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From: Jason James on 10 Aug 2010 15:29
I remember dad buying some parts for a stationary motor (Terrier I think)and
how the guy selling the parts (in a shop in Newtown Sydney) was complaining
about a new Holden he had bought,...now this was around 1962,..so it was
probably an FB or EK Holden. Both had the grey motor. His complaint was
about the piston-slap the engine had,...from the showroom floor!.

It's a commentary on engineering tolerances of the day. One fact is,..up
until recently, any workshop manual for any car, indicated a range or
"grade" of pistons were used in new engines. The Hemi Val for instance,
listed 3 different diameter pistons to suit the varying diameter of bores in
new blocks as the boring tool became worn.
Question is,..what has changed now? Or have they simply stopped listing the
multiple grades of pistons??

Jason


From: D Walford on 10 Aug 2010 19:44
On 11/08/2010 5:29 AM, Jason James wrote:
> I remember dad buying some parts for a stationary motor (Terrier I think)and
> how the guy selling the parts (in a shop in Newtown Sydney) was complaining
> about a new Holden he had bought,...now this was around 1962,..so it was
> probably an FB or EK Holden. Both had the grey motor. His complaint was
> about the piston-slap the engine had,...from the showroom floor!.
>
> It's a commentary on engineering tolerances of the day. One fact is,..up
> until recently, any workshop manual for any car, indicated a range or
> "grade" of pistons were used in new engines. The Hemi Val for instance,
> listed 3 different diameter pistons to suit the varying diameter of bores in
> new blocks as the boring tool became worn.
> Question is,..what has changed now? Or have they simply stopped listing the
> multiple grades of pistons??

They still selectively fit pistons to bores in the assembly plant but
due to the much better metallurgy and better machining and measuring
equipment the tolerances are a lot finer.
The variation in piston size would be too small for anyone to measure
accurately with a micrometer so there would be no need to list different
size pistons for a standard bore.


Daryl
From: Jason James on 13 Aug 2010 16:38

"D Walford" <dwalford(a)internode.on.net> wrote in message
news:4c61e48b$0$28669$c3e8da3(a)news.astraweb.com...
> On 11/08/2010 5:29 AM, Jason James wrote:
>> I remember dad buying some parts for a stationary motor (Terrier I
>> think)and
>> how the guy selling the parts (in a shop in Newtown Sydney) was
>> complaining
>> about a new Holden he had bought,...now this was around 1962,..so it was
>> probably an FB or EK Holden. Both had the grey motor. His complaint was
>> about the piston-slap the engine had,...from the showroom floor!.
>>
>> It's a commentary on engineering tolerances of the day. One fact is,..up
>> until recently, any workshop manual for any car, indicated a range or
>> "grade" of pistons were used in new engines. The Hemi Val for instance,
>> listed 3 different diameter pistons to suit the varying diameter of bores
>> in
>> new blocks as the boring tool became worn.
>> Question is,..what has changed now? Or have they simply stopped listing
>> the
>> multiple grades of pistons??
>
> They still selectively fit pistons to bores in the assembly plant but due
> to the much better metallurgy and better machining and measuring equipment
> the tolerances are a lot finer.
> The variation in piston size would be too small for anyone to measure
> accurately with a micrometer so there would be no need to list different
> size pistons for a standard bore.

Yep,..I can remember a time when engines used to go only 70,000 miles before
needing "rings, bearings, a valve-lap and decoke". [Al still thinks you need
to do this, which is why his Pantahh! is in bits on the bench all the
time:-)]

Modern engines and more importantly modern oils, have seen engines doing
3-400,000ks. Quite amazing really.

Jason


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