Removing the Bristol Camshaft: With the Engine In, or Out?

The question

Can the camshaft be replaced on a Bristol engine without taking the engine out of the car? An owner asked exactly that in July 2024, and then answered it himself over the following two years as the job progressed.

What he found

The obstacle turned out to be small and very specific: a single clip that secures the distributor drive gear in place. The camshaft cannot be released without removing the distributor drive gear, and reaching that clip means dropping the oil pan. From there the job unfolds:

• Dropping the oil pan to reach the distributor drive gear and its clip.
• Taking off the timing cover, which means pulling the damper carrier with a suitable extractor.
• The damper carrier sits tight on the crank nose and needs real room to extract.
• The damper sits immediately behind the steering pendulum and rods, which may have to come off to make space for an extractor and a long enough wrench.

His conclusion at that point was that it was not worth the hassle, and he took the engine out.

His own correction, which matters

He later revised two parts of that account himself, and the revision changes the answer, so it is recorded here as he gave it:

• It is possible to drop the oil pan with the gearbox in place. He had initially thought the gearbox had to come out, which would also have meant supporting the engine so it could not tilt back.
• It is possible to remove the timing cover with the engine in the car. That requires removing the steering parts to make room for an impact gun and an extension to loosen the front nut.

So the honest answer is this: harder than it looks, possible in the car, and the one owner who worked through it in detail took the engine out anyway.

Tools

Two practical notes from the same account, worth recording because they are the kind of thing that stops a job dead:

• A 1 inch Whitworth ring spanner is called for. He spent weeks finding one, and when it arrived it proved useless for the main nut. An impact gun was what actually loosened it.
• No standard puller fitted the damper carrier. A friend made a specific puller for it. Anyone starting this job should establish how they will extract the damper carrier before they begin.

The wider point is worth stating for anyone new to a car of this age. This is a Whitworth-era car, and Whitworth and imperial spanner sizes do not correspond to metric ones. An owner working in metric will need conversion charts and the right spanners and sockets in hand before starting, rather than discovering halfway through that the size simply does not exist in the toolbox.

What is not established

• Whether anyone has replaced the camshaft entirely in the car, from start to finish. The one detailed account ends with the engine out.
• How long the job takes either way. No figure was given.
• Whether the distributor drive gear clip can be reached by any route that does not involve dropping the oil pan.

If you have changed a camshaft on a Bristol engine, in the car or out of it, please get in touch, and the archive will record what you found.

Sources. This article draws on a discussion of replacing the camshaft in a Bristol engine on the AC Owners' Club forum, running from July 2024 to 2026. No individual member is named.

A record of one owner's experience of a major engine job, not a substitute for the workshop manual or a competent engine builder. Nothing here has been verified against a second car: confirm every step for your own engine, and if the work runs beyond what you can do safely, stop and consult a specialist.