Top guided rods / bottom guided pistons

[Steve200]

ok so the piston number is only on the box and is,
TS2100

The rod number is
625-5250.

And it appears the bottom of the rod is locked in place too (bottom and top guided ??).

The main issue is the roller bearings can move out of place too much due to the wider piston boss. So perhaps just the right kind of washer is what is need to keep them in place ?

[NICE PAIR]

ok so the piston number is only on the box and is,
TS2100

The rod number is
625-5250.

And it appears the bottom of the rod is locked in place too (bottom and top guided ??).

The main issue is the roller bearings can move out of place too much due to the wider piston boss. So perhaps just the right kind of washer is what is need to keep them in place ?

I had some of the big rods in a motor I tore down that had the wide base pistons with a skinny rod they had a thick washer on each side. I don't remember the thickness but I'd guess .080 to .100
Measure the piston boss to boss, measure the rod width at top, subtract from the big number, divide by 2, add a little clearance.
Now you need 12 of them. $ .02

[Steve200]

Hey Thanks Nice Pair, I'll get some hardened washers and put them in, just wanted to make sure that was acceptable to that.

Cheers and Happy Xmas to all.

[NICE PAIR]

Hey Thanks Nice Pair, I'll get some hardened washers and put them in, just wanted to make sure that was acceptable to that.

Cheers and Happy Xmas to all.

You want to be careful, ck with somebody that knows the difference. (and can explain it to you) I believe those thick washers were a Mercury part
What I did was a ways back and I don't remember all of it.

I had some (as I remember) 5250 top guided rods (the rod end was wide) and I had a machine shop cut them down to the same thickness as the bottom guided rods and used bottom guided pistons. (I think that is the setup that uses those cute little washers to keep the needles from falling out.

Have a great Christmas. NP

[tlwjkw]

this is tha right stuff.....

http://parts.promarineusa.com/produc...M50/1/1/4025-1

[NICE PAIR]

this is tha right stuff.....

http://parts.promarineusa.com/produc...M50/1/1/4025-1

I believe you're right, If he has the pistons to go with the washer and needle set you are showing, steve200 makes it sound like the piston bosses are too far apart.

[NZ Sidewinder]

Editededited

[NZ Sidewinder]

I had some of the big rods in a motor I tore down that had the wide base pistons with a skinny rod they had a thick washer on each side. I don't remember the thickness but I'd guess .080 to .100
Measure the piston boss to boss, measure the rod width at top, subtract from the big number, divide by 2, add a little clearance.
Now you need 12 of them. $ .02

This is what I'm looking for.
When you say add a little clearance, how much?

[NICE PAIR]

This is what I'm looking for.
When you say add a little clearance, how much?

I'm sorry NZ, its been a while. I cannot remember the reasons for or the dimensions. The difference was top guided rods verses bottom guided, and I was trying to run a wide piston slot with a narrow rod top. I wish I could be more help. I built my last 2.5's more than 15 years ago. Try Jay Smith (Texas?)

[NZ Sidewinder]

All good
I've settled on 9 thou.
I'm doing the same as you were.
Wide pistons with narrow rods.
Cheers

[NZ Sidewinder]

All good mate.
I've settled on 9 thou
Cheers

[Onetime]

Made these fat washers around 25-30 years ago. Can’t find my drawing for them.
As I recall had .010 clearance. More important they need to be hardened. Hardened needle bearings will be riding against them and if they’re not hardened the needle bearings will wear them.

Or you can use the stock thin washer, which is hardened, to go against the needle bearings and machine an aluminum spacer to make up the difference.

[NZ Sidewinder]

You are onto it.
Yes I agree they need to be hardend
I'm use a pair of shouldered washers from the bottom guided system each side.
One of those on each side is ground to 57.5 - 58 thou thick.
Combined they add up to .375 which allows 9-10 thou total clearance.
Those stock washers are thru hardend so work well even when ground.
They can't be cut with tungsten, only ground.
I use cylindrical grinder but surface grinder would be faster