knocking on start up

[redcorgi]

Hi everyone this is my first posting, had the exact same problem myself with a 948cc engine had always to prime the oil pump before starting oil pressure then good allday even when engine was off for a few hours through out the day, left overnight it needed primed again my thoughts were a weak oil pump on stripping the engine to find that the oil pump gasket had blown& leaking.

[philthehill]

A common problem with the oil pump gasket is the it being put the wrong way round. Smear the gasket in GP grease before fitting. This keeps the gasket supple and leads to better sealing and longer life.

[kevin s]

That's an interesting idea, there is nothing leaking externaly (well no more than the usual) but a leak between the inlet and outlet could certainly explain it, hopefully we will find out at the weekend. We are going to strip and inspect the engine anyway. Is it obvious which is the right way round?

[philthehill]

It should be obvious. Just make sure that the gasket does not shroud any part of the inlet and delivery passages.

[kevin s]

Today we pulled the engine and stripped it, results were unexpected.

Firstly pulled the head, all came off easily enough, what we found was suprising.

1 piston was a different make to the rest, no2 had pitting up the back of the bore and they all had radial markings.

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Also it looks like the head gasket was leaking which might explain why it's been difficult to start lately.

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We then drained the oil to find it only had a litre in it, it was half way between min and max on the dipstick so that may explain the oil pressure issue, it has the wrong dipstick!

Dropped the engine and box out which went easily enough.

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Then we pulled the flywheel and backplate of followed by the oil pump which looked perfect inside. Next up was the sump, which relealed this mess.

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Upon examining the bits we were suprised to find it was pulverised rubber rather than swarf and it was everywhere inside the engine.

Pulled the front cover off to find even more, it was the back rubber ring of the timing wheel which had disentigrated.

Then proceeded to remove the crank, appart from the big end bolts which were way too tight and rounded off it came appart easily enough, this revealed a pleasant suprise, the crank and all it's bearings look like new.

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[kevin s]

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So the conclusion is, oil pressure was probably a combination of low oil and bits of rubber but no damage seems to have been done. We do though need a re-bore, new pistons, the block and head skimmed and a new timing chain set (duplex). While we are in there Andrew is also thinking about a mg metro cam to support an eventual plan to add a hif44 su etc.

Tomorrow I will mic up the crank to check it is definitely ok and then we will have to find a machine shop, the one I usually use closed last year when the owner died, any one any experience of Thurstons in Ongar or Robertsons in Colchester?

[pgp001]

Make sure to clean the oil galleries very carefully with all that rubber floating around.

Phil P

[kevin s]

Fortunately there wasn't any in the filter but yes the pick up and galleries to and from the pump will need carefull cleaning, we'll get the block chemicaly cleaned when it's re-bored it too.

[geoberni]

We then drained the oil to find it only had a litre in it, it was half way between min and max on the dipstick so that may explain the oil pressure issue, it has the wrong dipstick!

I had that problem back in the mid 70s. I fitted a 1300 Crossflow to a Ford Escort and wondered why the oil lamp flickered on corners.

I had a Cortina dipstick, not an Escort one. Different dipstick. The sump was at the other end and I only had half the oil I was supposed to have......

[kevin s]

Measured up the crank, it seems fine the main bearing spec is 44.46 to 44.47 mm, which is only half a thou so I assume this is the machining tolerance, the rule of thumb usually being 1 thou for every inch of journal giving 1.7 thou or .043mm, I measured and 44.45 44.8 at the same spot its very difficult to get the same each time, and no measureable ovality. There does seem to be a slight ridge in the centre of the mains you can't really feel or measure any difference though so I think it's more the running area being polished. We've got some plastigauge on the way for a final check as well.

Andrew has also bought Vizards book so god knows what direction it will take next!

[oliver90owner]

Just out of interest, what precision and accuracy did you measure to, what device were you using and did you do a calibration check on it?

[kevin s]

It was a micrometer checked with the calibration rod that came with it, for ovality I just set it as a good fit across one direction locked it then tried in roughly 45 degree increments to see if there was any play or tightness anywhere else, they all felt exactly the same.

Andrew has now bought a new old stock fast road cam for it (piper hr255, pretty mild one power band starts at 1500rpm) it has a spider drive oil pump which is easy enough to get but are all 4 bolt, I understand this will need a extra bolt hole drilling, We will crack out the dial gauge to try and get it accurately timed as well. is there anything else we need to consider when fitting this to a 1098?

[philthehill]

As you have a dial gauge check that the camshaft end float is correct - it should be 0.007".
The end float can be increased or decreased by machining the central boss of the camshaft gear.
You can fit this pump without having to drill and tap the block but please check suitability before purchase.
http://www.minispares.com/product/Class ... o%20search
Here is a new star drive if you do not already have one.
https://www.ebay.co.uk/itm/Chm-108-Oil- ... Sw3ppgIWwV

[kevin s]

Thanks, is that with the pump fitted?

[philthehill]

The oil pump has no bearing on the camshaft end float. The oil pump of what ever type does not press on the end of the camshaft. The only contact between oil pump and camshaft is the drive and the force generated is radial.
Below - To reduce end float take metal off here

Camshaft end float 1.JPG (1.4 MiB) Viewed 933 times

Below - To increase end float take metal off here.

Camshaft end float 2.JPG (1.7 MiB) Viewed 933 times

[kevin s]

Thanks, so it is the triangular plate clamped between the front of the cam and the pulley which retains the cam and needs to have 7 thou clearance.

[philthehill]

The triangular plate is what keeps the camshaft in place. The end float is 0.007" max. 0.003" min.
The resistance to turning of the distributer/distributer drive shaft is what keeps pushing the camshaft forward and up against the rear face of the triangular plate. That is why the triangular plate has only one rear facing white metal bearing face which contacts the front face the camshaft. The rear of the camshaft gear should not be in contact with the triangular plate. The cam followers have no impact pushing the camshaft forward.

[kevin s]

Engine parts have gone for machining.

We had noted one piston was a different make what the machinist also pointed out was it was also a low compression one, so given we need new matched pistons we opted for a +20 thou rebore.
He is confident the top of the block will clean up OK too.

Head is being skimmed by 1.5mm so we can improve some of the valve shrouding in the combustion chamber and new hardened exhaust valves plus re-cut inlet seats are being done.

Should be ready in a week or so if we can get the new pistons too them quickly.

[philthehill]

Make sure that the re-bore is done/sized to the piston.
When the 'A' Series was being factory produced BMC had a selection of piston grades/sizes to suit the actual cylinder bore. The number inside the diamond on the top of the block adjacent to the respective cylinder bore and on top of the piston indicated the grade/size of re-bore and grade/size of piston. The two numbers should be/will have been matched i.e. block marked 2 / piston marked 2.
It was back then & even now not always possible to bore to the standard size (and/or plus re-bore size) on every bore and have every piston the same size/grade.
You may have four pistons but they may not all be the same size/grade therefore it is most important that the bore is sized to the piston.
Whilst the engine reconditioning company may in all probability re-bore to the piston it will do no harm to ask if they intend to do so.
Phil

[kevin s]

Yes he's already said he needs the pistons to do the boring and honing, Andrew's spending a small fortune with ESM as I write this, then dad or one of Andrew's mates will drop them off.