PTWA Cylinder Honing

[schmeky]

Building a 2019 5.0 as a project for one of my boys. Bought this complete engine out of a totaled 2019 Mustang GT with 10K miles. Checked all the cylinder bores and all 8 are dead nuts on 3.662". All bores are concentric and look near new (of course they would with low miles).

Since we are going with a new Mahle forged piston kit that uses a moly top ring, we need to lightly break the glaze on the cylinder walls to ensure good skirt lubrication and proper seating of the new ring set.

Can't find any reliable info on doing this with the PTWA cylinders. I am familiar with the R factor in establishing the proper hone characteristics. I am thinking I can do this with a 95 mm flex-hone x 600 grit, then come back and plateau the new surface.

Anyone have any info on doing this in a 5.0 PTWA block?

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[GregO]

Anyone have any info on doing this in a 5.0 PTWA block?

I don’t have a direct answer but I’ve been around countless coated aluminum cylinder to know enough to offer up a few precautionary questions.
How thick is FORD applying the PTWA coating and what is the thickness after finial finishing?
I do know Nikasil optimum coating thickness after finial finish is around .006
What composition PTWA does FORD use ?

I think a call or email sent to http://www.flamesprayusa.com/ will help answer your question. Flame Spray developed the coating, Ford perfected it.
I’d wager Mahle will have the exact answer your looking for.
There’s a good chance you won’t need to touch the cylinders. If your set on breaking the glaze I’d reach for a brush hone before a ball hone.
If you have access to a profilometer such as a “Pocket Surf” the Ra readings of the thrust side of the cylinder walls will reveal the condition of the PTWA coating.

 

[EFI]

Since we are going with a new Mahle forged piston kit that uses a moly top ring, we need to lightly break the glaze on the cylinder walls to ensure good skirt lubrication and proper seating of the new ring set.

Why do you say that you need to "break" the glaze on the cylinders?

I've used personally (and seen even more) engine setups where they use drop in pistons without touching the bore. Mahle themselves make drop in pistons specifically for the 3rd gen Coyote. That's also how Ford builds their aluminators, they just take out the old pistons and drop in new ones without touching the bores.

Is this something specific with PTWA liners?

 

[schmeky]

Greg,

Thanks for the links, I'll reach out and see what info I can get. Goal is to do this right the first time.

I know how critical proper surface finish is in the bores, having built quite a few cast iron engine blocks in the past when I and many of my friends were drag racing. The PTWA is different scenario, so the way it was done in the past does not apply to the 5.0 motors.

The BRM "brush" hones are not true hones, they are glaze breakers, which is what I need to do with this block.

I am going to go with the Mahle 12:1 CR forged piston kit on this build.

 

[schmeky]

Not buying or doing anything until I have sufficient info to move ahead.

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