Official ACL Rod Bearing Measurements

[AutoTalent]

ACL Bearings



ACL Race Bearing Catalog: http://www.aclraceseries.com/images/catalog.pdf
Wiki: Full Technical Specifications
Photo Blog: About 100 full resolution photos

ACL Bearings has a long history in the automotive and racing bearing market. They are the latest company to throw their hat in the ring of S65 aftermarket bearings. ACL markets these bearings as extra clearance. The measurements below will show them to have a little extra clearance over stock bearings.


Appearance:

At first glance, the ACL bearings look worn and/or damaged. To the untrained eye, they might look like they just came out of an engine showing excessive bearing wear. Don't let the looks deceive you. This is normal appearance for ACL race bearings. ACL addresses this issue in their catalog with a lengthy description of their appearance. (See "Picture Description" below for a direct citation from the ACL bearing manual.)






Tools and Calibration

All measurements are performed on new "virgin" connecting rods and "virgin" connecting rod bolts. These rods and bolts have never been used in any engine. Using virgin rods and bolts is an essential step for obtaining reliable and calibrated results. After use, every connecting rod big-end is deformed with extra diameter. Using virgin rods and bolts ensures that the measurements obtained will be the same reference as a new factory engine. It's the only way we know to ensure repeatable and reliable results.



The image above shows the tools used for this job:

• * Two virgin connecting rods (P/N: 11247838623)
  * Snapon electronic torque wrench (P/N: ATECH3FR250B)
  * Mitutoyo data-logging drop indicator (accurate to 0.00002 inch) (P/N: 543-562ACAL)
  * SPI bore gauge (accurate to 0.00005 inch)
  * 2-inch calibration ring
  * SPI gage blocks

The Mitutoyo drop indicator is used to measure each bearing thickness. It's a very pricey tool that is accurate to 0.00002 inch. It features the ability to data log to computer, categorize the results with go/no-go screen colors, and it's the same tool used by BE Bearings to measure each and every bearing shell thickness.

Before beginning to measure thickness, the instrument must be calibrated. The SPI gage blocks are used to set the proper instrument calibration.



The bore gauge used to measure the bearing clearance and eccentricity must be calibrated as well. The 2-inch bore gage shown in the picture is accurate to 0.00004 inch.




Production and Composition

Manufacturer: ACL

Composition: Trimetal steel/lead/copper

Coating: None

Part Number: 8B1580H (STD, +0.25 mm), 8B1580HX (+0.025 mm)

Target Market: OEM replacement market; Minimal increase in clearance over OEM rod bearings

ACL Bearings are a full custom rod bearing designed and manufactured by ACL. ACL manufactures the bearings to their own custom specifications.The composition is a standard lead/copper bearing. The bearing does not contain a low-friction coating.

Set Numbering
ACL RACE Series bearing sets are identified by the ‘H’ after the set number e.g. 8B663H-Std. Most ACL RACE Series bearings are also produced in a ‘HX’ version e.g. 8B663HX-Std. The ‘X’ signifies the set will give an extra .001” (.025mm) oil clearance on a standard size shaft when compared to the H-STD set. The wall size of these HX-STD bearings is .0005” (.013mm) thinner than the H-STD Bearings, in all other respects the HX set is identical to the H-STD set. There are selected con rod bearing sets that are manufactured with a dowel hole in the lower shell, to suit a dowel location in the con rod cap. These are designated with a ‘D’ in the set numbering e.g. 8B663HD-Std or 8B663HXD-Std etc.

Lead/Copper, Tri-Metal design
Tri-Metal, lead/copper are considered the world's best bearings. The steel backing is coated with copper, then topped with a soft lead. The lead is embeddable, meaning small particles can embed themselves in the lead without causing any damage to the crankshaft. Look in the best automotive engines, and you're likely to find a Tri-Metal bearing design.

Oil Clearances
Oil clearances are most accurately measured using micrometres and bore gauges. Bearing wall thickness measurements are taken at 90 degrees to the parting line (i.e. at the crown of the bearing) using a micrometre with a ball anvil, for use on the curved ID of the bearing.

