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Bevlesskeg

Hi guys I’ve done a compression test on my polo. 1.3 gk engine 1984 gl.

 

it’s got a gk cam in it and gn inlet,  exhaust and I ported/polished it on a rebuild a while back. It’s been running strong and fairly reliable since rebuild but I never did the bottom end.

 

Cyl1 - 80psi

cyl2 - 90

cyl3 - 90

cyl4 - 87

 

it’s pretty lumpy on idle but revs well otherwise.

 

what’re your thoughts? I think the compression is too low. I could do a bottom end rebuild but I don’t think I can take anything off the gasket etc because it’s already only just clearing. I had to bore out a little section on each cylinder to fit the new cam.

 

 

cheers

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Would anyone be interested in a build thread of my car? I’ve done a ton of (‘innovative’, atleast I havnt seen much of it before) development work with bump steer and some things with the handling and

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dvderlm

GK cam is not very wild. With high compression GK pistons too?

 

GK wear limit is 8 bar which is 116psi.

 

GL HB-Formel-E AAK AAU HK HZ MH NU NZ RC SC 2G 3F: 7 bar =101psi

 

HH HJ GT PY oldHB: 6 bar = 87psi.

 

Is that cold, dry test?

Do you trust the compression tester?

What does a wet test show?

 

Once I had honed and re-ringed my GK in 2014 I was seeing 15bar=217psi. 

Before was as low as 3.7bar=55psi but the CR tester was a shite Silverline and a borrowed Draper read about 7.3 bar=110psi best case.

 

Re-measured in 2018 (bar)

Cold dry 14.5 16 16 15.2

Cold wet 15.1 16 16 16

Warm 14 15.2 15 14

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Bevlesskeg

this was warm with closed throttle, it wasnt my tester just an ebay jobby from a friend so i cant retest for now. I may get a good tester and try again but im not feeling too concerned as the car drives pretty well, definitely not like its got badly low compression anyway. but who knows....

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mk2tastic

How  did you do your compression tests, engine warm or cold?

 

As already mentioned, are you also using a good quality compression tester with a known good accurate gauge? 

 

A wet test following a dry one will likely tell you the state of the bottom end.

 

How I do mine:

 

Ideally, engine cold, throttle fully open, battery fully charged.

 

Dry test: crank each cylinder until gauge reaches a maximum.

 

Wet Test: squirt of engine oil thru spark plug hole, crank until gauge reaches maximum.

 

If you get a large increase in the wet test results then it’ll be wear in the bottom end, pistons/rings/bores

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Bevlesskeg

Thanks a lot for that info, I’ll buy a tester  and get in the know.

 

can u elaborate a bit more on the wet test.. how much oil is a squirt? I have 1 bottle of engine oil I carry around so what shall I do with that, pour a bit in out the cap?

 

 

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Bevlesskeg

Would anyone be interested in a build thread of my car? I’ve done a ton of (‘innovative’, atleast I havnt seen much of it before) development work with bump steer and some things with the handling and also the engine. I work on it most days and have a workshop to make weird diy parts but the car is remarkably different to drive than in stock form. 
 

I’m just interested to share and have a good discussion and learn more. 

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mk2tastic
53 minutes ago, Bevlesskeg said:

Thanks a lot for that info, I’ll buy a tester  and get in the know.

 

can u elaborate a bit more on the wet test.. how much oil is a squirt? I have 1 bottle of engine oil I carry around so what shall I do with that, pour a bit in out the cap?

 

 


A squirt as in from an oil can, which is what I use.
 

It’ll only be few ML, so yes I suppose a small amount using the cap of your oil bottle to measure would suffice, anymore and it’ll smoke like you’ve put diesel in it, once you restart the engine🙂

 

 

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dvderlm

Flexible tube on a small can ( or tube on end of a tiny funnel) or it's too easy to miss the sparkplug hole when pouring.

image.png.bb7dd0c2e0fc0988c9d6e9925f5510b6.png

I do it with clutch and gas pedal pressed to floor just so it spins i a bit faster

 

I find 6or7 revolutions enough to reach max. And i disable the electric fuel pump and ignition if 3 other plugs are fitted. Suppose you could clamp a mechanical pump's inlet pipe.

 

 

Edited by dvderlm
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steveo3002

the engine is like a pump , the throttle needs to be wide open 

 

warm engine will give a higher reading than a cold one 

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