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1100s Rockers
https://www.ausmini.com/forums/viewtopic.php?f=2&t=84526		 Page 1 of 1
Author:  rodaz [ Mon Feb 10, 2014 5:00 pm ]
Post subject:  1100s Rockers
Hi All
Are these rockers standard on an 1100s motor.
Thanks

Image
Author:  TK [ Mon Feb 10, 2014 5:06 pm ]
Post subject:  Re: 1100s Rockers
I've only seen the pressed steel type used on 1100S engines.
Author:  drmini in aust [ Mon Feb 10, 2014 6:06 pm ]
Post subject:  Re: 1100s Rockers
Forged Cooper S rockers as in pic were used on early 1100S too. As well as duplex timing chain.

S rockers give less lift than all others. 850/998/1098 pressed ones are better, A+ sintered ones better still, 1100S pressed ones with oval pads were highest lift of the stock rockers..
Author:  TK [ Mon Feb 10, 2014 6:25 pm ]
Post subject:  Re: 1100s Rockers
There you go and I've stripped down a ton of thin flange, small journal engines but I must say that every 1100S I have seen has duplex timing gears.
Re: late A and A+ sintered rockers aren't very good because they are brittle and heavy according to Vizard.

edit; oops, spelling
Author:  drmini in aust [ Mon Feb 10, 2014 6:30 pm ]
Post subject:  Re: 1100s Rockers
TK wrote:
Re: late A and A+ sintered rockers aren't very good because they are brittle and heavy according to Vizard.


Yes they are, but for a road motor that won't ever see over 7000, I would use them if in good condition.
Their main problem for road use IMO is they are unbushed- when worn inside, you can't fix them.
Author:  MG Rocket [ Mon Feb 10, 2014 7:16 pm ]
Post subject:  Re: 1100s Rockers
Image

I have an 1100S with the same head and the same rockers.
The rocker pads seem badly worn tho'.
Author:  drmini in aust [ Mon Feb 10, 2014 8:02 pm ]
Post subject:  Re: 1100s Rockers
The pads on S forged rockers do wear, they are not as hard as they could have been. They can be refaced...
The other problem with S rockers is their ratio is inconsistent, giving variation in lift. GR noted this when he wrote up his smallbore engine project some years ago.
Author:  rodaz [ Tue Feb 11, 2014 2:03 pm ]
Post subject:  Re: 1100s Rockers
Thank you for your replies.
Author:  MG Rocket [ Tue Feb 11, 2014 5:49 pm ]
Post subject:  Re: 1100s Rockers
Does the above motor have a small journal or the large journal crank?
Author:  rodaz [ Tue Feb 11, 2014 9:29 pm ]
Post subject:  Re: 1100s Rockers
Can you tell when the engine is still assembled ?
Author:  drmini in aust [ Tue Feb 11, 2014 9:43 pm ]
Post subject:  Re: 1100s Rockers
rodaz wrote:
Can you tell when the engine is still assembled ?

Big journal cranks started at 1100S engine number 12YD/Ta/H10487/10488.

But these days, blocks can have been rebuilt with either a big journal, or a small one.
If you look through the fuel pump hole with a torch, check if the conrods have a big square lump on their caps. If so it's got a big journal crank in.
Author:  rodaz [ Tue Feb 11, 2014 9:52 pm ]
Post subject:  Re: 1100s Rockers
Ta/H9892
Author:  drmini in aust [ Tue Feb 11, 2014 9:57 pm ]
Post subject:  Re: 1100s Rockers
Would have been built with a small journal crank and `Cooper S' rods.
I like these ones better, as the crank and rods are lighter.

You can stroke the big J cranks then use narrowed S rods, but to do it properly (including wedge the crank) it's expensive for the 50cc gained.
Author:  MG Rocket [ Mon Mar 10, 2014 5:07 pm ]
Post subject:  Re: 1100s Rockers
Doc, from what I understand... The small journal crank seems to be the prefered crank so why did BMC
decide to make the journals larger? Was it to try to damp vibrations that fours are noted for?
Author:  drmini in aust [ Mon Mar 10, 2014 6:04 pm ]
Post subject:  Re: 1100s Rockers
MG Rocket wrote:
Doc, from what I understand... The small journal crank seems to be the prefered crank so why did BMC
decide to make the journals larger? Was it to try to damp vibrations that fours are noted for?

According to Vizard and others, it was to strengthen the crank whilst using EN16 steel, instead of EN40B (on an S).
However some evidence here since then seems to indicate they are more prone to cracking than the small journal EN16 tufftrided ones were. I'd say the heavy big J rods and heavier 1100S flywheel didn't help crank life either.

A few years ago, Spiro at St George Cranks had 6x big J 1100S cranks to regrind. He told me that when he tested, 4 were cracked already.
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