Vertical oil clearance is best measured by assembling the bearing in its housing, with bolts torqued to specification, then using a bore gauge measure the assembled ID of the bearings at 90 degrees to the parting faces. The mating crankshaft journal size is measured, and subtracting this measurement from the bearing ID bore size, gives the assembled oil clearance.

ACL RACE bearings can be assembled with .00075-.001” per 1” of journal diameter (0.020-0.025mm per 25mm of journal diameter) plus .0005” (0.013mm).

As an example for a 2.000” (50mm) journal diameter, 2.000 x .001= .002 + .0005 = .0025” (50/25 x 0.025= 0.050 + .013 = 0.063 mm) Bearings should not be polished with abrasive pads or paper, on the bearing surface, to change the oil clearance.

Picture Description

Questions about the appearance of the RACE Series bearings are quite common, as this series of trimetal copper lead bearings have a very different appearance to regular aftermarket “ACL Duraglide” trimetal bearings, which have a light silver /grey appearance.

The RACE Series performance bearings as manufactured have an appearance that is a dark tarnished colouration, which can vary from dark black/brown/blue colours. This colour comes from the electroplating which is the last manufacturing process. The electroplated overlay has copper as one part of its composition, which tarnishes to the dark colours described above. This tarnish colouration has negligible thickness, so once installed in the engine, the crankshaft journal contacting the bearing, will polish the bearing surface, removing the surface colour and leaving the bearings with a polished silver appearance.

Performance bearings do not start out with the silver grey appearance of regular aftermarket bearings, as there is no final silvery tin flash applied to these bearings. Not applying a silvery tin flash to these high performance bearings is a specific design feature. A silvery tin flash for appearance and long term corrosion protection, as applied to the regular aftermarket bearings, can under high loading and heat, move, with the plate migrating and causing high spots on the back of the shells, and distorting the bearing. For this reason the ACL RACE Series performance bearings do not have a cosmetic silvery tin flash applied, so there is no risk of any overlay plate movement on the backs of the shells, giving better bearing to housing contact and better bearing performance and function.

Standard (STD)




+0.250 MM, +0.010 INCH

Dimensions

Standard (STD)


+0.025 MM, +0.001 INCH


+0.250 MM, +0.010 INCH

Bearing Clearance Specifications

Clearance Measurements

Eccentricity Measurements

Bearing Eccentricity: ACL-H, ACL-HX Bearings vs. stock 702/703 rod bearings

Supporting photos

[Majdi]

What was the part number for the bearings you measured?

[Green-Eggs]

Originally Posted by 4org1ve

What was the part number for the bearings you measured?

STD bearings were measured. Measuring +25's would not be he very helpful.

Originally Posted by AutoTalent

ACL Bearings




...


Part Number: 8B1580H (STD), 8B1580HX (+0.25 mm)


...


Standard (STD)

...

[Helmsman]

Originally Posted by Green-Eggs

STD bearings were measured. Measuring +25's would not be he very helpful.

Thanks Green-Eggs. So does that mean one could assume nominal clearance on the +25s to be 0.075mm?

[elim11]

I appreciate the technical and thorough report. Nice work. Wish all vendors/mfgs would do something similar.

[groovetek]

So eccentricity and clearance variance look good then?

I guess it would have been nice to get the HX-STD measured as well, as most people are debating between that and the H-STD. I think there's some confusion here, ACL told me HX-STD is +0.025mm (0.001 inch) extra clearance, but retains the "STD" bit in the part number

Any talk of +0.25mm should be in reference to the extra thick bearings which can be used for where the crankshaft journals have been machined down (if they are damaged for instance).

With this info, would one opt for the H-STD as the clearance seems greater than OEM anyway? Or still go with HX-STD? Which I guess nominal clearance would be about 0.075mm?

[Majdi]

Originally Posted by groovetek

So eccentricity and clearance variance look good then?

