Cylinder Bore Diameter tolerance

I'm rebuilding a Hyundai 2.0t engine with 130,000 miles. I have just finished checking the bores Diameter with a bore gauge and found that the diameter in my number 4 cylinder is off the factory limit by .0005". All the other cylinders are with in the limit of 3.3853"-3.3871". The measurement for cylinder 4 near the TDC is 3.3876" measuring side to side and 3.3870" measuring front to back. It is with in the out of round limits per the manual of .0019", but the bore is bigger in that one spot only on cylinder 4. Would I still be able to use new factory pistons and rings, or do I now have to get my bore machined and get oversized pistons?

Thank you,

Wesley

Largely depends on the actual condition of the bores - are there any scratch marks, etc? What you expect from the engine - is this a simple "stock" rebuild where you just want to keep it a a 'runner', or are you planning on using more boost and leaning on it more?

If the former, a light hone and re-ring should be the best option - new pistons are a waste of money, unless...

If it's the latter, in which case new stock bore pistons are a waste of money - you should have the engine bored and honed to the next-oversize pistons so you have the optimum clearances for the pistons. When you consider the overall cost, the bore and hone is still only a relatively small extra cost if you were budgeting for pistons, anyway.

Also, with the latter, it gives you the opportunity to buy better pistons in case you might increase the power a little - BUT don't forget that other factors, such as con'rods, head gaskets, etc, may also be weaker than the "OEM" equivalent pistons, so spending extra there isn't always the wisest move.

Gord,

It's going to be a daily driver. I do plan on fitting the factory turbo with new turbine wheel and a new tune to put me at about 65hp over the stock and sitting me right around 300whp. All the stock components will do that with little issues, so I just need to know if I can use new oem pistons size being that slight bit out of recommended factory spec. I have a machine shop that can do the work and I have budgeted for new wizeco pistons, but I can't order them until I decide if I want them .5MM oversized or the stock 86mm

Well, I decided to just get the bores machined to .5mm over, so that solves that issue. Kia/Hyundai didn't have the best build quality for it's OEM parts in 2013, so even though most of the rotating assembly is fine, I'm going to eBay those off and order a new rotating assembly. I am going to try and keep the factory crank and just have it repaired by the machine shop paired with oversized bearings.

I would have liked to get a response from an expert or some kind of site tutor, however. How long do I usually have to wait to get a response from someone from HPA?

If you're going to be leaning on it, the rebore is a good idea. I don't know how strong/tough the connecting rods are - some engine's are able to take a big increase in cylinder pressure and rpm, but others are marginal. That said, if you are replacing them, don't just replace with the same OEM ones, but make sure you have suitably upgraded aftermarket ones that will survive the boost and/or rpm levels you may (potentiall in the future) wish to use. Same with the crankshaft - some will take a LOT of power increase, but others may be marginal.

Other things to consider are the head bolts (most made in the last two, or three, decades used TTY, and a stud or better bolt is a good idea.

At least consider the clutch that will be getting a lot more torque, and the transmission.

Depending on how hot it gets where you live, you may need to look at improving the radiator and, maybe, run a dedicated oil cooler for the engine and, if auto', transmission.

Gord is an expert on machining, engine building, and I totally agree with the advice he offered. For a modest power increase, the stock parts and bore are both fine, unless there's damage and parts need replaced, bores need oversized to clean them up.

Please let us know why the engine came apart. If there was an issue with the engine that led you to rebuild it, what was the issue, which parts are damaged? With more info on the situation we can better tailor our suggestions.

If this is a Genesis 2.0T, the stock internals seem to hold up well up to 350 wheel torque, 450 wheel HP.

Uh, NOT an "expert", Mike, but thanks - just been around a long time in this, and other, businesses and stuff, and got some thoughts and ideas developed over that time.

I've been on other, now deceased, forums and where possible I'd have an automated byline at the end with something like "These are my thoughts and suggestions - but sometimes I'm wrong", but it doesn't seem to be an option here.

It's also why I strongly recommend people get as much information as they can, from different sources, because it's THEIR time and money that's on the line.

I know you're humble, but I appreciate your insights from your lengthy experience.

As I do yours, and that of other folks - learning a lot!

No offence, intended for you, Gord. I was simply going off your title. I'm new to the forum, so I just wanted a Tutor title account to give more solid answers and be more direct. Lots' of money is involved in this process and I'm no Gordon Gekko, so I'm sure you get why I want it. I'm also extremely direct with people online, so I hope I don't come off as harsh, but I usually do, so my apologies in advance.

Mr. McGinnis,

Thanks for the reply.

