very high comp... good engine or worn rings?

[allencr]

i just want to confirm there's nothing wrong with it... a definite answer as to why

There's nothing wrong with it unless it's having trouble running on whatever octane you're putting in it.
There is definitly a smaller combustion chamber because of carbon buildup and/or piston crown and/or head/block machining & slight increase from the over bore, and I'd definitly stay away from anyone that said it had worn rings.

The cam timing marks are only 'vaguely accurate', and are just ment to be accurate within one tooth - plus or minus 10 degrees.

[crowncustom]

Was the test done hot or cold?
Was the throttle wide open or closed?
Cheers Brett.

[Vios-GT_07]

hmm .. okay... i had a strange feeling about it when he said the rings can be worn.. but it did make sense when he said it.. anyway i went to great lengths to find a good mechanic and so far a grand has gone to him for his work and it hasn't failed me yet, some more it's reasonable.. it's not easy to find a good and reasonable mechanic here..

okay i'm pretty sure there isn't much carbon buildup in the engine, i do plan to get the injectors cleaned out and if i have enough time and money, to open up the head to check valves and clear out any carbon buildup there is.. but if it's not broken, i won't go there.

yea the compression test was always done when engine is warm, after a cruise, wait 10 mins or so, and test, with throttle wide open..

i've done the test cold once, and the results were about on average 5 psi lower than when warm..

[love ke70]

long story short,
remove cam covers,
rotate engine so that the back of a set of lobes is directly over the buckets, and measure with feeler gauges, you should be able to do 4 valves, 2 inlet and 2 exhaust at each of these steps.
record your results and rotate again so the back of the cam (opposite side to the lobe, the lobe should be running on the same angle as the valve, away from it) anywho, so the back of the cam is at another set of valves, measure these.

do this twice more and you should have all cylinders measured.

your book should have valve clearance specs in it

[Dale]

Don't jap spec engines have higher compression? Your book is probably for aus spec 4age?

Also I wouldn't always trust the harmonic balancer's TDC to be spot on, have you checked it with it off? A timing gun won't tell you if your exhaust timing is out

I wouldn't be concerned about the high compression anyway, you don't know the engine hasn't been rebuilt or what's been done to it in the past, but you do know it's got no detonation or pinging issues and that your rings are fine so why worry about high compression? Be glad!

[Vios-GT_07]

it pings on really cold mornings.. that's about as close to any problem i got..

[Dale]

Pings on a cold morning? It should ping on hot days if anything

[dan05k]

why such a long thread?
there is nothing wrong with it!
just make shure you use premium grade fuel and it will be fine.
you said it has been rebuilt, thye may of used 20V 4age pistons or a thinner head gasket.
worn rings dont make higher compression, valve clearance and/or timing will make bugger all difference too compression figures for this type of testing.
not the difference you are refering too anyway.

[clubagreenie]

My thoughts exactly.

Spend less time here, more time building a bridge to get over it. Others spend money you haven't to get better comp. Don't like it sell it as a high comp motor.

[Mr Revhead]

the 140-180psi spec you quote is for the bigport engine
ie a 9.4:1 compression engine
small ports are 10.4:1

so, you appear to have a small port in perfect working stock condiotion

enjoy it

[Vios-GT_07]

hi

thanks for the feedback..

no idea if it's been rebuilt, i was just saying maybe.. as a means of explaining the high compression

there are plans to build this motor, and i just wanted to be sure it's not a dud, and it is really a good high comp motor.. and by build i'm talking a NA build, not glorious amounts of power but just for a little bit of fun.. cams, injectors and little things like that.. and yea being on a tight budget, i just want to know where to point my money rather than get things for fun, and and have the motor blow up in my face..

thanks everyone! cheers

[DigitalPho3nix]

I never had any issues with it Norman... I am pretty sure the guy I bought it from said he hadn't touched the internals at all either.

I reckon that engine would love some good cams hey.

[Vios-GT_07]

shh

bigport cams are otw..

[Mr Revhead]

bigport cams are not worth the effort.....
in fact in the only back to back dyno test iv seen, the bigport cams lost power....

[Vios-GT_07]

thanks for the info ..

but no the bigport cams aren't going in there as it is..

still 85% confident atm coz there's still that percentage of people that reckon somethings wrong with the motor.. and i have cracked one oil cap as it is, so yea..

when the cams get done i'll just check the valve clearances and all that.. i've got the strangest luck when it comes to cars, so yea... hopefully i won't get paranoid again