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

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

Post by oliver90owner »

Twenty years ago you could obviously get Cord rings. Won’t now, unless there is some NOS still around.
les
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Re: Engine in bits for a rebore-anything else worth doing?

Post by les »


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

Post by oliver90owner »

Reincarnated? Last time I looked for some, they had gone bust.
BobHood
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Re: Engine in bits for a rebore-anything else worth doing?

Post by BobHood »

Hello,

I can see why you used Cord piston rings, and why they wouldn't have broken. Here's a Cord catalogue page that clearly shows the rounded outer edges of the rings, that won't hit against the rounded edge of the wear ridge.
cords1.jpg
cords1.jpg (224.24 KiB) Viewed 2112 times
Bob's Boring! (or so I've been told) :D but I do honing as well!
See here: https://www.carandclassic.co.uk/car/C1053818
Or check out my website at https://www.bobsboring.uk
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

About to start rebuild, new main bearing shells finally delivered. Should I soak the shells in oil for 24hrs before fitting?

Cheers N
cheers N

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33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

No need to soak the bearings in oil but I would smother all bearings and cam followers/cam lobes bearings in engine build fluid especially if the re-build is going to take some time.
For example:-

https://www.ebay.co.uk/itm/Engine-Build ... SwNkJaS4g2

https://www.ebay.co.uk/itm/KENT-PERFORM ... SwVL1WA-0K

Smear the oil pump internals with general purpose grease so as to help the initial oil pick up.

You can remove the oil filter (1275cc Marina) or 5/8" UNF banjo bolt (1275cc Midget) and back fill the oil pump with oil before start up. Do not fit the plugs until you have oil pressure.

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

Post by paul 300358 »

Don't smear oil on the back of the bearings or the caps, fit the bearings dry and then smear with plenty of oil prior to offering to the well oiled crank journal.
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ndevans
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Re: Engine in bits for a rebore-anything else worth doing?

Post by ndevans »

Thanks gents. Crankshaft now back in, & turning freely, though not torqued down yet.

2 further questions if you don't mind!
1-How much endfloat should the crankshaft have? It's a 1275 engine, ex-Marina, not A+. Is the endfloat set by the centre thrust washers, or the thin washers in front of the front bearing?

2-should there be a seal in the rear main bearing cap, and in the piece that bolts to the block above it? Here is the rear main bearing cap:-
IMG_20190515_230501~2.jpg
IMG_20190515_230501~2.jpg (1.33 MiB) Viewed 2015 times
Thanks,
Neil
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

Crankshaft end float should be 0.003" - 0.004" and is set by the thrust bearings either side of the centre main. Make sure that they are fitted the right way round.

The thin washers at the front of the crankshaft set the alignment of the timing gears only.

There is no seal at the rear of the crankshaft just the return scroll.

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

Post by ndevans »

Having a problem getting the pistons in. The piston ring compressor doesn't seem to compress the oil control ring enough, the piston gets stuck every time. I don't recall having this problem last time.
Is there a trick to it?

Cheers N
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
oliver90owner
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Re: Engine in bits for a rebore-anything else worth doing?

Post by oliver90owner »

It might depend on the type of ring compressor tool you are using.

I have four different sizes of the type which envelopes the whole piston, let alone the ring area. Never had a problem with any of those, but they are a tad more expensive than some I have used.

Give us a clue as to the type you are trying to use.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

This is the type of piston ring compressor I use:-

https://www.ebay.co.uk/itm/PISTON-RING- ... Swd-xcpbo9

Check that the compressor size is suitable for the pistons/rings being fitted.

The rings have to be held tight by the compressor and both piston and compressor have to be well coated in engine oil.

A sharp tap on the top of the piston whilst holding down the compressor will get the piston and rings entered into the bore.

Have you checked the piston ring gaps?

When fitted there must be a gap between the ends of the piston ring to allow for expansion. Details of ring gaps are in BMC wksp manual.

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

Post by ndevans »

Have you checked the piston ring gaps?

When fitted there must be a gap between the ends of the piston ring to allow for expansion. Details of ring gaps are in BMC wksp manual.
No, I haven't. Do I need to check the oil ring gap as well?

Here is a pic of my ring compressor-same as yours:-
IMG_20190517_074652~2.jpg
IMG_20190517_074652~2.jpg (1.19 MiB) Viewed 1945 times
IMG_20190517_074713~2.jpg
IMG_20190517_074713~2.jpg (1.47 MiB) Viewed 1945 times
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
oliver90owner
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Re: Engine in bits for a rebore-anything else worth doing?

Post by oliver90owner »

ndevans wrote: Fri May 17, 2019 9:14 am
No, I haven't. Do I need to check the oil ring gap as well?
Yes. It will expand with increase in temperature, just like any other ring.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

All of the rings including the oil control rings (not the wavy bit) need to have the ring gap checked.

Push a ring (right way up) into the bore with an inverted piston to get the ring square and then measure.

It cannot be assumed that the bores are spot on and therefore match the pistons/rings - so the need to check the ring gap.

Whilst BMC had a good selection of graded pistons/ring you will have to work with what you have.

The numbers in diamonds stamped into the top of the block indicate bore grades and matching pistons were fitted by BMC to suit.

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

Post by ndevans »

Ok, just checked ring gap in no. 1cyl. Both compression rings were undersize at 0.004-0.005". For a Marina 1275, allowing 0.003" per in cyl bore, that should be 0.008". Both now filed to 0.008".
However, I then re-read the ring instructions, and it says "top moly ring must not be filed", see below photo.
Does this mean I should not have filed both compression rings, even though the top one was undersize?

Cheers N
IMG_20190517_213225~2.jpg
IMG_20190517_213225~2.jpg (1.88 MiB) Viewed 1909 times
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
les
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Re: Engine in bits for a rebore-anything else worth doing?

Post by les »

Looking at those pictures, piston ring compressors have come a long way. Mine must been made just after the internal combustion engine was invented! :D

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

Post by philthehill »

Whether moly or any other type of piston ring the clearance gap must be right otherwise the ring will break on expansion.

The BL marina/Ital wksp manual Pt No: AKM4580 gives the piston ring fitted gap for the 1275cc engine as:

Top ring...……………...0.011" to 0.016".

Second and third...….0.008" to 0.013"

Oil control ring fitted gap...….Rails 0.010" to 0.040"...…...Spring 0.012" to 0.028"

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

Post by ndevans »

All piston rings checked and gapped to 0.012" for the top, 0.008" for 2nd. All oil rings checked, not in need of adjustment as all at around 0.035".

Still can't get the pistons in, it fouls on the oil ring every time. The compressor is done up as tight as I can get it, the rings, compressor and bores are well oiled. This is what happens every time:-
IMG_20190518_164114~2.jpg
IMG_20190518_164114~2.jpg (923.84 KiB) Viewed 1850 times
cheers N

Image
33063, Eridge, Sept 2021 by Neil Evans, on Flickr
'69 Traveller, 1275, discs.
philthehill
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Re: Engine in bits for a rebore-anything else worth doing?

Post by philthehill »

Your piston ring clamp does not appear to be fitted square to the piston.

Fit the piston ring clamp to the piston with the bottom of the clamp at the bottom of the gudgen pin - but do not fully tighten the clamp.

Place the piston with clamp fitted into the bore.

Lightly knock the piston down to square the clamp. The clamp must be square to the piston and therefore square to the bore to be effective

Tighten the clamp and tap the piston down sharply whilst pressing the clamp down hard to the top of the block.

The rings should enter the bore without any difficulty.

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