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Just got my engine bearings coated...looks great

In a prior thread I was commenting that the new rod and main bearings I bought were .0005 undersized (verified). My current main bearings looked like new, my rod bearings had very slight wear... The new bearings opened the clearance up another .001, which I don't want. The old bearings, on the other hand looked good, but were old. I felt nonproductive just putting those back in...

In that thread, Ollies had recommended sending them to HM Elliot for their high tech race coatings, which only add .0002 back to the bearing. I understand that this is used for pistons and valves also...

Just got the bearings back, they look pretty darn good. The coating as I understand it is teflon?

I can tell you its pretty hard, and scratch resistant, unlike the stock coating which easily comes off... A light scratch with a knife tip isn't taking it off...

Bearings look brand new...

Once I get my bore indicator, will see which bearings give the better fit (new, or old)...

Not sure how "embeddable" this stuff is for micro debris, but seems lots of folks are using it, race teams, etc.

I was also told it should last forever, as long as the crank doesn't run clear of oil, at which point it comes into play...

Thoughts? Anyone else used it? I see that the new clevite bearings are also coated with a black similar substance, thought I don't know if its the same thing?

As a side note, getting this treatment done is SUPER reasonable cost wise...

Comments? Positive? Negative? I see in the assembly videos of 930 motors on the net they also have a black coating... same? Don't know...



Last edited by bpu699; 10-03-2017 at 03:41 PM..
Old 10-03-2017, 03:39 PM
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Just did some more research...

https://www.facebook.com/HMElliottIncCoatings/

According to their site this is the coating that is placed on clevites!!! Also the coating Mahle uses, and now also used by Oem manufacturers on new high end vehicles.

Cool videos on their website... used in NASCAR...

If it's good enough for a high end daily driver, should be great in our cars...

Pretty darn cool...
Old 10-03-2017, 04:39 PM
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I think PTFE has become pretty common on ESS vehicles. It is a cheap insurance. The thing is, all those bearings are lead-free, so they have lost a lot of the conformability that Porsche bearings still have. So, maybe not hurting, but not helping that much either.
Old 10-03-2017, 07:34 PM
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Quote:
Originally Posted by Speedy Squirrel View Post
I think PTFE has become pretty common on ESS vehicles. It is a cheap insurance. The thing is, all those bearings are lead-free, so they have lost a lot of the conformability that Porsche bearings still have. So, maybe not hurting, but not helping that much either.
I am just learning about all of this... it is fascinating...

I don't know the prep that's used when they do the coating. As it adds thickness, it would seem that this is an overlay to what ever the original bearing had...

The coating is some kind of proprietary concoction that includes several lubricants, including PTFE (Teflon)...

The coating does seem to "hold" oil in, when coated, as I know they also do other coatings that shed oil. Obviously, you don't want to shed oil off a bearing/bushing.

The point you mention is a good one. It seems, unless I am misundesratnding the function, that you are loosing the embedibility of the 1980's technology bearings...

Perhaps a pro can chime in on this...

But newer cars are running 0-20 oil, with tiny tolerances much smaller than what our cars run. I would think that the lack of foreign body embedibility would be much more troublesome for these cars with tight tolerances. Yet, the newer cars are apparently going this direction.

I find it unlikely that new cars would be suing this if there weren't some kind of net positive.

Also, the brand new clevite bearings I bought for the rods, have a similar/same coating on them? According to the HM Elliot site they coat all the Clevite bearings... If that's so, then the new "high end" bearings available for our cars have the same coating?

For as prevalent as these coatings seem, there is very little on the internet chat boards discussing the pluses/minuses.

Still debating whether to go with the new glycol mains/clevite rod bearings I also have. But I am very pleasantly surprised how well the coating on the prior bearings looks...
Old 10-04-2017, 05:18 AM
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They look great, can you share how much the coating services cost you?
Old 10-04-2017, 07:49 AM
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Is coating a bearing the new Snake Oil?

