OF SOUTH AUSTRALIA INC |
Piston Grades |
OF SOUTH AUSTRALIA INC |
From: | Ken Shaw [kenshaw(at)cyberone.com.au] |
Sent: | Wednesday, April 02, 2003 9:41 PM |
To: | hillman@can-inc.com |
Subject: | "Hillman – " I need help to get started |
This message forwarded by the Hillman List.
G'day all
I am sure that this will be the first of many questions to help me build my Hillman engine back to "as new" condition.
I do not comprehend the A.B.C.D. system that Rootes have for an engine description. I have a Series III medium compression (1494cc No. AA 1970356 MWUO) engine. Is it A,B,C or D? How do I tell?
From the front of the engine the pistons have this stamped on the top:
No 1 C @ 12 o'clock L @ 3 o'clock
No 2 B @ 1 o'clock L @ 4 o'clock
No 3 C @ 12 o'clock
No 4 C @ 12 o'clock W @ 9 o'clock
All the pistons have four ring grooves. Does this all mean anything? If I have to have the cylinders rebored does all the above make any difference? I thank you now for any help that you may be able to give me.
Regards
Ken Shaw
Canberra
Australia
From: | Ed Meadowcroft [ed_meadowcroft(at)snap-tite.com] |
Sent: | Wednesday, April 02, 2003 10:55 PM |
To: | Ken Shaw |
Cc: | Hillman |
Subject: | Re: "Hillman – " I need help to get started |
This message forwarded by the Hillman List.
Ken,
Unlike most mass produced engines these had 4 sizes of standard bore piston which were matched precisely to each bore. The grades were A,B,C and D. This gave the engines a longer life than say BMC engines before reboring is neccessary. If your engine is in good shape and you intend to reuse the pistons make sure they are returned to the cylinder they came from. If you rebore the engine you will only be able to get +.020", .040" etc. and the precisely graded ones will not be available [I don't think they ever were for oversize pistons] so it won't matter. I presume your pistons have 3 grooves at the top and a 4th one on the skirt. In early production engines the skirt ring was left out with the recommendation to fit it after a certain mileage but this silly idea was soon abandoned and 4 rings were fitted in the factory.
If you don't rebore it [any idea of the mileage?] I would recommend fitting a set of oil control rings which have a stepped top ring to avoid hitting the wear ridge in the bores and two lowest rings with a ring of spring steel under the ring itself to ensure the rings fit the bores reasonably tightly. I don't know what the availability of these is nowadays.
Ed
From: | Ed Meadowcroft [ed_meadowcroft(at)snap-tite.com] |
Sent: | Wednesday, April 02, 2003 11:02 PM |
To: | Ken Shaw |
Cc: | Hillman |
Subject: | Re: "Hillman – " I need help to get started |
This message forwarded by the Hillman List.
Ken,
Forgot to mention, the piston grades do not feature as part of the engine number, they are only marked on the pistons themselves, you have an engine with 3 C grades and a B.
Might have confused you re oversize pistons, they are available [or were] at + .010" thru +.060" at 10 thou intervals. I've no doubt other list members local to you can advise you of availability.
Ed
From: | alkon [alkon(at)bigpond.com] |
Sent: | Thursday, April 03, 2003 9:17 AM |
To: | hillmanlist |
Subject: | Re: "Hillman – " I need help to get started |
This message forwarded by the Hillman List.
Hi Ken
Others have mentioned the grading system that Rootes used for factory selecting the best fit
pistons. They paid much more attention to detail than many of their contemporary
manufacturers, and certainly more than Chrysler ever did.
No wonder the Minx had such a good reputation for reliability :–))
If you are rebuilding the engine the first thing to do is to get everything
measured, write it all down.
If the block doesn't require reboring it is absolutely imperitive that every
part goes back where it came from.
This includes cam followers, pushrods, rockers, valves, bearing caps (same
way round). Sorry if this sounds a little like telling granny how to suck eggs :–))
If you can get away with replacing stock size pistons, you will need to use
a ridge breaker to remove the lip that appears between the top of the top
ring and the top of the bore. Also need to hone the cylinders to remove
glaze so that the new rings can bed in.
I have never gone this way. Mostly the engines I get to rebuild have been
abused in some way or other. So I just bite the bullet and run the boring
bar through the bores to the next oversize. If your machine shop is any good
they can bore to suit the pistons you have. Most cheap engine rebuilders
just bore to the nominal oversize and stick the pistons in. Works most
times. The good motor machinist will only rebore after he has the new
pistons in his hand and does the final hone to give the correct running
clearance. Same with the crank, if there is any "ovality"?? in the journals
they should be reground to the next undersize. Again the good guys will
check the bearing shells first.
Don't forget the cam bearings, a real pain to replace but often a source of
phantom oil pressure loss.
