Page 1 of 1

How do I stop tappet noise?

Posted: Fri Jul 06, 2018 7:33 pm
by highlandstag
I have recently bought a rover V8 powered Stag. I have a problem with a noisy tappet which sounds like a resonance (not ticking) that comes and goes mainly between 2000-3000rpm. The engine is old and tired. The previous owner replaced the tappets without success. However, he did find that using fully synthetic oil the noise disappeared. I am a firm believer in 20w-50 mineral oil with zddp, changed every 2-3k. Also, the crankcase was breathing excessively so I decided to change the oil back. Unfortunately, the tappet resonance has returned.

My question is: Does anyone have experience of this and how was it fixed?

The engine most definitely needs a rebuild. However, for reasons I dont want to go into now, I dont want to rebuild/replace it.

The engine details are:

1974 Rover P6 3500s
3528cc 9.25:1cr
Weber 38DGMS on modified original manifold
Tubular manifolds + standard stainless Stag exhaust
SD1 timing / ignition

Internally original (except tappets)
Unkown mileage (min 85k, probably not more than 180k)

Good points: lovely idle, plenty of torque and power, smooth
Bad points: crankcase breathing (improved with mineral oil), brown/black inside, cam worn

Current usage: mostly gentle criusing, occasional overtaking, rare blasts (does my age show?)

Re: How do I stop tappet noise?

Posted: Sat Jul 07, 2018 10:21 am
by Quagmire
I always thought tappets and cam should be changed together, If the previous owner changed the tappets without also replacing the cam they may unfortunately have swapped one issue for another.

Whats the oil pressure like?

Re: How do I stop tappet noise?

Posted: Sat Jul 07, 2018 10:28 am
by DaveEFI
If the cam is worn - as is said - it is silly just to change the tappets. But I have had a noisy tappet and changed just it. Cam OK. I found it by using a feeler gauge between valve and rocker with the engine idling. The old tappet still had a flat face where it runs on the cam - if it were dished, I'm not sure I'd have tried it.

I'd have though on a Stag with an RV8, you could change the cam without removing the engine?

Re: How do I stop tappet noise?

Posted: Sat Jul 07, 2018 3:19 pm
by JP.
Its not the tappets, you have probably some worn rockers. Easy to check. Remove them from the bar and look inside for their wear pattern.

Re: How do I stop tappet noise?

Posted: Sat Jul 07, 2018 6:57 pm
by highlandstag
Hi, Thanks for the replies. The reason the cam was not changed is that the engine needs to come out - with the gearbox and overdrive - after jacking up the back - using high lift crane to clear the top panel - etc etc - I've seen the photos of it going in in 1983 and thats where it's stayed :-) I will check the rockers - It didn't occur to me they might the culprits.

Why would synthetic oil make a difference? Would moving back to synthetic in this age/condition engine be its downfall or is it too far gone to matter?

Thanks in advance, Chris

Re: How do I stop tappet noise?

Posted: Sun Jul 08, 2018 8:27 am
by DaveEFI
My brother has Stag but with the original engine. I thought after removing the rad and grille, there was quite a large opening to the front. Not possible to raise or lower the engine if the cam fouls the edge of that? The cam can tilt quite a long way once forward of its bearings.

Re: How do I stop tappet noise?

Posted: Sun Jul 08, 2018 8:52 am
by GDCobra
Can't you get the engine out without the 'box? I can do it on my Cobra and while it's not easy it is possible to unbolt the bell housing.

Re: How do I stop tappet noise?

Posted: Wed Jul 11, 2018 5:54 pm
by highlandstag
I definitely cannot lower the engine. It can be raised a little, but not nearly enough. However, it looks like it might be possible to lower the gearbox and tilt the engine up on its mounts. If this is possible, I dont see why the gearbox could not be removed making removal of the engine significantly easier. Anyway, apart from the rockers, there doesnt seem to be a quick solution. If its not them I'll leave further work for the winter. Thanks very much for all your help. Cheers, Chris

Re: How do I stop tappet noise?

Posted: Wed Jul 11, 2018 5:58 pm
by DaveEFI
Just for reference what would the cam foul on if attempting to change it engine in?

Re: How do I stop tappet noise?

Posted: Wed Jul 11, 2018 7:41 pm
by highlandstag
The lower edge of the headlamp panel - or upper edge of the lower valence.

Re: How do I stop tappet noise?

Posted: Thu Jul 12, 2018 3:09 am
by unstable load
Could you not be able to get enough movement by dropping the rear of the box to tilt the engine up?

Re: How do I stop tappet noise?

Posted: Mon Jan 28, 2019 2:24 pm
by Bruce R.
I don’t know about Rover engines, but I’ve had the same problems with buicks and it turned out to be one of the oil feed passages up to the rocker shaft pedestal. Every time I had the problem, I would pull the rockers out and sure enough in one end of the head or the other the oil passage was blocked, I would just run a coat hanger down through it and then spray some gumcutter in there and the noise would disappear. Hope this helps. B.R.

Re: How do I stop tappet noise?

Posted: Fri Feb 01, 2019 10:38 am
by Mc Tool
I bought a well worn 3.5 as a rebuilder . I found that while there was a lot of rocker/rocker shaft clearance by far most of the wear was on the underside of the shaft where the rocker bears against it( I believe that crap in the oil embeds itself into the surface of the relativly soft ally and then abrades the steel shaft ). The rockers look ok but must be biffed in the bin. As a diagnostic fiddle I rotated the shafts 1/2 a turn and the noise went away. It's possible that the preload on each lifter being different, the excess clearance on the shaft may be accommodated by some of the lifters with more preload ...not all. The inserting of a feeler gauge mentioned by one poster may well be taking up rocker /shaft clearance . ............buggered cam will never help😆
Hamish

Re: How do I stop tappet noise?

Posted: Fri Feb 24, 2023 6:44 am
by jp928
Late to the party as usual, but...my engine also 74,9.25:1 CR. Some tappet noise. Probably 315k kms. Underside of rocker shafts badly worn, so I replaced with aftermarket shafts and rockers, couple of oil changes. Now nice and quiet. Genuine rockers are crazy $$$, and I am never going to wear these cheap parts out.
jp 74 P6B S