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Old 03-10-2016, 08:29 PM
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Thumper460 Thumper460 is offline
Y Rated - 186 mph
 
Join Date: Dec 2006
Location: Orange Park Fl. 32065
Posts: 113
Default Damn... More Camshaft stuff !!

Pre-load on the Hyd Lifter !!


Lifter Pre-loading
Setting Hydraulic Lifter Pre-load (Non-Adjustable Valve Train)

COMP CamsŪ recommends ensure the proper pre-load.
" Hydraulic lifters have the ability to automatically adjust themselves and maintain zero clearance in the valve train by supporting the pushrod plunger on a small chamber of pressurized oil, regulated by a precisely controlled oil bleed rate. Valve train noise is prevented because the lifter is preloaded, eliminating any clearance.
Hydraulic lifter preload is the distance the pushrod plunger is depressed below the retaining lock. Preload should be between .020"-.060" for the lifter to perform properly. With too little preload, the valve train will be noisy and the retaining lock may fail (break or pop out) due to excessive hydraulic force against the retainer. Conversely, too great a preload (more than .060") will produce excessive lifter pump-up, causing the valves to open longer and lift higher, drastically reducing cylinder pressure and hurting engine performance. The engine will also have very low vacuum, causing it to idle very poorly. "

The Base circle on the r53 camshaft is 1.185 inch. when you remove the material off the Base circle ( to increase the valve lift , or add duration) you will make the base circle smaller. ( ie: 1.185 stock to a 1.120 modified), this will allow the lifter to extend and remove the correct amount of Pre-load.
By adding a 'Lash Cap' to the top of the valve tip, you can remove the distance loss of .045" in base circle, ( this example) and bring the lifter back to the correct position ( Factory set Per-load ).
The example here is the Schrick Cam. On the Exhaust lobe it contacts the spark plug tube, and we are advised to "ding " the tube for clearance. With the stock BMW base circle and the total lobe lift.. the Cam has a 8.9 mm lift at the Valve ( .352" !!) Therefor ANY camshaft for the r53, that has more lift at the Exhaust Valve of 8.9 mm ... HAS TO HAVE a smaller base circle and thus removing the 'factory pre-load'.

Is this a critical area for performance ?? LOL, YEP !!

Hope this helps when you are building or just changing camshaft.
Thumper Performance

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