camshaft swap

[dipstick36]

I've got a '99 chim 450 with 65k on the clock - a so called 'specialist' changed the cam and followers etc for a previous owner at 48k and followers only were changed again at 58k - not good practice I know but that's how the car came to me - anyway the cam's gone again!!! - it's fitted with a TVR435 which I've been told has a reputation for being heavy on the valve train and wearing quickly - don't know if that's true but judging my car it could well be. Can anyone please tell me if I'm better off going for an alternative grind eg hybrid 218/MC1 (or other) over the stock item? Ideally I don't want to go down the re-chip route if possible and don't want a lumpy drive round town. Any thoughts would be much appreciated.

[kwacker]

Had a 218 put in mine years ago, but wish I hadn't. Mine is quite lumpy in town, not easy to drive smoothly. From what I understand if you get it rechipped it is much better. One day I might get it rechipped, until then I'll just keep it above 2000rpm.

[cerby4.5]

Just had mine done along with the Mark Adams chip! Revs and pulls smoothly at all speeds. I reckon if you go for the chip you will really notice the difference!

[greenv8s]

Based on that history I wouldn't feel particularly confident that the right springs and followers were used, or that the cam had been installed and bedded in correctly on either occasion. You should really talk to a V8 specialist to find the most suitable cam for your application, there are plenty to choose from. On mine (4.6) I ran a 218H for a couple of years and it was very tractible, I get the impression that the newer 404 cams offer significantly more power if that's what you're after, possibly at the expense of tractibility at low revs. Whichever cam you go for I suggest you get the engine mapped to suit it, it's a false economy not to.

[mongoose]

As Peter says,i'd talk to a V8 specialist like V8Developments if i were you.I think i'd be inclined to have a new TVR435 cam,new lifters,and most importantly the new,correct vave springs.Apparently its the overly strong springs that were originally fitted that can cause premature cam wear in these engines.If you replace these three components,then a re-map will definately not be necesary,and people like V8D will set the car up properly as part of the job.V8d are very familar with this not uncommon problem and are highly recommended by many of us

[dipstick36]

thanks very much for all your comments - from what I can see the car was definitely not set up properly when it was last done - the rocker pedestals were not shimmed out which leads me to believe the preload was not checked/set - maybe it was spot on without shimming but I somehow doubt it. I hadn't considered the springs but as I'm changing everything alse ie rockers, cam, tappets, timing gear,etc I may as well fit the right springs whilst the engine's in bits. I'll give V8Developments a bell!

[trackcar]

greenv8s and mongoose as usual have hit the nail on the head .. the 4.5 came with very strong springs that can cause premature wear on cams .. V8developments are defo the daddies when it comes to camshaft replacement so give them a call as mentioned in teh other replies, you won't be disappointed as what they don't know about RV8 engines isn't worth knowing.

[dipstick36]

Thanks

[v8 racing]

the mc1 / 218 etc only requires single springs so the longevity of the whole valvetrain is much longer, if you want good driveability go for a cam with a wide lca as well, peak power will be down but it spreads the torque curve

[macdeb]

Had an mc1 in Griff' Very nice drive.

[Ian_greaney]

Ok, please excuse me if I hijack this thread, and ask a silly question.

How do you know if your cam is gone/going?

My Chim500 (modified see my profile) seems not to pull as hard as she used to. Now I use her everyday, and have racked up 14000 miles in 11months (76000 miles on clock.)
She starts, run's smoothly and has never failed me. just doesnt seem as fast through the whole rev range etc. Is there an easy way to check for cam wear?

thanks

Ian

[cerby4.5]

I found out that my cam was knackered when it went to Austec for the Mark Adams chip to be installed.
They did a diagnostic run on the rolling road and power was down significantly and it petered out after 4,000 RPM.
After a number of tests, injectors cleaned/re-fitted etc they were able to be fairly certain that it was the cam, as the engine already had numerous other bits replaced/worked on, rocker arm shafts/assemblies, new leads, spark plugs, coil etc.
Sure enough when the cam was removed there was significant wear on 7 & 8.
They fitted a 218 cam as opposed to a straight swap with a std (similarly priced) unit.
I am not sure how other places with rolling roads work, but Mark and Paul told me they always do a diagnostic/test run, on any car they have not worked on before; to check the state of the engine before re-mapping/modifications. From my point of view I found this to be very helpful as it prevented any further damage occuring.
It was a bigger bill for me in the long run, but am pleased with the overall result as the car has been transformed!!

[radzoule]

There are a couple of ways you can tell whether the cam is knackered without stripping the inlet manifold off to inspect. One method would be to set up a dial guage on the top of each pushrod/lifter (being careful to ensure you use a clamp/bracket which will give you a standadrd base reading across all rods) which will give you a figure for the full lift of each lobe. If you have an exhust/inlet pushrod which lifts a material amount lower than the average for the other exhust/inlet lifters (as the case may be - lift may well be different between exhaust and inlet lobes), chances are you have cam/tappet problems and you will have to dismantle further to visually inspect. Pull the pushrod first though and check its not bent.

A number of people seem to have the lobes towards the back of the engine go. There was no explanation for mine - some were perfect, others nearly ground completely round - both inlet and exhaust and some were in between. The life of the cam is going to depend to a large extent on how it was treated in the first few thousand miles. While many may have been run-in properly by sympathetic owners, it must be true that many of our cars will have been bought new on the back of a big city bonus by someone who was not so sympathetic.

[dipstick36]

I've taken the good advice given above and, having spoken to Shaun at V8Developments I've gone for an MC1 and new single springs etc - very helpful company and highly rcommended. Out of curiosoty more than anything else I ran a straight edge over the valve stems to see if they were all sitting at the same height - turns out that three or four were sitting up to 3mm lower in the head - presumably the preload would've been all over the place and not doing the valvetrain any good - Anyway I've got the heads off now but there's no sign of valve seat regression or poorly seated valves - other than odd length valves I can't understand it - anyone got any ideas? I'll strip the heads down over the weekend for a closer look before sending them off for machining.

[radzoule]

I had this on my heads - apparently it can be due to inaccurate machining of the valve seats in the first place - more likely to be the case if your car had the TVR big valve heads fitted rather than standard RR heads. You will probably have to have the seats re-cut to sort this.

[dipstick36]

Thanks. I think you're right about getting the seats re-cut - I think they're RR heads and the valves that are sitting highest at the rocker side are all inlets - I've got the valves out and there's no obvious seat wear/re-gression which I would've expected to be more exhaust than inlet anyway - I can't think of any better reason other than your suggestion that it was poorly machined in the first place.