zekgb

Thanks Jeff, I appreciate it

danglerb

Calif is due for its 30 days a year of bad weather, pull the motor and sort it out. Its way too easy to buy a used motor, hope for the best and if it runs ok never put in the fixed one.

Speedtoys

Would an S4 motor be of any use to an S3?

AO

Exhaust is different, can't remember if S3 headers can bolt up to S4. 2-bolt vs. 3 bolt. But I think that's about it.

Imo000

I say pull the head and have a look before buying anything. Pay close attention to the hydraulic lifter for the exhaust port on that cylinder. This is the cheapest way to find out what you are facing.

GlenL

One of the problems with asking a question like this on this forum is that you're audience contains many ambitious mechanics of all levels of ability. If that was my engine, it'd be swinging on a hook by now. That's a shared view by many.

The problem with 928s (let's be honest, folks) is that replacement parts are horrendously expensive. If the problem is more extensive, or there are follow-on issues, you're wrenching through thousands of dollars and multiple months.

A bad valve sounds likely. Bad rings will show higher pressures and a holed piston will show lower.

Mongo

I agree with others on pulling the heads. At least you know what the motors looks like internally. You will also be able to inspect the condition of the cylinder walls for any deep scoring and scratches.

Glen makes a good point on a bad valve (exhaust maybe). However, I'm a little perplexed as to what would cause a bad valve other than a collapsed lifter, or some sort of binding.

Mongo

Going through your options in my head, I think sourcing a motor from Mark would be your best bet, and then performing maintenance on the gaskets (head gasket and anything else holding back oil & coolant). I am positive Mark compression tests those motors prior to letting them go, or even shelving them.

zekgb

Picked up a cheapie HF leakdown tester today, I guess this engine needs at least some rings as well?

1 - 20%
2 - 25%
3 - 20%
4 - 20%
5 - 25%
6 - 45% - Leaking into crankcase
7 - 30% - Leaking into crankcase
8 - 60% - Leaking into intake and exhaust

Imo000

With this new information, I would just look for a replacement engine and don't even bother fixing this one.

Mongo

I agree with IMO. Stop here and call Mark Anderson up.


I'm a little shocked that at your mileage the motor is toast. The previous owner must have drove it like he/she stole it.

FredR

Kevin,

Please excuse me for asking but are you comfortable with the leak down test procedure? Ideally this should be done with a warm motor but no idea what impact room temperature would have other than it would not explain your numbers I rather suspect.

Assuming your numbers are there or thereabouts, those numbers do not look too encouraging and confirm your suspicions about something being wrong with Number 8, yet alone the rest of the cylinders.

I posted a thread some time ago when I did my leak down test if that is of any interest/use.

Given the info available I would say your first action is to pull the motor and remove the heads and the pistons to make a further evaluation of exactly how deep/where the damage is. Only after that canyou meaningfully evaluate your options.

Regards

Fred

Speedtoys

Those are not reliable #s at the PSI it runs at.

But still, option #2 is cheapest & fastest route to a running car. #8 still needs exploratory work.

I would say 1-7 are just fine.

Mongo

Still leaning towards a stuck/floated valve.

zekgb

Very sure that I caught TDC on each cylinder and calibrated the HF tester correctly, however the tester only operates at 15 psi which in conjunction with the less than warm engine may explain the relatively high leakdown percentages across the board. After posting I got some PM feedback that this tester can also have undedected leaks at the base of the hose spark plug adapter, further skewing the results. So as Speedtoys says these results don't really tell us anything other than #8 valves aren't sealing.