Engine in bits for a rebore-anything else worth doing?

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philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Mon Aug 12, 2019 7:19 am

The pushrods will not become out of alignment if the rockers are moved sideways to improve alignment with the valve stems.
When the 940 head was produced the valve were placed further apart so a production misalignment between cam follower, push rod and rocker became the new norm.
Even with the standard misaligned arrangement you should check the clearance around the pushrod where it goes through the head.
Below is a photo of a 940 head with realigned rockers. The different thickness of spacers can be seen.
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Last edited by philthehill on Mon Aug 12, 2019 7:25 am, edited 1 time in total.


Declan_Burns
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Re: Engine in bits for a rebore-anything else worth doing?

Postby Declan_Burns » Mon Aug 12, 2019 7:24 am

You can machine the pedestals to align the rockers.
Regards
Declan
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Regards
Declan

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Mon Aug 12, 2019 7:39 am

Declan
I personally would not recommend machining the later type rocker shaft pedestals to accommodate the later type sintered rocker. Too much metal has to be removed from the sides of the pedestal which reduces the metal around the stud holes which then could and can lead to cracking of the pedestal.
Removing metal from the centre of the flat sided pedestal will not alleviate the fact that the sintered rocker is also flat sided so it will not fit into a hollow centre machined pedestal - whereas the forged or pressed steel rockers are shaped and can be accommodated and centred by removing metal from the centre of the pedestal as I have done in the photo below and used in the assembled photo above.
If the pedestals needs to be machined the best pedestal to use is the forged steel pedestal fitted to the Cooper S and early 'A' Series engines and used in conjunction with either the forged Cooper S rocker or pressed steel rocker.

Phil
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pgp001
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Re: Engine in bits for a rebore-anything else worth doing?

Postby pgp001 » Mon Aug 12, 2019 8:26 am

What sort of lathe is that Phil ?

It looks to be fairly vintage, probably an old flat belt drive at a guess.

Phil

paul 300358
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Re: Engine in bits for a rebore-anything else worth doing?

Postby paul 300358 » Mon Aug 12, 2019 10:07 am

For a normal road going engine I would leave them as they are. That's how BL designed them.

Declan_Burns
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Re: Engine in bits for a rebore-anything else worth doing?

Postby Declan_Burns » Mon Aug 12, 2019 10:54 am

Phil,
That was just a photo for demonstration purposes with the sintered rockers. I machined the pedestals to fit the pressed steel rockers on the 940 head but I never took a photo. That was 9 years ago.
Regards
Declan


Regards
Declan

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Mon Aug 12, 2019 3:19 pm

pgp001

The lathe is branded ASTER and was made somewhere around 1895 1910. and is driven by a flat belt.

http://www.lathes.co.uk/aster/

I know the whole history of the lathe and who had it before me. It has featured twice in the Model Engineer some time back.

The lathe is fully concentric as confirmed by using a dial gauge.

I also have a second similar lathe branded George Adams http://www.lathes.co.uk/george-adams/index.html again with a known full history which is featured in the lathes.co.uk website. It is the green lathe pictured right at the start of the link.

Both lathes came with a selection of chucks and accessories which allow me to undertake a variety of turning and milling tasks not that I do anything very serious but it is very handy to have available.

I have used the George Adams as originally driven with the flat belt off the flywheel and once up to speed is very easy to keep running.

Both lathes are in excellent condition considering their age though the George Adams lathe has had little use.

Phil


philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Mon Aug 12, 2019 3:40 pm

Declan
Many thanks for the reply.

I found that it is near impossible to machine the rocker pedestals for the sintered rockers and still have sufficient metal left around the pedestal stud holes. In the end I called it a day and the pedestals and sintered rockers went into the scrap bin.

So having tried to align the flat sided pedestals and flat sided sintered rockers and found the process near impossible I certainly would not recommend that alignment is attempted.

If the sintered rockers are in good condition I would recommend that the rockers are used as ex factory with no attempt to align rocker and valve stem.

Phil


ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Postby ndevans » Mon Aug 12, 2019 7:14 pm

I've got new rockers and a new rocker shaft, so shall I leave the rocker/valve spacings alone? The pedestals have some wear, but nothing to sweat about.
Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Mon Aug 12, 2019 7:29 pm

I would just put it back together with the new rockers and new rocker shaft plus the locking peg and forget about the centering of the rockers over the valve stems.
With the locking peg in place the shaft will not be turning as most likely was so a little wear in the pedestals will not go amiss.

Rebuild and enjoy.


ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Postby ndevans » Mon Aug 12, 2019 11:17 pm

Ok thanks, that's what I'll do.

Head surface and block surface are now clean to my satisfaction. The tappet adjusters are now in, so all is ready to go back together.

Head gasket (new one) is ready to go back on now. Do I lightly grease both sides of the gasket?

Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Tue Aug 13, 2019 7:11 am

Lightly grease both sides of the gasket.


ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Postby ndevans » Fri Aug 16, 2019 10:52 pm

After the usual two steps forward, one step back, I finally got it running tonight.
Of course when I tried starting it, it wasn't having any of it. Dead as a doornail. So I checked everything, ignition, fuel pump, leads on the correct way, rotor arm present (been there before!).....it wasn't playing.

It always the simple things isn't it?

Staring at it in the garage, cursing it in my head, the reason became obvious. The brake servo take off hose wasn't connected!

I reconnected it, and off it went first time. Sounds pretty sweet too, except for an annoying shriek as I increase the revs slightly. Think it may be the fan belt, but it doesn't seem too loose. It sounds horribly like something rubbing, but I can't think what. It wasn't there a week ago, before I took the head off.
Last edited by ndevans on Sat Aug 17, 2019 12:21 am, edited 1 time in total.
cheers N
'69 Traveller, 1275, discs.

paul 300358
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Re: Engine in bits for a rebore-anything else worth doing?

Postby paul 300358 » Fri Aug 16, 2019 11:19 pm

It may make the belt screech if you have run the battery down.

ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Postby ndevans » Sat Aug 17, 2019 12:03 am

Good point, I must have tried it about 20 times. I'll give it a run tomorrow.
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Sat Aug 17, 2019 12:31 am

If you have an alternator fitted the fan belt needs to be very tight otherwise when giving the recharge after starting up the belt will slip noisily.
Also try some talcum powder shaken onto the belt and pulley grooves as the belt may also be greasy. The talcum power will dry the fan belt and give grip.


oliver90owner
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Re: Engine in bits for a rebore-anything else worth doing?

Postby oliver90owner » Sat Aug 17, 2019 7:34 am

Have to disagree a little with PTH on this one.

A belt tensioned too little will slip but one too tight may well reduce the alternator bearings or finish off the front bearing if it is at all close to end-of-life. That means the tension should be kept strictly within the specs.

Another reason is worn or incompatible belt/pulley combinations. Many people tend to keep tightening V belts, even though beyond their expected working life. If the belt is ‘bottoming’ on the pulley, it is far past its service life.

The oft adopted alternator can also be part of the problem. Single small section belts are not designed to transmit a horse power or more at slow speeds. The Morris Minor was designed around a dynamo developing 20A at full speed. Even if only 50% efficiency (they are likely far better than this) that is only a third of a horsepower - but at high speed. A 60A alternator is a completely different generator to the original dynamo.

A poor battery only makes things worse, so that may be yet another unconsidered factor!

ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Postby ndevans » Sat Aug 17, 2019 8:10 am

Ok thanks gents.
The belt is about 18 months old, and it's not the standard belt, it's slightly longer to take account of the taller 1275 block- I couldn't get the standard belt on. It's a Gates v6271, from memory. It's not worn, and as far as I can tell, not bottoming in the grooves. There is about 1cm of play in the longest run.
It doesn't look greasy, but there could be water on it from when I drained the coolant-I don't have a drain tap on the radiator, so I have to pull the bottom hose off, the stuff gets everywhere! I'll give the belt a wipe.
The battery could well be quite discharged after quite a few attempts at starting last night, so if it's a discharged battery causing the problem, then an hour or so on charge should sort it out.

Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Postby philthehill » Sat Aug 17, 2019 8:18 am

To quote chapter and verse from the BL wksp manual for both dynamo and alternator:-

'When correctly tensioned a total deflection of 0.5" (13mm) under moderate hand pressure should be possible at the midway point of the longer belt run between the pulleys'

The initial rate of charge with an alternator after engine start up can be quite high which provides a high torque resistance to turning within the alternator which if the belt is not sufficiently tight can lead to slippage.

There is no point in having the belt set to the factory setting if the belt is constantly slipping. The tightness of the belt has to reflect the realities in that it has to be tight enough to resist slipping. A constantly slipping belt will soon wear out and usually breaks at the most inconsiderate time.

Unlike the dynamo which has a ball race bearing at the pulley end and a plain bearing at the rear end the alternator has ball race bearings at both ends which helps with the loading on the alternator bearings. The alternator also has a smaller diameter drive pulley than the dynamo, therefore rotating the alternator faster so inducing a larger charge at lower engine revs.

Coolant on the belt and pulleys does not help and that is why I suggested putting talcum powder on the belt and pulleys. It also gives a nice smell to the engine bay :D


paul 300358
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Re: Engine in bits for a rebore-anything else worth doing?

Postby paul 300358 » Sat Aug 17, 2019 10:47 am

Before doing anything, I would go for a run and see if it stops. I would then try it with the lights on and see what happens, I would also consider fitting the new spare fanbelt.


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