Rods dragging after Moly coating

[Tippy]

Hey guys, been years since I've posted.

Question, I have a couple of rods dragging after DIY Moly coating my rod bearings on my 3.4 (3.2).

It isn't a hard drag but it'll suspend the rods weight until you nudge them.

Will the crank journals burnish the coating or am I due a teardown to correct?

[Henry Schmidt]

Originally Posted by Tippy

Hey guys, been years since I've posted.

Question, I have a couple of rods dragging after DIY Moly coating my rod bearings on my 3.4 (3.2).

It isn't a hard drag but it'll suspend the rods weight until you nudge them.

Will the crank journals burnish the coating or am I due a teardown to correct?

It sounds like the coating may be too thick. Did you coat the bearing with assembly lube or oil before torquing the rod cap in place?
The question you have to consider is: if the coating is too thick, is there a chance it will migrate and cover the oiling hole?

[Tippy]

Originally Posted by Henry Schmidt

It sounds like the coating may be too thick. Did you coat the bearing with assembly lube or oil before torquing the rod cap in place?
The question you have to consider is: if the coating is too thick, is there a chance it will migrate and cover the oiling hole?

Used oil only.

I should add that regular rubber bands around the small ends hooked around the studs will hold the rods that are sticky (they don't bang on the spigots if you will while rotating the crank slowly). So, it's not a lot of resistance but there is some nonetheless....

[otto_kretschmer]

I would understand moly coating the piston skirts but the rod bearings?

With good bearings the rods should drop when let go, even with a hefty dose of assembly lube. If the rods are sticky with bearings that have been coated with a moly or dry film lube, I would take the rods off and scuff some of the film off.

If you have the engine assembled and back in the car and now having 2nd thoughts I would have a dilema. If the car was my old 64 Scout, I would just run it but my 76 911 I don't know.

You need oil flow for the oil wedge in the bearings and also oil thrown onto the cylinder bores. Hopefully the oil coming off the mains (and squirters if you have them) will give the rings and walls enough oil.

How much money do you have tied up in this build?

I would probably drop the motor and fix it.

[otto_kretschmer]

Originally Posted by Henry Schmidt

if the coating is too thick, is there a chance it will migrate and cover the oiling hole?

Henry,

the oil pressure should push the film out of the way in your scenario

I would be more worried about the film flaking off and preventing he oil film forming properly

oil is used as a lubricant and also to remove heat from bearings

[Neil Harvey]

Did you measure the journal size and the two rod BE sizes?

The BE without the bearing shell installed and the ID of the bearing shell installed. You are checking to see the BE is round and that the shell clearance to the journal is correct.

It can be the coating is uneven as its typically sprayed on or the ID of the bearing is not correct.

Always best to check.

[Henry Schmidt]

Originally Posted by otto_kretschmer

Henry,

the oil pressure should push the film out of the way in your scenario

I would be more worried about the film flaking off and preventing he oil film forming properly

oil is used as a lubricant and also to remove heat from bearings

Seen it happen. Improperly applied coating creating a build up restricting oil flow.

[Henry Schmidt]

Originally Posted by otto_kretschmer

I would understand moly coating the piston skirts but the rod bearings?

With good bearings the rods should drop when let go, even with a hefty dose of assembly lube. If the rods are sticky with bearings that have been coated with a moly or dry film lube, I would take the rods off and scuff some of the film off.

If you have the engine assembled and back in the car and now having 2nd thoughts I would have a dilema. If the car was my old 64 Scout, I would just run it but my 76 911 I don't know.

You need oil flow for the oil wedge in the bearings and also oil thrown onto the cylinder bores. Hopefully the oil coming off the mains (and squirters if you have them) will give the rings and walls enough oil.

How much money do you have tied up in this build?

I would probably drop the motor and fix it.

The combination of oil and dry-film moly greatly reduce coefficients of friction.
The issue for us has always been proper application.
We love the stuff. We apply it to bearings, piston skirts and rocker pads. With dry film lubricants and our custom DP-4 rocker bushings our tests suggest that there might be as much as 3-5 % hp increase over a stock 2.7RS spec engine.

