Z120 3 5/16" flat top pistons do exist

Jason S.

Well-known Member
I've heard several people say that when you use the 3 5/16" sleeves in a z120 block that the only piston you can get now is the dished piston like was used in the z129 and z134 engines. Z120's of course originally had flat tops pistons. I got a set of pistons from Federal Moguls for the z120 with 3 5/16" bore and they are flat top but there is a catch. You have to bore the sleeves .030" to get the proper clearance. Which isn't much because those sleeves are pretty thick. I've had my machine shop look at it and they said it would be easy to do and would work fine. The upside is it raises the compression to 7.0 to 1. So you will have a more fuel efficient and better burning engine. The best part is if you have a z120 that already has those sleeves installed and you were thinking about rebuilding it and buying new sleeves, just have your worn sleeves bored, get these pistons and you are ready to go.

DB5EF9A5-8C58-477E-980D-DDBAC91CFA51-15914-00001376B48455D3_zps0db11ba1.jpg


7FD77C64-CBCC-4A5C-BBE4-FD307E2A92CB-15914-000013764E407EE3_zpsffa24ae1.jpg
 
I'm confused. The piston in thepicture is clearly a .030 oversize piston. It is marked .030. Therefore there must be OTHER corresponding oversizes too and therefore a standard size.

So there should be no reason to bore the sleeves if the std size version of the piston is available as it should be because an oversize is available.

The real question here:
What OTHER non-ferguson application does this piston fit????? Or to put it another way: The piston is not a Ferguson piston but rather some piston that fits some other more popular or widely used engine.

Also not that there appears to be a rather odd welded seam mark from gudgeon pin to botom of piston skirt. This very unusual as pistons in general go.
 
My computer resolution is rather poor. But the piston appears to have 2wo compression ring grooves and 2wo oil ring grooves. Again very odd.
 
That seems like a fair price. All of the cylinder heads that I sell go to the machine shop to be degreased, bead blasted and mag checked.
4 cylinder gas run about 58.00
4 cylinder diesel about 68.00
I recently had 3 sleeves removed and 3 installed in a perkins diesel, cost was under $200.00

Any idea what the same type of work would cost at your shop?

Thanks,
Dave
 
Nope... .030 and .060 is all they offer in it. You can look it up
on Federal Moguls E catalog. It is for a Ferguson TO 20 with a
Z120 engine and 3 5/16" sleeve. That mark you see below the
wrist pin is a reflection of the seam in that box.
 
Distance from crown to top of first ring groove looks unusualy wide. Also there appears to be no (or too small) champfer at the top of the piston. Cheque piston for gudgeon pin offset against any marks on the top indicating "front" of piston.

Got a FM part number or is that the part number on the top of piston???
 
They have 2 3/32" grooves and 2 5/32" grooves. If I
remember correctly it was the z129 that had two compression
rings and two oil rings. That set up isn't that uncommon
actually.
 
Truthfully no...I haven't had any diesel engine machine work done. I built lots of car engines and gas tractor engines but no diesels.
 
(quoted from post at 03:10:49 01/16/13) Distance from crown to top of first ring groove looks unusualy wide. Also there appears to be no (or too small) champfer at the top of the piston. Cheque piston for gudgeon pin offset against any marks on the top indicating "front" of piston.

Got a FM part number or is that the part number on the top of piston???

How is this? One of the Federal Moguls next to an original z120 piston. I put the wrist pin thru both pistons to line them up. You were talking about the chamfer at the top of the piston, look closely. The original has no chamfer at the top. But you can see a very small one on the fm piston.

A9218B05-7006-4426-9C2F-B493B687303A-15914-0000138CB452C579_zps9b5815c7.jpg


7CBCB11C-E33E-439B-B324-DFAA8A93CFD7-15914-0000138CAEC778FB_zpse6a12616.jpg
 
I just found this yesterday while looking for Wisconsin pistons.
http://www.fme-cat.com/CommercialApplication.aspx?brand=FP&make=Continental&engineCode=Z120&engine=2.0L%20120%20OHV%20L4%203.1875%22%20Bore&prodcat=PISTONS%20%26%20COMPONENTS
 
RE; Piston pic with both pistons aligned with wrist pin:
New piston crown appears to set slightly lower than old piston crown.
 
It is, I was gonna measure it and see but I"d say it"s not more
than .010 lower. Which is common for rebuilder pistons. I see
it a lot in car engines. I don"t know if they do it because they
know most people get the heads cut and they lower the
compression height of the piston slightly to keep the
compression the same as original.
 
Did you purchase online or auto parts store?
I can find them in the online catalog but not who sells them.
thanks.
 
I bought these from northernautoparts.com. I think they had to have them shipped straight from federal mogul.
 
That"s where I bought my Fel Pro gasket set from for my TO20. Way better than that Tisco gasket garbage. Most people don"t know you can go to federal moguls e catalog and look up gasket sets, pistons,valves,bearings,etc for most anything made, and then go buy them from northernautoparts or summit racing much cheaper. I bought a complete fel pro gasket set for my 1940 John Deere A from summit for $69.00. Deere wants almost $100.00 just for a head gasket. It pays to look around and shop cause you can find good quality parts sometimes at a lower price than the cheap quality parts.
 

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