The V8 Owners Forum -

on my 3.5 RV8 if i drive at speed before the engine is fully warmed up i would get a noisy tappet/lifter, would last about 10-20 secs then stop again.
last weekend i went to MITP at santa pod, all was well going there, but coming back i would get this noisy lifter about 1/2 dozen times for no reason. this is the first time it has been driven on a long run (45 mile each way) the easiest way i found to stop it was dip cluctch and rev it up so pressure went over 3 bar.
oil is new, halfords 20/50, new filter, pressure is good, 2 bar + when cruising and its not running hot.
whats the most likely cause, might i have not shimmed the lifter preload right? or could it be a failing lifter. this engine has only done just over 800 miles from rebuild, new cam and lifters ect

Probably not enough tappet preload.

I have the same on my 4.6, and I believe it is because the valve stem heights are all different, so there's no rocker shaft shim that puts all eight valves within preload spec.

Chris.

so it might be worth just dropping down to the next size shim, and see what happens.
if there is too much preload what might happen that end? i assume you could get to valves not closing properly in extrame cases

The danger as you say is that a valve may not close properly. Which might give interesting backfires into the inlet manifold, or exhaust, and burned valves.

But it would be an easy test to do I guess.

Chris.

If your running a standard cam it should be safe to use the next shims down, if you have a cam with more lift you need to check that the valve spring has enough clearance at full lift or it could cause an expensive problem.

Kevin.

If you are going to the trouble of re shimming, why not pull the manifold off and check the pre loads?
what cam are you using?

i'm using a Hurricane cam, i might take manifold off any way to take a look at the cam, make sure i've not done any damage.

when checking the preload, will i have to bleed the lifters first?

is it likely to be anything else causing this, would a better oil help i am planning on going for Valvoline VR20/50 on the next change

I drain my lifters everytime I refit them so I can check the pre load.

Hi
Worse case, you may have to go adjustable push rods does seam strange only does it on a run or is it when it gets warm,ie.if you left it ticking over on the drive? What condition are your rockers and shafts in,pad wear on a rocker
Cheers John.