Acceptable cylinder pressures?

michaelridgeway@tiscali.co.uk · Dec 7, 2007

2.25 petrol; 1982. Changed the head, new gasket etc.

Manual states 165 psi

Pressure test shows 110 psi

If rings are a bit worn I am not too concerned, but if valves not seated properly then I may need to take the head off again.

Thanks

Old Bloke

iannotts · Dec 7, 2007

Are all 4 within 10-20 psi of each other?

slob · Dec 7, 2007

my 'big book of landies' sez it should be 145 psi with a 7:1 head and 160 - 170 with an 8/1 head

if yer worried about it try a squirt of oil down yer bores then do another test. if yer pressures go up its yer rings if it stays the same, suspect valve seaTs.

if yer can access a leak down tester that pin point th eproblem fer yer

CharlesY · Dec 7, 2007

I think Slob meant valve SEATS rather than valve seals.

Compression pressures are also dependent on how fast the starter whirls the engine over; the throttle should be jammed wide open, and all the other spark plugs should be OUT during the test.

CharlesY

slob · Dec 7, 2007

CharlesY said:
I think Slob meant valve SEATS rather than valve seals.

Compression pressures are also dependent on how fast the starter whirls the engine over; the throttle should be jammed wide open, and all the other spark plugs should be OUT during the test.

CharlesY

well thems the figures from the 'OH! facial big book of landies" so am assuming the LR knows how to do a comp test.

michaelridgeway@tiscali.co.uk · Dec 7, 2007

Thanks guys,

Yup. All 4 s`linders are 109 p.s.i.

I`ll try the squirt test.

How do I tell if it`s a 7:1 or 8:1 please?

Old Bloke

CharlesY · Dec 7, 2007

[email protected] said:
Thanks guys,

Yup. All 4 s`linders are 109 p.s.i.

Suspicious .... if all 4 cylinders tested EXACTLY the same, check the gauge.

I`ll try the squirt test.

Only a little oil or you will fill your tester with oil.
Too much oil will partially fill the combustion space, which will cause false readings, like too high.

How do I tell if it`s a 7:1 or 8:1 please?

If the 109 psi figures are right, start thinking LOW compression. It looks too low to me.

Make sure your valve clearances are good - all eight valves dead-on the mark at 10 thou, because if they are too TIGHT valves will be held OPEN longer, and REDUCE the compression figures somewhat.

CharlesY

iannotts · Dec 7, 2007

Could they be low due to a slow cranking speed?

CharlesY · Dec 9, 2007

iannotts said:
Could they be low due to a slow cranking speed?

Most definitely!

Taken to the ridiculous extreme, even if the engine was perfect, but you took 5 minutes to turn it over once, you wouldn't see much on your compression gauge.

So, glow plugs out, warm engine if possible (drain and fill the block with very hot water if need be), anda good starter motor and battery.

The faster it turns on test the better.

CharlesY

iannotts · Dec 9, 2007

That what i thought, the 4 idendtical reading could be a perfect engine turning slow then

Acceptable cylinder pressures?

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