Question about main bearings

Ok, I have another question(have lots, I'll try to space them out) The motor in the car currently has ACL race bearings in it I believe. I know they aren't stock STI for sure. Little over a year ago when I was having the motor built I thought race bearings would be good because I do alot of AutoX and want to get into HPDE, I've been to one. As the year has gone, I've put some miles on the motor and had a chance to see just how my plans have worked out.

I do autoX alot, should make 9 of the 10 events this year, but my budget only allows for really one, maybe 2 at the most HPDE's a year. The car is also my DD and I'll put close to 12k miles on it in a year(its 4 miles from the driveway to the parking lot.) At this point I'm wondering if it was really necessary to put aftermarket bearings in.

Here's the facts: 2.5 hybrid, got 10k on it, stock bore Mahle pistons, stock sti crank and rods, gets AMSIOL SSO 10w-30 at between 3.5-4k. AMSOIL EA type filter.. I don't rev past 6.5-6.7k, and after I upgrade the turbo(~1 year from now), probably won't change that. Don't know what else might be important, let me know if so.

SO, I guess its a 2 part question:
1. (And I'm pretty sure I know the answer to this one, lol) Are race bearings helping or hurting me in my situation?

2. Is it feasable to replace the main bearings without rebuilding the rest of the motor? If its decent idea, can it be done dropping the oil pan w/ the engine in the car?

Reason I ask is that I read somewhere that the difference between race and stock bearings is that racebearings are thinner for more oil flow, but have correspondingly less life. How much less? I don't know(surely depends on how hard the engine is worked,) but I don't want to find out when I spin one and have to replace Alot of stuff, ya dig?

Obviously this question is brought up thinking about my future budget, but I will do what is necessary to keep the engine healthy, just a matter of money being spent in the right places, not wasted you know? Thanks a bunch guys, and if there are any higher milage guys with aftermarket bearings, feel free to tell me to. "quite fing worrying about it!" lol Though I feel that parts of this may be of help to people who are honest with themselves on their goals and thinking about that built motor.

Ray

Personally I would stick with the race bearing.

The stock bearing tolerance is WAY too tight IMO and the issues come when you sustain high revs (above 4000) for long periods of time. In Auto X events it is very easy to have that. This is why you see people spining bearings on an otherwise healthy engine.

With the race bearings it is not likely you will spin a bearing because of the extra oil clearance unless you starve the engine of oil by not checking it and running low. The reason for the extra oil clearance is to get more oil in there but not necessarily for the purpose of lubrication but more for the purpose to absorb and remove more heat. The tight tolerance of the stock clearances don't allow for this in sustained high engine speeds.

Furthermore there is little difference in whether a race bearing will last longer than a stock bearing. They are certainly more durable and since they are being used in a race application, any bearings life will be compromised. ACL's construction is proven. Other bearing manufacturers have proven them selves also in the small block chevy and ford world.. those like Clevite and and King to name a couple.

The only thing you have to remember with the race bearings is you have to use a thicker oils. Some recommend 10W40.

If you are replacing the bearings it is likely that you will need to also replace the rings. You have to remove the pistons to get ate the bearings and once you disturb the ring seal it will be nearly impossible to get them to seal properly again. At that point you need to hone the block so it would probably be prudent to just do it all.

Ok, so it sounds like I may be fine for a while yet. Thank you very much for the info! I'll look into a heavier oil. Should be getting some results back from my last oil change in a few weeks. My old SgtMaj is an amsoil dealer, I took a sample and he sent it off for me a while back. I've never looked at an analysis before, but hopefully he can walk me through it. Plus I've got all the FSM's and the old EJ20 block out in the garage, I can tear that down and put it back together a few times, get some practice for a rebuild down the road.

I believe Jordan from Defined has a thread highlighting Amsoil. He includes an analysis and some explanation. Also if you visit the Amsoil sight they have allot of technical info that explains allot.

I can't find his thread because I'm mildly retarded but maybe he will chime in and give you some insight there.

The tare down and re-assembly of the motor is fairly cut and dry. The hard and time consuming part of it all is checking and rechecking all of your oils clearances. That is the single most important part of engine assembly. The other part is properly positioning the rings. And also make sure your parts are spotless and clean because one tiny particle could ruin it all.

I think I found it at one point, I'll look again. Oh, and the old motor got pulled from a blown headgasket, so I figure its safe for practice, lol. I may rebuild it one day though.

EDIT- this things been noisy since day one, maybe that little bit heavier oil will help that.

bugeye_fever said:

I think I found it at one point, I'll look again. Oh, and the old motor got pulled from a blown headgasket, so I figure its safe for practice, lol. I may rebuild it one day though.

EDIT- this things been noisy since day one, maybe that little bit heavier oil will help that.

Click to expand...

Maybe. Amsoil or red line for sure will help but the only way to truly get rid of the noise is to properly measure and adjust all the clearances... Match the bore to the piston... Torque plate bore and hone... Essentially, a proper machining. No one ever get this right and a noisy engine is only the result of something not being done properly.

The most noise you should ever hear out of a motor is on start up when it is cold and only for a minute. then it should go away. However I am of the opinion that there should never be any noise at all if the machine work and process was done correctly. :tup:

Yeah, I new going into it that it wouldn't be the best. It wasn't torque plated, but I didn't know what that was at the time. The builder said that the piston to wall clearance was in Mahles specs when I asked him about the noise, he said, "Some of them just make noise." Yeah.. sure. But there wasn't much I could do at the time, needed the car running. Kinda just told myself that it would run and at some point it would break, I'll take as much care of it as I can, but when it's time I'll take time and do it the right way.

Only noise I get is at idle and when the engine is decelerating under about 2.5k. Like if you sit at a light and rev it up with no load on the engine. Thanks again for all your help, i truly appreciate it.

Cool thanks! I've been using it about a year now, very happy with it, but this will be the first time I see an analysis of it, so I'll post it up or something.