9 replies to this topic

[neon1991]

Morning all!

 

what reading should I be getting from a 1380 engine with standard rockers.  it's had a recent rebuild and the previous owner drove it a few hundred miles and reported no problems.  I stuck a tester on it and only managed around 50psi across the cylinders.  test was on a cold engine (had only run for a couple of mins) all the plugs out and dry bores (no oil down them)

 

although the reading was low,  it was even and the colour of the plugs was nice and brown.  just puzzled by the really low reading.  the engine had no numbers so dont know what it was in previously... could it have been a turbo engine with the turbo removed?? they are meant to run at a reduced PSI but surely not 100psi lower?

 

 

[Bat]

Hi,

Depends on the cam, if it's a long duration the valves will be open longer and therefore less compression.

You need the throttle wide open to do a compression test really and a hot engine.

Cheers 

Edited by Bat, 21 August 2018 - 10:31 AM.

[neon1991]

Hi,

Depends on the cam, if it's a long duration the valve will be open longer and therefore less compression.

You need the throttle wide open to do a compression test really and a hot engine.

Cheers 

sorry thread is in the wrong place.  The throttle was wide open.  even on a cold engine I'd expect more than 50psi wouldnt you?

[nicklouse]

yes I would expect more BUT there are many many variables that can effect the result including the cranking speed.

[neon1991]

yes I would expect more BUT there are many many variables that can effect the result including the cranking speed.

from the write up I had from the owner it was a "standard cam"  the turnover speed wasn't noticeably different from any other mini I've tried to start. all the plugs were out so it was turning over freely enough.

[imack]

Is the compression tester accurate?

[neon1991]

Is the compression tester accurate?

yep plugged it into my compressor at home to check at various pressures and all good.

[Bat]

Hi,

It does seem low. l can't remember what I got when I tested mine, sold it years ago.

How's it drive?

Cheers 

[neon1991]

Hi,

It does seem low. l can't remember what I got when I tested mine, sold it years ago.

How's it drive?

Cheers 

that was my reason for posting,  I wasnt able to drive it,  saying the ball joints were loose.  It sounded a bit rough when revved but ticked over fine (as often they do)  Ive walked away from the sale now.  it would have been a gamble at £500 but the seller wants a lot more for it. 

[Bat]

Hi,

I sold mine for £1000 years ago with a 285 cam, weber 45 and omex wasted spark ignition system with dyno charts and test drive to prove.

Cheers