Noisy top end - now fixed?

[SLB]

A couple of weeks ago I decided to bite the bullet and investigate an annoying "tick" and noisy top half to the engine when hot, especially in the summer. It's an 88 350i with 76k miles on the clock, oil changes every 3k for the last 5 years and laid up for a few years before that. The engine has had 20/50 oil in it plus hydraulic tappet oil addative for the last two years. Expecting an expensive new camshaft which I couldn't afford to get done at a garage, I plucked up the courage to remove the inlet manifold and have a look.

After reading various articles on Pistonheads and having had broken rocker pads in the past on another car, I felt confident enough to have a go and now I'm writing this up in case it helps others with their cars.

On trying to remove the inlet manifold bolts, I struggled with the front one nearest the distributor and the one nearest the driver because the valley gasket seal was starting to fail letting moisture rust the bolts. Other than this it came apart ok with a couple of other manifold bolts under the plenum being a bit loose.

The engine was lovely and clean inside and to my surprise the cam looked in decent condition. With the help of a relative who has worked on these engines in the past, we measured and concluded their wasn't enough wear on the cam to warrant replacing it so my attention turned to the tappets and rockers. All the tappets were fine from a hydraulic perspective, but a couple in the middle on the nearside were showing a lot more wear than the others. When I put a straight edge along the top of the valves, both sides had valves that were up to 12 thou lower than the others. The lifter in the photo came from one which was 8 thou lower on the nearside. I measured the pre-load on a normal valve as per the V8 Developments website http://www.v8developments.co.uk/technical/valve_tr... and found it to be in tolerance at around the 65 thou mark, despite all the lifters appearing to be on their maximum limit when I first removed the manifold.

Although the rockers showed little or no wear, the rocker shafts had a thou of wear on the underside so I turned them over and turned them around when re-assembling. To sum it up I thought there was a build of wear making a couple of tappets outside their tolerance, probably as it wasn't set-up brilliantly in the first place. With no shims under the rocker posts I decided to machine 22 thou off them as a good friend has a milling machine in his garage. When we put them on a rocker shaft for machining, although the tops were all level the bottoms varied by about 6 thou which would not help the tolerance build-up. After de-burring, cleaning, new composite valley gasket and four new tappets it went together really well.

I was advised by parts people to replace the cam at the same time as the tappets for various reasons, but I decided not to do this as the cam appeared fine and I didn't want damaged tappets hitting a reasonable cam. Cost, hassle and the fact I do 3k a year hopefully means it will last another 10 years before needing doing again when the cam will want doing anyway, probably.

Only a couple of runs so far, but the engine is lovely and quiet now and the smoothest at low revs it has ever been. I can't feel any real power increase but I am a lot happier, all for £36 (plus some antifreeze and some RTV sealant) and a couple of late nights in the garage.

[SLB]

The worst of the tappets - some you could hardly see any wear on at all.

[Number 7]

Seems like a cost effective fix, and a good way to get to understand the engine. Useful to know someone who understands them as well. Wear patterns like that can be induced by excessive idling, as the tappets don't start to spin until the revs go up a bit. My only concern would be whether any case hardening has been worn away. Is the cam the original?

[SLB]

I believe it's all original and I too have a concern about the removal of the case hardening. I'm told you should always change cams and tappets together due to wear patterns but I couldn't face changing a decent looking cam or put an obviously worn tappet back in. This was by far the worst so I'm prepared to give it a try and If it goes pear shaped I'll update this thread.

I wouldn't say I understand these engines but I have been given bad advice in the past. A previous car I had over revved for literally a second due to a seized throttle cable. TVR experts said it was everything from a damaged cam to a bent engine but turned out to be a broken rocker pad due to valve bounce only discovered after an expensive engine out job. I think this has given me the confidence to give it a go myself.

Here a tip - a few months after getting my previous car I replaced the sump gasket only to find the strainer had fallen off in the bottom. I had it rebrazed and then a few years later the strainer saved an even more damaged engine by collecting the pieces of my broken rocker pads.

[Rockettvr]

Good post! Some good pointers there for me as my 350i seems to be suffering the same malady - quiet as a church mouse when cold then as the engine warms an annoying ticking comes in. Gave the cam, lifters and rockers a cursory inspection when I stripped off the intake manifold to repair a rusted pipe that runs underneath and found nothing untoward - cam nice and pointy no obvious wear to lifters or rocker shafts etc. All I did notice was no shims under the rocker posts .Didnt want to get into it too much then as performance was ok (185bhp at last wedge fest even with a faulty throttle pot and failing fuel pressure regulator)
It would seem that the top end has been rebuilt at some point and re assembled incorrectly. Think a more detailed inspection is due once I find some time and the weather improves....
Cheers

[The Hatter]

Ron,

Rover never put shims under the rocker posts, most likely that your engine is totally original. My replacement cam turned out to be made of chocolate so attempting to keep the original cam and replacing the cam followers is an interesting alternative.

[SLB]

Time for an update. The mod and new followers worked to a certain extent but there was still a slight tapping only when hot. So whilst at a Landrover sortout I bought a spare pair of heads from a 1989 3.9 ( same as a 3.5) for £50 which were aledgedly good. I could see there was similar wear on the rocker shafts but took a gamble.

Later I diisassembled the car and compared them. Although the shafts on my car were slightly less worn, the rockers from the 3.9 had less wiggle side to side on both mine and the 3.9 shafts so I switched the shaft and rockers over, careful to keep the rockers matched to their positions on the shafts. I kept my modified shorter rocker posts on the car.

After plenty of high speed high temperature runs and long idles when hot, I have to say I think it's fixed. So to sum it up I'd say on my car it was due to worn/wiggling rockers , which probably contributed to damaging a few followers not helped by the varying valve heights taking the hydraulic followers out of their tolerance. With hindsight a new set of rockers and a few followers may have fixed it, but I feel happy to have done the mod too. Steve.