Rover V8 cam walk
Discussion
Apparently, the odd noise I get between 1200-1500rpm (sort of a metal rubbing against metal but quietened by oil noise) could be "cam walk". The only references I've found to this is with respect to roller tappets.
Can anyone confirm if you would get cam walk at such low loads (the noise seems to dissapear higher up the rev range) and that it would happen with normal hydraulic tappets? Is it not normal to fit a cam thrust button to Rover V8s to stop this?
If it is cam walk, how important is it to get it sorted (it sounds like a lot of work to fit a cam retaining plate).
Cheers,
Ian A.
Can anyone confirm if you would get cam walk at such low loads (the noise seems to dissapear higher up the rev range) and that it would happen with normal hydraulic tappets? Is it not normal to fit a cam thrust button to Rover V8s to stop this?
If it is cam walk, how important is it to get it sorted (it sounds like a lot of work to fit a cam retaining plate).
Cheers,
Ian A.
round here, could you (or someone) explain what this is?
There is a cam retaining plate as standard, just behind the input flange, there a groove which the plate slots into and stops any fore-aft movement. That said I've only ever seen SD1 and later engines in bits, mabye the P6 lumps are different.
I'd say check the timing chain tension.
Matt
I'd say check the timing chain tension.
Matt
OK, I've spoken to V8 Developments (the stars who rebuilt the engine, installed the cam and answered all my techie questions patiently) and we've come up with the probably cause.
As I understand it, the serpentine engines are fitted with a cam retaining plate to hold the cam in position as the serpentine engine doesn't have the dizzy drive to force it backwards. However, some replacement camshafts don't work with the plate (something about the duplex timing gear being too wide) and hence they can't refit it. Instead, the camshaft is fitted with a "thrust button".
The cam is normally held back by the tappets which are angled very slightly towards the rear of the engine. However, under a trailing load when the load is suddenly removed from the tappets, they can angle towards the front of the engine allowing the camshaft to slide forwards. At this point, the thrust button hits the timing cover and stops the camshaft sliding further forward. The noise is created by the thrust button spinning against the front cover.
It all sounds plausible to me (probably influenced by it costing no money to fix).
Ian A.
As I understand it, the serpentine engines are fitted with a cam retaining plate to hold the cam in position as the serpentine engine doesn't have the dizzy drive to force it backwards. However, some replacement camshafts don't work with the plate (something about the duplex timing gear being too wide) and hence they can't refit it. Instead, the camshaft is fitted with a "thrust button".
The cam is normally held back by the tappets which are angled very slightly towards the rear of the engine. However, under a trailing load when the load is suddenly removed from the tappets, they can angle towards the front of the engine allowing the camshaft to slide forwards. At this point, the thrust button hits the timing cover and stops the camshaft sliding further forward. The noise is created by the thrust button spinning against the front cover.
It all sounds plausible to me (probably influenced by it costing no money to fix).
Ian A.
IPAddis said: OK, I've spoken to V8 Developments (the stars who rebuilt the engine, installed the cam and answered all my techie questions patiently) and we've come up with the probably cause.
As I understand it, the serpentine engines are fitted with a cam retaining plate to hold the cam in position as the serpentine engine doesn't have the dizzy drive to force it backwards. However, some replacement camshafts don't work with the plate (something about the duplex timing gear being too wide) and hence they can't refit it. Instead, the camshaft is fitted with a "thrust button".
The cam is normally held back by the tappets which are angled very slightly towards the rear of the engine. However, under a trailing load when the load is suddenly removed from the tappets, they can angle towards the front of the engine allowing the camshaft to slide forwards. At this point, the thrust button hits the timing cover and stops the camshaft sliding further forward. The noise is created by the thrust button spinning against the front cover.
It all sounds plausible to me (probably influenced by it costing no money to fix).
Ian A.
Serp engines have a retaining strap which is C shaped. It bolts to the block and fits into a groove in the cam. So, if you order a trick cam get them to machine a groove in it to accept the strap. Also, all the pre serp engines didn't have the strap and yes if you wanted to you could fit a teflon nosed button into the front of the cam but that was alwas a bit fiddly and never done by the factory. I never heard mine rubbing because it was teflon. The idea would be to have say .004" between the button and the timing cover. The lifters are convex underneath and should revolve in the bores if working correctly. I don't think the lifter bores are angled though. That sounds like twaddle or a misunderstanding. If you can hear rubbing noises which you think are cam related then I suspect the chain is rubbing something or mis-aligned.
It could be something else. Hope it's ok.
boosted ls1 said:yes if you wanted to you could fit a teflon nosed button into the front of the cam but that was alwas a bit fiddly and never done by the factory.
What is "a bit fiddly"? Up until recently, RPI also had a note on their web site which said something about their camshafts being incompatible with the plate. I believe they fitted a thrust button instead.
The lifters are convex underneath and should revolve in the bores if working correctly. I don't think the lifter bores are angled though.
The lifter bores aren't angled but as I understand it, the camshaft lobes are angled at something silly like 1/2 degree to rotate the lifters, allowing them to fill with oil.
Anyway, it seems fine now and accelerates up hills as if it's been shot out of a cannon.
Ian A.
Hello Ian, to fit the thrust button you have to first measure the thickness of a compressed timing cover gasket. Then measure how far it is from the inside of the cover to the forward face of the button. After that you start filing off small amounts from the nose of the teflon button. Once you have a clearance of say .004" appx, job done. I reckon it's easier to have a groove made in the camshaft and use the existing strap. I've had it done a few times.
I'm not sure the cam lobes are angled, they could well be though. It would seem logical or maybe the lifters rotate because there may be a small amount of offset. I've not given that a lot of thought.
Glad that your engine's sorted though.
I'm not sure the cam lobes are angled, they could well be though. It would seem logical or maybe the lifters rotate because there may be a small amount of offset. I've not given that a lot of thought.
Glad that your engine's sorted though.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff