After quite a bit of reading and searching trying to figure out the exact thickness of the ACL HX model Race Bearings for the mains and rods I've come up with a few different numbers. The bearings are for a b18a bottom end, motor is being built specifically for circuit racing, ls vtec, pnp head, cams, ect. I don't need to go into great detail because it's not really relevant.

I'm looking to use the ACl's because of the tri-metal hardened design. I don't want to be worrying about an oem bi-metal bearing holding up to the abuse of a slightly less than ideal rod-stroke ratio spinning up to 9000rpm+. I'm aiming for 0.0020" to 0.0025" on the mains and 0.0020" to 0.0022" on the rods. I can't accurately calculate anything if I don't know exactly what I'm looking at as far as bearing thickness goes. I'd rather not buy them just to measure and find out they are too thick.

I've come up with 0.0783" per bearing half for the mains and 0.0584" per bearing half on the rods just from looking around on various honda related forums.

Looking on ACL's website I've come up with what I think is the thickness of the main and rod bearings. From there website, if I'm interpreting it correctly, I'm getting 0.0785" per half on the mains and 0.0587" per half on the rods.

So which set of numbers is correct, if either?

Also, are there any known issues with the ACL bearings in question? Such as oil holes being off, oil holes not being there, ect., things of that nature.

Thanks for any help.

 

Look here, on page 5: http://www.aclus.com/content/ACL07(1).pdf

The HX are 0.001" thinner for a thousandth more clearance... so take that into consideration.

Mark

 

I was just on their site today checking the STD sizes

http://www.aclperformance.com.au/us/...Bearingsus.htm

 

So the "max wall at crown" is the overall thickness?

Mark, according to that chart sizing would be 0.0582" on the rods and 0.0780" on the mains taking into account the increased clearence for the HX model. Would you interpret it the same way?

 

Have you measured your clearance? this would be detrimental before purchasing a set of bearings.

 

I was going to clearence everything tomorrow. Like I said, I would like to have a definitive answer on the thickness of the bearing halfs so after I take my measurements I can throw the thickness of the bearings into an equation and and see where they will put me for over all oil clearence on the mains and rods before I buy them.

Why would measuring everything before buying bearings be detrimental? That makes no logical sense. You want to measure then buy bearings based off your measurements; at least that applys the way I do it which is with a dial bore gauge and a micrometer.

 

I'm just going to give ACL a call tomorrow.

 

I'll walk you through the math as I see it.

Rod and Crank specs are from here: http://goo.gl/BBrve

Nominal size for the rod tunnel: 1.8898" -1.8907" (0.0009" service limits)
Nominal size for the rod journal: 1.7709" - 1.7717" (0.0008" service limits)
Difference between the tunnel and rod journal (gap within which bearing fits):

1.8907 - 1.7709 = 0.1198" (using max tunnel and min crank).
0.1198 / 2 = 0.0599" clearance per half shell
0.0599 - 0.0587 (HX bearing) = 0.0012" clearance, at max service limits

1.8898 - 1.7717 = 0.1181" (using min tunnel and max crank)
0.1181 / 2 = 0.05905" clearance per half shell
0.05905 - 0.0587 (HX bearing) = 0.00035" clearance at min service limits

NOTE: Those clearance numbers are for HALF shell. Multiply X 2 for the total.

This means, depending upon the tunnel and crank measurements, the HX bearings will give you between 0.00035" and 0.0012" of rod clearance as long as your rods and crank are within normal service limits; this for each half of the bearing. TOTAL is then 0.0007" to 0.0024" of rod clearance.

You can double-check this way using the earlier .1181" clearance:

Multiply HX bearing X 2 (two halves) 0.0587 * 2 = 0.1174. So... 0.1181 - 0.1174 = 0.0007 total clearance for a rod, this is minimum you will see if crank and block are in-spec. For the max, 0.1198 - 0.1174 = 0.0024" (2.4 thou).

That lines up pretty well with this post: http://goo.gl/kIywd

Plug your rod tunnel and crank journal #'s in and there you go.

That's my take - how'd I do on the math?

Mark

 

For the rods, I see (here: http://goo.gl/BBrve): 0.592" for H and 0.587
for HX

For the crank, I see (same place): 0.0790" for H and 0.0785" for HX

Those numbers are shell thickness.

You can plug them into my previous post, once you get your rods, crank, and block measured.

Mark

 

Mark I owe you one for that. Thanks buddy. Really appreciate it. I couldn't ask for a better explanation

Tomorrow I must measure things and do maths. Lol

 

You're welcome. Glad to help.

Note that I've updated the "math post" to clarify; the initial figures were clearances for each bearing half. So double that and you have 0.0007" to 0.0024" range of clearance for the rods using the HX bearing as long as your crank and block are within spec.

Note the implication here. If you used the H bearing, with 0.001" LESS clearance than the HX, AND at the same time had a block/crank combo giving you the minimum... you would probably seize the bearing as your clearance would be -0.00003".

In reality, if you pick the middle you should see about 2.4 - 0.7 thousandths, or 0.0017" clearance on the rods with the HX assuming your block and crank are mid-range.

You can see why Honda uses the colored bearing scheme - probably saves a lot of crank / block combos that would otherwise fail or be discarded as unusable... or require additional labor for pairing with a suitable counterpart.

Mark