I guess it would have been nice to get the HX-STD measured as well, as most people are debating between that and the H-STD. I think there's some confusion here, ACL told me HX-STD is +0.025mm (0.001 inch) extra clearance, but retains the "STD" bit in the part number

Any talk of +0.25mm should be in reference to the extra thick bearings which can be used for where the crankshaft journals have been machined down (if they are damaged for instance).

With this info, would one opt for the H-STD as the clearance seems greater than OEM anyway? Or still go with HX-STD? Which I guess nominal clearance would be about 0.075mm?

HX-STD is the one to go with. It doesn't seem like the measurements were done of HX-STD. Which is unfortunate. Hopefully they can do one about the HX-STD bearings.

[MaximusB]

Originally Posted by 4org1ve

What was the part number for the bearings you measured?

Did you really have to quote the whole post??

[Green-Eggs]

Originally Posted by groovetek

So eccentricity and clearance variance look good then?

That's between you and your engine builder. Earlier you were concerned that Bert would introduce a bias just by measuring and reporting the results. If he answers this question, then he'd be introducing a bias. All of the measurements and graphs for all of the different bearings are at his wiki page. That's the place I'd go if I wanted to compare them and see for myself.

I guess it would have been nice to get the HX-STD measured as well, as most people are debating between that and the H-STD. I think there's some confusion here, ACL told me HX-STD is +0.025mm (0.001 inch) extra clearance, but retains the "STD" bit in the part number

Any talk of +0.25mm should be in reference to the extra thick bearings which can be used for where the crankshaft journals have been machined down (if they are damaged for instance).

With this info, would one opt for the H-STD as the clearance seems greater than OEM anyway? Or still go with HX-STD? Which I guess nominal clearance would be about 0.075mm?

Originally Posted by 4org1ve

HX-STD is the one to go with. It doesn't seem like the measurements were done of HX-STD. Which is unfortunate. Hopefully they can do one about the HX-STD bearings.

Bert does all of this work with his own money and his own time. He bought all of the connecting rods and measurement equipment, and then bought and measured all of the bearings on the market. He's had the H-STD and H+25 for about four or five months. You can see he just got around to doing this, mostly because I kept asking him to do it. He's not going to buy a set of HX shells and spend any more time than he has to. If you wanted to buy a set of HX shells and send them, I'm not sure if he'd do the work or not. It never hurts to ask though.

[Majdi]

Originally Posted by Green-Eggs

That's between you and your engine builder. Earlier you were concerned that Bert would introduce a bias just by measuring and reporting the results. If he answers this question, then he'd be introducing a bias. All of the measurements and graphs for all of the different bearings are at his wiki page. That's the place I'd go if I wanted to compare them and see for myself.

Bert does all of this work with his own money and his own time. He bought all of the connecting rods and measurement equipment, and then bought and measured all of the bearings on the market. He's had the H-STD and H+25 for about four or five months. You can see he just got around to doing this, mostly because I kept asking him to do it. He's not going to buy a set of HX shells and spend any more time than he has to. If you wanted to buy a set of HX shells and send them, I'm not sure if he'd do the work or not. It never hurts to ask though.

Man. That's awesome! Tell him the ///M community appreciates his work!

I can buy a set of of bearings and send it to him. That's the least I can do. So please let me know.

My comment was in reference to that fact I wish it was the "HX-STD" ones that were measured and not the other ones.

[pbonsalb]

Originally Posted by Green-Eggs

That's between you and your engine builder. Earlier you were concerned that Bert would introduce a bias just by measuring and reporting the results. If he answers this question, then he'd be introducing a bias. All of the measurements and graphs for all of the different bearings are at his wiki page. That's the place I'd go if I wanted to compare them and see for myself.

Bert does all of this work with his own money and his own time. He bought all of the connecting rods and measurement equipment, and then bought and measured all of the bearings on the market. He's had the H-STD and H+25 for about four or five months. You can see he just got around to doing this, mostly because I kept asking him to do it. He's not going to buy a set of HX shells and spend any more time than he has to. If you wanted to buy a set of HX shells and send them, I'm not sure if he'd do the work or not. It never hurts to ask though.

