[jvanabra]

Thought I would cross-post this to make get some more eyes/reactions.

SPG was apart for several months - failed head gasket led to a bunch of mission creep, blah blah.

Yesterday during it's first idle in months I found out the hard way I forgot to tighten the cam sprocket bolts... the engine just stalled from idle, and I found the key on the intake cam sprocket had sheered off. OMGWTF.

Replaced the cam sprockets fearing the worst, but it started up and idled great.

Today I drove it to work - about 9 miles. Generally drove well, but there was some weird hesitation at higher engine speeds as boost came up. Nothing on Tech II indicated a problem - car is T5'd.

On the way home, the hesitation was gone on the car drove fantastic.

Based on my sprocket screw up, I did a leakdown test:

#1 = 0% leakdown - 80 in, 80 held
#2 = 0% leakdown - 80 in, 80 held
#3 = 12% leakdown - 80 in, 70 held
#4 = 25% leakdown - 80 in, 60 held

In both the leaky cylinders, all loss was through the BOTTOM. Tangible airflow from the valve cover. On #4, I made the mistake of putting my finger over the hole in the valve cover which resulted in a GLOP of oil bubbling up through the dipstick. Whoops.

I have no history on this car other than it has 250,000+ miles, its original grey block, and a B212 head. The head was in CRAP condition - but is now 100% rebuilt, good as new. It does not have its original transmission - the GM tag is gone, so I don't know what it is, but it's definitely a newer gearbox with self-centering but DOES have a drain plug. That's all I know. Bottom end could be original, or could have been replaced at any point. :shrug:

I then did a compression test:

#1 = 170psi
#2 = 170psi
#3 = 165psi
#4 =160psi

Seems clear there is no valve problem, and I am wondering if maybe I have some sticky rings from the engine sitting for so long... something that might loosen up with time.

I'm gonna run the car like this til it explodes, just curious about folks' reactions.

 

[Jim Mesthene]

Run some thin synthetic oil in it for a while, then test again.
I've seen sticky rings, especially associated with sludge.

 

[jvanabra]

Makes sense to me. I've got some cheap synthetic 5w-30 in there now, which is just to clean it out a bit post work, but I will go back to 5w-40 and put a new filter in after a few more miles. Idle is very smooth, so I don't have reason to suspect a major cylinder imbalance... which is supported by the compression test. I'll check back in on it in a few hundred miles. Which will probably be mid-summer.


(Unless I can get my act together in the next two weeks & drive this ***** out to Colorado!)

 

[Jim Mesthene]

Retarded cams could do that also.
A friend claims that you get a little more top-end at the expense of a perfect idle if you advance the intake a couple of links. The converse may be true.

 

[jvanabra]

Retarded cams could do that also.
A friend claims that you get a little more top-end at the expense of a perfect idle if you advance the intake a couple of links. The converse may be true.

How could cam timing result in a leak to the sump? What am I missing?

This car actually has adjustable cam gears on it, so I can move fractions of a tooth in either direction on either cam. As soon as it successfully smogs, I'll move the intake cam about half a link forward, which IME gives a decent boost at higher engine speeds with little to no low-end repercussions. I found it a good place to be with the Super60 turbo.

http://sacsaabs.org/sacsaabs.org/misc/85spg_camgears.jpg

 

[Jim Mesthene]

I'd pay more attention to the compression than leakdown.

 

[jvanabra]

Agreed - I am moving on!