It has been suggested that when using either the camshaft retaining plate or the camshaft thrust button, the wear on the skew gears when subjecting the engine to high rpm is significantly greater than would otherwise occur when such devices are not used.
Has this been your experience?
My retired 3.5 litre V8 with 203,000 miles (327,000km) accumulated, no camshaft retaining plate or thrust button used, showed insignificant wear on the skew gears. Oil pressure for most of the engine's life was 45psi at 100kph.
Ron.
RV8 skew gear wear
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I had a modified 3.9 in my Dax Rush. A well-known RV8 specialist built the engine.
The car was used for spirited driving and trackdays.
My skew gear failed on the start of another trackday with the engine done less than 6000 miles after re-built.
The problems are not only the loads from the camshaft, it is also the added strain from the oil pump. This is especially trough if your engine spends a lot of time at the higher revs.
I changed to an intermediate front cover with integrated crank oil pump and had no problems since.
The car was used for spirited driving and trackdays.
My skew gear failed on the start of another trackday with the engine done less than 6000 miles after re-built.
The problems are not only the loads from the camshaft, it is also the added strain from the oil pump. This is especially trough if your engine spends a lot of time at the higher revs.
I changed to an intermediate front cover with integrated crank oil pump and had no problems since.
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jefferybond
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I've heard similar things about the use of the thrust button, but I can't believe how that influences skew gear wear.
Maybe a camshaft locking plate might have an effect on the oil feed to the skew gears though? The oil feed normally comes from the front cam bearing, through the spacer/key way, and then out through a narrow gap between the spacer and the gear. However, if the gear is fitted backwards, the gap will be non-existent.
The only loading on the skew gear is from driving the distributor (negligible) and the oil pump. I can imagine that fiddling with the oil pressure relief valve to get higher oil pressure might increase the load/wear, but not much else.
Jeff
Maybe a camshaft locking plate might have an effect on the oil feed to the skew gears though? The oil feed normally comes from the front cam bearing, through the spacer/key way, and then out through a narrow gap between the spacer and the gear. However, if the gear is fitted backwards, the gap will be non-existent.
The only loading on the skew gear is from driving the distributor (negligible) and the oil pump. I can imagine that fiddling with the oil pressure relief valve to get higher oil pressure might increase the load/wear, but not much else.
Jeff
I have also read that fitting a button can cause extra wear on the gears but can't see why it should. On the other hand Des Hammills book states that you must fit either the button or a locking plate so who knows!
What I can say is that I've seen two 3.5 engines that have both done something slightly odd with regards to the ignition timing, neither of them has any form of cam walk control. What happened is that the ignition timing actually retarded about 4 degrees just as the revs were taken above tickover. One of the engines is mine and I spent along time trying to figure out what was causing the retardation. In the end I decided that it must be the cam floating about!
Both engines were vertually new with regards the the cams and followers so the rearward thrust of the followers should not have been an issue, i.e lack of it.
Pete
What I can say is that I've seen two 3.5 engines that have both done something slightly odd with regards to the ignition timing, neither of them has any form of cam walk control. What happened is that the ignition timing actually retarded about 4 degrees just as the revs were taken above tickover. One of the engines is mine and I spent along time trying to figure out what was causing the retardation. In the end I decided that it must be the cam floating about!
Both engines were vertually new with regards the the cams and followers so the rearward thrust of the followers should not have been an issue, i.e lack of it.
Pete
I shredded 3 dissy drive cogs (the one on the cam) is as many days racing.
I had no retainer or button, apart from the dimple cast into the pre sd1 cover. I had drag raced the car on gas for a year with no problems. Then I fitted the hi-flow oil pump kit..Big mistake. Thats why the gears were stripping. I changed the oil rom 20/50 to 15/40 and it lasted a bit longer. Then I dumped the pump and fitted a standard one back on with a 5th cog and dragged it for another year before changing to the 4.6 and there is no appreciable wear on that cog now.
I've kept the standard pump on the 4.6 and an using the thinner oil as well.
So far no problems.
I had no retainer or button, apart from the dimple cast into the pre sd1 cover. I had drag raced the car on gas for a year with no problems. Then I fitted the hi-flow oil pump kit..Big mistake. Thats why the gears were stripping. I changed the oil rom 20/50 to 15/40 and it lasted a bit longer. Then I dumped the pump and fitted a standard one back on with a 5th cog and dragged it for another year before changing to the 4.6 and there is no appreciable wear on that cog now.