Clearly I am not being entirely serious but many of these new technologies seem to now be an essential part of any engine rebuild and again costs just keep ratcheting up.

Reducing clearances does have some benefit but this tends to be associated with very highly loaded bearings that are used in modern diesel engines that increasingly look as if they may not see out the decade.

I believe coatings have been developed to deal with the reduction of embeddability of the harder bearings needed in these types of engine.

Clearly increasing bearing loads increases the fatigue susceptibility of the traditional bearing hence the new materials.

I still remember - but only just - my first practical class at college where I initially studied Metallurgy and we were provided with sample bearing kits supplied by Glacier which stepped though the properties characteristics of bearings from the early days of Babbitt alloys and the development of the Thin Wall bearing, which until recently had changed very little since their introduction in around 1947.

I have been collecting data on clearance, oil viscosity, power loss, minimum oil film thickness and surface finish for the last few months to try to improve my overall understanding in this area and have only just started to try to correlate the information and come to a conclusion about the best way to proceed.

I also wonder what the impact of applying an even thickness over the surface of the bearing has on the crush relief which is where we tend to see the initial development of fatigue cracks.

All very interesting.
Old 10-04-2017, 09:11 AM
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Actually, assuming this is a viable alternative its CHEAPER.

For example, I bought new Clevite bearings... $350-400. New Glyco mains, $200. Lets call it $600.

Cost to have my main bearings redone (which looked like new).... $40

Cost to do clean/surface/coat rod bearings? $35.

Grand total, with shipping $100. And, this is at a place with a stellar reputation doing OEM work. When I opted to try this, I figured that worse case scenario I'm out $100 and used bearings. But, oddly enough, the bearings look great. I don't know their process, or prep...

For me, this isn't a cost issue. I am pretty much into the thousands at last count...
But, it is a clearance and quality issue.I am curious by nature, and love learning and exploring new way to do things. This is a great board to share info, figured this might help someone.


The new bearings are .0005 undercut. So, your clearance will increase .001. That may or may not be an issue, it depends. My understanding is that one can buy the Porsche measured bearings, and those are in spec (from other posts on here)...

But a lot of guys disassemble their motor, and their bearings look great. But you always have that nagging feeling, that you might as well replace the bearing anyway. Perhaps, this is a viable "improvement?"

I did email HM ELLIOT to get more info on the process. Does the babbit layer stay? Get removed?

Im nervous to use these, as I don't see a lot of info on here in regards to this. But it looks like the 944 guys have been coating their bearings back to 2004 if the posts on here are accurate.

The fact that Mahle and Clevite use this process is a plus...

Should make for an interesting discussion.
Old 10-04-2017, 10:42 AM
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I've been getting my bearings coated by Calico. I think some of the other builders like Henry have also used Calico dry film in the past.

However, if Ollies and Clevite are using HM Elliott, I'll definitely look into that for my next sets. Thanks for posting this info.
Old 10-04-2017, 11:41 AM
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[QUOTE=bpu699;9761864 The new bearings opened the clearance up another .001, which I don't want.

...

In that thread, Ollies had recommended sending them to HM Elliot for their high tech race coatings, which only add .0002 back to the bearing.[/QUOTE]

So... can you please explain this?
I'm new in this grinding and replacing bearings thing and I've read some other threads in which they are looking for a specific clearance.

Why is this important? and what affect does the measurement have on the cranks, cams?
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Old 10-04-2017, 11:49 AM
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I had missed the fact you were re-using bearings - a parctice that in itself can generate significant debate.

I do feel that we become very excercised by bearing clearance which does have a reasonable tolerance in which to operate.

We always seem to try to measure these clearances beyond the limits of the basic metrology we genarally have to hand.

If we fit the crank and measure its's vertical clearance in a cold workshop it will differ by more than the 0.0002" we are considering as a change in ambient temperature of 25 degF will change the journal diameter at least 0.0004" and the crankcase will change more.

Apart from boundary lubrication dueing stop/start I am not sure howa dry film helps reduce friction.

The surface finish of the crank - within limits- and the type of bearing has virtually no impact on fricton once the bearing is operating hydrodynamically heence my comments concerning snake oil.

In fact the presence of circumferntial groovers on the journal with a plateau finish seems to produce the l;owest fricton due to an ability to retain a film of controlled thickness.

I am also unsure as to why a sprayed on dry film improves the strength of the bearing and would welcome an explanation.

Calico Coatings don't really provide much real data about CT-1 which is fairly diasappointing.

Coatings which shed oil would seem to be best avoided for use with cranks and rod bearings.

Did you measure the crush on your freshly coated bearings?

The problem with bearing fatigue is that the bearing will have accumulated damage before it becomes visible and the fatigue performance of the bearing is unlikley to benefit from a dry film coating.

Some of the new PVD coatings bei g developed do help with fatigue but these systems tend to be applied during manufacture.

Im am sure there is a small benefit from Dry Films but I think that the claims are a little OTT.

We have used Graphogen in all of our engine assembly since we started racing back in the Seventies and still use it now.

Graphogen | Home
Old 10-04-2017, 01:07 PM
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Quote:
Originally Posted by Trakrat View Post
So... can you please explain this?
I'm new in this grinding and replacing bearings thing and I've read some other threads in which they are looking for a specific clearance.

Why is this important? and what affect does the measurement have on the cranks, cams?
My understanding is that you want a certain clearance range that's acceptable. There are several threads on here where folks have bought brand new crank bearings, and found that there clearance was now "too big." They put their old bearings in, and it was fine.

That why I measured the new bearings from Glyco and Clevite. They are .0005 thinner than the old warn ones. Thought it was a fluke (or everyone would question the ability to measure it), so I called Automobile Associates who makes the Clevites for Porsche, and they verified they are in fact cut .0005 thinner. They are intended for race applications.

This added clearance may or may not put your clearance out of range.

So, others have popped in their old "look like new" bearings, as their quality may be better than the "new bearings."

I did find reference that HM ELLIOT and other coat old exotic bearings for rare cars, as no one makes the correct bearing.

No point in coating an old "bad bearing", but what about ones that look like new?

I have no issue getting and paying for new bearings. In fact, I did. I didn't expect them to be thinner than the bearings I was removing... Frankly, I expected them to be thicker!
Old 10-04-2017, 01:46 PM
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Originally Posted by chris_seven View Post
I had missed the fact you were re-using bearings - a parctice that in itself can generate significant debate.

I do feel that we become very excercised by bearing clearance which does have a reasonable tolerance in which to operate.

We always seem to try to measure these clearances beyond the limits of the basic metrology we genarally have to hand.

If we fit the crank and measure its's vertical clearance in a cold workshop it will differ by more than the 0.0002" we are considering as a change in ambient temperature of 25 degF will change the journal diameter at least 0.0004" and the crankcase will change more.

Apart from boundary lubrication dueing stop/start I am not sure howa dry film helps reduce friction.

The surface finish of the crank - within limits- and the type of bearing has virtually no impact on fricton once the bearing is operating hydrodynamically heence my comments concerning snake oil.

In fact the presence of circumferntial groovers on the journal with a plateau finish seems to produce the l;owest fricton due to an ability to retain a film of controlled thickness.

I am also unsure as to why a sprayed on dry film improves the strength of the bearing and would welcome an explanation.

Calico Coatings don't really provide much real data about CT-1 which is fairly diasappointing.

Coatings which shed oil would seem to be best avoided for use with cranks and rod bearings.

Did you measure the crush on your freshly coated bearings?

The problem with bearing fatigue is that the bearing will have accumulated damage before it becomes visible and the fatigue performance of the bearing is unlikley to benefit from a dry film coating.

Some of the new PVD coatings bei g developed do help with fatigue but these systems tend to be applied during manufacture.

Im am sure there is a small benefit from Dry Films but I think that the claims are a little OTT.

