4 Ring pistons

ZV 5.4L · Jan 26, 2009

Any experience with 4 ring vs. 3 ring? Was wondering what people prefer. Most of the kits come with 3 rings...

Zach

Bruce (VA) · Jan 26, 2009

I can't recall the entire discussion, but the short version is that the 4th ring was added w/ the idea that it would reduce oil consumption. What it did in reality was cause more wear on the sleeve. If that's not precisely correct, someone will be along soon & add to the response, but the bottom line is use the three ring pistons.
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Anonymous-0 · Jan 26, 2009

Have heard this one before but dont buy it.Ford v8s used 4 ring pistons and most wear occurs in the top of the bore.It cut down on piston slap.Some experts claim it even cut down on engine power because of increased friction.Half the info on forums tends to be BS anyway.

Bruce (VA) · Jan 26, 2009

Yea, to which half do our comments belong?!

I don't think piston slap would be much of a problem at 2400 RPM.

Do you recall if the old Merc V-8's used 3 or 4 ring pistons? Allegedly, the N engine used the same cylinders as the old Merc V-8's.

ZV 5.4L · Jan 26, 2009

So it doesnt help in increasing compresson? hmm.... on our racecars we always use totalseal, where each ring is 3 piece, and it most difentally increases compresson and longevity.

Zach

Anonymous-0 · Jan 26, 2009

The mercury always had a 3 and 3/16 bore as did Ford big trucks.My 46 engine in the coupe has 4 ring pistons.Ford went to the same bore as tractors in cars in 1946.Some Ford cars engines had sleeves some didnt.Early Mercs Ive been into had 4 ring pistons.They have an 09T number thats a truck part number.The 8n can use 49 thru 53 valve train parts.Later lifters should be used also.Ford used flat top pistons, dome top pistons too in V8s.My v8 is due for an over haul.If it needs pistons Ill use what I can get, 3 or 4 ring.Ford seemed to use what they had on hand.Ive seen tractors with hoses missing on the air cleaner and cups missing.

Leroy · Jan 26, 2009

To answer your question about Merc 3 or 4 ring pistons I got out my 1,750 page shop manual that covers 1940 to 1953.

Merc 1940 to 42 a 3 ring
Merc 1946 to 48 a 4 ring
Merc 1949 to 52 a 4 ring
Merc 1952 a 3 ring
On the 3 ring they did not use an oil ring but on the 4 ring they did

Ford 1941 to 42 V8 3 ring
Ford 1941 to 47 6 cyl a 3 ring
Ford 1946 to 48 V8 4 ring
Ford 1948 6 cyl 4 ring
Ford 1949 to 51 all 6 & V8 4 ring
Ford 1952 6 cyl 3 ring
Ford 1952 V8 4 ring
Ford 1953 both 6 cyl & V8 3 ring

And I can provide the dimminsions for all of the above if anybody wants them.

Eldon Booth · Jan 26, 2009

To increase the compression ratio you would have to decrease the size of the combustion chamber. The easiest way to do this is to plane the head, but then you get into piston and valve clearance problems. A question on a mechanics exam dating back to the 1930’s was, “ How many rings do you need on a piston in a four cycle engine?" The answer was one if it will hold the compression and the oil. I have seen one ring on two cycle engines but then you don’t have to worry about the oil. With the N series being at such a low compression I wouldn’t think a four-ring piston would be necessary. After all there are diesel engines with two and three ring pistons and they are running at a lot higher compression than the N Fords. These old engines weren’t designed to rev over 2000 RPM with today’s material I would think a three-ring piston would work just fine
Cheers
Eldon

Dell (WA) · Jan 26, 2009

Zach........actually the 3-ring piston is really a 5-ring piston. Oil ring is 3-rings (grin) The 4-ring piston was an attempt to reduce oil consumption and did so well that the upper cylinder wore faster and lost compression. Remember, oil is the final seal between the compression rings and the cylinder wall.

Iff'n yer replacing pistons with new sleeves, use 3-ring pistons. .......Dell

ZV 5.4L · Jan 26, 2009

(quoted from post at 08:08:04 01/26/09) To increase the compression ratio you would have to decrease the size of the combustion chamber. The easiest way to do this is to plane the head, but then you get into piston and valve clearance problems. A question on a mechanics exam dating back to the 1930’s was, “ How many rings do you need on a piston in a four cycle engine?" The answer was one if it will hold the compression and the oil. I have seen one ring on two cycle engines but then you don’t have to worry about the oil. With the N series being at such a low compression I wouldn’t think a four-ring piston would be necessary. After all there are diesel engines with two and three ring pistons and they are running at a lot higher compression than the N Fords. These old engines weren’t designed to rev over 2000 RPM with today’s material I would think a three-ring piston would work just fine
Cheers
Eldon

Not combustion compression ratio, i am refering to leakdown. Some of these 9Ns have over 100lbs per cyclinder, spec calls for 90. I was wondering if the N's with over 100lbs were 4 ring pistons.

We used to run a race engine 7.5:1 with total seals, where a 4 ring piston would have 9 rings total...

We do all sorts of techniques to raise or lower compression in out racecars, from shaving heads, blocks, adding shim gasket, welding combustion chamber and die grinder work.

Zach

gahorN · Jan 27, 2009

Compresson rings are not intended to control oil. They are intended to maintain compression. Adding a (4th) compression ring was not for the purpose of controlling oil. It was for maintaining compression (and therefore hp) at the lower RPMS at which some implements operated. Unfortunately it also increased upper cylinder wear and cost.

Use three ring pistons. IMHO.

4 Ring pistons

ZV 5.4L

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Bruce (VA)

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Anonymous-0

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Bruce (VA)

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ZV 5.4L

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Anonymous-0

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Leroy

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Eldon Booth

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Dell (WA)

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