D15. If you are a hardcore booster with a huge turbo and want the engine to last with less fear of bending rods, then this is a good upgrade.

OVER boring requires sleeving on open deck blocks. The cylinders are surrounded by water and if you bore it out too much, then the walls get too thin and are more prone to warping and breaking. There are OEM replacement pistons offered that require a larger than stock bore. There is some tolerance to the stock sleeves to allow a couple rebuilds before you are in need of replacing the sleeves or getting a new block. If you want to get any larger than what OEM parts let you do, then sleeving replaces the stock sleeves with larger and stonger material that allows over boring.

V8 guys have closed deck blocks. They are reltively a chunk of metals with holes in them. They are limited to how much they can over bore by the oil and water passages in the block.