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MG Midget and Sprite Technical - Loosening tappets!!!!

Hi all,

I'm having some issues with my newly rebuilt 1500 engine, for some reasonmy tappets are consistantly loosening themselves and I don't know why!!!!

I had the engine rebuilt and rolling roaded at a respectable 102.7bhp which for the mods I have put on (fast road 83 cam, stage 3 head, custom performance exhaust and header, roller rockers, 40 thou overbore, twin 40's and elec ignition)is around the right mark. I then took the car to a trackday a couple of weeks later to stretch her legs a little further than road use. Car performed fine on the way there and the first couple of sessions were great. during the 3rd session the tappet noise grew and the car started to overheat.

I thought that combustion gasses were getting into the cooling system, perhaps the head gasket had gone. After ther trackday I stripped the head off replaced the head gasket, checked for any undue wear on cam, followers, roller rocker tips, pushrods, reseated all of the valves and put everything back together.

Once all back together the tappets were set and off for a drive, now the car feels less powerful and almost immeadiately after driving off from setting them up you begin to hear them rattle, which only gets worse even over a distance of just a mile. I have tried setting the rollers both with a 10 thou clearance and so that they preload the valves slightly and in both instances the tappet noise is there almost straight away.

Any advice would be greatly appreciated as this is becoming a real problem.

Dave
D Prince

I have had tappets slacken off a lot when a valve has beome stuck in the guide. When that happened to me on an A Series engine the car would rev to about 3.5KRPM then would seem like it had hit a brick wall..

This was when we first started using unleaded with bronze guides. The resolution was to give the guides more clearence, which I would expect all engine builder are doing when unleading a cylinder head.
Robert (Bob) Midget Turbo

Dave,
Newly rebuilt engine, but did you check the condition of the rocker bushes and rocker shaft? The 1500 engine is known for poor oil feed to the rocker shaft which could possibly be worn and causing the symptoms that you describe. There is a special kit, originally developed by BL Special Tuning, which adds an additional oil pressure feed to the rocker shaft.
Not sure, but worth checking?

Guy
Guy Weller

Hi Bob

when you say a valve stuck in the guide, presumeably this would account for only 1 clearance widening, whereas my problem seems to happen accross all the rockers, all valves moved freely by hand through guides but was this the case with yours?

Hi Guy

The rockers were one of the few things not brand new but shaft appears free from wear, I have the extra oil feed plus oil cooler with thermostat. There is no movement on any of the pedestals on the rocker shaft or the rollers themselves or around the bushings, which I guess would be there...
Thanks
Dave
D Prince

Dave,
I am not an expert on the 1500, but I would like to ask whether the 10 thou setting you mention is endorsed by the cam grinder. Yes, it is correct for the standard (no pun intended) 1500, but frequently a hotter cam asks for more clearance.

Next question. Are the rockers standard ratio or high-lift? Since the clearance that really matters is between the cam and the follower, a 1.5:1 rocker requires greater clearance at the valve than would be the case with a 1.3:1 rocker.

Finally, NEVER run with no clearance (double negative correctly used). To do so is to invite burned valves.
David "neither a cam nor a follower be" Lieb
David Lieb

Dave,
Doesn't sound like rocker shaft problems then does it. It was just a thought, and worth suggesting. No other ideas I am afraid!

Guy
Guy Weller

Is it possible that the locknuts of the roller-tip rockers are not up to the job? Could be the reason the previous owner passed them along...
David "knew a 948 that got replaced with a 1275 because an adjuster walked out..." Lieb
David Lieb

Dave,

I had similar problems with a newly rebuilt 1500. Mine was a stock rebuild (I can only dream of 102.7 bhp.)

Excessive valve lash and even dropped a push rod a couple of times.

I threw some Marvel Mystery Oil in the crankcase and fuel and drove it. I think it was just the extra miles, but could have been the additive.

After about 1000 miles it all settled down and works just fine now.

I would just drive it for awhile and turn up the radio. As David Lieb suggests, no noise is not good noise.

Lee
Lee Fox

Dave,

Im not certian if you have roller rockers or roller tiped rockers, On roller tiped rockers, you have to insert the feeler gauge from the side NOT the front like on regular lifters.

If your inserting the feeler gauge from the front, then it would certianly account for all the rockers loosing there settings. as they never took to begin with.

prop
Prop***The End in 2012

Yes Dave (P) mine was just a single tappet, but was on a straight out of the box race engine that began causing problems after 5 great laps around silverstone. Naturally the problem only manifests itself due to heat, so my engine experienced rapid build up. I am wondering if the problem was on a more sedate usage whether it would be possible to affect all valves.
Robert (Bob) Midget Turbo

Hey all,

Reset all the clearance to 0.35mm (0.014ish) yesterday, noise tappety though it didn't seem to get too much noisier after a quick drive, what I did notice was a problem with low oil pressure once it had warmed up. Since the rebuild if the oil pressure dropped to 20 or below a quick blip of throttle would send it back to the 40 mark, on this occassion I struggled to keep pressure above 20psi with short sustained bursts of 3-3500 revs!

Could this oil pressure problem be linked to the tappet adjustment side or is this a whole different problem? The whole oil system on the car was rebuilt with engine so new oil pump, uprated pressure switch, oil cooler with thermostat, baffled sump, valvoline vr1 20-50w oil and oil pressure guage fitted.

Prop - roller tipped rockers they are and I was shown about feeler guages on this occassion but good point well made.

dave - Checked lock nuts by marking all their positions after last setting clearances with marker but none had moved after a 10 min spirited drive.

Robert (bob) - do you think that the problem could stem from incorrect/no shimming under the rocker pedestals? I know that the top of the block was faced off so some material would have been lost, therefore I guess if they weren't shimmed the angle of the rockers could be out. Would this give the symptoms suggested or is this one of those red herrings born out of frustration.

As always all help greatly recieved

Dave
D Prince

How did you break in the camshaft, what procedures did you use ??? what about camshaft lube during assembly as well as engine assembly lube esp. on the lifters?

Im woundering if the lobes are wearing down, there should be some esp. during break in of the camshaft, Im assuming the lifters are new and not re-used

how many miles on the new engine?....If less then 3000, I fear for your rings and clyinder walls creating "glazeing", Due to the valvoline VR-1 engine oil not allowing the rings to bed in...(granted Im not sure about valv. VR-1 oil) but the oil needs to be a cheap...vary basic oil)if glaze is occuring, creating engine blowby meaning positive pressure in the crank case leading to "OIL Leaks"....the only way to correct is bust open the engine and re-hone the cly.s

Also did you use pipe cleaners to clean out the oil galleys after the machine work, lots of junk can get caught in those passage ways

Prop
Prop***The End in 2012

low oil pressure after a rebuild yep sounds like the triumph engine

one solution .... Fit an A-series
Onno Könemann

Its a 1500 !!!, Well theres your problem. thats a triumph engine, toss it in the trash, and get you a real engine, as onno suggest...LOL,

sorry just having fun

prop
Prop***The End in 2012

Prop its a 1500!!!, tells you that in the second line of the very first post!!

David if it was sticking valves then that would cause the locknuts of the tappets to come loose and wind themselves out, so if yo have marked them and they are tight then that is not the problem.

I would be tempted to put a DTI on the pushrod and measure he lift of each cam lobe. Then in a few weeks if the tappets have loosened off measure the cam lift again. May well be wear on the cam lobes :-((
Robert (Bob) Midget Turbo

Hey all,

I know what the general conception of the 1500 is but work with what you've got,that's my theory! I might also remind everyone of there superior performance from factory (at least over here in the uk) more bhp, more torque and a higher top speed! ;) lol

This is my daily runner/thing of fun, I also have a fully restored to original 1971 1275, genuine 1 owner from new that is about ready to MOT and put up for sale, still with it's original bill of sale and logbook don't you know! But the future project is another 1275 I have that is going to get similar performance modifications to the 1500. Basically this is a dry run on that, even though each engine has very different characteristics to the other there are still lesons to be learnt!

Prop - What's the issue with VR1 as an oil? You say cheap are we talking £6 for 5L multigrade kind of oil? By the way all new cam, followers, pushrods.

Bob - good test, hope it's not cam trouble, when the head was off last week I did do a visual check from above and the was no visible signs of wear at all on the cam, but I suppose we don't always see these things!

Dave :)
D Prince

I think I recall back in the 1960s when I was working in a Standard Triumph garage that occasionally this problem would happen due to some problem with the ball and socket of push rod to rocker. Whether it was due to wear (lack of lubrication) or bad batch of parts I cannot remember. The issue was that the rocker would keep settling more and more into the push rod, hence the increasing tappet gap.

Roly
Roly Alcock

Dave,

I would find another oil pressure gauge and check its reading O.K.
Low oil pressure should not be connected with tappet clearances and is not good news.
Have you run it with the rocker cover off at tickover -assume nothing is peeing out ?

Richard.
richard boobier

But low oil pressure could most certainly be associated with noisy tappets. And worn rocker shaft would also reduce oil pressure. I also wonder if the use of the extra oil feed to the rocker shaft could also reduce the oil feed back pressure, thereby lowering the oil pressure to the rest of the engine - and oil guage.

What oil are you using?
Guy Weller

D Prince,

Sorry, we were just having some fun about the 1500, and I had forgotten that it was a 1500 you had mentioned

As to oil for break in, you want something that wont allow reduced friction, you want the rings to really curse hard in the cly. and wear in, creat there own grove, other wise the rings will glaze allowing gaps between the rings and the cly. walls, my fear is the VR-1 valvolinemotor oil will do to good a job reducing friction.

I hate to re-ask this question, no offence intended by it, But, How did you "break in the camshaft, what procedures did you use???


prop
Prop***The End in 2012

Hey prop,

No offence taken, the best thing about these cars 1500 or 1275 is that they're fun, so is learning about them (most of the time!!)

Can't tell you the break in procedure at the moment as the friend who helped me build the engine, specifically the more technical aspects, is a race technician who is racing minimotos in spain for a week!! How rude eh!?!

Guy - I do have the external oil feed, since the occassion of very low oil pressure I have re adjusted the tappet gap again and been out for a couple of short runs and not had such a significant drop. The car has probably only done about 300 miles since rebuild and all of that has been done on valvoline vr1,

I think maybe I shall switch to the cheaper oil and keep an eye on the pressure guage and hope that the tappet gaps are just initial wear and that I am being over paranoid! It's just after spending so much on the rebuild the last thing I want is serious damage to occur!

As always thanks for all the info and any ideas are welcomed

Dave
D Prince

Hi,

Had exactly the symptoms you are describing. Tappets repeatedly going out of adjustment every couple of hundered miles (I have roller rockers too), Loss of oil pressure, etc. This immediately followed a rebuild by an experienced MG race guru.

They went through replacing the pushrods, tappets etc. etc. to try and cure it. In the end it was actually traced to the camshaft eating it's way into the block. Had bearings put in to solve this, apparently 1500's don't have cam bearings in the block as standard. It was only found it after it got really bad i.e. created a nice burn mark on the side of the block corresponding to the location of the camshaft resting point.

They said it was because the camshaft was particularly hard but my theory was that the roller rockers put extra load onto the camshaft and hence it's location points.

Thanks.
Rob.
ra hollingsworth

Hey D.

Unfortantly I dont know much about uk oil products, here in the sstates thay make a "break in oil" a vary popular one I have seen in the last couple years is made by "purple"...But ask around or start a new thread here on the BBS as to what is a good break in oil in the uk.

Unfortantly I know even less about 1500 then I do my own toothbrush but RA, above reponse sure looks promising...(I hope not...thats alot of work)

If the engine was built by a pro, then no doulbt he broke in the camshaft and used camshaft lube, my fear is that it was just started up and ran as normal, that will certianly knock the tops off the lobes like you where talking esp. with high lift rockers

Another thing to watch, is with a hot street engine is that you run at a higher rpm at idle then a stock setting, slower idle means the cam lobe takes longer to drag across the lifter face and that will cause faster wear on the lobes and lifter faces


I wounder if there is any way to test if the camshaft is eating into the block, without an engine out and disassembly. to test what RA was referancing

prop
Prop***The End in 2012

Dave,

Did you mean 300 or 3000 ?

'The car has probably only done about 300 miles since rebuild'

With a power check on a rolling road (102 bhp) and a track day as well ?

No running in ?

Richard.
richard boobier

Dave,
I have recently bought and fitted an oil cooler to my 1500, It came from Moss and they suggested fitting an uprated oil pressure relief valve to combat a lowering of oil pressure due to the cooler, I have not fitted it yet so I can't comment on whether it works or not, but the oil pressure does seem slightly lower since fitting the cooler. I also bought the external oil feed to the head and again Moss suggested a smaller banjo bolt if there was a drop in pressure, sorry to say I have not fitted this either, but it might give you a couple of options to try. I don't have part numbers to hand but I could dig them out if you need them.

HTH
Alan
A Pritchett

Hi all! I have a 1275 midget with 1.625 ratio roller rockers (that I have found to be noisy!). Can't wait to try out the "insert guage from side" technique this weekend, as I was otherwise unaware of that trick. Careful - your postings on the this site may have unintended (but beneficial!) consequences!.

D. Prince, good luck! I hope your problem "goes away".

Phil
Philip S Jones

I couldn't resist this one... Prop wrote:

>>> Its a 1500 !!!, Well theres your problem. thats a triumph engine, toss it in the trash, and get you a real engine, as onno suggest...LOL. <<<

Umm, Prop... whose engine blew up last summer? Not my 1500...

;-)

-:G:-
Gryf Ketcherside

Prop,

I'm with Gryf. Mine is working fine, too. :)

Lee
Lee Fox

LOL...HAhahaha...toshay guys, toshay....good one!!!


Hahahaha

prop
Prop***The End in 2012

A few points:

Firstly the Triumphtune 'Fast Road 83' is essentially the same as the Kent TH7:

Fast Road 83: Inlet = 37-63, Exhaust = 74-28, 280 degrees duration, 0.288" lift.

Kent TH5: Inlet 37-63, Exhaust 73-27, 280 degrees duration, 0.293" lift.

The reason behind this is that Terry Hurrel of Triumphtune (TT) copied what was being done by Triumph engine builders in the early '80's. It's also the reason the Kent profiles are now called 'TH' (for Terry Hurrel). The TH profiles are actually Ford X-Flow ones.

The correct valve clearances for these cams are:

0.022" Inlet
0.024" Exhaust

These figures are given for the stock rocker ratio of 1.5 : 1, so setting 0.014" is WAY off and you will get burnt valves/valve seat regression in about no time squared!

Additionally, if you are using the TT 1.65:1 roller rockers then you need to widen the valve clearances further - it will be of the order of 2 thou Inlet and 2.5 thou Exhaust.

Are you using tubular pushrods? These are a must with roller rockers on the Triumph 4-pot. There were issues with the standard pushrods not engaging with the TT roller rockers properly (IIRC the TT rockers were originally produced by Vulcan Engineering), so this may be your problem with the clearances appearing to loosen (ie because the ball on the rocker is not seating accurately in the push rod, the clearances aren't being set up correctly in the first case).

If you have skimmed your head to raise the static CR, then the chances are your rocker geometry maybe out such that the roller tips are rolling off the edge of the valve stem, which may also give you problems to setting the clearances.

The way to check this is to set the rocker clearances then apply some engineer’s ‘blue’ to the valve stems. Turn the engine through a full cycle then whip the rockers off and inspect the valve stems.

If the blue is to the centre of the stem then you have the correct rocker offset. If the blue is predominantly to the manifold side then you need shorter pushrods else you will get excessive loading on the guide that could lead to premature failure of the valve / guide. If the blue is predominantly to the rocker shaft side then, as long as its not too far out you are ok, otherwise the pedestals should be shimmed.

As an example, the 1500 I recently built for a customer had 55 thou skimmed from the head in order to get the CR up to 10.5 : 1. This required me to shim the rocker pedestals by 30 thou to get the geometry right.


If you are going to use an external rocker feed then BEWARE! The kits sold by Moss and Rimmers show a FUNDAMENTAL misunderstanding of the peculiarities (and weaknesses) of the Triumph 4-pot and come with VERY misleading instructions.

Firstly, if using an external rocker feed you MUST cap the internal oilway between the block and the cylinder head. I do this by tapping and then loctiting an 8mm grub screw into both the block and the head.

Secondly, all the external rocker feed kits take the oil from the main gallery by using an adapter that screws in place of the oil pressure warning switch / gauge feed (1/8 NPTF). Ladies and gentlemen this is a BAD idea! The major weakness of the later Triumph 4-pots, especially the 1500, is that the oil supply to the centre main bearing is a wee bit marginal (and it is this that feeds big ends numbers 2 and 3). If you route oil the way the kits tell you then you are taking it directly away from the feed to the centre main! Furthermore, while the kits use –3 sized aeroquip they don’t have a restrictor in the adapter take off which makes matters even worse. The correct way to do it is to bin the adapter, get a –2 JIC to –3 JIC male-male adapter and take the feed from the rear tapping on the main gallery (feed to number 3 main) – to do this you merely remove the 5/16” threaded plug and screw in the JIC adapter.

What I do when building a 1500 (or a ‘large bearing’ 1300) is to increase the oil supply to the centre main. I remove the distributor pedestal bush and drill and ream the oil feed to 5/16” (7.95 mm). I also ‘teardrop’ the oil pick up holes in the crank in the direction of rotation so as to aid pick up at higher rpm. Finally I bottom tap the centre main bolt holes and fit 3 1/4” under head length cap bolts with hardened steel washers so as to better support the crank and to put the stresses deeper into the block – this helps to reduce any crank flex at higher rpm.

I am a bit worried about your poor oil pressure. It could be a stuck pressure release valve or it could be indicative of something worse, eg damage from a poor bed in procedure. The 1500 I have just built gave 50 psi when cold cranking.



With regards to bed in procedure, I smother the cam and lifters with a good quality cam lube to protect from scuffing. I use a basic 20/50 mineral oil (Halfords Classic) to avoid piston bore glazing. I then start the engine and bring it straight up to 3000 rpm and run it at this speed for 20 minutes – this is to bed the cam and lifters in. I then shutdown and change the oil and filter (Halfords Classic again), then run the engine in over 500 miles varying the engine load, and staying at 3000 rpm or less (this is to bed in the piston rings). Then its another oil and filter change, this time to something like Valvoline 20/50 Racing. Its at this stage that the oil cooler is plumbed in – if you do it any earlier and you get any particles from the bedding in procedure they will find their way into the cooler matrix rendering it scrap (because they cannot effectively be cleaned out).

Deborah Evans

This thread was discussed between 06/03/2009 and 19/03/2009

MG Midget and Sprite Technical index

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