When i pull each lead off the engine the first cyl makes a big difference and the rpm drops a fair bit but on number four when i pull the lead off it doesnt make much diference. why is this?, ive swaped plugs and leads between the two but its still the same outcome.

How can i diaognose/what are the signs of a blown head gasket other than oil in the water & water in the oil?

thanks

Can't explain the rev drop but your other question about diagnosis. A compression check on each cylinder can in some circumstances help diagnose a headgasket issue (particularly if you had a benchmark previously which suggested they were similar to begin with).
KB

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1&4 should drop the same rpm, but if motor has a big cam in you will probably find 2&3 have less rpm drop than 1&4.
Blame the siamesed inlet ports I think...

If 1&4 are different it could be a leaky valve, or worn rings, in one cylinder. Not always a head gasket....

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

number 1 cylinder will always have a bigger effect than the rest.

this is because the engine is timed to number 1, and the other cylinders "follow" along.
every engine has a certain amount of tolerance (+ or -), this goes for the crank journal timing in relation to each other, they can be (and usually are) a few degrees out.
rod lengths can vary, affecting compression ratios in each cylinder.
even the cam lobes are not always perfect.

unless you have "blue-printed" your engine there will be differences in how each cylinder works, its a compromise.

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Go buy a compression gauge - they are cheap enough. I check my cylinder pressures at every oil change and write them down.

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol