uh-oh... compression results

[DavidT]

on a COLD engine and only the front bank I got:
1: 40 psi
2: 185 psi
3: 60 psi
Is this because of a cold engine. or do I have some major problems?
Supposedly when I bought the car 2 years ago ( BUT before 18 passes at the track )
all 6 cylinders checked out right at 175 psi. Supposedly.

 

[MotoArts]

EEEeee, yaaah! Something's definately wrong. Bad sealing in spark plug hole to the compression gauge, maybe? I've never seen an engine run with 40/60 psi in 2 cylinders, at least not one that wasn't toatlly clapped out. That sucker should've been bucking like mad at idle. My '82 Suburban has just short of 300K, never been apart for any engine work (6 trannies though...). It runs rough, but it runs.

Cold cylinders won't make that difference (40/185). Dump some oil (teaspoon or so, not too much) in the weak cylinders and try again. If the compression rises a lot, look towards a piston ring sealing problem. If it doesn't, it usually points to bad valve sealing (bent/bad seats/sticking stems in guides). Could be incorrect valve timing also, but the 185 cylinder kinda rules that out.

 

[DavidT]

well it runs and idles smooth as silk.
The only problems are:
1. missing around 25-35 hp
2. oil consumption (1 quart every 300 miles (without Lucas ) and blowing lotsa smoke out the tailpipes at high rpms.

 

[MotoArts]

That's a (un)healthy oil diet. eek!
Make sure ALL 6 spark plugs are out, not just the front 3. Redo test dry first, then do the oil trick. Compare readings.

High RPM smoke usually means rings. Smoke on start up is usually valve seals/guides. The HP loss is no doubt from one or all of these:
1) lack of compression
2) oil fouled converters and O2 sensors (guaranteed)
3) cruddy exhaust valves (and their seats)
4) cruddy PCV system

Pete

<small>[ November 22, 2003, 08:04 PM: Message edited by: MotoArts ]</small>