9 replies to this topic

[MIJ]

I'm having and issue with worn cam followers. My previous engine wore out a follower to the point it went cone shaped it had worn away that much. It would rattle constantly. I replaced the follower but it did it again as the follower hole in the block had worn due to it rattling around.

So I built another engine, and yet again it has started rattling. It does it coming to junctions where I'm coming from higher revs to lower and slowing down. It rattles. Everything was brand new, I've checked to see oil coming up through the follower holes to the head...it does. Brand new cam, oil pump, everything.

The only thing I have had sissie with on both engines has been the head gasket going where water has seeped under the gasket. Could this be the cause? Water going down the cam follower holes and sitting on top of the follower?

I'm at a complete loss, the engine runs fine, starts fine and builds good oil pressure straight away (75 cold) (50 when warm)

Any ideas, help would be appreciated. I really don't want another engine strip down.

[Ethel]

What cam, rockers & springs?

 

Can't see the head gasket having any effect.

[Mini Manannán]

What followers are you using?  If they don't have the correct 'domed' top they'll stick in one position and wear quickly.

[Spider]

There was some 'talk' of poor quality followers on the market for a while. I buy some follower, not loads of them, but I never found any bad ones.

 

All the same, it could be a soft follower, poor grind on the follower (as Tim mentioned), poor grind on the Cam (no lobe taper).

 

The other thing is new Cams, re-ground Cams, new Followers and re-ground Followers - fit any of these, and they need to be assembled with a 'Cam Lube' and then 'broken in', where the revs are kept above 2000RPM for the first 20 minutes of run time.

 

Any chance you could throw up a photo ?

[Magneto]

Also, are you using oil with a good amount of Zinc in it? If not, it will eat the cam and followers in a short amount of time.

[MIJ]

The first followers were minispares, I was running 1.5 rockers which I thought may have been the cause. I changed back to standard rockers and the same thing happened again.

I'm now running this new engine, with a swiftune cam and swiftune supplied the followers, running standard rockers and double valve springs. All the push rods were checked and straight and replaced In the same position they came out.

I'm running valvoline 20/50 which I believe is high in zinc.

It starts where I'm coming to a junction, coming down the gears and the revs build between each gear, and it rattles. When I put it back under load it goes again. It starts like this and eventually gets worse until it constantly rattles.

[Spider]

It starts where I'm coming to a junction, coming down the gears and the revs build between each gear, and it rattles. When I put it back under load it goes again. It starts like this and eventually gets worse until it constantly rattles.

 

Is it a Follower ?

I ask as engine load will have no effect on the Loading applied to Cam Followers.

 

One thing that sprung to my mind on first reading this was Con Rod Little End, though, I'd be happy and relieved to be wrong on that.

 

Next time it does it again, try and get a feel for it at idle speed if it's rattling at Crank Speed or half that, that will steer you where to look.

 

I had a noise recently that I'd never heard before, at Idle Speed it sounded very bad, on any amount of Revs, it went away. I knew it wasn't serious, but turned out the Keyway in the Crank Sprocket had flogged out   Easy fix !
 

[MIJ]

I had the car running today in the garage. I started it from cold and the noise isn't there, as the engine temp increases the tapping starts to appear. It is not loud but it is there. However having had the running sat in neutral it sounds more like tappets (I hope/think) and the noise appears a lot louder from the cockpit rather than listening from the engine bay.

I got the engine up to temp and when I blipped the throtttle to about 3k and let the revs drop back down, the rattle increased in noise. If you can imagine revving it up and instantly taking your foot off the throttle to let the revs drop, that is when it sounds like the rattle intensifies. This is what I'm hearing when pulling upto junctions or slowing the car down as the car is higher revving then as I start to reduce the revs the rattle appears. Could this be wear on the rocker shaft? The tappets clearances are fine, but I'm running standard 1.3 cast rockers which I had second hand, so could be slightly worn? I'm confused because it definitely only rattles when the engine is up to temp. There is also oil reaching the rockers so no issue with oil starvation.

Edited by MIJ, 26 October 2020 - 04:03 PM.

[MiniLuke]

Could it be your timing chain?

[Ethel]

More likely, but as Moke says, the valve gear is always going to be under load because you're always compressing valve springs. Sure, the more the revs the faster the load, but there wouldn't be any "overrun" as the valves can't stop with the springs  extended.

 

I suppose a sticky valve stem is possibility as that could create extra work for the spring(s) so it can't keep up with the cam when it's allowing the valve to close, but that ought to get better as the revs drop - though it might be more audible over the exhaust sound. But there are many other options that don't involve the valve gear.