I think the new only ACL bearings that anyone should have invested time and money measuring are the ones that compete with the extra clearance bearings on the market, the ones sold by VAC and BE. I don’t think BE really wants there to be a set if competitive bearings at half the price, so I doubt BE will measure them even if someone buys a set and sends them. If the ACL are just as good in terms of clearance, all BE can argue to justify their much higher price is better quality control (less variation among bearings in a set) and coatings. As a consumer, I like competition among suppliers.

[Green-Eggs]

Originally Posted by pbonsalb

I think the new only ACL bearings that anyone should have invested time and money measuring are the ones that compete with the extra clearance bearings on the market, the ones sold by VAC and BE. I don’t think BE really wants there to be a set if competitive bearings at half the price, so I doubt BE will measure them even if someone buys a set and sends them. If the ACL are just as good in terms of clearance, all BE can argue to justify their much higher price is better quality control (less variation among bearings in a set) and coatings. As a consumer, I like competition among suppliers.

Full disclosure: I'm the guy Bert called to order the ACL bearings for him. I know it was a bunch of months ago, but I don't think an HX bearing was available. All I remember is Bert telling me to order one of everything, and that's what we got.

I don't think you need the HX bearings to figure out the clearance from the current data. The thickness between STD and +25 is exactly what ACL claimed it would be. Just assume the same holds true between STD-H and SDT-HX.

[AutoTalent]

Originally Posted by pbonsalb

I think the new only ACL bearings that anyone should have invested time and money measuring are the ones that compete with the extra clearance bearings on the market, the ones sold by VAC and BE. I don’t think BE really wants there to be a set if competitive bearings at half the price, so I doubt BE will measure them even if someone buys a set and sends them. If the ACL are just as good in terms of clearance, all BE can argue to justify their much higher price is better quality control (less variation among bearings in a set) and coatings. As a consumer, I like competition among suppliers.

Bert already measured the H bearings, and it's easy to figure HX from there. I think that alone shoots that theory down.

I really don't think BE has anything to worry about. Be has...

• Better warranty. At least they have a warranty, and it's documented on this forum. Can't say that about anybody else.
• Better manufacturer. Clevite is hands-down a better manufacturer, more experienced, better quality, used by world championship race teams all over the world.
• Better design. Indy-500 winning, NASCAR winning, and Dinan were all involved in the design of BE. Nobody can say where or how the others were designed.
• Better testing. BE tests the effects of their bearings on oil flow, oil pressure, oil temperature. They've done this since day-1. Nobody else does any testing...just releases to the public.
• Better materials. Clevite=77 has been the top bearing in the world for at least 50-years. Then add the Clevite Tri-Armor coating and you've got the best S65 bearing on the market.
• Better quality control. Yes, every single bearing is hand-measured, sorted, and binned. This is done to ensure every customer gets the same target clearance as every other customer. The reason the S65 has the problems is because of tolerance stacking. BE Bearings takes measures to ensure their bearings don't tolerance stack. Nobody else does this.

So, long and short of it, BE has absolutely nothing to worry about and welcomes any competition that can compete on the same level.

[SYT_Shadow]

Originally Posted by AutoTalent

• Better warranty. At least they have a warranty, and it's documented on this forum. Can't say that about anybody else.
• Better manufacturer. Clevite is hands-down a better manufacturer, more experienced, better quality, used by world championship race teams all over the world.
• Better design. Indy-500 winning, NASCAR winning, and Dinan were all involved in the design of BE. Nobody can say where or how the others were designed.
• Better testing. BE tests the effects of their bearings on oil flow, oil pressure, oil temperature. They've done this since day-1. Nobody else does any testing...just releases to the public.
• Better materials. Clevite=77 has been the top bearing in the world for at least 50-years. Then add the Clevite Tri-Armor coating and you've got the best S65 bearing on the market.
• Better quality control. Yes, every single bearing is hand-measured, sorted, and binned. This is done to ensure every customer gets the same target clearance as every other customer. The reason the S65 has the problems is because of tolerance stacking. BE Bearings takes measures to ensure their bearings don't tolerance stack. Nobody else does this.

