Issues with head

[andrew.searston]

Hi everyone
I have taken off my cylinder head and it looks to be a 1275 on a 1098 block
Issue i have is looks like valves have been hitting the block. Can anyone shed some light on what i should do

[philthehill]

The head is indeed a 1275cc 940 head.
You are correct in that the valves have been hitting the head.
Those valves need to be removed and checked for trueness.
They can be checked by putting the valve back into the guides and rotating the valve and see if they are true.
The valves can be recessed into the head so as to give the required clearance between valve and block when the valve is open.
Use the search facility for clearance between head face and valve cylinder face when the valve is shut
viewtopic.php?f=4&t=62830&p=581140&hili ... ad#p581140
There is plenty of information to be found reference sinking the valves when using the search facility.
You were very lucky as the head of the valve could have been snapped off with disastrous results.

[andrew.searston]

Yeah i am lucky. Ive never done anything to the engine but gasket looks new so might reuse it?
Thought id investigate the mentallic noise and found that. Also going rebuild the bottom end as alot of endfloat in crank

[les]

Don't use the old gasket! Not worth risking the possibility of having to strip it again.

[andrew.searston]

Okay thanks
Just taken valves out feel sloppy in the guides. Looks like carbon build up has been cracking of on valves hitting compared to others. Does the head look like its unleaded?

[les]

From the picture, I'd say no. Many say it's not necessary, unless belting up the motorway. True or false I don't know.

[andrew.searston]

As im rebuilding the bottom end as its worn is there any worth while mods that wont break the bank to compliment the head?

[philthehill]

Fit a duplex timing chain assy and if not already fitted the later timing cover which has a neoprene seal.
Replace front pulley with a crankshaft damper.
Fit a spin on/off oil filter assy.

[andrew.searston]

as im building it myself would i have to get it balanced?
whats the benefit with crank pulley?

[philthehill]

You would not have to get it balanced.
The damper helps to absorb and dissipate the vibrations commonly associated with the 1098cc engine.
Here is a 1098cc engine with the damper, spin on/off oil filter, duplex timing chain & later timing chain cover fitted.

[andrew.searston]

thanks
whats the best cam to fit with that head?
also can i sink the valves myself or machine shop job
ive been reading that a 1275 copper head gasket is required would that add more clearance over the fibre one on mine?
would sinking just the exhaust valves by 40thou be enough to clear the block?

[philthehill]

The best production cam is the MG Metro camshaft but not so cheap these days.
You can do the job yourself with a valve seat cutter or coarse wet and dry under the valve head.
In the link post above BMC quotes 300 thou as the required distance between valve head and cylinder head face.
What have you got currently?

[andrew.searston]

can i check by measuring the valve when its fully seated. between surface of valve to surface of head? then it should be roughly 300-320 thou for it to clear?
thats with head off the car on workbench

[Declan_Burns]

Andrew,
There is no "roughly" in engine building. Measure it. The depth-it should be 8mm (320 thou).
If you don`t have a calipers as in the photo, you can use one of the cheapy tyre thread digital depth gauges from fleabay which cost little or nothing nowadays. They are actually quite accurate and can also be fitted to a lathe tailstock!
http://www.ebay.co.uk/sch/i.html?_from= ... al&_sop=15
Regards
Declan

[don58van]

Elsewhere on this site there is reference to another method to get the required clearance--shaving the face of the valve. This of course would depend on whether your exhaust valves have enough meat to do this safely.
I can't comment on whether this is a sound practice--I'm just noting that another member has had success using this approach.
Don

[andrew.searston]

So ive taken pistons out of the block
Are these standard. As the numbers mean nothing to me

[andrew.searston]

No1 doesnt look good

[philthehill]

The piston appears to be a grade 2 standard diameter piston as there are no (plus) 0.010", 0.020", 0.030" etc. on the top of the piston indicating that the bore are larger than standard.
The other numbers are manufacture(s) numbers and can be discounted.
The bores though should be measured to confirm their size.

[andrew.searston]

Whats the measurements for standard size, No1 is pitted badly no numbers showing on crown. Think ill have to order new standard pistons, hopefully get away with just glaze busting bores if they measure correct

[philthehill]

For a 1098cc engine the standard bore size is 2.543" / 64.58mm.