20 replies to this topic

[spiguy]

I've kind of asked a similar question before in a related thread (I think) but here it is directly. I note that if I watch the pushrods with the rocker cover off and the engine running, that some of them don't appear to be spinning. Now I can't say of course if they spin once the car is driving, or even if maybe they spin after it warms up some more, but certainly at cold and warmish idle (after a few minutes) 3 out the 8 aren't spinning. A couple of the ones which do spin, do so immediately, though they speed up as the car warms, and then a few more start to spin after a couple of minutes, but that still leaves 3 not spinning. They move back and forth a bit though.

 

I can spin all of them by hand when the valve isn't rocking. Does the lack of observed spin imply that the follower isn't spinning?  Is this lack of spinning an issue?  I've done 5000 miles in the car this year, and have noticed no change in noise and the valve clearances aren't changing either.

[Spider]

 Does the lack of observed spin imply that the follower isn't spinning?  Is this lack of spinning an issue? 

 

Yes and Yes.

 

Sounds like the followers maybe not right as well as the cam being possibly worn.

 

Only guesses until you take a look.

[spiguy]

Thanks Moke. Looks like I am going to get my first experience of taking my engine out (well, that is taking it out and working on it rather than just taking it out!) This and the possible idler gear noise plus the strange cold start ticky ticky noise certainly imply that some investigation is required. Guess I will need to strip down to the drop gears and also split the engine / box and take a look at cam, followers etc.

 

Strangely, the car runs really nice!

[Spider]

Yeap, I've been reading your posts for about a month now (enjoying them) but maybe it's time to bite the bullet. It does appear to me that some issues are beginning to develop and rather than let them turn it to something that my mother in law would make for breakfast, maybe best nip them in the bud.

 

Maybe pay a visit to someone with some good Mini experience and get their opinion too.

 

They always seem to run best just before they get very ugly.

[spiguy]

thanks moke. Got a few more runs with the club (Car isn't a daily drive) that I don't want to miss, then I think I will probably just have to bite the bullet as you say. Pretty nervous about it mind you! I've done plenty on minis and all the other cars that I have owned, but never pulled a clutch or removed a cylinder head, split a box etc. Hope I don't muck it up!

[Spider]

Hope I don't muck it up!

 

Yeah, I say that to myself every time too,,,,,,

[spiguy]

At the risk of deviating into a different thread, as I seem to have your attention...     If I am taking the cam out, and assuming I find that it is worn, is there any benefit / downside to putting a 'better' cam in if I end up replacing it anyway?  I plan at some stage to get a decent head on it, maybe a calver or dodd head or whatever people recommend (not researched it yet) and would likely want to do the cam at the same time, but if opportunity knocks earlier as it were, can you run a higher performance cam with the standard head, rockers etc or will that be counterproductive ? I wouldn't mind not realising the cams potential just as long as it didnt reduce the engines performance or muck up my chances of continuing to pass the emissions test (it's an SPi - just passed it's MOT the other day, and emissions were fine - phew!)

[Spider]

Being an SPI I believe it can be done OK, but I'd prefer others with experience on those engines and your local laws to comment.

[jaydee]

Nice topic, didnt expect to find such a question on a forum to be honest

Followers not spinning cause lobe wear, next set of followers check they're not flat, the should be convex, you put them on a glass table and push them on a side with a finger, the other side should leave about 3 thou of gap

Cam wise..There are a few cams you can use with the spi cooper, the MD246 and the MD274 are both great cams, avoid any cam with big overlap (even the mild MG metro cam will not work due to the overlap)

[Ethel]

Do they need to spin?

 

Surely the followers can spin without imparting the same motion to the rods. Just adjuster ball vs. rod ball friction.

[Carlos W]

Are the tappets set correctly?

 

I think it'll make a difference, but I may be wrong

[spiguy]

Thanks all for the excellent input as always. Carlos - yes, tappets are all set as they should be. As I said, the interesting thing is that after 5000 miles there has been no significant change in clearances - I've checked them several times, played with different clearances (ie 12 thou all round and 15 thou on exhausts / 12 inlets) to prove to myself that it made no difference to the cars performance or to my weird ticking noise on cold start. Each time I have checked the clearances before adjusting, and they have never been 'out' which would seem to suggest that excessive wear is not occurring.  Maybe it is just the pushrods on these valves that aren't spinning?

[jaydee]

About the not spinning pushrods and cam wear..-i shoud have added before!-

The standard spi cam is very mild with short duration like 230/250 and the low standard lift, coped with soft valve springs.

Thats not likely to grind the lobes off enough that you'll see a big change in valve clearance in5k miles

On a big duration high lift cam coped with strong valve springs then it can be a problem and can grind the lobes enough to write the cam off in 10-15k miles.

 

About cold tappet noise, can be due to a several ammount of things, i strongly advise you check at together with some mini expert (i mean a good reputable engine builder) rather than investigating on your own. It will be better if you're planning to get further deep into these little pushrod engines and want to build your own.

The forum is a good source of advise but there are a few tips and workflows that have to be learnt with someone showing 'how to' on your engine.

[ACDodd]

Most new followers that are supplied in the uk and around the world have insufficient radius ground on the end. This leads to poor rotation and accelerated wear. Keith Calver has spotted this problem and took the very expensive route of buying his own follower grinder. Having used these reprofiles followers myself and comparing to a number of other off the shelf suppliers I can say the standard of the off the shelf ones is pretty poor. Get Keith to reprofile your followers during your rebuilds. This way you can be sure of correct lobe/follower geometry and hence correxct rotation.
So in essence, to anwer the question above, the lack of rotation was probably like that the moment the followers were first installed and nothing to do with wear.
As ever building a successful engine is all about checking sizes and work done by others, you the builder are responsible for every component that goes into your engine as you build it. Follower radii and cam timing understanding are just a small part of a successful machine.

Ac

Edited by ACDodd, 06 August 2015 - 10:25 AM.

[Spider]

Yes, I too have found some of the followers pretty poor, but that's been the case (at least in these parts) ever since I have been playing about with them. I have found those from APT and Isky spot on and fairly priced, right off the shelf. The original factory radius was 36" and that well suits factory grinds, however what ever follower is fitted really should be suited to the grind of the taper on the cam lobes.