uneven cam wear !!
Discussion
Removed the cam from my griff now and measured the lobes just to see how bad it was. The exhaust lobe on piston one had worn off nearly 4mm compared to cylider 8 exhaust the inlet of 0ne had worn 2mm the exhaust of cylinder two had worn 3mm and the inlet 2mm. All the other lobes seemed ok this cam had only done 24k miles, so I am asuming that it must be some sort of oil starvation or perhaps just a bad cam that wasn't hardened well on the first 4 lobes.
Is there a seperate oil feed for the cam lobes or are they just splash fed from the crank? I really dont want to have to do this every 20k miles if I can possibly help it so any help would be appreciated.
Cheers
Chris
Is there a seperate oil feed for the cam lobes or are they just splash fed from the crank? I really dont want to have to do this every 20k miles if I can possibly help it so any help would be appreciated.
Cheers
Chris
chris52 said:
well i would hope for a mininmum of 40 to 50k so there must be something wrong, no idea if the preload was done though as it was last done at a TVR dealer but that was 5 years ago. The valve springs are double springs is that standard on a serp 500?
Chris
Yep, double springs is right. My understanding is that 'Power' fitted springs good for 8K RPM so the loads on the seats and lobes are high. I think springs in most cam kits for road-use use springs of lesser rate; whoever your supplier is will tell ya.Chris
a higher lift cam will require stronger springing to open and close the valve correctly. As 2Munkys says, TVRs are generally agreed to be "over-sprung" and that increased spring pressure eats through the case hardening on the cam prematurely via the lifter. Once that goes the soft cam steel dis-integrates in a few hundred miles.
A std RV8 cam can last 60K, TVRs can last as little as 6k on an engine thats rarely used. Long peroids of non-use means the cam dries completely and a revvy start increases wear again.
Add to that the water like oil recommended (0/40) when the block galleries were designed for thick mineral oils of the 40s, and there lies your cam wear.
All well known now and sortable by a decent specialist...if you ask.
Andy
A std RV8 cam can last 60K, TVRs can last as little as 6k on an engine thats rarely used. Long peroids of non-use means the cam dries completely and a revvy start increases wear again.
Add to that the water like oil recommended (0/40) when the block galleries were designed for thick mineral oils of the 40s, and there lies your cam wear.
All well known now and sortable by a decent specialist...if you ask.
Andy
Cheers for the responses. so it sounds like I have just a normal cam, it just seemed really strange that only the first 4 lobes were so badly worn when all the others were fine but I guess thats the joys of TVR ownership
just another question, two tips had come off the rockers and damaged the valves which I am replacing should I replace all the rockers or just the damaged ones?
Sorry guys for multiple posts on the same basic subject,
Chris
just another question, two tips had come off the rockers and damaged the valves which I am replacing should I replace all the rockers or just the damaged ones?
Sorry guys for multiple posts on the same basic subject,
Chris
This was the state of my cam, 66k miles.
Lobes were measured back to tip, which I know some say isn't the way to do it - but you don't need a micrometer to see its fooked!
Lobe 5 worst
Lobe 11 best (I assume relatively unworn)
This is more impressive though from the wedge forum
Lobes were measured back to tip, which I know some say isn't the way to do it - but you don't need a micrometer to see its fooked!
Lobe 5 worst
Lobe 11 best (I assume relatively unworn)
This is more impressive though from the wedge forum
Edited by Barkychoc on Tuesday 5th May 10:13
I believe there is an oil feed hole that is behind the bucket tappet .. I'd suggest something like an old fashioned pipe cleaner to clean it but I dont think that will be the problem.
The problem is most likely to be a partially blocked sump strainer .. with silicon gasket being trapper on the mesh. Whip off the sump and check it's OK .. it's only help on by 4 small bolts - worth inspecting it's all OK..
The problem is most likely to be a partially blocked sump strainer .. with silicon gasket being trapper on the mesh. Whip off the sump and check it's OK .. it's only help on by 4 small bolts - worth inspecting it's all OK..
WOW that wedge cam is something else
I have been told by a local rover engineer that it is possible that the conrod on no 1 or no 2 cyclinder has been put on the wrong way round and as a result it won't be splashing the oil up onto the camshaft for the first 4 lobes. Aparently this can and does happen. the only way to tel is to remove the sump and check the markings on the conrods. I have totally stripped the whole top end of engine now and am now debating on removing the engine completely from the car and investigating the bottom end aswell, at least with the engine out it will be a hell of a lot easier to rebuild it.
the exhaust manifolds are a nightmare with the engine still in the car.
