Timing chain tensioner-Marina 1275 engine

[ndevans]

Morning.

I'm fitting a Marina 1275 in my Minor. I am fitting a new timing chain & tensioner-can anyone tell me how I should set up the tensioner please? How tight should it be on the chain?



Thanks,
Neil[frame][/frame]

[bmcecosse]

Just snug - not tight. It's just to stop it flapping about.

[philthehill]

Did you install a hole in the front engine plate for the head of the tensioning pad pivot pin?
It does need one if you have not installed one.
Whilst some do not bother with the central bolt holding the bulge of the timing chain cover to the front engine plate - it is better if the hole and bolt are installed. Less chance of oil seepage between the bolts.
There is clearance for the bolt head at the rear of the plate.
Below is a modified Minor front engine plate with all the required holes for fitting a simplex timing chain and tensioner assy.[frame][/frame]

All the holes in the Marina front engine plate do need to be replicated in the Minor front engine plate.[frame][/frame]

[ndevans]

No, I haven't. So the head of the pin goes the other way round does it? In the post below, it looks like it's on the front of the tensioner bracket.

http://www.mg-cars.net/mg-midget-sprite ... 516850.htm

cheers N

[philthehill]

The pin goes the other way round unfortunately.
The head of the pin sits in the larger (central) hole (large because it allows the tensioner to move through an arc) and the tensioner plate holds the head of the pin into the hole and stops it moving outwards.[frame][/frame]

[ndevans]

Ok ta. I'll get the plate off & drill it!

Cheers N

[philthehill]

If you have the original Marina front engine plate use it as a template for the Minor plate by placing the Marina plate (right way up) under the Minor plate and bolting through both the Minor/Marina plate using two of the 1/4" UNF timing cover bolts. That way the additional holes will be spot on.

[ndevans]

I have the original Marina plate. Do you know the size of the holes? Particularly the pivot pin hole?

Cheers N

[philthehill]

As you have the original Marina front engine plate - just measure the holes in the Marina plate and whatever they are is the size of the holes required for the Minor front plate.
I will not guess the size of the holes as I will be invariably wrong and my two spare modified front engine plates are buried in amongst a box of other spares so a quick answer will not be forthcoming.

[bmcecosse]

The pin head was originally fitted head down in a blind hole - but someone came up with a way of doing it without that hassle - although I have always made the blind hole .

[Declan_Burns]

Roy,
I think this is what you are referring to. I don't know where it came from but that is exactly what I did when I installed the tensioner. It is pretty easy to do.

Phil's photo also clearly shows how the plate should be drilled to allow for the extra hole in the plate which in my case I didn't know about at the time-it never leaked though.

Regards
Declan[frame][/frame]

Peened tensioner[frame][/frame]

The "redundant" hole[frame][/frame]

[ndevans]

Ta Declan. Might have a go at that -I doubt if I have a suitable drill bit for the pivot pin hole.

Cheers N

[Declan_Burns]

Just use as close as you can get to 4mm and drill it approx. 3mm deep. I used old steel bearing balls to peen the pin in a vice. Start with a small one, go up in size and finish with a large one. That's about it.

Regards
Declan

[ndevans]

I meant the larger hole in the backplate actually! I reckon its about 16mm. Think I have a suitable peening tool somewhere.

Cheers N

[philthehill]

Declan
Reference modifying the pin so as to fit the opposite way to original.
Whilst I am aware that it has been done successfully it is not a modification that I would or could recommend.
With the tensioner set to give the correct tension to the timing chain there is a fair bit of chatter of the tensioner pad as the timing chain passes under it.
Unless the drilling / countersinking and peening has been done absolutely correctly there is a good chance that the pin will work loose and detach itself from the inner flange of the tensioner support bracket and rattle away and possibly break the pin or tensioner support bracket or even both which could lead to the failure of the engine.
With the pivot pin secured as produced by BL there is very little chance if any of the pin detaching from the tensioner support bracket as the security of the pin is designed in.
I am certain that BL would have produced a throw away tensioner assembly with a riveted pin if they thought it would work.
Whilst it is up to the person doing the work to choose the method of securing the pin I prefer and would recommend every time to fit the tensioner and pin as BL intended with the head of the pin located between the tensioner support bracket and the front face of the block using the hole in the front engine plate as the blind hole.
Phil

[philthehill]

A post by Neil reference fitting a nut and bolt instead of the pin has disappeared
If you could fit a bolt and nut the nut would have to fit in the space/blind hole originally occupied by the head of the pin because the tensioner pad fully occupies the space between the two flanges of the tensioner support bracket.
You are therefore back to square one!
Even if you could fit a nut and bolt the other way round the head of the bolt would occupy the space originally occupied by the head of the pin.
Again back to square one.
Phil

[ndevans]

I deleted the post, realising it was a stupid question!

[ndevans]

You could enlarge the bottom hole of the tensioner bracket so that the head of the pivot sits in the bracket, flush with the face of the block. It's still not going to move anywhere, and sounds easier than a c/s and drilling the pin. Thoughts anyone?

Cheers, N

[bmcecosse]

It's very easy to make the blind hole for the pin head - and the position is not desperately critical either. Just mark it from where you have the pivot now. The larger extra bolt hole is not necessary - never done it, never had a leak. You're over-thinking this - it's simple ! (resists urge to add an s....) And yes - Declan's sketch is what others have done - but honestly it seems too much work compared to drilling a wee part depth hole !

[philthehill]

The hole for the head of the pin has to be a minimum of 3.5mm deep (or the thickness of the front engine plate) x 8mm dia if the position of the pin has been determined so giving the correct chain tension.
The hole for the pin head should be much larger than 8mm otherwise the tensioner cannot be moved through an arc (pivoting around the bottom hole/set screw) to apply/vary the tension to the chain.