Thread: Interpreting cylinder compression results

Originally Posted by walker

I did a compression test on the Rangie yesterday. It has been blowing a bit of blue smoke, but mostly on over-run down hills (ie at high manifold vacuum) and my thoughts is that it is worn valve guides.

But, I thought I would test the cylinders first just to see how they are. It is a 4.6l block onto which I put my reco'd (except valve guides) 3.5 heads onto.

The results were:

Dry test – From the front :

Drivers Side –
124
130
130
130

Passenger Side -
122
110
117
120

Wet test – from the front

Drivers Side -
130
130
134
130

Passenger Side -
130
120
133
142


It seems the entire passenger side is low but how low is bad????


Also I was told you can test for worn valves/valve guides using a vacuum guage, does anyone know anything about this?

IMHB...it's not too bad.....I, like you, not really chuffed about pasenger side - esp 2nd cyl there....but they all come up OK-ish when wet.

It's been a long time, but from memory: hook up guage to full manifold [NOT ported!] vacuum......note readings (1) @ curb idle (2)@ fast idle (3) accelerate up to say 2000rpmand ....note if needle flickers rapidly[but only vry small amount], especially under deccleration...

best done under driving/under load conditions.....hook up a long hose and lead back to cabin....you get more meaningfull results.

All above is fom memory, it won't surprise me if someone corrects me - I'm just trying to help.

PS- you know that early [i.e. 3.5 pre 86?] heads didn't have valve guide seals, LR later sugested they should be retro fitted when heads were next worked on

G'day Walker,

This may be of use http://users.bigpond.net.au/ergoff/vac1.htm


HTH


LRH

and this one

http://users.bigpond.net.au/ergoff/vac2.htm

Thankyou, that is an awsome site...very helpful.


Byron, I did know pre86 heads did not have seals but I put them on when I rebuilt the motor last Christmas.

Thats a damn handy couple of pages LRH

NWs guys

Walker - let us know how you go, as I will be using these pages when I come to do my V8 in the D100.

LRH

those compressions are ok.....you may have one of the heads shaved more than the other....
all the compressions in the test are pretty close so there really isnt any problem that i can see.....

except for the back cylinder on the passenger side which jumped up the most on the wet test.....
the rings may not be 100% on that cylinder.....but its still ok.....


a problem engine would have had less than 70 on one of the cylinders....
thats when you start to worry......


keep driving lad.....its fine.....

Thankyou, that's what I wanted to hear!

I will see what the vac guages say. I plan to pul the motor out sometime next year when it gets transfered into the new project so i will put new heads on then.

The next step is to efi the motor. I was going to wait till the new project was built but I can't afford to wait anymore. I thnk my main problem is the WW Stromberg carby can't cope with the 4.6l engine. It uses too much fuel when you put your foot down but is underjetted when cruising. I upped the jets again and on the last day out got 46l/100km.

I will be getting a 3.5 efi manifold with the new truck I have bought. Does anyone have suggestions for a computer? I am going to put in the Jag injectors which were recommended.

I was told the Wolf was not really that good. I was wondering what the Megasquirt was like? I think I need something failry simple. I'm sure I will learn quickly but something which comes with base setting would be perfect.