Hydraulic Tappets, Info Please.

[Richie-Van-GTi 70 2 Cars]

Hope someone can clear this up, on an XU10J4R engine should the hydraulic tappets be in constant contact and also should they be slightly pressed at all times, If yes by how much roughly. Also if anyone know the 'height' of a good standard hydraulic lifter that would be very useful.

[welshpug 1,623]

Yes due to their nature they are self adjusting by hydraulic pressure so will be in constant contact with the camshaft.

 

The height depends on the base circle diameter and the length of the Valve and whether the valve seat has been cut.

[Richie-Van-GTi 70 2 Cars]

working on the assumption the valve seats are as standard apart from being lapped in last time the head was off. I thought the constant contact was the case but needed to be sure. Should they be slightly pressed at minimum/no lift off the camshaft? Got to look at one with noisy tappets on the inlet but it has an aftermarket cam. I suspect its coming clear of the tappets and hoping I can get a close enough measurement to establish if I can make up some shims to set on the valve tops.

[welshpug 1,623]

Shims wont help a dead hydraulic tappet, usually to diagnose one just give them a prod with a non metallic object (so you don't mark them) If one moves easily then they need replacing.

[petert 554]

You can buy shims in various thicknesses from places like Summit Racing. You need to be careful however that they don't touch the collets. There should be at least 0.5mm in lifter pre-load.

Edited September 14, 2012 by petert

[Richie-Van-GTi 70 2 Cars]

Shims wont help a dead hydraulic tappet, usually to diagnose one just give them a prod with a non metallic object (so you don't mark them) If one moves easily then they need replacing.

 

 

I dont suspect any dead tappets, I suspect the cam is losing contact with the tappets, Hoping a simple shim under the tappet will cure as the car is mapped to the cam.

You can buy shims in various thicknesses from places like Summit Racing. You need to be careful however that they don't touch the collets. There should be at least 0.5mm in lifter pre-load.

 

Thats exactly what I need to hear, if I do find clearance I know I can shim up to the clearance + 0.5mm. Will be interesting if Im correct to see what effect this has on performance.

[welshpug 1,623]

ahhh is it a regrind? maybe the base circle is too small.

[Richie-Van-GTi 70 2 Cars]

Welshpug yes it is a regrind, have had it apart yesterday and can confirm it has too much taken off the base circle as it clears the lifters by nearly .5mm, also note it has a approx 2mm less overall lift. Now confident the issue is the camshaft and that it is costing power. Will probably put a standard cam in for now to at least get it running nice then look into options for performance at a later date if required.