It is incredible how quickly people forget these items when comparing extra clearance bearings.

BE is the only one that we have extensive information on. Anyone else provides almost zero information and people have to test things out of the goodness of their hearts.

ACL certainly seems better than anything VAC touched but it is clearly not at the BE level

[deansbimmer]

Too many people get hung up over dollars and cents. BE is the gold standard for the S65/S85 bearings. The others will 'work', but if you're going to do them why not get the BE and have the confidence of their data and warranty to back you up?

[pbonsalb]

ACL is a quality bearing as well. I would not hesitate to put them in my S65 when I do them again, and am happy to have the choice. Deansbimmer has used ACL main bearings in motors he has rebuilt.

For its premium price, BE has the coating going for it and possibly less variation among sets (better quality control).

[deansbimmer]

I've used ACL rod bearings before but only when I couldn't get my hands on BE's and had no choice. WPC treated OEM's for mains.

[Scharbag]

Great to have options but here is my thought on this:

Consumable items:
Tank of fuel ~ $50 and the S65 uses lots of go-juice
Set of 4 tires ~ $1000 and she likes to eat the rears...
Oil change ~ $100 if you do it yourself

Non wear items (install cost/effort is same for either option):
Set of BE bearings = $530.10 (shipped from Redline360 right now)
Set of ACL bearings ~$250 (cannot remember exact price but close enough)

Difference is ~$270 for something that SHOULD last for the life of the car.

Price, IMHO, is not a factor when considering rod bearing replacement. The material cost is only a pittance (~5 tanks of fuel, set of rear tires etc.) compared to the cost/effort to change rod bearings. Furthermore, a rebuild/swap is going to cost 20x the cost of rod bearings.

Again, it is nice to have options. Competition is good when it is apples to apples products such as Brembo vs Stoptech etc.

But apples and oranges should not be compared as equals - cause we all know that oranges are better.

Cheers,

[pbonsalb]

Originally Posted by deansbimmer

I've used ACL rod bearings before but only when I couldn't get my hands on BE's and had no choice. WPC treated OEM's for mains.

Ok. I thought you had written you had used ACL main bearings.

[pbonsalb]

Originally Posted by Scharbag

Great to have options but here is my thought on this:

Consumable items:
Tank of fuel ~ $50 and the S65 uses lots of go-juice
Set of 4 tires ~ $1000 and she likes to eat the rears...
Oil change ~ $100 if you do it yourself

Non wear items (install cost/effort is same for either option):
Set of BE bearings = $530.10 (shipped from Redline360 right now)
Set of ACL bearings ~$250 (cannot remember exact price but close enough)

Difference is ~$270 for something that SHOULD last for the life of the car.

Price, IMHO, is not a factor when considering rod bearing replacement. The material cost is only a pittance (~5 tanks of fuel, set of rear tires etc.) compared to the cost/effort to change rod bearings. Furthermore, a rebuild/swap is going to cost 20x the cost of rod bearings.

Again, it is nice to have options. Competition is good when it is apples to apples products such as Brembo vs Stoptech etc.

But apples and oranges should not be compared as equals - cause we all know that oranges are better.

Cheers,

Is Shell better gas than Exxon/Mobil? Shell says it is the best. But Exxon/Mobil also said it is the best.

[deansbimmer]

Originally Posted by pbonsalb

Ok. I thought you had written you had used ACL main bearings.

Just rods but maybe I mis-typed somewhere. As far as I know ACL doesn't make mains for the S65. I use WPC treated mains.

[Scharbag]

Originally Posted by pbonsalb

Is Shell better gas than Exxon/Mobil? Shell says it is the best. But Exxon/Mobil also said it is the best.

BE never ever said they are the best. BE shared all of their data and engineering decisions and their reasoning.

People are free to make their own informed decision.

Cheers,