040 Stamped on pistons.

[1984ranger28]

Heres a picture of one of the bores. All other 5 look very similiar. This is after honing.

Obviously, this doesnt mean the bore is completely cylindrical, but there was no deep scoring. If I had the money, I would definitely bore it over.

 

[Uncle Gump]

Money is always an issue... we all live it every day. However think of the cost of doing it over again. Doing it right the first time is truly cheaper in the long run.

It's really hard to see from an internet picture...

I would run it up to the machine shop and get them to maybe put a bore gauge to it and evaluate it's condition.

 

[alwaysFlOoReD]

You received new pistons. What was the recommended piston wall clearance? Those old pistons look as if there wasn't enough clearance, so it makes sense to check so it doesn't happen again. Maybe ran dry on oil? The new bore looks pretty good, I don't see any sign of a lip at the top of the bore. See if you can borrow or rent the correct measuring tools. You should measure at the top of the bore and the bottom. There shouldn't be more than about .004 taper, tho I might go too .007 if I was really strapped for cash. Also measure N - S and E - W to make sure the bore is round.
Be aware that I'm not a machinist, just a hobbiest.

 

[Uncle Gump]

My guess to what happened is the block was bored and someone put 0.040 rings on a stock piston... the OP said they were stock size. The damage was likely from the piston trying to turn itself over being a sloppy fit. Either way... something went horribly wrong and it failure needs to be root caused before proceeding with assembly.

 

[G8orFord]

Th OP stated that the pistons were stamped 040 in the first post. I'd like to see a pic of those stamps. I find it hard to believe they were stamped 0.040" over but measure to the standard bore size. That galding and scoring could also be from the piston not having sufficient clearance in the bore. I don't know what the spec is off the top of my head, but I'd guess it to be around 0.008". Do not try to run your new pistons until you've had this all verified by qualified people with accurate instruments.

 

[1984ranger28]

Th OP stated that the pistons were stamped 040 in the first post. I'd like to see a pic of those stamps. I find it hard to believe they were stamped 0.040" over but measure to the standard bore size. That galding and scoring could also be from the piston not having sufficient clearance in the bore. I don't know what the spec is off the top of my head, but I'd guess it to be around 0.008". Do not try to run your new pistons until you've had this all verified by qualified people with accurate instruments.

Heres the stamp I was talking about.

 

[G8orFord]

Well that certainly looks like a .040 over stamp to me. I can't imagine that being on a stock piston. What did you measure? Stock bore is 3.66" so the piston should measure pretty close to that at about 1/2" above the bottom of the skirt. A 0.040" overbore should be 3.70".

According to this sheet: https://www.therangerstation.com/stock-ranger-specifications/ford-ranger-2-8l-v6-engines/
piston to bore clearance is only about 0.001"-0.002". That seems a little tight to me, but it is only a 2.7" stroke.

 

[1984ranger28]

I got the taper measured today, and the average taper was .015.

 

[fastpakr]

If I'm reading that right, you have several times more taper than allowable.

 

[1984ranger28]

Sorry, 0.0015 lol

 

[Ranger850]

IIRC .040 bore comes with shaving the heads a little? I once warped the head om my '83 I4, and had the head shaved and cylinders bored to .04.
{Almost 30years ago, and I was a scruffy teen then, so my memory could be fuzzy? Does this sound right to any of ya'll or am I spewing nonsense AGAIN.}

 

[Uncle Gump]

I'm so damn confused...

850... was that even English? lol

 

[alwaysFlOoReD]

IIRC .040 bore comes with shaving the heads a little? I once warped the head om my '83 I4, and had the head shaved and cylinders bored to .04.
{Almost 30years ago, and I was a scruffy teen then, so my memory could be fuzzy? Does this sound right to any of ya'll or am I spewing nonsense AGAIN.}

Nonsense again....

 

[Ranger850]

Nonsense again....

ok thanks
and i retract my last post.

 

[alwaysFlOoReD]

Sorry, 0.0015 lol

What was the worst taper?
What was the bore size, smallest to biggest?