[Dpmulvan]

Which brand do you prefer Henry ?

[Henry Schmidt]

Originally Posted by Dpmulvan

Which brand do you prefer Henry ?

We've had equally good success with Dow and Techline.
Tecline is a little more labor intense but is higher temp. Both fulfill the needs of our 2 valve engines, even turbos.

[otto_kretschmer]

Originally Posted by Henry Schmidt

The combination of oil and dry-film moly greatly reduce coefficients of friction.
The issue for us has always been proper application.
We love the stuff. We apply it to bearings, piston skirts and rocker pads. With dry film lubricants and our custom DP-4 rocker bushings our tests suggest that there might be as much as 3-5 % hp increase over a stock 2.7RS spec engine.

The DFL is going to wear off, especially on the cam lobes and rockers. I wouldn't bother with it.

Tippy,

You're probably ok to run as is. Maybe you should use a top quality synthetic 10w40 oil like Redline. I would use their motorcyle oil in a 911 air cooled engine.

Henry,

Have you ever bought oil at Fallbrook Oil? I found the right Redline gear oil for my GMC Yukon XL differential there.

[Tippy]

Originally Posted by otto_kretschmer

I would probably drop the motor and fix it.

I just put the cases on around the crank a long time ago. Finally got around to replating the Nikasil and was going to finally build it back up. The light dragging started to concern me.

The ones that have a little drag still rock back and forth, so there is clearance. It must be some small high spots. I was under the impression it would burnish itself.

[Tippy]

Originally Posted by Neil Harvey

Did you measure the journal size and the two rod BE sizes?

The BE without the bearing shell installed and the ID of the bearing shell installed. You are checking to see the BE is round and that the shell clearance to the journal is correct.

It can be the coating is uneven as its typically sprayed on or the ID of the bearing is not correct.

Always best to check.

Hello Neil,, I measured the 1st time I rebuilt it (all in spec and had the rods resized).

I don't know why but I pulled the rods off (I pulled it down to fix oil leaks, then discovered Nikasil damage I believe from too tight of ring gaps - I am boosted). I should have just left on, but I guess I wanted to see if I had detonation issues. Bearings looked perfect to me. So Moly went on as an additional protection.

[Tippy]

Originally Posted by otto_kretschmer

Tippy,

You're probably ok to run as is. Maybe you should use a top quality synthetic 10w40 oil like Redline. I would use their motorcyle oil in a 911 air cooled engine.

Funny you mention 40 weight as that was my plan to allow burnish during break-in and sufficient oil flow later moving to 50 weight for the turbo and central TX heat.

I was even thinking 30 weight but didn't want to have 30 weight floating in the oil system.

[otto_kretschmer]

Originally Posted by Tippy

I just put the cases on around the crank a long time ago. Finally got around to replating the Nikasil and was going to finally build it back up. The light dragging started to concern me.

The ones that have a little drag still rock back and forth, so there is clearance. It must be some small high spots. I was under the impression it would burnish itself.

It will burnish itself if you run it either way. The question is really is there enough oil flow to provide an adequate oil wedge and enough oil to keep those bearings within their thermal limits.

Think of the gap between the rod bearing and the crank pin as an orifice in an oil line. Too big an orifice and you will have too much oil flowing thru and not enough pressure. Too small an orifice and you will have too little oil flowing thru. By adding the DFL or moly coating you made the orifice smaller.

Is it too small? I don't know. You could test it by taking your car to Laguna Seca and flogging it thru the corkscrew for an hour. If it doesn't blow up or spin a bearing then you will know its ok.

[Tippy]

Originally Posted by otto_kretschmer

It will burnish itself if you run it either way.

Last night I messed around with the dragging rods and rocked the small end back and forth longitudinal with the crank while turning the crank about an 1/8 turn each time.

The rods are totally free now, all of them. It burnished from working them.

I then put my Dewalt drill on the crank bolt while holding the chains spinning around about half the speed of the drill. She is nice and smooth so my confidence is much better!

I will do the 10-40wt for break-in so any other subsequent "burnishing" that may occur while providing "easier" oil flow and then switch to 15-50wt later.

