View Single Post
Old 03-12-2016, 03:55 PM
Thumper460's Avatar
Thumper460 Thumper460 is offline
Y Rated - 186 mph
Join Date: Dec 2006
Location: Orange Park Fl. 32065
Posts: 117

Bad ASS Performance Camshaft for the modified MINI r53

Racing is a demanding sport !! Power and torque curves are all important !! Bearing longivity at high RPM is critle, Choosing a camshaft for your Track and Performance level. Indexing the Camshaft for the power when you need it. Getting powerful boosted the air in and then out is a major factor. Valvetrain operation.. valve guide wear, or those racing springs wear when busting 7800-8000 revs !! OMG.. this sport is demanding.. as they say, IT is only a Hobby !! WTF !! hobby?? sure! Bounce that statement off your Wife a few times !! LOL

We have a 'install and forget it' rocker arm assy's.. right?? Throw in a camshaft and rock !! Oh Hell yeah !!

But with the Hydrolic lifters we use ( designed to not need adjustment).. there is a certain 'Pre-load ' that is required to keep and maintaing the correct pressure on the lifter to allow the valve to open at the designed 'Lift' on the camshaft.. or even stay open for the duration it was intended for. Cam manufactures know this.. engine builders know this. IF you remove some 'pre-load off the lifter.'. the valve will not open as far as it is intended. Example a .400 Lift cam will only be in there at .385 " Lift. Shit !! just wasted all that money on less performance than you expected!!

Well screw that.. how and why is this happening ??

Well mainly this is do to the Camshaft having to under cut the base circle in order to make higher Lift numbers so that the clearance issues on the r53 Head are minimumized !! SO.. with the basce circle in at 1.181" this allows the correct pre-load on the hyd lifter. ( or it sets the lifter at a certain position in the rocker arm). Using the BMW Schrick camshaft as an example.. Using the stock 1.181 base circle..the max lift at the valve is .350 " Lift !! and Schrick says to 'ding the sparkplug tube for clearance' Cool??

SO.. if you have a camshaft that is showing ANYTHING over the .350 @ the Valve ( exhaust)... they have under cut the base circle to get more lift and no clearance issues !! And when the 1.181" is made smaller for more lift ( like 1.140 ) that it now unloads the Lifter by .041" !! OMG !! The lift on the cam lobe is correct !! it is at .395" open at the valve. However with the load off the lifter.. actual lift is going to be less than that !!

What to do.... Well the way to remidy the issue is to add a lash cap to the tip if the valve and remove the add'l clearance from the under cut base circle. Lash caps are in certian thicknesses !! And to add to the exhaust and then different to the intake, we decided to KISS !! Or Camshaft is designed to run with certian thikness caps, replacing to the correct pre-load. Now we can have over .450" intake lift .. and more than .388 -.400 exhaust lift ( and no interference issues) Insuring the valve spec follows the Cam lobe as intended.



THUMPER HEAD Nitrous Fed Methanol Injected Screaming Supercharger all BRG 06 MCS!! The fun begins at 4K in 6th
Reply With Quote