i have 144k+ miles on my gsr, when i changed the oil i put 5w 30 in the engine (bad move) within a 2 days light driving i noticed a slight rod knock. i'm in the process of changing the bearings. Im in high rpm alot, with that said should i buy undersize acl bearings or stock size acl mains and rod bearings?
Thank You

 

you need to measure and if you have a knock your probably gonna need to turn the crank anyway

 

This should be left to the machine shop if you don't have the proper tooling to measure the crank and clearances. You wont know what bearings to buy (whether aftermarket or oem), until this is done.

 

You first need to meashure if your crank can be saved, then after repair meashure the rods you intend to use and the crank with a micrometer. after that you go ahead and buy whatever bearing fits the app.

btw I use 5w30 in my 600whp b16 reving 9300rpm all day. dont think your oil caused the problem, if it wasnt to hot.

 

General rule for race motors is to run them at .002 clearence on bearings, so that oil can more easily lubricate the parts.

 

If no crankshaft damage was done then you would use stock size.

 

what is the undersized rod bearings used for? the space between crank journal? What are the oversized rod bearings used for? the space between the rod journal?

 

 

nice response but just say you do not know. I see not to many ppl understands or knows the difference between the 2, obviously they are both made for a REASON. I was under the impression that the undersized rod bearings were used to compensate space on the crank journal from having the crank grinded down. Not to sure on oversized

 

See it's responses like this that makes me not want to start a nOOb build thread atleast you manned up and helped the guy lol

 

Undersized would be used with a crank that has had material removed for whatever reason.

 

ok so i was right now what about oversized? Thanks for helping me LEARN SOMETHING, guys need to realize we all were not born with the knowledge of mechanics I am sure we were all "noobs" once.

 

I'm a nOOb till I die! So I claim no knowledge and also not responsible for what you do with what I say!

But didn't 1998GsRIntegra explain what "oversized" would be used for? like I said I'm a learner too, but this makes sense to me.

But what everyone is trying to get at I think is: untill you crack her open and measure it than you really can't guess on what the problems is or what you need to do to correct it???

 

Sweet Jesus, Man....you are literally too ignorant to realize where he was going with his statement.

I've never heard of a machinist or engine builder even MENTION an "oversized" bearing. They're referred to as "Undersized" b/c the term is referring to the size of the journal where you're using them. i.e...if you take .020" off the journal, your journal is now .020" UNDERSIZED, so you need "Undersized" bearings. "Undersize" bearings are THICKER than normal bearings. Granted, it's a misnomer..and kinda counter-intuitive.

You guys want to jump on the knowledgeable ppl for "talking sh*t," and you come around and say stuff affirming that not only do you not know sh*t....you don't even know enough to know that you don't know sh*t.

Word of wisdom: It's better to remain silent and be THOUGHT a fool than to open your mouth and remove ALL doubt.

 

I can't tell if I am being reffered to as a moron or not.

Either way I was reffering to when you are assembling the motor. When you install the bearings and use plastic gauge to check the clearences. For a race na motor you usually shoot for about 2 thousants clearence on the bearings. It allows the motor to run a bit looser than if you were to rebuilt it to factory spec. If it were built to factory spec it would run with less bearing clearence i.e tighter. The reason for running a motor looser is because it makes it easier for oil to lubricate the bearings at high rpm. When I build a race motor I usually end up with a combination of honda yellow and honda pink bearings to end up with 2 thousants clearence. OP if you are rebuilding to factory spec then use the bearings as indicated on the bottom of your block. There is a code that tells you what oem honda bearings to use. You would only use undersized bearings on a factory spec rebuild if you had to have the crank machined.

 

Cool, I never defended my ignorance. Nor did I jump on anyone, was just picking on Bam which I respect highly. true I should keep my unhelping comments to myself, but if it stirred you up enough to answer the OPs question and I learn something from it, well then it wasn't a complete waste was it? Really I was assumeing that the "oversized bearing" he reffered to was meaning it had a larger gap from the journal. But assuming got me in trouble so I'll take your advice and stay out of topics I do not have an answer to, thankz.

 

Again, am I the one being reffered to in this post? I don't mind answering questions at all. I just posted again because it seemed like my vague original post was being mis-interpreted. There is no need to bash each other. I have noticed lately that everyone seems to be really touchy for one reason or another.

 

Really? How many motors have you built? I find it highly doubtful that its been too many...if you're just regurgitating info be sure to add a disclaimer.

 

Thank you I greatly appreciate your input, you have cleared this up for me. This all I was asking for a simple explanation. Thank you again for your time sir.

 

Well then let me be the first.

An oversized bearing is somewhat new to the automotive industry. A lot of new engines use a cracked cap style connecting rod where the surfaces that the rod and cap meet fit together like a puzzle piece.





This is what they look like, this one specifically coming from a SRT-4. Most of GM's LS engines as well as Ford's OHC Mod Motors have the same style.

If you know how connecting rods are resized, you would know that on a typical "old-school" connecting rod these surfaces are flat so the machinist can cut them to reduce the housing diameter and then be honed back out to spec. Since these are the cracked cap style, you don't want to do that.

Enter the oversized bearings. Instead of cutting the parting surfaces to reduce the bore diameter, machinists are supposed to just hone the rods out about .002" larger and use the oversized bearing for the larger diameter bore.

 

ok cool makes sense

 

Ppl are "touchy" on here b/c a lot of us remember what this board USED to be like...and get fed up of people asking ignorant questions.

As for YOUR Reply, 1998GsRIntegra, I wasn't even referring to your post.

I guess I showed some ignorance of my own. I'd never even heard of anyone refer to an "Oversize" bearing. Granted, this is probably due to the fact that it's not really applicable in a B-Series engine (due to the type of connecting rod used). I've been around old-school GM Small Blocks and Honda B-series. So, never heard of an "Oversize" bearing. I'm guessing it's referring to the bore in the connecting rod being "oversized"?

 

I like to think of HT as a more sophisticated network of people. There are plenty of honda forums out there where the forums are just loaded with how much hp would this be or what parts should I use or what should this dyno threads. I steer away from those type of forums. And I think alot of members on here don't mind helping others and attempt to provide the best help possible. No one here knows everything, but collectively, there are some pretty smart cookies around here and I do think members try to police these boards in an attempt to keep unintelligent or already answered questions to a minimum. It would be more beneficial to just read and learn. And if you do have a question, present it in an intelligent manner so that members can better help clarify things for you.

 

Started when I was 13 and I have done 8 so far. I'll list them if you like beacuse I can tell you don't believe me.

 

I believe volvo uses these type of conrods as well.