Scratched Bores- How Much is Too Much?

Alright guys, I need some advice. I'm building an H22A4 for the (hopefully) next Challenge. I bought a disassembled, aborted Type-R project from someone that's almost completely disassembled. I'm going to reassemble it with an eBay gasket and ring kit, and have a pretty damn cheap powerplant, but there's a little problem.

The #3 bore looks like this:

It'll catch a nail, but barely. I don't have bore mics, but with my calipers, everything appears to be round to within the 0.0005" I can measure or so.

So I'm looking for a judgement call here. Run it? I really don't have room in the budget for another block, and I really don't care if it lasts much beyond the Challenge. Eventually I'd like to turn this car into a WRL car, so I wouldn't be above pulling the motor and sleeving it after it's done as a Challenge car. This this will be good enough?

Have you honed it yet?

I'd hone, it good throw some rings in it, and run it if you're doing it on the cheap.

Catches your nail= 0.010" typically.

Knock the edges down and run it for the 6 min it might run at the challenge.

Problem is, it's got that goofy FRM liner setup that from what I've read, can't be honed in a conventional fashion, and even then, it's a crapshoot if there's enough material left to hone.

Relevent video: https://www.youtube.com/watch?v=iYpzeVNcEG4

If you're only looking for a 201x challenge? I'd probably hone the piss out of it, make sure I got the water AND oil warmed up before thrashing it, realizing that you'll probably be down a touch of leakdown/compression and up on oil consumption, along with an increased chance of total failure due to piston slap.

Edit: Liner cylinder vs cast iron? Yep, forgo the hone and just rering it and hope for the best if that's all the budget allows.

tpwalsh wrote: Relevent video: https://www.youtube.com/watch?v=iYpzeVNcEG4 If you're only looking for a 201x challenge? I'd probably hone the piss out of it, make sure I got the water AND oil warmed up before thrashing it, realizing that you'll probably be down a touch of leakdown/compression and up on oil consumption, along with an increased chance of total failure due to piston slap. Edit: Liner cylinder vs cast iron? Yep, forgo the hone and just rering it and hope for the best if that's all the budget allows.

Cool, thanks for the video. I was planning on going by HF today for a new engine stand, I'll probably pick up some bore gauges while I'm there to make sure the block isn't completely buggered.

In reply to unevolved:

A quick read says hone with 600 grit stones.

a rigid hone using a GC-600-J or finer stone designed for nonferrous metal was used to finish hone the cylinder bores. Honing pressure should be adjusted to 29-43 psi (200-300 kpa), while the hone head is rotating at 45-50 rpm. The desired crosshatch pattern is 60° for a proper piston ring seal. To prevent stone loading and debris build-up, cleaning the stones every five cycles is recommended.

In reply to unevolved:

Just as a heads up he has a TON of videos that are just as a high quality as that one. Many are 4G63 specific, but most have lots of good info on engine building.

Just for the record, THIS much is too much. 3rd cylinder in my 1275 MG Midget vintage race motor. These are interference fit wrist pins and one got loose. Turned a rering/bearing job into a sleeve and bore. Sigh.

That's pretty gnarly.

Challenge = dingleberry hone it, slam it together and run the crap out of it. If it has a bit of blow by/leak down because the rings don't seat perfectly, so be it.

Real build = don't do what I detailed above. Fix it right.

I'm leaning towards option A.

Light hone, run heavy oil.

Hone it, use cast rings. Moly rings take forever to seat anyway, and they'll never wear into imperfections. Cast rings will be a better choice. Dingle berry will give a good surface prep, but I would prefer stones to actually cut down the ridges a little. Dingles will kinda bounce in and out of the scratches and not give a uniform cut. Kinda like color sanding paint, you would use a sanding block instead of your fingers to get an even, flat cut.

^what he said.

I had a set of moly rings that never did seat properly.

After that, every race motor got cheap iron rings and a good, coarse hone to make everything seat well.

You're looking for a 3000 mile rebuild interval, not a 300,000 mile one. It's a budget race motor, be honest with yourself.

Even if it uses a bit of oil, oil is cheap.

Fwiw, the mx6 had scratches that make that look like normal crosshatching.

Still ran hard as berkeley.

Swank Force One wrote: Fwiw, the mx6 had scratches that make that look like normal crosshatching. Still ran hard as berkeley.

Yeah, I've seen someone else's "rebuild" that looked like someone swiped a dingleberry hone for five minutes in the engine above that shifted a wristpin, and it ran acceptably well.

It's amazing what you can get away with sometimes.

When I pulled my motor apart all four of the cylinders in the 1200 looked worse that and it was still revving to 7500 rpms. Due note it only had 80 PSI in each cylinder (which was why I pulled it apart). For a challenge car like everyone else said slap it together and let er rip.

Tom

Thanks for all the input, guys. I'll just go ahead and throw it together with an eBay gasket and ring kit.