I've kept the standard pump on the 4.6 and an using the thinner oil as well.
So far no problems.
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
Standard engines do have cam walk control, its in the form of a cast in lump on the front cover. It isn't the tightest though which is why the cam button came about so you could set it more precise. Why it would cause more wear I have no idea. Des Hammill saying you MUST fit one or the other is either stupid or has been taken in the wrong context from the book i.e the part he says that he is on about full race high rev engines. If you don't want gear wear its simple, don't mess around with the oil pressure relief valve settings. This puts a huge amount of extra strain on it.
I do the same with my new 4.6. I keep the engine revs down, certainly not exceeding 2000 rpm till the engine is up to temperature, and the oil starts to thin out a little.
My 4.6 uses an sd1 timing cover, custom ground camshaft, no camshaft retaining plate or thrust button. The grind on the camshaft and interface with the lifters keeping the cam in position.
The oil pump front cover is a brand new P6 model, with the oil pressure relief valve being as factory fitted.
At 3000rpm, with oil temperature at or near 80 degrees C, coolant 75 to 80 degrees or so, oil pressure is a good 55psi.
I rarely exceed 3000rpm for any length of time at all, mindful of the wear that is possible to the skew gears.
Ron.
My 4.6 uses an sd1 timing cover, custom ground camshaft, no camshaft retaining plate or thrust button. The grind on the camshaft and interface with the lifters keeping the cam in position.
The oil pump front cover is a brand new P6 model, with the oil pressure relief valve being as factory fitted.
At 3000rpm, with oil temperature at or near 80 degrees C, coolant 75 to 80 degrees or so, oil pressure is a good 55psi.
I rarely exceed 3000rpm for any length of time at all, mindful of the wear that is possible to the skew gears.
Ron.
4.6 Rover 3500 P6B
My dizzy cogs are knackered but have never bothered changing either of them. I think that may have been more to do with the fact my dizzy bearing went for a poop though and ran like that for a while not knowing the cause of the poor running, until I had the dizzy out for something else and noticed.
I don't think failure is imminant.
I can't possibly think why the cam button increases wear, but I have read that also in David Hardcastle's book.
Many engine builders drill a hole in the timing cover, pointing at the cog, and insert a hose to squirt oil at the cog, taken from the pump.
This maybe a silly question. One for the experienced engine builders, but is it not possible to ditch the normal pump, and employ a belt driven one, thus relieveing load on the gear? I'm not necassarily talking about a whole dry sump system. You would have to fashion some sort of take off and a shaft to replace the original oil pump gear.
I don't think failure is imminant.
I can't possibly think why the cam button increases wear, but I have read that also in David Hardcastle's book.
Many engine builders drill a hole in the timing cover, pointing at the cog, and insert a hose to squirt oil at the cog, taken from the pump.
This maybe a silly question. One for the experienced engine builders, but is it not possible to ditch the normal pump, and employ a belt driven one, thus relieveing load on the gear? I'm not necassarily talking about a whole dry sump system. You would have to fashion some sort of take off and a shaft to replace the original oil pump gear.
You can fit a later front cover with a crank driven oil pump.
Not sure about the issue of space in an MGB bay though. I've not actually seen one of these crank driven front covers myself.
Not sure about the issue of space in an MGB bay though. I've not actually seen one of these crank driven front covers myself.
Perry Stephenson
MGB GT + Rover V8
9.62 @ 137.37mph
Now looking for 8 seconds with a SBC engine
The crank driven oil pumps are an integral part of the timing covers, and depending on your requirments, come either with the provision to mount a distributor, as fitted into the "interim" 3.9 and 4.2 litre engines or not as fitted to the 4.0 and 4.6 litre engines along with the very last of the 3.9 litre engines.
Type of sump that you can use, position of waterpump to name but two will impact on the suitability to use one of these covers in your application.
With reference to the sump,....the interim timing cover has two large bolts at the base of the cover designed to fit into the leading edge of the sump, as fitted to the LRs and RRs. If you can't use such a sump due to engine crossmember clearance problems, then there may be a problem with using such a timing cover too.
Ron.
Type of sump that you can use, position of waterpump to name but two will impact on the suitability to use one of these covers in your application.
With reference to the sump,....the interim timing cover has two large bolts at the base of the cover designed to fit into the leading edge of the sump, as fitted to the LRs and RRs. If you can't use such a sump due to engine crossmember clearance problems, then there may be a problem with using such a timing cover too.
Ron.
4.6 Rover 3500 P6B
