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Brian Eldred

Cam lobe wear, replacement?

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Dear gurus,

I've been adjusting the tappets on my 4A and noticed that no.3 valve was lifting much less than the others (also had very wide clearance). So I did a crude measurement with a straight edge across the valve collars and some calipers. Most valves had a lift of around 10.5mm, about correct I gather, some a bit less, but no.3 was 4.5mm. So it looks like an extremely worn cam lobe!!

First question: is it safe to run the engine like this or am I inviting a major catastrophe? It runs fine, apart from what I've for a while considered lack of power (no wonder...)

Secondly, obviously I'll need to replace the cam. The engine is pretty much standard apart from the exhaust which is of unknown origin but I suspect big bore and pretty raucous. I've considered adding a tubular manifold. The car is used for days out and touring (French road trip planned for this summer) so something close to standard would fit the bill. I've seen recommended on here the Newman PH1 and Moss  TT1104N, both a similar price, but any other suggestions will be most welcome! Also there's a second hand standard cam 307036 for sale on eBay at the mo, but with all the effort of changing it I'm not sure if it's worth compromising...

Speaking of effort, I've read that the cam can be changed with the engine in situ, but any tips or advice on potential pitfalls would be greatly appreciated. II's many years since I stripped an engine, and that was an MGB...

Thanks, Brian

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Hi Brian,

    it can be done with the engine insitu.

Remove bonnet, remove radiator, remove head

The Newman PH1 is nice. Very similar to a standard cam but has sparkle when the pedal goes down.

The Moss TT1104N is a 'Kent' cam and has a bit more sparkle than the above.

Don;t forget to replace the cam followers. Don;t get cheap ones. Newman do some nice chillied iron ones. Moss do some lightweight followers that work well.

You will need a DTI and an angle disc to set the timing.

Take it slowly and methodically.

If you want to try the Moss TT1104N I have a virtually new one (apprx 1000miles use) for £120.

Roger

 

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About to rebuild a couple of ordinary road going 4 pot TR engines, so I have just bought 2 off PH1 cams and 16 followers from Newman. 

Newman suggest you use their followers with their cam, and they take about 14 days to complete order/manufacture.

link to Newman.  http://www.erstellen.co.uk/newman-cams/PRICELIST-BROCHURE_2019-TRIUMPH.pdf

Cheers

Peter W

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Thanks both for the info. I looked up both the Moss and Newman cams and the specs look similar, though they don't mean much to me I confess. Roger did I see in another post that the Moss wasn't very good at low revs and that's why you changed it? Whatever I'm tempted by your used one, particularly if there is 14 days wait for a new Newman. I'll PM you.

Anyway I'll start stripping down tomorrow. Hoping the head comes off without too much bother -  I don't know when it last came off, if ever. 

Brian

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Hi Brian,

I found the TT1104 to have a highish tickover RPM and it just felt too sporty for me.

However after I fitted the Newman that too had a slightly highish rpm (not quite a s high as above) but with a few miles it started to settle down.

I suspect if I refitted the TT1104 it would have been a little calmer.

That is why I said take your time over the alignment and get it to as near as spot on as possible.

Roger

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Brian, if the "engine runs fine, but lacks power" ...a worn cam lobe would not be the culprit... a complete engine rebuild is appropriate.

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Hi Brian,

I drove my 4A until the cam had no exhaust lobe at all (i didnt realise at the time). I was on a road trip across Malaysia, looking back there was a symptom...it lacked full power and at full throttle it made a funny noise...at the time it thought is was a belt problem. As the cam degraded the noise started to happen at any application of power...i thought it was a burnt valve. On hills the car made a deep thumping noise, like a heavy gun, clearly startling other motorists. The noise was the combustion products of No4 being forced back out of the inlet valve/manifold/carb as the exhaust was not opening to any extent.

Back home I changed the cam in the car, not so difficult...certainly not worth removing the engine just to change the cam. Some will say the engine needs a complete strip because its full of metal that was ground off the cam... I just changed the cam, followers, head gasket & oil+filter...I cleaned the 'fur' off the magnetic sump plug. Engine runs fine, have done many thousands of KM since, including runs to singapore (750km) with no issues...these old tractor engines are tough, even when full of metal filings.

is yours an exhaust or inlet lobe failure?

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3 hours ago, ctc77965o said:

Hi Brian,

I drove my 4A until the cam had no exhaust lobe at all (i didnt realise at the time). I was on a road trip across Malaysia, looking back there was a symptom...it lacked full power and at full throttle it made a funny noise...at the time it thought is was a belt problem. As the cam degraded the noise started to happen at any application of power...i thought it was a burnt valve. On hills the car made a deep thumping noise, like a heavy gun, clearly startling other motorists. The noise was the combustion products of No4 being forced back out of the inlet valve/manifold/carb as the exhaust was not opening to any extent.

Back home I changed the cam in the car, not so difficult...certainly not worth removing the engine just to change the cam. Some will say the engine needs a complete strip because its full of metal that was ground off the cam... I just changed the cam, followers, head gasket & oil+filter...I cleaned the 'fur' off the magnetic sump plug. Engine runs fine, have done many thousands of KM since, including runs to singapore (750km) with no issues...these old tractor engines are tough, even when full of metal filings.

is yours an exhaust or inlet lobe failure?

Wow!

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Brian,

Don’t know how well you know these engines, (and apologies if I’m telling you something you already know).

