Re: Low Compression 1990 200TQW IA Stage I

[four.rings@mcione.com]

Forhan, Thomas wrote:
> 
> The bad news: 100/110/115/65/110, with a 25% leakdown on all five
> cylinders. Also, light oil leakage at #4 sparkplug. Oil consumption is 1qt
> per 2500 miles, no radical change over time.

Should be a lot higher on your late 200 w/ 8.4:1 CR. The #4 is really screwed.
Bentley sez compression should be 123psi to 144psi for a brand new MC
engine (my guess is that the lower value is for my single knock MC
w/compression ratio 7.6:1 and the higher value is for a late dual knock
MC w/compression ratio 8.4:1 ). Wear limit is 92psi, max delta between
the cylinders should be no more than 44psi.

You can do just the valve job but what if after you assemble the motor (with all
new head studs and EM studs/nuts!!!) the #4 does not come on par with the rest
of them? You'll need to pull the head again and do the rings.
OTOH, what if just the valve is burned on the #4.
In any event, pull the head and examine the valves/seats. Then rotate the crank
and examine the cylinder walls for scoring.

> 116000 miles total.

Just broken in.

> I bought the car used at 82K , unknown history.
> Switched to Mobil 1 and added  IA Stage I chip and spring mods, within a
> few months of buying it.

No problem here.
 
> Struggling through the archives, seems like rings are unlikely. It sounds
> like one or the other of (1) a complete valve job (2) just guides (3) just
> the guide seals.

With the 25% leakdown and such a low compression I'd suggest a complete valve
job: hot tank the head, magna-flux it, cut the valves, replace the guides/seals.
 
> I'd appreciate any and all thoughts, and I am particularly interested in
> estimates of the time needed to R+R the head. Anyone know what the flat
> rate books suggest?

Sorry, can't help you with this. I've done all the heads myself.

Igor Kessel
'89 200TQ - 18psi (TAP). Head work done this past Spring.
Some previously lobotomised fleet:
'89 Mirage
'85 5000s
'84 M-B 220
'86 Lada 2107
'84 Lada 2105