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.
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.
ok...i went one step further 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
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.
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
Those posts should be seen by all who seek more...
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.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.