Oil pick up pipe basket securing bolts

[moggiegeek]

Hi, in building up new /1275 engine decided to use centre main bearing strap which the cap was duly machined to take. ( I know it's not really needed given engine spec but I did have one)
As the securing bolt for the oil pick up basket locates on the centre cap I'll need to drill and tap a new location point. What is the thread for the bolt in question?
Or would I be better going for a metric bolt size and if so what would you suggest that has easily available tap and clearance drill.?

[philthehill]

Use the same bolt as standard 1/4" UNF. Tapping drill size....5.5mm, Clearance drill....6.5mm.
The strengthening strap is drilled and tapped - you do not have to drill a clearance hole through the strengthening strap to the main cap
Just amend the oil pick up filter basket bracket by bending and cutting to suit.
The strengthening strap is 7/8" square and of good quality steel.
The centre main cap should be machined with just sufficient clearance to allow the 7/8" strap to fit between the thrust bearings tag locating shoulders. The main cap should not be machined with a totally flat top surface.
I have the same arrangement on my spare 1400cc MG Midget block.

Make sure that you use good quality longer bolts or Allen screws (grade 12.9 as a minimum) to secure the main cap.

[moggiegeek]

Thanks for that. Strengthening strap is from minispares so assume it is of correct dimensions to allow thrust washers to sit vertically.
The strap isn't threaded for the main cap retaining bolts it has clearance for the high tensile bolts supplied.
What did you mean by not machining the main cap level?
Thank you

[philthehill]

The centre main cap if machined fully flat can reduce the ability of the centre main cap to locate the anti rotational tangs of the thrust washers. The grooves in the side of the centre main cap for the thrust washer tangs must be still be of a depth to accommodate the full height of the tang after machining.

http://www.minispares.com/product/Class ... o%20search

I am aware that the strap has clearance holes for the main bearing bolts as I have recently purchased one of Mini Spares straps for the 948cc/998cc engine I am building in slow time. I also had a strap fitted to the 998cc engine previously fitted to my Minor.
The strap fitted to my 1400cc engine also has clearance holes through the strap.

My 1400cc centre main cap was machined by Oselli as a trough for the strap to sit into so retaining the full depth sides for the thrust washer tangs.

[moggiegeek]

Thanks, I understand what you're describing and why it needs to be able to give the thrust bearing tangs the full height to locate into.
I'll have to hope the experienced company who did the work realised this cos I didn't specify it. You don't know what you don't know when doing something new.
If they have machined to too low then is it permissable to reduce the height of the tangs slightly to suit? Not ideal but maybe better than having to have new centre cap machined and I guess line bored to suit?

[philthehill]

You will have to see what the main cap to thrust washer tang relation ship looks like when you get the centre main cap back.

The height of the tang on a 1275cc thrust bearing is 5mm so I would advise against reducing the height of the tang.

Your centre main cap may be perfectly acceptable after machining flat but it is best to be aware of possible problems.

[panky]

I fitted the Mini Spares centre strap to my Mini engine. After getting the bearing cap machined down there was still enough groove left for the thrust tang.

[moggiegeek]

Here's hoping. Now have all the machined parts back. Will look tomorrow.

[moggiegeek]

All was well. Exactly the right space for the tangs. As the guy said he's been doing this ( well) a long time.
Have drilled and tapped centre cap for oil pick up basket bolt.

[moggiegeek]

Oh dear. I fear I have a serious problem.
When I was assembling the engine today what seemed ok turned out not to be.... Re the centre cap
The centre main bearing cap has been machined down too much. Thus the thrust bearing tangs are free to rotate. The strengthening strap fits inside and has insufficient width to machine or file retaining slots for the tang.
Two options I can see:
A) get new main bearing cap, have it line bored and properly machined to take strengthening strap at correct depth.
B) I do have steel bar if the exact dimensions of the centre strap ( 3cm by 0.5 cm) .... is it completely mad to drill this for the securing bolts and accurately file a slot for the tangs on each side then assemble on top of centre cap and below strengthening strap. Is it a recipe for a big expensive bang?
Advice welcome

[philthehill]

A photo of what the problem is or not would be helpful in making a constructive reply/advice.

I would suggest that you do not make a decision until we have seen photos of the main bearing cap and strengthening strap.

Have a look at this You Tube video:-

https://www.youtube.com/watch?v=dlBqJqJFTgc

[moggiegeek]

Tangs and centre cap

IMG_20191005_204228.jpg (413.56 KiB) Viewed 1637 times

Tangs and centre cap 1

IMG_20191005_204029.jpg (630.58 KiB) Viewed 1637 times

Centre cap and thrust washer

IMG_20191005_204259.jpg (1.12 MiB) Viewed 1637 times

Not sure if the photos have worked. However having seen video above the depth of the centre cap is hugely reduced in my situation.

[moggiegeek]

Strengthening strap

IMG_20191005_204121.jpg (1.56 MiB) Viewed 1636 times

Strengthening strap

[philthehill]

Thank you for posting the photos.

Unfortunately I have to say that in my opinion the cap is now not useable. The depth of metal has been so reduced that I could not trust the remaining metal to hold even with a strap on top.

I have to ask - what was the machinist thinking about especially as you said in an earlier post that they had done this simple job before.

Looking at the photo - the finish to the top surface of the machined cap is very poor when it should be perfect (see video link).

To get over the problem I would be looking at either a good S/H centre main cap which means line boring or even better a steel centre main cap with either two or four bolts but again requires line boring. My preference would be the four bolt steel cap as then it is fit and forget for ever.

I would be looking elsewhere to do any future machining/line boring

http://www.minispares.com/product/Class ... o%20search

Here is a set of suitable main caps:-
https://www.ebay.co.uk/itm/Set-of-3-Mai ... SwxapdiRQY

I would also get in touch with Peter May engineering and see if they can provide you with a standard centre main cap from a race engine that has been fitted with an upgraded centre main cap.

https://www.petermayengineering.com/

Phil

[moggiegeek]

Thanks Phil, pretty sickening really. As a remedy I'll go for the 4 bolt steel cap option I think. Costs of secondhand caps roughly equal new steel 4 bolt.as you say it's a considerable upgrade too.
I'll look further afield for a machine shop too and will go back to the one who did this work to complain. We'll see. They have a really good reputation and everything else looks good and went together perfectly.
Question 1: with the line boring I assume I can reuse main bearing shells/ thrust washers etc?
Question 2: will the block require renewing the oil gallery stoppers again to facilitate cleaning?
Any other advice gratefully received....

[philthehill]

Fitting the 4 bolt cap will be an excellent upgrade and well worth it in the long run. I have a 4 bolt cap fitted to my 1275cc/1380cc block.

The bearings can be re-used without problem.

As regards cleaning the block after line boring - I would suggest that you need to clean the block thoroughly even if it means taking out the oil gallery plugs to do so. One small flake of machined metal can do a lot of damage.

My main advice is to not get despondent as these things happen and with modified items it often takes several goes and several pounds to get it right.

It will all work out right in the end.

You are right to go back to the machine shop and complain.

Phil

[Banned User]

I'll look further afield for a machine shop

Where are you based? Maybe someone can recommend someone who's familiar with the A series, rather than just a place that does machining.

[moggiegeek]

I'm based in Bath/Bristol so recommendations very welcome

[Banned User]

Slightly the other side of Bristol from where you probably are, but well worth the drive http://www.slarkraceengineering.co.uk/

[moggiegeek]

Thanks for the suggestions and advice. In the end I've gone with Peter May Engineering to fit steel bearing caps. As a bonus you get high tensile big end bolts and the rear oil seal conversion. It seemed sensible to have it balanced too.
Not the level of sophistication I'd planned at all but as Phil says,fit and forget...
Glad it's a slow build project so I can work to finance it.
My learning is to never assume and to be really clear about what's being specified...
All this started as a low budget bolt on extra.