Ausmini
It is currently Sat Jul 19, 2025 7:46 am

Board index » Mini Chat » Mini Chat

All times are UTC + 10 hours




Post new topic Reply to topic  Page 1 of 1
  [ 11 posts ] 
  Print view Previous topic | Next topic 
Author Message
mooman10_0
 Post subject: rocker question
PostPosted: Sun Oct 30, 2016 4:10 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
Do 998 rockers and 1275 rockers interchange with each other? Talking about a 12g940 head.
Thanks, Steve
Top
 Profile  
 
drmini in aust
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 5:40 pm 
Offline
religious status
religious status
User avatar

Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39754
Location: near Baulkham Hills, NSW
Valve spacing on all 1275 heads is greater, the exhaust guide centres were moved out. You can fit 998 rockers if you put a flat washer next to the pillar for exhaust rockers only.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
Top
 Profile  
 
mooman10_0
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 5:46 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
thanks for that, any way of telling by looking if a set I have are 998 or 1275, can I measure something?
Thanks,
Steve
Top
 Profile  
 
gtogreen1969
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 5:48 pm 
Offline
1275cc
1275cc
User avatar

Joined: Fri May 02, 2008 3:07 pm
Posts: 5123
Location: The Internet
mooman10_0 wrote:
thanks for that, any way of telling by looking if a set I have are 998 or 1275, can I measure something?
Thanks,
Steve

If you have pressed steel rockers the 1275 have oval pads and the small bore have round pads.

Image
Top
 Profile  
 
drmini in aust
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 6:14 pm 
Offline
religious status
religious status
User avatar

Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39754
Location: near Baulkham Hills, NSW
The oval pad 1275 ones have a bit more lift too, if you find some.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
Top
 Profile  
 
mooman10_0
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 6:41 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
the ones I have are rectangular pads?
Top
 Profile  
 
drmini in aust
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 7:32 pm 
Offline
religious status
religious status
User avatar

Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39754
Location: near Baulkham Hills, NSW
Are they flat on sides and curved on top? Or are the square pads wider than the body?
The former are the late sintered rockers used from about 1976 on. They have no bushes in.
The latter ones would probably be Cooper S/early 1275 rockers. These give less valve lift than all others.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
Top
 Profile  
 
mooman10_0
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 7:40 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
I would say squarish pads, wider thean the arm which had a thinner ridge running along top.
Top
 Profile  
 
mooman10_0
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 7:43 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
junk?
Top
 Profile  
 
drmini in aust
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 8:54 pm 
Offline
religious status
religious status
User avatar

Joined: Fri Mar 19, 2004 6:19 pm
Posts: 39754
Location: near Baulkham Hills, NSW
mooman10_0 wrote:
junk?

I tested standard rockers a while back in 2007 using an RE13 cam, stock pushrods on a fully assembled 1275 head (12G1316) and .016" valve clearance.

I measured the S forged rocker ratio at 1.16:1.
You can fit offset bushes to them, this gives a bit more lift (maybe .020")
Similar to this, the pressed steel ones can be done too--
Image
Note the rocker posts need the stud holes all drilled out 1.5mm and the assembly pushed back when bolting down.


Other rockers:
A+ sintered rockers 1.18:1
850/998/1098 pressed steel round pad rockers 1.21:1
1275 pressed steel oval pad rockers 1.25:1 approx.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
Top
 Profile  
 
mooman10_0
 Post subject: Re: rocker question
PostPosted: Sun Oct 30, 2016 9:09 pm 
Offline
1098cc
1098cc

Joined: Fri Sep 10, 2004 6:39 pm
Posts: 1770
Location: Kaniva / Adelaide / Melbourne
Thanks, doc
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  Page 1 of 1
  [ 11 posts ] 

Board index » Mini Chat » Mini Chat

All times are UTC + 10 hours


Who is online

Users browsing this forum: No registered users and 79 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  

cron

© 2016 Ausmini. All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.