I have access to an engine lift so its just the bellhouse bolts to remove and pull it out (ha ha wish it was that easy)
what started as a relatily easy manifold gasket job looks to have turned into full engine out and strip down job
anyone heard of the conrod issue before, the engine was rebuilt only 24k miles ago with new rings shells etc at a TVR main dealer although this was 5 years ago is it possible they put a conrod in the wrong way round??
Chris
I have been told by a local rover engineer that it is possible that the conrod on no 1 or no 2 cyclinder has been put on the wrong way round and as a result it won't be splashing the oil up onto the camshaft for the first 4 lobes. Aparently this can and does happen. the only way to tel is to remove the sump and check the markings on the conrods. I have totally stripped the whole top end of engine now and am now debating on removing the engine completely from the car and investigating the bottom end aswell, at least with the engine out it will be a hell of a lot easier to rebuild it.
the exhaust manifolds are a nightmare with the engine still in the car.
I have access to an engine lift so its just the bellhouse bolts to remove and pull it out (ha ha wish it was that easy)
what started as a relatily easy manifold gasket job looks to have turned into full engine out and strip down job
anyone heard of the conrod issue before, the engine was rebuilt only 24k miles ago with new rings shells etc at a TVR main dealer although this was 5 years ago is it possible they put a conrod in the wrong way round??
Chris
Hi Chris,
Could be wrong but I've been told a view times by indies that cams on RV8's generally need changing at around 60 thou due to the design of the engine, ( originally Buick I think? ), not supplying oil to all of the top end as well as it should. Obviously there will be exeptions to the rule but un even wear is not uncommon as a result, (apparently). Let me know when back up and running and we can get out for a blat. Just got mine back from Track v Road with new ball joints, geo set up, oil leak sorted so ready to go.
Could be wrong but I've been told a view times by indies that cams on RV8's generally need changing at around 60 thou due to the design of the engine, ( originally Buick I think? ), not supplying oil to all of the top end as well as it should. Obviously there will be exeptions to the rule but un even wear is not uncommon as a result, (apparently). Let me know when back up and running and we can get out for a blat. Just got mine back from Track v Road with new ball joints, geo set up, oil leak sorted so ready to go.
Yeah really good. Combination of new tyres, spot on pressures, ball joints, spacers put in top wishbone, + geo all make it feel great. Prob get shocks at end of year when in for service + poss brake upgrade? On the other hand may see if any funds left in the pot to sell and buy a really good later example that someone has already spent lots on? Thing is I know mine will be fairly well sorted in the important departments but year/mileage means it's value will not be that great when it comes to sell therefore I'm a little reluctant to spend loads on tasteful upgrades. I'd sooner put money into a car than an ISA and treat it as a fast/loud/smelly investment! Until then I'll look forward to enjoying it this summer.
Edmundo2 said:
Yeah really good. Combination of new tyres, spot on pressures, ball joints, spacers put in top wishbone, + geo all make it feel great. Prob get shocks at end of year when in for service + poss brake upgrade? On the other hand may see if any funds left in the pot to sell and buy a really good later example that someone has already spent lots on? Thing is I know mine will be fairly well sorted in the important departments but year/mileage means it's value will not be that great when it comes to sell therefore I'm a little reluctant to spend loads on tasteful upgrades. I'd sooner put money into a car than an ISA and treat it as a fast/loud/smelly investment! Until then I'll look forward to enjoying it this summer.
Hopefully when I get mine back up and running we can both enjoy the summer
Back on topic I measured all the lobes today and it doesn't make that bad a read compared to some I have now seen.
starting from the front 30.51, 33.31, 31.88, 34.04, 32.70, 33.10, 34.18, 34.13, 34.30, 34.23, 32.72, 32.62, 32.42, 34.36, 33.05, 33.13.
Also checked the conrods and they are all fitted the correct way round, oil feeds to the cam bearings are lined up and nice and clear. so hopefully I have now got to the end of the taking apart and can start putting everything back together.Did notice one thing which I dont know if right or wrong and that is the piston bores still show the emmery marks from when it was rebuilt some 24k miles ago. I would have thought these would have been polished away with the rings after that amount of use??
last point running the cam in should I use a good mineral oil of say
Chris
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