Cylinder wear - max permissible

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Gone

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The book tells me 0.12 is max permissible wear and I’m well inside that.

What do people consider maximum permissibile taper and ovality?

Putting together an 807 motor (bore = 77mm) with new pistons and used liners.

For this project I will not be buying new liners.

P
 
What sort of pistons? Strutted? Forged? Hypereutectic?
 
Thanks Cole.

Sorry Peter, I can’t tell you. They sold me new without the liners.

See attached:

IMG_5653.jpg
IMG_5654.jpg
 
I can see steel struts, which are used to control expansion and thus would normally run a tight clearance as was found in most road cars of the period. Excuse me for talking in imperial here, that's what I'm use to. From the factory, a piston that size would be lucky to have any more than 0.0015" (0.04mm) clearance. A clearance of 0.0047" (0.12mm) is very loose for a strutted piston. Have you measured the liners accurately? If you don't want to buy new liners, I'd get the liners honed in a fixture, to say 0.0025" max. Fit new rings, gapping correctly and it will be fine. It may rattle a bit on start up. Don't skimp on the hone. If the reco place doesn't recommend a fixture you're at the wrong place. If you value the engine and the workmanship, I would send the liners to Baker Precision Engines in Molong. They're only people I trust with Peugeot liners.
 
PeterT said:
I can see steel struts, which are used to control expansion and thus would normally run a tight clearance as was found in most road cars of the period. Excuse me for talking in imperial here, that's what I'm use to. From the factory, a piston that size would be lucky to have any more than 0.0015" (0.04mm) clearance. A clearance of 0.0047" (0.12mm) is very loose for a strutted piston. Have you measured the liners accurately? If you don't want to buy new liners, I'd get the liners honed in a fixture, to say 0.0025" max. Fit new rings, gapping correctly and it will be fine. It may rattle a bit on start up. Don't skimp on the hone. If the reco place doesn't recommend a fixture you're at the wrong place. If you value the engine and the workmanship, I would send the liners to Baker Precision Engines in Molong. They're only people I trust with Peugeot liners.
Click to expand...

Yes 0.0047" or 0.12mm was what a service manual had as the maximum permissible wear on the liner, and that seemed awfully wide to me.

I'm well within that on most of the liners I have to choose from. What concerns me most is ovality. Some of the cylinders are at about 0.06 in an otherwise ok liner which suggests a possible overheating event sometime in its past.

I have a new set of rings other than those on the new pistons, which were likely factory set to a new liner. I also purchased a ring grinding tool which should ensure the ends are ground square. I'm confident I'll get good compression and very little blow by.

I may not have access to a fixture tho I may be able to get them honed on a lathe with a ball hone. Best I can do in these parts.

Thanks again
 
Can you take your liners to a machinist and ask if they can hone the liners straight within the tolerance?

That said, I can see on top of the piston JEU 0.03 which means clearance 0.03mm so Peter might be right.

How did you measure the liners?
 
The point of the fixture is to load the liner in compression, as it would be loaded in the engine from head bolts/cylinder head. If you hone them unloaded, they will be become oval. It's the same principle as torque plate honing.

You have Australia Post? Make a wooden box and send them to Molong.
 
I had some 1250cc R12 liners bored out to 1289cc, the guys that did the work asked for the engine block so that they could do the job properly.
 
schlitzaugen said:
Can you take your liners to a machinist and ask if they can hone the liners straight within the tolerance?

That said, I can see on top of the piston JEU 0.03 which means clearance 0.03mm so Peter might be right.

How did you measure the liners?
Click to expand...

Used a bore gauge - the rocker type.
 
I've never heard of a fixture for honing but it seems like a good idea to compress them.

I used to rotate the liners in 504s and 505s so that number one and number 4 were swapped and the two middle ones also. That way, each liner had as its new thrust face what used to be the rear face. Never had a problem, and in my own car I even used the original pistons. Did it at 180,000 Ks and sold the car, till going strong and hardly using any oil, at 400,000 Ks.
I also had the ring grooves enlarged and used wider, harder, non-chrome rings.
 
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