: How does this valve train stay in adjustment?
Jul 4th, 2005, 06:38 PM
I pulled off the valve cover to see what I would be up against, should I change to a more performance oriented cam shaft. I see that the rocker arms have rollers that ride directly on the cam lobes and the valve actuating end has what appears to be an oil seal on the tip, but I don't see what keeps it all in tolerance. What keeps the valves from being held open by a tight rocker(valve actuating) arm? I see no adjustment and no hydraulics. Please enlighten me! -Jeffy.
Jul 4th, 2005, 07:45 PM
The MINI head runs hydraulic tappets I think you'll find...
Sorry I can't be of more use than that though :rolleyes: :)
Jul 5th, 2005, 01:36 AM
Where are the hydraulic tappets hiding? I could plainly see the rollers against the cam lobes... Maybe my brain fell out my ear while looking! -Jeffy.
Jul 5th, 2005, 08:56 AM
Nearly every OHC engine with rocker arms and hydraulic adjusters hides said adjusters in a machined hole in the rockers above the valvestems. Those "oil seals" you saw are likely the adjusters, which operate under oil pressure from the rocker trunnion.
Jul 5th, 2005, 12:49 PM
To help Jeffy ive got some pics for you of the head and valves...you can just see the yellow caps above the valve that attaches to the rocker arm on the second pic....
Hope this helps ;)
Jul 5th, 2005, 01:08 PM
ok...i went one step further :D i stripped down the head to show you one of the rockers....the tip (where the yellow bush is) has a swivelling ball (to follow the travel of the valve going up and down) inside the tip of the rocker houses a small hydrualic peice that can be pushed up and down etc etc.....hope this answers your question :D ;)
Jul 6th, 2005, 05:41 AM
A swivelling ball, eh? What if the contact area were made larger- could I get a little more valve lift? Since you've seen the ports in these heads, tell me: are they perfect like in a race engine, or can I gain some power by porting? I never port to just enlarge the tunnel; I just remove aerodynamic disturbances left by mass- produced machining. My results have always been very good, but I did once run into some BMW heads that I couldn't improve- they were very clean. I really appreciate the photos accompanied by explanation. That was excellent! -Jeffy.
Jul 6th, 2005, 01:10 PM
Heres a picture of the valve contact surface with relation to the rocker...as you can see its quite precise in measurements so im not sure if increasing the surface area would amount to much.
A bad picture of the exhaust port of the head...MINI heads are renowned to breathe much easier with porting but upon viewing both the exhaust and inlet theyre not to bad really...unless you intend knife edging the ports then thats a different matter ;)
Glad to be of assistance ;)
Jul 6th, 2005, 04:15 PM
This is what I call a post that helps... come to think of it, my post doesn't help at all :D
Revolution Mini Works
Jul 6th, 2005, 05:28 PM
this might be a better photo http://www.mini2.com/gallery/personal/28127/64755.jpg
Jul 7th, 2005, 02:46 AM
That really was some good stuff! I could see some area for improvement in the first exhaust port pictures, then was impressed with the slick port work by Kumho Kid. When people take the time to respond to a post like you guys did, the whole forum and, therefore, the world of Modified Minis is benefited. Thanks for the pics and info. Now I know that I could definately gain some power by pulling the heads for port work. After seeing how the rockers work, I realised that changing the camshaft would be the better choice- provided there are cams available for these, to include non-supercharged cars. Otherwise, I could probably get a custom ground cam from a California shop like Crower. They made me one for my old BMW 2002- for a third as much money as Schrick, who were the race/high perf. cam designers for German fast cars. -Jeffy.
Revolution Mini Works
Jul 7th, 2005, 01:39 PM
there are major clearance issues with the spark plug guides
even the biggest schrick cam needs you to dent them to clear.... :rolleyes: