The V8 Owners Forum -

My old engine had fold over locking plates on the exhaust manifold bolts, sort of wind-out protection...are they really necessary? Has it been known for the exhaust manifold bolts to vibrate themselves out?

My mates Land Rover 101FC has locking plates on the exhaust manifold bolts, but the manifolds are fitted without gaskets. I used standard bolts and spring washers along with gaskets, as per SD1, and have never had a problem with the manifold bolts coming loose.

My old engine was a right old match up of parts! As the new one is having polished stainless manifold bolts I would rather not use them. I tried to look them up on the rimmer site and they are not even listed! I thought they were standard rover v8 fair but it appears not.

They're a Land Rover item, my mate got his from our local Land Rover specialist (John Craddocks), they were only a few pence each IIRC. My manifold bolts have never loosened using just bolts and spring washers, although I doubt the spring effect lasts long due to the heat off the manifold.

The exhaust manifold locking plates were also fitted as standard to the V8 engines in the Rover 3500 P6B from circa 1968 till 1976. Land Rover was building all Rover V8 engines from 1972 onwards, so they likely appeared on all around that time.

I retain the P6 manifolds on my 4.6, fitted as per original without gaskets and with split washers beneath the bolt heads, they would nearly all work loose in a very short space of time, so at least weekly I had to nip one or more up.

I replaced this arrangement with a set of OEM locking plates that I purchased from a P6 specialsit some years ago, fitted them and no more loose bolts...

Ron.

You can get special rawl plug type bolts that will never shake loose.
Have a look at Summit Racing for these little gems.
I think there was an addin Custom Car back along aswell.
Cheers
Paul

I advocate some kind of lock washer, doesn't matter what type. Otherwise the bolts will work loose.

Chris.

Will Reeve wrote:My old engine had fold over locking plates on the exhaust manifold bolts, sort of wind-out protection...are they really necessary? Has it been known for the exhaust manifold bolts to vibrate themselves out?

I use 3Ms Scotch-Clad 776 on every thread that goes into ally on these engines.

It has three functions:-

Prevents corrosion.
Locks the fixing
Seals the tread.

Strangely it was specified for early engines which also had the locking plates for the manifolds, but seemed to disappear off the horizon on later ones.
It costs about 30 quid for a 1 litre tin and can be hard to find, but works perfectly. No more broken water pump and thermostat bolts.