Honda / Acura K20a K24a Engine Forum banner

1 - 20 of 58 Posts

·
Registered
Joined
·
49 Posts
Discussion Starter #1
I heard today that the k-series bearings are too thin for big boost and big power. Does anyone have experience that the high compression + boost = smashed bearings?

I plan on running 5-7psi on my stock k20a with 11.5:1 CR and a small turbo like gt28rs.
 

·
Registered
Joined
·
154 Posts
You'll be fine. I've been running 30psi for 2 years with no problems.
 

·
Registered
Joined
·
457 Posts
They are small, I bet you will be fine, or Honda would not have put them in there. Just make sure your oil pump is good, and you have good oil pressure and level. I spun a #4 bearing due to oiling failure. When we rebuilt it the first time, we called Calico Coating and bought their bearings, the are ceramic coated ACL bearings for a B18, I forgot with letter code though, they have it. It is slightly bigger and works. When we tore the motor down again 17K miles later and over 100plus drag passes and the last 3K miles I didnt care and abused it, ran it waaaaaaay low on oil, raced it like that, etc, we pulled the bearings, they had ZERO, yes that is right, ZERO signs of wear.
 

·
Registered
Joined
·
386 Posts
Why would the bearing being thin, make anything weaker or more prone to wear? Because, in theory anyways, the amount of material that is being used on the journals creates less friction due to it's size right? Correct me if I'm wrong please, because I want to understand this myself. I've heard of using H22A engine bearings in the K series bottom ends, but I'm unsure why that would be beneficial at all.
 

·
Registered
Joined
·
14,750 Posts
It doesn't have anything to do with friction.

Picture it like this. Take a hammer and hit a piece of sheet metal. It will probably bend. Now Take that same hammer and hit a 1/4" plate of steel. Probably not going to budge. Thats basically what's happening when those bearings are going round and round.

A thinner bearing will take less force.

get it?
 

·
Registered
Joined
·
12 Posts
If you run good quality oil you'll be fine! The hydrodynamic wedge created by the oil is what supports the crank and rods not the bearings. the bearing are there for protection in case the oil film breaks down and to help embed small debris particals.
 

·
Registered
Joined
·
81 Posts
We've done a lot of testing over the last few years on this (supposed) bearing situation, and I've concluded that the problems seem to only occur on engines built with too much bearing clearance, assuming the oiling system is working correctly.
 

·
Premium Member
Joined
·
5,000 Posts
We've done a lot of testing over the last few years on this (supposed) bearing situation, and I've concluded that the problems seem to only occur on engines built with too much bearing clearance, assuming the oiling system is working correctly.
Mr Wizzard - can you or anyone else here add what you feel would be appropriate clearances for both main & rod bearings? thanks in advance
 

·
Registered
Joined
·
386 Posts
I've had engine builders that told me to be specific about builds. Like the bearing clearances on an all motor set up should be smaller than a turbo set up, apparently anyways. So, there is no one size fits all bearing clearance for every set up.
 

·
Registered
Joined
·
81 Posts
We run .017" on all the bearings in the road racing K series we build. Drag racing NA combinations run .0018" and we run .0019" on turbo applications that are race only. If the turbo is a street-strip, we run .0018".
Cranks must be absolutely straight...unlike many of the aftermarket cranks, journals must also be straight when measured across their widths, and the main bores in the block must also be straight.
We ONLY use Honda bearings, as their system is the only one that allows us to fit bearings to less than a "tenth".
 

·
treblictuned
Joined
·
1,422 Posts
I heard today that the k-series bearings are too thin for big boost and big power. Does anyone have experience that the high compression + boost = smashed bearings?

I plan on running 5-7psi on my stock k20a with 11.5:1 CR and a small turbo like gt28rs.

i made over 600whp on my stock k20a2 shortblock. you will be fine
 

·
Registered
Joined
·
140 Posts
I might be off base, but as the journal and bearing don't touch (hopefully), and as the bearing when bolted in place essentially becomes part of the block/rod due to torque forcing it into complete contact with the saddles, and given the same clearances, is not the bearing heat and how well the block and rods act as a heat sink to wick away heat from the bearings the only thing that would be different from a thin and thicker bearing?

That is to say, the only thing within reason. A bearing .25mm thick obviously wouldn't be a good thing. It would seem a thinner bearing would transfer its heat more efficiently.
 

·
Registered
Joined
·
81 Posts
The originator of this thread should have stated "too narrow" rather than "too thin".
The ongoing debate relates to the width's of the crankshaft rod journals, the connecting rod big ends, and the bearings. This has nothing to do with the thickness of the bearing inserts.
As for the cooling of all these components....engine oil provides the cooling for all the lower-end pieces.
 

·
Registered
Joined
·
266 Posts
So from what i have read, is that its no big deal about what bearings to use, just make sure the gap between the rod and crank, + the gap between the crank and mains, Is proper. I am debating right now over ACL's, and OEM.
 

·
Registered
Joined
·
320 Posts
So from what i have read, is that its no big deal about what bearings to use, just make sure the gap between the rod and crank, + the gap between the crank and mains, Is proper. I am debating right now over ACL's, and OEM.


Bearing selection is very important...in my opinion anyways....eerybody's view may be different. OEM and ACL bearings certainly differ in both material and physical design. Whether or not these differences are advantageous or disadvantageous will have to be decided by the engine builder.

But I'd venture to say, bearing clearance is perhaps the most important "spec."
 

·
Registered
Joined
·
81 Posts
We fit bearing clearances to tolerances of less than .0001". I refuse to build Honda engines with aftermarket bearings...but then again, we unconditionally warranty the race engines we build.
 

·
Registered
Joined
·
320 Posts
We fit bearing clearances to tolerances of less than .0001". I refuse to build Honda engines with aftermarket bearings...but then again, we unconditionally warranty the race engines we build.
:wow:

Now THAT is just scary to me from a business aspect...but I don't have a business :p
 
1 - 20 of 58 Posts
Top