When you take the head off don’t forget to clamp down the cylinder liners (just look it up on this site, lots of advice on how to do it.) otherwise a worn cam will be the least of your problems!

Charlie.

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15 hours ago, Malbaby said:

Brian, if the "engine runs fine, but lacks power" ...a worn cam lobe would not be the culprit... a complete engine rebuild is appropriate.

Lacking power and a tappety cam would be exactly what you would expect from a worn cam.

Once cylinder would be down on power but likely still firing, just lacking lift to get the optimum power from the affected cylinder.

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Well, I've got the head off - and yes Charlie I did clamp the liners down. Just using my own initiative :rolleyes: I put two suitably sized sockets over each of the two closest studs and fixed them down with the stud nuts. I'm stuck on the crankshaft pulley now - got the bolt off with a 2ft bar on a socket, but the pulley won't shift so I will have to go buy an extractor.

It's the inlet valve on cyl no.2 that's the worst - I've got the followers out and that one looks horrible. But no. 1 exhaust is grim too. That and no.4 inlet were down on lift by about 2 mm, less than the 6mm on no. 2 inlet but still a lot!. I'll post some pics when I've got the cam out. 

The bores look good and the head looks fine though I haven't removed the valves yet. I was wondering whether to get it converted to unleaded, but running on unleaded hasn't been a problem in the 7 years I've had the car so I'm inclined to leave it be if the valves look OK.

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If the head is off get hardened exhaust valve seats fitted - the seats will fail sooner or later and it's a false economy while the donkey work has been done.

 

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Hi Brian,

            have you got the original valve springs installed. if yes then good.

 

Do not be tempted to fit uprated springs if touring/normal speeds is your aim.

 

Roger

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Well I finally got the cam out this morning. Pics of No.3 lobe and follower. What can cause them to wear like that?

Regarding the head, I've not removed the valves yet (spring compressor too small) but it looks like there are seat inserts for the exhaust valves so I might be in luck. The car was re-imported from the US in 1995, which is just before leaded was banned, so they may have been fitted before then.

Roger has sent me his spare Moss cam and I've ordered some Newman chilled iron followers.

Cam.jpg

Follower.jpg

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as an aside....what engine oil have you been using?

Peter W

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5 minutes ago, BlueTR3A-5EKT said:

as an aside....what engine oil have you been using?

Peter W

Good question Peter.......that lobe and follower look horrible. ? Not enough Zinc in the oil ( as ZDDP) :-)

Also is there evidence of the followers sticking in the bore?

Iain

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Halfords has about 700 PPM Zinc in it's ZDDP, (same as Comma) recommended amount is between 1100 and max of 1400Zinc in it's ZDDP, I don't know if that's why you have your problem but it's why I don't use it anymore.

Mick Richards 

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This is normal old-age failure mode, once the case hardening is breached the follower degrades rapidly. Use a good engine assembly lube and a high zinc old -fashioned oil when you run it in. Don't idle it once started, get it up to 3000 rpm and hold it there for 5-10 mins.

Then you'll be good for another 100kmiles.

Beware scope-creep, it's important to get the engine back together for summer... Hardened valve seats can wait for a burnt valve later.....I am still waiting after 30yrs

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Hi Brian,

        I used Halfords classic for a long time. I think it worked quite well.

When I fitted my new cam two or three years back I decided to go up to the next step and have been using the Classic-Oils Heritage 20W50

https://www.classic-oils.net/Classic-Oils-Heritage-20W50

I am aware of no difference between the above two products but who knows what is going on underneath.

Similar price to the Halfords oil.

Roger

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I use Penrite Classic Light.  It costs about £30 for 5 litres which is £7.50 more than 5 litres of Halfords Classic which to me is an irrelevant amount extra.

Rgds Ian

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I'm puzzled now Roger

"I am aware of no difference between the above two products but who knows what is going on underneath."

Saying it as you have there is no difference between the products, yet the picture of the Classic Oils container shows it quite clearly, " c1300 ppm expressed as Zinc in the ZDDP" whereas the Halfords (and Comma) products are acknowledged by the Halfords specification (which has been enquired about many times before, because they don't quote it otherwise) when questioned as being circa 700ppm expressed as Zinc in the ZDDP.

That's as much as a difference (nearly 100% more) in the Classic Oil Heritage Zinc amounts at 1300ppm which has always been acknowledged as being one of the main anti scuff ingredients (important for our flat tappet engines) available to manufacturers to avoid scuffing and camshaft/tappet wear. That was one of the reasons I decided to move onto the Classic Oil product 3 years ago. Previously the oil manufacturers high Zinc specification (almost all oils had it) has been proved by 60 plus years of "in use" testing. Whereas these days it's a common thread amongst the older car fraternity to experience advanced camshaft and tappet wear on the newer oils...hhmmmm.

Mick Richards  

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Hi Mick

I am interested in your feedback on this, I use Penrite 20/60 but see that the Classic Oils 20/50 is very similar except its a Grp 1 base oil as opposed to Group 2. 

How do you find its performance when hot? With the Penrite even after a 250 mile run, tick-over oil pressure is a good 35psi.

Iain

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If you use a proper assembly lube then whatever oil you use will be flooded with ZDDP during initial startup thru first change...that's the period that's most important to bed-in the cam.

So, I believe the Zinc spec of the engine oil is not so important.

https://www.penriteoil.com.au/applications/motocycle/greases/cam-assembly-lube#/

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