1mm Overbore pistons safe?

[mjsstanley]

I recently got my hands on an F20B short block that I plan on building N/A. I came across a set of Forged Pistons made by Bisimoto with a bore of 86mm. Bisi's site says it's completely compatible with stock F20B sleeves which has a bore of 85mm. I know the F20B has one of the strongest blocks that Honda has ever made and also iron sleeves, however I'm still a little weary about 1mm overbore on stock sleeves. Most info I've read says that's completely fine but I've also seen a few people said it's not. I do know that Bisi makes some great products. Any input or experience with 1mm overbore?

[mjsstanley]

Anybody?

[Raf99]

Considering some JE Pistons require 0.0020 - 0.0025" (0.0635mm max) I am thinking 1mm is way too much. You'll want sleeves installed to meet proper clearances. I imagine Bisi has some installation instructions which state such clearances that you will have to follow too. I'd go by the book on this one!

[mjsstanley]

Hmm ok. Sounds like I may need to give Bisi a call directly and see what they actually recommend.

[deevergote]

1mm overbore should be just fine.

I'm not sure where you heard that the F20B is one of the strongest blocks Honda ever made. It's an open deck design, which is inherently weaker than comparable closed deck designs (such as that found in the H22A1.) Resleeving as Raf99 suggested is definitely the best option, but it adds a minimum of $1200 to your build cost. It's up to you if you want to risk it... but I believe it will survive as long as it is done correctly.
Assuming the F20B's cylinder sleeves are comparable to the F22A's, then a 1mm overbore will be fine. Plenty of people have gone 1mm over on the F22A without issue (unless they were looking to boost... weakening open deck sleeves is a bad idea for boost.)

Also, Bisi doesn't make pistons. He simply orders them from Arias, supposedly to his specs. A member here previously discovered that Bisimoto's F22A pistons were really just Arias pistons for a 4G63.

[Raf99]

I mean to start my last post with "I'm no professional" But seriously, I am no pro so don't take my word for it. So Deev, does one have to order different rings to accomodate for the extra clearances or what is the consequences of not meeting these clearances?

[deevergote]

what extra clearances? Pistons and rings made for an 86mm bore, and the cylinders bored from 85mm to 86mm. Shouldn't be anything extra going on there.
That being said, I'm no professional either, nor have I ever overbored an F22A.

[mjsstanley]

Thanks for the input Deev! I came across King Motorsports which is rumored to be one of the best places to get your VTEC Honda motor built. I gave them a call and he suggested that I just get the stock bore of 85mm bored to 86mm (a service of $250 by them). Doesn't sound like a bad idea at all. They also do complete long block builds from about $3,500 with supplying all the parts yourself. Seems pretty tempting. Going to be looking for about 225whp for this build.

[deevergote]

$3500 just to put together customer supplied parts? That's outrageous! Aside from machine work, any amateur with a good manual and proper tools can do that themselves. Slowly, the first time...

[mjsstanley]

Yeah I also thought that was a little pricey. I'm not sure if you remember Deev but my H22 swap was a huge mess and the motor eventually blew so I definitely want things to go better this time. Here is the link that shows exactly what the rebuild consists of... http://www.kingmotorsports.com/c-318...s-process.aspx

So they do both the head and the block but still with supplied parts. Seems like a good bit of work that I'd have no clue where to even begin. The only reason I would even consider paying that much is because they specialize in Honda engine builds. They're very familiar with all B/D/F/H series. And the guy that did my swap the last time didn't seem very knowledgeable...

[mjsstanley]

Gave them a call today for more info and it seems as though that definitely won't be happening. He explained that the prices START at $3,500. And seeing that I would have to ship them the motor as well as all the parts, I will definitely end up finding a local shop here in Atlanta instead.

[deevergote]

The price is likely due to their reputation, too. They have a good reputation, so they can charge more for it.

[mjsstanley]

That they do have. Would be a lot better if they're weren't 800+ miles away from me. I'd hate to pay shipping to have a 300lb motor sent to them only to get an $5,000 quote on the work. I'm sure I'll be able to find a good shop here.