Thank you guys!

[Henry Schmidt]

Originally Posted by otto_kretschmer

The DFL is going to wear off, especially on the cam lobes and rockers. I wouldn't bother with it.

Tippy,

You're probably ok to run as is. Maybe you should use a top quality synthetic 10w40 oil like Redline. I would use their motorcyle oil in a 911 air cooled engine.

Henry,

Have you ever bought oil at Fallbrook Oil? I found the right Redline gear oil for my GMC Yukon XL differential there.

"I wouldn't bother with it" Hummm?
That is why proper application of the DFL is paramount.
In our process, we clean the surface completely, low pressure blast with aluminum oxide to expose the pores in the material, then repeat the cleaning process. At that point the part is heated to open the pores and the DFL is applied. After air drying, the part is baked at the recommended temperature (depending on the material). Application thickness is between .0005"-.001". As the engine is run through the break-in process, the top layer of DFL is burnish off and the material embedded in the surface remains. Because the DFL we use is rated a above 350,000 psi and temperatures exceeding 2000 F the anti-wear properties are enhanced and friction coefficient is exponentially reduced.

[otto_kretschmer]

Originally Posted by Henry Schmidt

"I wouldn't bother with it" Hummm?
That is why proper application of the DFL is paramount.
In our process, we clean the surface completely, low pressure blast with aluminum oxide to expose the pores in the material, then repeat the cleaning process. At that point the part is heated to open the pores and the DFL is applied. After air drying, the part is baked at the recommended temperature (depending on the material). Application thickness is between .0005"-.001". As the engine is run through the break-in process, the top layer of DFL is burnish off and the material embedded in the surface remains. Because the DFL we use is rated a above 350,000 psi and temperatures exceeding 2000 F the anti-wear properties are enhanced and friction coefficient is exponentially reduced.

Henry,

I have a 2010 Moto-guzzi Griso 8v and I had to upgrade the cam and lifters to a roller kit. Moto-guzzi used flat lifters for the first 4 or 5 years of the 8 valve engines and in 2012 they switched to a roller lifter. I bought the bike new from Pro Italia in Glendale and 2 years ago I first read about lifter failures on the flat lifters. I pulled the cam box out to inspect the lifters and found my lifters were just starting to fail.



Moto-guzzi used something called Diamond Like Carbon on the lifter surface. I can only speculate why they used this surface treatment. I best guess is it was a band-aid to get the engine into production and it didn't work in the long term. I got on one of the guzzi forums and learned from a guzzi guru that its not if the lifters will fail, its when they will fail.

If I kept riding the bike I could expect the lifters to look like this



The original Porsche rocker and cam combo work good enough for me so why reinvent the wheel? During my investigation I read somewhere that NASCAR engine builders use a DLC coating and if they can get another 2% bump in hp that makes sense.

The first picture I uploaded and the 2nd picture I found on wildguzzi.com

[Henry Schmidt]

Originally Posted by otto_kretschmer

...edit...
The original Porsche rocker and cam combo work good enough for me so why reinvent the wheel?

For years we saw almost no issues with cams/rocker interface. The only failed rockers we saw were oil starvation (clogged squirters) or happy shift mishaps (broken rockers).
Things have changed. We see heavily worn cams, rocker and bearings previously unseen. DFL help to counteract this phenomenon.
Casting quality is inconsistent and oil lubricity has been neutered by environmental concerns.
Porsche was excellent at developing the 911/2 valve engine but that development was discontinued 20+ years ago. What we are doing now is enhancing the breed not reinventing the wheel.

[jpnovak]

The DLC and DFL coatings are very different. DLC is a hard coating that has low friction properties. DFL is used primarily as a low-friction surface. The mechanisms are quite different between the 2.

Agree with Henry that proper application technique is key to making them work.

Those lifters look like they had oil film issues. The DLC will just prolong life but this type of stressed system will not hold up to lack of oil.

I have been using various coatings for almost 15 years. They do reduce friction. They can slough-off but the friction savings are still there. I use DFL coatings on just about all rotating and friction surfaces.