We have used Graphogen in all of our engine assembly since we started racing back in the Seventies and still use it now.

Graphogen | Home
HM ELLIOT has some videos on their site. The one that made sense to me, talked about the fact that the risk of bearing wear, and spun bearing, is greatly reduced with Teflon based coatings. The crank "digs into" a soft babbit bearing under low oil film, not so with the coating.

As with any relatively new tech, I am somewhat weary. But the fact that its being used in the new stop/start vehicles/nascar/and dragsters, seems to carry some credence.

I figured it might decrease a spun bearing at the cost of greater crank wear... but if new cars are using it, that may not be so. I am sure a new manufacturer expects 150k miles out of their cars...

Does anyone know if the Calico coating are different than the HM Elliot ones? They all seem to be Teflon based in one way or another....
Old 10-04-2017, 02:01 PM
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Originally Posted by bpu699 View Post
Does anyone know if the Calico coating are different than the HM Elliot ones? They all seem to be Teflon based in one way or another....
There is so little information provided it is difficult to say.

Calico seem to offer a Dry Film coating and Elliot offer HM30 and HM14 neither of which seem to be well defined.

Did you use the HM-14 Coating ?

Mahle 'Stop/Start' Bearings are coated in a PAI resin (Torlon) with a Moly-Disulphide Dispersion acting as a solid lubricant.

This applied to an Aluminium based Bi-metallic bearing.

I can imagine that a PTFE coating can help with friction in a Stop/Start condition and if bearing fit is marginal then it may help with preventing spin.

In real terms if bearings spin then the crush of the bearing must be inadequate.

Applying a coating to the back of the bearing may help to increase crush but 0.0002" will have a very small impact and more measurement is needed before the coating thickness could be specified.

We also get back to the problems of measurement that we also discussed recently.

Vertical clearance measurements will be temperature sensitive to some extent and if we look at the journal it will change size by around 0.0004" for a change in temperature of about 25 degF. The crankcase will change more so measured clearance will differ slightly but probably make little difference.

For $100 I am sure it can't hurt and will probably provide some benefit.

If the suppliers of these processes provided better technical detail of both the process and how the improvements were obtained it would be helpful.

Last edited by chris_seven; 10-05-2017 at 12:14 AM..
Old 10-05-2017, 12:11 AM
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Quote:
Originally Posted by chris_seven View Post
There is so little information provided it is difficult to say.

Calico seem to offer a Dry Film coating and Elliot offer HM30 and HM14 neither of which seem to be well defined.

Did you use the HM-14 Coating ?

Mahle 'Stop/Start' Bearings are coated in a PAI resin (Torlon) with a Moly-Disulphide Dispersion acting as a solid lubricant.

This applied to an Aluminium based Bi-metallic bearing.

I can imagine that a PTFE coating can help with friction in a Stop/Start condition and if bearing fit is marginal then it may help with preventing spin.

In real terms if bearings spin then the crush of the bearing must be inadequate.

Applying a coating to the back of the bearing may help to increase crush but 0.0002" will have a very small impact and more measurement is needed before the coating thickness could be specified.

We also get back to the problems of measurement that we also discussed recently.

Vertical clearance measurements will be temperature sensitive to some extent and if we look at the journal it will change size by around 0.0004" for a change in temperature of about 25 degF. The crankcase will change more so measured clearance will differ slightly but probably make little difference.

For $100 I am sure it can't hurt and will probably provide some benefit.

If the suppliers of these processes provided better technical detail of both the process and how the improvements were obtained it would be helpful.
Chris, I had the standard bearing coating applied, I believe its mh30. Its only applied to the bearing face, and tips, not the back.

Not sure how one measures or assesses "bearing crush." The bearings did have resistance in the case when removed, and had resistance when popped back in. They do coat the bearings tips (for lack of a better word), so each tip would increase in length by .0002-.0004. That would increase its diameter slightly, improving "crush."

