Working out piston sizing and clearances for a honed block, help required.

[TERRA Operative]

I'm currently rebuilding a 5E-FHE and am looking at getting new pistons (I found that they're cheap as).
I'll also be getting them ceramic coated.

My question is, how do I work out what piston numbers to get? (1, 2 or 3).
I have the old pistons, but the bores have been honed and the ceramic coating (I assume) on the new pistons will add a bit of thickness.

How is this sort of thing normally worked out? And how do I work out how big each piston size actually is?

[jonathan yee]

did the pistons you've pulled out have numbers on them?

[TERRA Operative]

Yea.
I think I've worked things out.. I found I had a Toyota 4E/5E manual sitting on my shelf.
Problem is it's all in Japanese... But I've worked out the piston specs.

Size 1 - 73.90 - 73.91mm
Size 2 - 73.91 - 73.92mm
Size 3 - 73.92 - 73.93mm

Bore clearance - 0.09 - 0.11mm

Piston wear limit - 0.13mm


I have the following pistons and measured diameters (23mm from the crown as per the Toyota manual).

1 - 73.85
2 - 73.85
2 - 73.86
2 - 73.86

So all my current pistons are within wear limits, I just have to check the bore size since they've been honed to make sure the piston to bore clearances are ok.

How much thickness should I add to the piston to account for the ceramic coating?
Also, how do I find out the maximum 'out of round' specs for the piston? The book doesn't mention it at all. I want to make sure the pistons haven't been deformed when the wrist pins were removed.

[TERRA Operative]

As measured with vernier calipers, my bores are all at 74.00mm I'll have to get a bore gauge to check them properly.

If so, that means my pistons are 0.04mm too small. The friction coating adds 0.013 - 0.038mm (x2 for both sides) so that should close up the gap?

[cambelt]

Get the highest mark toyota make , even with friction coating id say the clearance still wont be as tight as the book.
Dave

[jonathan yee]

i was under the impression that with ceramic coated pistons you can run tighter bore clearances as the ceramic coating will keep the pistons cooler and they won't expand as much? but maybe that's with forged item's as they generally expand more than the factory ones yeh?....?

[TERRA Operative]

I'm not sure.

I'm getting a bore gauge in the next few days so I'll be able to check the exact measurements of the bores.
How do I measure the pistons for our of round? Is there any particular procedure to do it?

[allencr]

How do I measure the pistons for our of round?

There thrust face is always 'out of round' compared to across the wrist/gudgeon pin, except cheapies.

[TERRA Operative]

Ah, so when I measure both perpendicular and parallel to the wrist pin on a genuine piston, it's normal for it to be slightly different?

Ok. So all I need to do now is wait for the bore gauge to arrive..

[thechuckster]

ceramic coating is only on the top of the piston - it shouldn't affect OD of the slug at all.

[oldcorollas]

unless it has oil coating on the sides as well?

[MRMOPARMAN]

ive seen some ceramic coatings go down around the ring lands.

[TERRA Operative]

I think the ceramic coating is just on the tops of the pistons. There will be an anti-friction coating applied to the sides of the piston too, that's the numbers I posted above for the thickness of the coating that will be applied.

[oldcorollas]

ive seen some ceramic coatings go down around the ring lands.

the ring lands and the piston top are generally smaller diameter than the skirt, so should have no effect if they are coated?

[TERRA Operative]

Ok, I measured my bores with a dial bore gauge. Here's what I got:
(first measurement parallel with the wrist pins, second measurement perpendicular)

Cyl 1: 74.00mm, 74.015mm
Cyl 2: 74.01mm, 74.02mm
Cyl 3: 74.02mm, 74.01mm
Cyl 4: 74.01mm, 74.015mm

This means I need piston numbers 1, 2, 2, 2 to fit correctly as per factory.

With my current pistons (and a little shuffling around), I'll have the following clearances as measured perpendicular to the wrist pins.

Cyl 1: 0.165mm
Cyl 2: 0.16mm
Cyl 3: 0.16mm
Cyl 4: 0.155mm

The Toyota specs are 0.09 - 0.11mm clearance, so my pistons are a little small.

Is that going to be a problem? Will the coating help, or should I get new pistons?