Need advice on machine shop error on Ford Mod block

[rebelrouser]

Just got off the phone with Mahle and learned some interesting stuff. Calling them was a good recommendation, thank you.

The coatings on the skirts are another 0.0005” per skirt, so there is automatically 0.001” extra clearance by design. He said that my concern was on point as these (iron Ford mod blocks) are one of the worst engines to go over spec on, especially with Hyper-eutectic pistons. At 0.003” over bore tech support said there will be noise and a lot of it and that they should not be run. Ideally these should be run at 0.001” - 0.0014” clearance, and that they will be happiest at 0.001” and will run a full lifespan at this clearance.

Not the news I was hoping for but at least it’s fairly definitive.

Not an engine I built, but the machine shop that does my boring was working on an engine from the local chevy dealer, when I was picking up some stuff. And the specs were really tight, don't remember the number, but it was scraping off a little of the piston coating as the pistons were being installed. The machinist was showing me that he had never seen an engine this tight on piston to bore, but it was on factory specs and he like you called the piston maker. So this may be a trend on newer OEM engines.

[mag2555]

That shop you where working in great detail with needs to buy you a new set of oversized pistons & rings in the least! Then you need to decide if you will use there services again.

They could have made that same phone call that you did to confirm if you where correct in what you wanted out of them, and then in turn how they should bore and hone your block. But the chose not to!

A 5 minute call could have saved them the cost of now providing you with new pistons , rings and the installation of those pistons on your Rod’s.

[HDBD]

"Ideally these should be run at 0.001” - 0.0014” clearance, and that they will be happiest at 0.001” and will run a full lifespan at this clearance."

So given that there is .001" of coating is this clearance over the coating, I assume? How does that number align with the theoretical bore size?
Mahle are very high quality pistons IME.

[Momus]

"Ideally these should be run at 0.001” - 0.0014” clearance, and that they will be happiest at 0.001” and will run a full lifespan at this clearance."

So given that there is .001" of coating is this clearance over the coating, I assume? How does that number align with the theoretical bore size?
Mahle are very high quality pistons IME.

The coating is semi sacrificial and a conformity type of thing if it is like the graphal stuff I am familiar with.

What would be informative is to measure a good running engine's clearances.

I would assume that if the running clearance from Mahle is 001" that will be sans coating, at least at the measurement point.

[Crazy Dirt]

Thanks guys. I looked into the piston powder coating, looks to be about $300 for the set. I didn’t realize that it could be used in a long term application (thought it was race specific technology) so that’s pretty cool.

I gave the shop a second shot and asked them to take it to 20 over and supply new pistons and rings. I’ve made enough of my own mistakes to know honest mistakes happen. Unfortunately, they refused to take the block in again, said that those numbers were the best they could do. I even offered to bring the block out so they could mic it for themselves and we could figure out a plan but they’re uninterested in seeing the block, or even knowing what my measurements are, which I found strange. Perhaps he already knew he was sending substandard work out the door. At this point I’m going to cut my losses and stick to the high road. I’ll shelve this .010 piston and ring set for the next time I’m into one of these engines and will eat the cost to go to .020. However, I am pursuing a full refund for the $600 I was charged for the bore and hone. We will see how it plays out. One way or another this truck will be done right.

[Crazy Dirt]

"Ideally these should be run at 0.001” - 0.0014” clearance, and that they will be happiest at 0.001” and will run a full lifespan at this clearance."

So given that there is .001" of coating is this clearance over the coating, I assume? How does that number align with the theoretical bore size?
Mahle are very high quality pistons IME.

The way I understood it from Mahle is that the 0.001”-0.0014” clearance is on top of the skirt measurement with the coating thickness included. That is to say that if the skirt coating was stripped, the actual measured clearance would be closer to 0.002”. That would make sense then as to why they did not provide windows in the coating to mic directly to the aluminum. I got the impression that the coating would not withstand an out of tolerance bore and would abrade faster as a result.

[modok]

The box says the pistons fits a 90.46mm bore, aka 3.5614"
I take this to mean the minimum bore size

being .001" over is probably ok, but more than that is just sloppy, and, possibly refundable
And mahle rounding the tenths off the bore size converting to inches is also sloppy.
And if you can't use a micrometer to measure a size within +/-.0002" then that's sloppy too.... tho that's another subject... perhaps some thumb pressure whilst locking it. To determine the correct thumb pressure, place your thumb between the piston and the micrometer anvil and measure "as normal" might be a good "rule of thumb" to FEEL what force you are measuring with Sure to learn something or another.
And then you can duplicate that to set the micrometer to a size, or measure with less pressure, depending on how much it hurts.

I would love to have customers that know what size hole they want.
Futzing around measuring coated pistons, I certainly feel your pain. Just give me a size
Box has two sizes and a clearance and they don't even add up. That's not helping things.

[BILL-C]

I suggest doing an experiment with block and torque plate to possibly find out where job went wrong. Install torque plate quickly and immediately measure bores in several areas near middle and top of bore previously circled with a sharpie marker. Record findings. Then let block sit for a couple of hours undisturbed and re measure in same exact spots and compare readings. Iron blocks only creep a little, but aluminum blocks usually move a lot. Letting the block and torque plate settle for a little while helps with accuracy but really kills productivity in a busy environment. The 5.4 block is iron and I've found them to only move a couple tenths in past. Another thing to consider is that 2 people can have very different "feel" with measuring tools and come up with a couple of tenths different reading on same clearances.

[BillK]

cd,
Just curious.... ignoring the clearance numbers, what did the bores actually measure ?

[dunnitagain]

I use Line 2 Line Coatings , They can Build up to .010 with abradable graphite , the Promod guys do it all the time , its a pretty impressive coating.
I have a setof JE in an Offshore Marine 572 blower engine making north of 1200hp . With .005 on the skirts . Ive borescoped it twice now through the pan . Zero visible wear on the coating , 60Hours. It gets BEAT hard.

[HDBD]

45 years ago I learned a similar lesson with a Mercedes block. Ironically the pistons were Mahle. Understand that back then there were guys that dealt primarily with American engines and they had their own ideas about clearances. The Mercedes small bore 2.2L m180 6 required about .0008" clearance. That was exactly what you got if you honed to 80.25mm. Problem was that the shop told me they would never send out any block without at least .002 clearance. I was a gullible inexperienced kid. The engine never was right. Next one I built was a M127 6 and I went to another shop and specified the size and said I would be checking it. I used Kolbenschmidt pistons on that build, also very high quality. Very good running tight motor that lasted over 175K miles. Lesson learned. Problem is today not all pistons fit to the nominal bore size will get you the proper clearance. The German Mahle and Kolbenschmidt could be trusted. Measuring over coating is dicey if looking for accurate numbers IME.

[ClassAct]

I use Line 2 Line Coatings , They can Build up to .010 with abradable graphite , the Promod guys do it all the time , its a pretty impressive coating.
I have a setof JE in an Offshore Marine 572 blower engine making north of 1200hp . With .005 on the skirts . Ive borescoped it twice now through the pan . Zero visible wear on the coating , 60Hours. It gets BEAT hard.

This^^^^^^^ is the ONLY coatin I would use to clean up your clearance issue. The abradable coating will sea itself in so the running clearance is essentially zero. Better ring seal too.

[HDBD]

Swain offers alternatives as well.

[Crazy Dirt]

cd,
Just curious.... ignoring the clearance numbers, what did the bores actually measure ?

Bores ranged in size from 3.5627 - 3.5636.

[modok]

Darn, that sucks