I'm attempting to rebuilding my ITR engine which recently threw a rod bearing and was wondering if I should just rehone or go .25 over. How much power or what pros/cons would I have for an overbore?

TIA

 

why not over bore while it's apart anyway? get that extra power out of it

 

Your gonna see little to no power gain from boring it .25. Id say just rehone it and save some money, unless it needs to be bored.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by reddohcvtec &raquo;</TD></TR><TR><TD CLASS="quote">Your gonna see little to no power gain from boring it .25. Id say just rehone it and save some money, unless it needs to be bored.</TD></TR></TABLE>
Exactly what I was thinking. Anyone else? Boring is going to cost me $200 more for new pistons on top of the money to bore instead of honing. If it's not worth the extra $300, I don't think I want it.

 

depends on the condition of the cylinders they need the bore to clean them up

 

I always go with the over bore option. Why? because chances are that your cylinders are oval now. 2) because honeing will create a larger piston to wall clearence. 3) You can now have a perfictly new bore to specs and know that it been done right. All your saveing is about $50 avg. Ussually the bore and hone is sold as package at most machine shops. Some won't just do a hone. As for power, you could not even notice the diffrence. Why, Because the .25 on the honda piston is not of an inch actually your talking of .25 of 1 millimeter. that 1/4 of a mm. about .005 of an inch.

 

everybody has there own opinion.

i always believed if the block doesnt need to be bored just hone it.

 

for $35 you can buy a high quality flex hone form goodson.com and run it yourself on a drill with some motor oil, about 6-10 strokes will clean up any cylinder that is okay for reuse, more than that and the scores are a little deep.

ive had 3-5% leakdown on several reringed motors with over 100K now. a plateau hone can also reduce break-in time apparently, havent tried one yet.

 

honda recommends 400 grit, but i have used 220 on it and they are both the same in my opinion. Except 220 leaves better markings due to the lower grit

 

Price difference is only about $40 more to bore instead of hone. Since I'm replacing my USDM ITR pistons with JDM ITR, I'm thinking that I might as well get oversided and pay for the boring.

cptengineer - You bring up some good points on why to bore. Are there any negatives or reasons not to? Could the machine shop tell if my cylinder walls are oval?

If this was for my beater or a car I really didn't care about, I would consider just honing it out myself and seeing what happens.

 

I'm sure they could by just takeing two measurements, one in the X and one in the Y direction. The elongated part of the oval should be in the maifold to header direction. Also by bore & honeing you have a fresh start with the clearences you desire wether they be factory spec or your own, it won't just be a, "looks good to me". The proper way to add new pistons is always bore & hone. It's up to you wich route you take, Like YOU said it only $40. Good luck.

 

you can hone .25 over,no need to bore .25 of a mm. take a look at a ruler. consider getting higher comp pistons if you want a little extra air to work with.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boylovecar &raquo;</TD></TR><TR><TD CLASS="quote">you can hone .25 over,no need to bore .25 of a mm. take a look at a ruler. consider getting higher comp pistons if you want a little extra air to work with.</TD></TR></TABLE>

.25 is approx .010 as the conversion is 25.4 and 82 mm is .040 std. I wouldnt hone it .25mm i would bore to insure roundness and then hone for the rings. If the cylinder is out it will continue to be out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boylovecar &raquo;</TD></TR><TR><TD CLASS="quote">you can hone .25 over,no need to bore .25 of a mm. take a look at a ruler.</TD></TR></TABLE>.
Wow you guys insist on doing things the wrong way over a matter of $40. I refuse to continue to add to this thread, as most posts are very backyardish . If any machienist could add to this thread, it would be a better benifit.

.25/25.4=.00984. so yah .010 0f an inch.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtecmissle &raquo;</TD></TR><TR><TD CLASS="quote">

.25 is approx .010 as the conversion is 25.4 and 82 mm is .040 std. I wouldnt hone it .25mm i would bore to insure roundness and then hone for the rings. If the cylinder is out it will continue to be out.</TD></TR></TABLE>

Yah, what he said.

 

who owns thousands of dollars worth of equipment and doesnt charge $60+ per hour? a $40 bore sounds like someone is cutting corners. it takes me 25 minutes just to set up the block and indicate for squareness. then another 15 to set up/doublecheck the tooling, and another 15 to punch in the numbers for the program (CNC boring/surface machine)

maybe im just slow, but i know im skilled and ill tell you from experience that its easier to make a cylinder tapered on a rigid hone (like sunnen CK series, etc) than it is to keep one straight.

with the amount of horror stories i hear about "machinists" these days, and the things ive witnessed from "competent" engine builders personally, a $40 bore job is something i would avoid if at all possible. good work takes time, and time isnt cheap, especially with mortgages on high end equipment. ask jim justice, RLZ, donF, larry widmer or whoever else does good work if theyd do a block for $40.

 

just to clarify, im all about a bore and hone when its required, but not one that is so cheap the operator cant afford to slip a bore gage in each cylinder more than once. nothing like a fresh bore with .002" excess wall clearance to ruin your build.

 

I'm sorry, should have been more specific. It's $10 per cylinder to hone and $20 per cylinder to bore which made the difference of $40 overall. Hrm, I wonder if their bore job includes a hone or would I still have to pay another $40 on top of the $80.

 

its probably billed separately. it should be.