Compression 20V Blacktop

[Adash=P]

Just got a rolla with a 20V blacktop and it seem sluggish. Checked timing, seemed alright. Checked compression, 70ish PSI across. Dropped some oil in, 90ish.

Is the compression ratio 11.1 ? Could the timing belt be out by a tooth on one of the gears?

I was expecting a pocket rocket but I've ended up with a lemon

[J0RD0]

11 to 1 yes, standard ecu?

[Adash=P]

Indeed.

Found a workshop manual on the net. Standard compression is 193psi or more and minimum 156psi.

[emp?]

yeah 70psi is rooted, maybe cam timing is way out?

[Adash=P]

Mmm...I'll check it out tomorrow morning. It felt like it went harder when the timing was heaps advanced.

[adamaw11]

Those compression figures are so low that you might have done the test wrongly?

Did you remove all the spark plugs or just one at a time?
was it cranking over fast enough?

you held the accelerator flat while cranking?

I did mine the other week, and it was 155, 160, 160, 165, and I'm thinking even thats getting a little low.

11.0 : 1

[KARNAGE]

adam when i did the compression test on mine it was 160, 165, 165, 160 and it was running perfectly so i think in practice that is normal

[Adash=P]

Those compression figures are so low that you might have done the test wrongly?

Did you remove all the spark plugs or just one at a time?
was it cranking over fast enough?

you held the accelerator flat while cranking?

I did mine the other week, and it was 155, 160, 160, 165, and I'm thinking even thats getting a little low.

11.0 : 1

Nah, it was done properly. All the sparks were taken out, the battery was good so no problems with engine cranking speed and the throttle was wide open.

What sort of millage has your motor done?

[Adash=P]

adam when i did the compression test on mine it was 160, 165, 165, 160 and it was running perfectly so i think in practice that is normal

No worries. I would think that with such a high compression ratio the results would be higer.

[allencr]

It felt like it went harder when the timing was heaps advanced.

Timing changes, ignition not cam, should make very great & significant changes in power, especially when it is done in 'heaps'. The 'It felt like' description sounds like there was barely any change at all, which would happen with a nearly dead engine but not with one that had bad ignition or cam timing.

A wild cam or off timing can lower the PSI, but no where near 70, that's about half of the lowest it should be at. The rings may be temporarily gummed up if it has had a lot of short runs & cold start ups & ignition and/or fuel problems.
Does it idle smooth & rev freely with no load?

[adamaw11]

Nah, it was done properly. All the sparks were taken out, the battery was good so no problems with engine cranking speed and the throttle was wide open.

What sort of millage has your motor done?

unknown total mileage but I guess I've done at least 10k ks on it. It was from a '98. I'm guessing its at least over the 100 000 total. Its unopened but the valve stem seals are pretty worn (blows smoke on vacuum) - it still goes as good as ever.

hows your compression tester? was it sealed into the spark-plug hold well enough?

The fact you added oil and it only came up to 90 is also pretty strange.

Is it a decompressed turbo build thats had the turbo removed?

adam when i did the compression test on mine it was 160, 165, 165, 160 and it was running perfectly so i think in practice that is normal

thats good to hear, I guess it means less excuses for rebuilding mine.

[Adash=P]

Timing changes, ignition not cam, should make very great & significant changes in power, especially when it is done in 'heaps'. The 'It felt like' description sounds like there was barely any change at all, which would happen with a nearly dead engine but not with one that had bad ignition or cam timing.

A wild cam or off timing can lower the PSI, but no where near 70, that's about half of the lowest it should be at. The rings may be temporarily gummed up if it has had a lot of short runs & cold start ups & ignition and/or fuel problems.
Does it idle smooth & rev freely with no load?

With the timing advanced it reved out quicker.

The idle is pretty high 1500rpm and it revs alright when stationary.

[Adash=P]

unknown total mileage but I guess I've done at least 10k ks on it. It was from a '98. I'm guessing its at least over the 100 000 total. Its unopened but the valve stem seals are pretty worn (blows smoke on vacuum) - it still goes as good as ever.

hows your compression tester? was it sealed into the spark-plug hold well enough?

The fact you added oil and it only came up to 90 is also pretty strange.

Is it a decompressed turbo build thats had the turbo removed?

Compression tester is an old one but high quality unit. Doubt it was once turbs, NA all the way

[Adash=P]

Alright, the cam timing was out according to the workshop manual. There a 2 grooves on the exhuast cam and the pin was in the wrong groove.

I took it all apart and put back together the way its meant to be but now it won't start. The rotor doesn't line up to the 1st cylinder instead its on the 2nd one WTF

[Adash=P]

Can someone with a BT take a photo of cam gears when the motor is at TDC?

Do ST and BT use the same timing marks? I tried going by the manual and it didn't make sense, the lobes where in the wrong place.