Well, on my new motor I now have high left BLMS when the throttle is closed. In cell 16, I have 160L/130ishR BLMS, and BLM cells 17 & 18 show a big split, but less (L-140ish).

So, I've been doing all the typical split BLM diagnoses stuff. No exhaust leaks, vacuum leaks, or visibly arcing wires. Clean MAF. New O2s, twice. Sealed IAC passages and closed the blades progressively up to all the way, with IAC-~40. Tried various closed TPS advance settings. None of this fixed it.

Here's the kicker: I had been changing out the oil too often to notice during break-in, but now that I've left some in for a while, I found I'm using 1.5 to 2 qts every 1000 miles!!! It must be leaking internally. No puddles or external leaks. Plugs all have oil on the threads, but no major crusty buildup like I would expect with this kind of oil dissapearance, although they have been in less than 2k miles.

Compression during cranking (throttle open) is 230/230/230/240 psi for 1/3/5/7 on the left side, where the problem is. The 140 on #7 was after I put the charger on it, and it cranked a little faster, so I think that explains the oddball higher number. I didn't check the right side. I cranked 10 revs each for consistancy, even though the readings stabilized at about 6-7 revsI don't think the rings coud possibly be sealing poorly enough to cause this kind of oil consumption, especially on a fresh motor.

An intake-to-head leak would seem to explain all of the above, wouldn't it???

Can anybody think of another possibility? I hate to pull that intake again, but it looks to me like I have to.

I re-torqued the intake today, and a couple of bolts were less-than-fully tight, but LH BLMs still 160 @ idle.

 

It could be the valve guides...

 

Really? I didn't know they could leak that bad. Thanks for the suggestion, speed demon, I'll look into it. Could even ONE bad guide use oil this badly? I DID have one suprisingly tight-fitting valve guide when I took the heads apart before ever running them, to change the springs. Someone suggested lapping the guide/valve stem together until they fit like the others, so I did that. All the other guides seemed OK and I left them alone. New valvestem seals, too.

How do I diagnose bad guides? Do I just pull the cover and wiggle them? There is no visible smoke on decel, at least not that I can see in the mirrors.

More Data on BLMs:
Today was hot, so I had the A/C on. Idle split BLMs get MUCH better (L/R 123/128) with A/C on. With A/C on IAC increases from 40 to 80, and airflow goes from 9 to 12.

So, maybe the oil issue and BLM issue are not related, and this is just typical intake/cam/IAC interaction. Or, if it is an intake leak, the leak is small enough that the higher idle airflow made the leakage insignificant.

Any more opinions or similar experiences?