If I have time this weekend I will measure the bearing thicknesses again, after coating. And, time permitting, bearing clearances.

I have to say, its actually enjoyable to rebuild a motor, along as you enjoy the process and take your time. You do learn an aweful lot.

A lot of these coatings have been available for over 10 years in one form or another. Yet, searching the internet, you find very little info. Some of the hot rod sites have used them for a long time.

If they "work" and help protect the engine, I am not sure how one would know for certain. If they caused engine and crank damage, you would think there would be lots of threads somewhere on the internet about it...
Old 10-05-2017, 05:13 AM
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Measuring bearing crush is easy; bolt the case together with bearings but no crank and use a dial bore gauge to see what you have. Or less accurately, do the same thing with crank and use plasti gauge.

It may have been said already but what instrument are you using that measures as accurately as .0005?
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Old 10-05-2017, 08:06 AM
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Originally Posted by Catorce View Post
Measuring bearing crush is easy; bolt the case together with bearings but no crank and use a dial bore gauge to see what you have. Or less accurately, do the same thing with crank and use plasti gauge.

It may have been said already but what instrument are you using that measures as accurately as .0005?
Micrometers ... Measured the new bearings, and immediately measured the old, and they (old) were usually half a thousand thicker. Sometimes less, sometimes more. Again, once I found this I did verify with AA who makes Clevite rod bearings that they are intentionally made that way... I asked if they have batches that are make in the stock thickness, and they said no.

The new bearings are clearly thinner than the old ones no matter how I measure. Started with calipers, then bought micrometers, same results...

I thought bearings crush had to do with the bearing end pressing against each other, causing a tight fit in the case so the bearings don't move?

What you are describing, I thought was the method to measure clearance, not "crush"?

Still awaiting arrival of the bore gauge...

Found this awesome link, explains every failure mode of bearings and findings

https://www.mahle-aftermarket.com/media/local-media-north-america/product-files/ceb-2-1114-engine-bearing-failures-brochure.pdf

"crush" is defined as the part of the bearing that extends past the rod half, and is compressed once tightened. Excess crush will cause pinch lines."

So, I suppose one could assemble and then use a boregauge to measure the bore size at the pinch line once bearings in and torqued in...?

Last edited by bpu699; 10-05-2017 at 10:43 AM..
Old 10-05-2017, 10:28 AM
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However you want to define it, the bearings take their final set once the case is torqued around them. The number you are left with is the actual bore size...no guessing, no estimates.

It is not a common number to generate, but you sound like you need to know.
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Old 10-05-2017, 01:20 PM
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Measuring bearing crush is not too difficult as shown above and is included in the ISO Standard for Thin Wall bearings.

I would say around 0.002" for a road engine and up to 0.004" for a race engine.

If you measure a bearing carefully you will find that the 'babbitt' alloy is not the same thickness around the complete perimeter.

The bearing material has a 'lemon slice' profile which provides the crush relief.

If you look at fatigue failure in the Mahle document you will find that they normally start to crack in this area.

I would be interested to know what the impact of coating has on this profile and the consistency of the thickness.

HM 30 appears to be a dry film coating but the information is not really very complete.

I would imagine that if you want to reduce clearance it may be better to coat the back face of the bearing with a more durable surface.

You could also pack the bearing with an old-fashioned razor blade

Last edited by chris_seven; 10-05-2017 at 01:33 PM..
Old 10-05-2017, 01:27 PM
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Just be sure you check your clearances after coating, any coating worth doing is going to add roughly .0004 per shell, so if you were on the tight side before it won’t end well
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Old 10-25-2017, 09:15 AM
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Was on the loose side before... That's one of the reasons I went with the coating...

Will recheck again when reinstalled... Have had little time to work on this unfortunately.

Again, the range Porsche lists for crank is .0004 to .0028. Which is one helluva range.

My rods measured out at .0022 coated with arp... Range is .001 to .0035.
Old 10-25-2017, 11:32 AM
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