"Please let us know why the engine came apart. If there was an issue with the engine that led you to rebuild it, what was the issue, which parts are damaged? With more info on the situation we can better tailor our suggestions.

If this is a Genesis 2.0T, the stock internals seem to hold up well up to 350 wheel torque, 450 wheel HP."

The engine seized from a spun rod bearing that melted to the crank. The Hyundai 2.0t is known to have weak rod bearings and lots of failures because of that. I took it to the machine shop and the they said they could repair it to one under so the whole stock parts thing went out the window. I need oversized rod bearings and with 130,000 mi on the block, I found the last bore was out of spec using the techniques I learned in the engine building course so I'm doing the bores .5mm over. I already ordered wiseco pistons to 86.5mm which is .5mm over. I went with arp main studs and head studs, too, so I have to get all that machined to realign and hone everything. I kind of already knew what I needed, Truthfully, I just wanted a tutor to reassure I was making the correct decision and I'm following the classes correctly. This is my first lower end build, so I'm treating it like a college course. I wanna go into the test with nothing left on the table to question and Ace that MFer... And I'm not trying to do this twice. I still have a Dodge Challenger 6.4l and a 3.0l Nissan 300zxtt to build right after this. My GF volunteered her vehicle to me to learn... and because I'm free labor ;)

BTW this build is meant to be a daily with no more than 300whp. I was trying to use all stock components and replace just the crank and rod bearings that went bad... But like I said before, that went out the window the more I learned in the courses and measured my bores and learned about arp main studs... This is my learning process.

Don't know why you're apologising, Wesley, it's YOUR money, I EXPECT you to be cautious of how you spend it, and I EXPECT you to get as much information as you can get for what you're doing. Remember, these are MY thoughts, and opinions - they are NOT definitive, I may be mistaken, or overlooked something, or expressed something poorly, or something else.

As far as I'm concerned we're ONE HUNDRED PERCENT COOL!!! :-) BTW, I have the same problem, sometimes going back and apologising if/when I think I was harsh and/or someone seemed upset - usually if someone was determined to do the wrong ( in MY "opinion") thing.

That said, you say they have a reputation for "weak" rod bearings? That is a concern and the root cause needs to be identified - common isues are insufficient crush, too tight clearances (including side and radius, if used) - oil flow is needed to carry away the heat generated by the viscous friction, low oil pressure - the oil has to pass through the block oil-ways, against the centrifugal force at the main bearings, through the crank and to the rod bearing.

Different folks will have different thoughts, if it's an OEM tolerance issue, new rods may have the same issue, you may be better having your machine shop check and resize the rods you have. If it's a problem with the oil supply, opening up the galleries with a drill may help - oh, don't forget to check the various oil hole line up and the shells are correctly fitted. If it's a low pressure problem, and the oil pump is in good condition, simply shiming or replacing the pressure relief spring may be all that's needed.

Whatever the cause is, it needs to be identified, and rectified, as otherwise you may be risking the same thing happening again.

Please keep us updated.

Wesley, thanks a bunch for the additional background info. That really helps us understand what you're working with and how best to proceed.

Gord's mention of resolving the root cause of the failure may seem obvious, but quite often folks don't do that, so I'm glad he mentioned it.

In this case I don't know if you're the first owner of the vehicle, so it's possible some wear happened before you got the car due to poor maintenance or abuse and you're just the unlucky one it finally failed on.

I don't agree with the factory oil weight or the oil change interval on that car, and that's common these days because oils are being chosen for fuel economy, intervals for CAFE credits and advertised lower cost of ownership, all with the goal of the engine making it past the warranty period, but not living a long life.

I tell people 5w40, change it every 3k on that engine unless you do lots of short trip driving and then significant gas contamination of the oil can occur within that 3k window. Having oil analysis performed will help better inform that decision in the future.

Long oil change interval, fuel dilution, thin oil not protecting the rod bearings well on that engine can lead to premature bearing failure, and as Gord mentioned factory tolerances may not be great to start, but that part is being fixed now.

Replacing all oiling components is key to avoid a repeat failure when a bearing fails. Not just the oil pump, but any oil coolers, the turbo, any variable cam components as well. Then any components that are scored or otherwise damaged from debris may need replaced i.e. cylinder head internals. I'd also replace the main o2 sensor.

How is it being tuned? That car doesn't have many options for tuning, and knock while near peak tq area can pound the rod bearings out, so that's something to make sure is set up in a safe manner as well. Even with all the internals upgraded, knock can take a rod bearing out just as easily.

Monitoring oil pressure and temperature will also help you keep an eye on the engine and ensure it's being operated in a safe range. Ideally you'd be able to datalog these things, and the pressure portion at a high speed so you can see what's going on far more than a standard gauge can offer.