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MG Midget and Sprite Technical - Anyone ever knocked a hole through a cam bucket?!?

Hi all,

Just wondering if anyone has ever had a pushrod smash the bottom off a cam bucket under mid to hard acceleration in a 1500?

Had it happen to me earlier this month which has pretty much ruined the bottom end, certainly the dizzy drive gear has lost a tooth, which makes me assume the cam is also ruined (haven't removed head or engine yet but taken sump off and retrived 2/3rds of the lower part of the cam bucket in pieces!) Most annoying whole thing was rebuilt with new uprated followers from Moss less than a year ago!

Annoying is not the word really, just wanted to know if I was unlucky and got a set of followers with a defect or if this is a known weakness in a relatively highly tuned engine. Prior to faliure oil pressure, temps and running were excellent, then a big bang pulled over in 20yards and towed home to discover a pushrod free floating :(

Any advice welcome, p.s anyone got a 1500 standard engine for sale for a quick transplant? I think i'm going to go the zetec route as I already have a 5 spd conversion fitted but would like to get the car moving in the interim. Also may have some 1500 performance parts for sale soon i.e. high lift roller rockers, stage 3 big valve head, twin 40 long reach manifold and linkage, tubular manifold ect. Enquiries welcome as decision will be made soon!

Dave
D Prince

Dave -
In no way can a pushrod "smash the bottom off a cam bucket", since the thing is just a solid spacer between the cam and pushrod at that point. The follower has to have broken up for other reasons, and the most likely one is metallurgical failure. If you gathered up every little bit and did a forensic reconstruction, you would pretty certainly find an inclusion or preexisting crack in the follower. It could be as simple as somebody dropping it somewhere along the production/selling process, or bad heat treat conditions. About the only other possibility is that the follower failed through side loading with a drastic cam, rockers and springs, but that should be a more common occurrence if the "uprated" parts are still that marginal. Deb Evans ought to know if this is a common failure in hot motors.

Not sure what you could do next, except scream at the supplier, who will likely say it's out of warranty and an unwarranteed comp part anyway. It would be good to inform them in any event, since bad parts are unknown to suppliers if people don't tell them.

FRM
Fletcher R Millmore

>>>>>>>>who will likely say it's out of warranty and an unwarranteed comp part anyway<<<<<<<<<<<


HuH!

No Im certian they will honor the warranty....Heres your 1 free replacement lifter...sorry about the rest of the engine.


Prop
Prop

The so called 'uprated followers' from Moss aren't worth the money they charge. They are a hangover from the original 'Triumptune' stock (from when Moss bought out Triumphtune), and they were bloody useless 25 years ago, let alone now.

I saw innumerable failures of the sort you describe in race engines in the early 1980's. The problem seems to be that, in creating a lightweight follower, Triumphtune failed to machine them correctly and left stress raisers in the (too thin) bearing face. Additionally the followers are too short and 'tip' in the follower bores which exacerbates the problem, ESPECIALLY with high lift (1.65:1) rockers (which are a waste of time anyway since there is no flow benefit on a Triumph head at such valve lifts).

There is currently another problem with standard followers being supplied by the likes of Kent Cams. There was a batch produced by BL in the 1970's that were not correctly radius-ed, but which found their way into the stocks of aftermarket suppliers. These are now rearing their ugly heads and causing premature cam failures (in as little as 200 miles from cam break in).

The ONLY person currently supplying Triumph cam followers that I would recommend is Mark Field at Jigsaw Racing.
Deborah Evans

OK, we both speak English ans all,
but ... what the heck is a Cam Bucket??
chuckc

Cam bucket = Cam follower = Tappet

Technically Cam Bucket refers to the (inverted)followers used in Overhead Cam Engines where the cam bears directly on the follower (ie no rockers present).
Deborah Evans

So the 1500 spridget mill is an overhead cam
engine?? I did not know that.
chuckc

No, Chuck. It was Deborah that answered your question, and she called them followers. It was Dave who called them buckets.

That was news to me, Deborah. I just figured that since they couldn't hold liquid on an OHC being upside down, they wouldn't make very good buckets, eh?

Charley
C R Huff

I can vouch for Mark @ Jigsaw racing aswell-he did me avery nice engione a couple of years ago that's still going (very) strong!
l snowdon

I checked out his website & did a bit of day dreaming!
Dave Rhine ('78 1500)

Dave Did your engine have a reground highlift camshaft by any chance. ??? Willy
WilliamRevit

Hi all,

Sorry been away from the net recently, about the terminololgy I just use the phrase cam bucket instead of follower out of laziness but I mean follower in my previous post. As for Mark at Jigsaw I have had dealings with him and find him informative and all parts purchased superb. I only use Moss so frequently as their Bristol branch is local and my impatience has clearly been my downfall on this occasion!

The cam was brand new, the kent(???iirc)equivilent of the triumphtune fast road 83 as recomended by Deb about 6 months ago, after the first cam wore into the original block on the first build. Since then I have had a second block fitted with the equivilent cam mentioned above with the inclusion of 1300 cam bearings (not fitted to the standard 1500)

I will post a pic or 2 of what I found in the sump in a day or two.

D
D Prince

There's an engine on ebay at the moment, just down the M4...

http://cgi.ebay.co.uk/mg-midget-1500cc-engine-1977-45-000-miles_W0QQitemZ250592004504
Dave O'Neill 2

Dave
The reason I asked if your cam was a regrind or not sort of follows on from Deborah's info on the short length of the followers.
We've had a little problem here recently with a Holden V8. Tha cam had been drastically ground to get monster lift but in the process the base circle diameter had to be seriously reduced to fit the grind profile on the cam.
The result was that when the follower was on the back of the smaller dia.lobe it poked a whole lot further out of the block leaving less in the block for support and with the heavier valve springs and all,when it was under serios throttle and the load was on everything the followers jammed across in the block and the camshaft snapped the bottom off the followers - broke the cam as well, a real mess. Might be what's happening to you
Cheers Willy
WilliamRevit

Hi Willy,

The cam Dave is using is the Kent TH5 (equivalent of the Triumphtune Fast Road 83) which is a 280 degree Duration cam with 10.74mm of lift, ie about a mm more than stock.

Even with (correctly) shortened followers this shouldn't produce a problem given that full race profiles are using around 12mm of lift.

Having said that, the Moss followers are (in my experience) too short and I suspect they aren't radiused correctly at the cam face.

Jigsaw do a lightweight short follower as well as a lightweight (nearer) standard length follower. Both have a teardrop oil bleed hole which assists with lubing the tappet bore as the follower rotates as well as in reducing the oil build up inside the follower (lessens the reciprocating mass).

The latter are what I recommend in a 'fast road' engine.

Additionally, before build up, the tappet bores on the Triumph 4-pot should be assessed for 'trueness' and wear. Any more than about 2-3 thou out of round and the block really is scrap.

Dave, when you get the engine apart could you provide me with some photo's of the cam itself please? I have a horrible suspicion that (if it is a Kent regrind) the cam wasn't properly case hardened after grinding (if at all), so it may well be cam lobe failure that led to the tappet failure - I had this happen to a customer's engine within 200 miles of cam 'break in' (which was expensive since it wrote off the engine - let alone bloody embarrassing).

Kent cams had a problem with this around 10 years ago and it seems to be happening again.

After chatting with Mark Field (I did some consultancy work for him last year), we have come to the conclusion that the later 'large bearing' Triumph cams don't have enough case hardening as stock for successful regrinds (albeit I have had 'small bearing' cams successfully ground to race profiles).

To this end we both recommend cams made from billet or, failing that, chilled iron cams from 'Bastuck' in Germany (who will do any profile you want).
Deborah Evans

I've had too many bad experiences with Kent cams to ever consider using them again.

649 cams more than 10 degrees short on duration, lobe centre angles way out, even on expensive blanks.

I have, however, had good experiences with Piper cams.
Dave O'Neill 2

This thread was discussed between 12/03/2010 and 16/03/2010

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