Apart from the machining you can do most of the dissassembly and reassembly yourself.
Cleanleness and attention to detail are best attributes. Don't rush anything.
It is worthwhile to remove all welsh/frost/core plugs and clean out cooling
passages before fitting replacements. Most engine shops hot tank the whole
thing anyway which means the reassembly is all clean parts.
If a new or reground cam is used then new cam followers/lifters will be needed. Do not try and reuse the old ones; they will just destroy the new cam surface.
I don't know if you have done this stuff before but there are some good
general publications available on engine rebuilding and blueprinting.
Petersens had some good ones but they of course are no longer with us. If
you are doing your own assembly you can pay attention to the balancing and
blueprinting which are time consuming but give dividends in smoothness and
longer engine life. It is surprising how much engine balancing can be done
with a balance or a set of accurate digital scales.
Example all con rods the same weight and the same weight at big and little
ends. All pistons the same weight. Dynamic balance of crankshaft, flywheel
and clutch assembly. All combustion chambers the same capacity. I saw an
Austin 1500 engine (three main bearings) that would idle smoothly at 150 rpm
after being assembled using this sort of attention to detail. May not make
fire breathing power but so smooth :–))
If you do some of the above then you will have your engine better than as new :–))
Keith
55 Californian
From: | Jan Eyerman [jan.eyerman(at)usa.net] |
Sent: | Thursday, April 03, 2003 12:25 AM |
To: | Ken Shaw; hillman@can-inc.com |
Subject: | "Hillman – " "A", "B" "C" etc |
This message forwarded by the Hillman List.
Ken,
The Rootes (hence Hillman) 1390–1725cc OHV engines were all "selective fit" engines. They were in essence, hand fitted engines. It was a cheap way to produce Rolls Royce quality in assembly.
Each engine component was measured and weighed and then marked. Engines were assembled from matched components. There were 5 different (I am working from memory – so there might have been more) bore "grades" or sizes – each one 5/10,000ths of inch bigger. At that time, the most accurate machining was only to 1 and 5 /1000ths, so a Hillman had roughly an order of magnitude tighter tolerances.
The pistons and rods were also measured and matched and were also installed in matched weighs. This simplified balancing the rotating parts and actually gave a better balance because each component was balanced rather then just the whole assembly.
Someone has described the procedure as a "blueprinted production engine".
On rebuild, be sure to mark everything and put it back to where it came from!!! The bore coding is meaningless once the engine is rebored. It also means that a rebore will never be quite as good as the original. Same is true of cutting the crank...
Although totally unimportant and meaningless today, Hillman engines absolutely
required CAREFUL break-ins. You could destroy all of the careful assembly
work in the first few hundred miles. That might explain why my '69 Arrow ran
as well at 115,000 miles when I sold it as it did when it had 15,000 miles....
I had carefully broken it in. Too bad they didn't have something to keep the
body from rusting away!
Anyway, that is the story behind the letters. Replacement parts are not letter coded – they are just the middle (I think "C").
Since my manuals are not handy, I don't remember where the codes are stamped on the block...
Jan Eyerman
From: | alkon [alkon(at)bigpond.com] |
Sent: | Thursday, April 03, 2003 9:58 AM |
To: | hillmanlist |
Subject: | Re: "Hillman – " "A", "B" "C" etc |
This message forwarded by the Hillman List.
Measuring to the tighter tolerances is done by operatives with go/ no go gauges.
Semi skilled operatives can achieve quite amazing accuracy by this method.
Jan or some other knowledgeable person has mentioned how Rootes bedded in
the engines. Using a test running engine to rotate the next one for a number
of hours to let all the moving bits get accustomed to their place in the
world before actually starting it.
We could emulate this procedure quite easily if we desired by mounting a
small induction motor in place of the alternator and belt driving the engine
(with plugs removed) for several hours. Best to have oil in the sump and
rotate the engine the correct way. Induction motors typically rotate at
about 1500rpm in 50Hz countries.
Running in an engine is perhaps more complex than people realise.
The engine needs to run with a light load, but not no load. So idling for
long periods is not a good idea. Use medium rpms, probably no more than 3000
and change down early to prevent the engine struggling at low revs. The
reasoning behind this is that the rings need to bed in under some load, if not they form a
glaze on the bores and often never bed in properly. This causes premature oil use.
Do not use friction modifiers (molyslip, STP etc.) during run in. Often during
the run in period the engine will build up heat more than in normal
operation, if this happens it is best to stop the car, allow the engine to
idle for a few minutes for temperatures to stabilise then shut it down and
allow to cool. When building an engine for sensible street use we assemble
using tighter tolerances than the race car or production line engine
rebuilders so need to take more time to let it all settle down.
Patience is rewarded by a smooth running quiet engine :–))
However fit an aftermarket revcounter so you can see the engine is running :–))
Keith
55 Californian