Noisy tappets

Simeon · Post by **Simeon** » Wed Mar 30, 2011 11:48 am

Now I don't know whether I've done something wrong but this is the very first engine I've rebuilt. My RV8 standard buils aprt from Piper 270 cam is quite noisy in the tappet area and will not quieten down. Don't slag me off but I got a set of hydraulic lifters and adjustable rods from an engine that had only done 1000 miles before he smashed the car up. Now I assumed the lifters would be empty of oil which they may have been and subsequently set the pre-load. The engine runs great but it is so tappetty knocking loud. If I adjust the paushrods to take out all the slack plus a couple of flats it lifts the valve slightly and loses compression.

What have I done wrong?

SuperV8 · Post by **SuperV8** » Wed Mar 30, 2011 12:15 pm

Hi,
You shouldn't use worn tappets with a new cam.
Even though they had only done 1000 miles they will have bedded in to that old cam. If you then use them on a new cam unfortunatley you may end up trashing the can lobes as they wont bed in propperly. Some chaps do report chat you could re-use slightly used tappets with a new cam if you flat them off, did you do that?

To me unfortunatly it sounds like you will need a new cam and tappets!

Tom.

Simeon · Post by **Simeon** » Wed Mar 30, 2011 12:35 pm

Hi Tom

Thanks for the reply

Fair call on the tapets but is a new cam really necessary It's brand new?. Since the rebuild the engine has only run in total about half an hour.

Simeon · Post by **Simeon** » Wed Mar 30, 2011 3:37 pm

OK I've been having a think

If I replace the lifters they will be empty of oil. So how do I set the pre-load with adjustable rods?

With the lifter off the lobe of the cam

Is the aim to acheive - closed valve - rocker to rod to lifter plus 20 thou?

Post by **katanaman** » Wed Mar 30, 2011 4:02 pm

pretty much as the guys told you how to do it in one of your own posts http://v8forum.co.uk/forum/viewtopic.ph ... ght=#61662

It takes 20 minutes to harden a cam through running, if the cam has done less than that you might get away with it. Thats why you run a cam in at 2000 rpm for 20 mins. If it has done more I would change the cam and put it down to experience. Your cam may already be trashed which is why its rattling in the first place.

DEVONMAN · Post by **DEVONMAN** » Wed Mar 30, 2011 5:35 pm

Could it be that you have Rhoads bleed down type lifters??
These will normally sound tappety until the revs build up.
Regards Denis

DaveEFI · Post by **DaveEFI** » Thu Mar 31, 2011 9:06 am

SuperV8 wrote:Hi,
You shouldn't use worn tappets with a new cam.
Even though they had only done 1000 miles they will have bedded in to that old cam. If you then use them on a new cam unfortunatley you may end up trashing the can lobes as they wont bed in propperly. Some chaps do report chat you could re-use slightly used tappets with a new cam if you flat them off, did you do that?

To me unfortunatly it sounds like you will need a new cam and tappets!

Tom.

I'd like some clarification on what actually takes place.

The tappets are case hardened and start off with a flat high polish finely machined surface. The cam a 'normal' ground one. So initially, the cam beds into the followers.

After some considerable mileage, the followers can develop a dished surface - which of course is matched by the individual cam lobe.

On the odd low mileage cam I've looked at, the followers are still perfectly flat, and show no signs of any wear.

So just why would these damage a new cam?

FWIW I always soak new tappets in oil for a day or so before fitting. If removing them for any reason I store them in individually numbered jam jars again in oil. Saves that worrying clatter at subsequent re-start.