Geek,
Thats basically the problem, it has LOTS of engine mods. From boring to porting to the edlebrock throttlebody to proms, name it, its been upgraded or altered....Even the big edlebrock TB was polished inside. I left the bottom end pretty much stock except for the balancing of the rotating assy.
I'm having to un-do things until it gets to an acceptable level and returning temporarily to a semi-stock form. It still runs great, But I can tell that throttle response is more sluggish, and the power-band is a bit flatter with the removal of some mods.
Yeah, its running rich somehow, somewhere. I have managed to isloate the #7 cyl as "dirty" and suspect it as part of the problem. Oil or fuel is the big question.:confused.
I now suspect the fuel after compression testing cylinders today and finding them ALL within 2 lbs of each other. #5 & 7 were exactly the same. #1 was maybe a lb or 2 lower. Pressure calculations show 10.2:1...almost exactly what it was estimated to be when built.
As far as the #7 cyl is concerned, That injector might be damaged or slow to close when pulsed. Something is getting that spark-plug dirty and it ain't oil from rings. A valve seal maybe, but thats a long shot since no others are leaking.
Yesterdays fuel pressure leak down test had good results with 18 lbs present over 2 hrs after charging system to over 40 and allowing it to bleed down on its own. Started at over 40, lost much less than 1 lb per minute until it got down to 20...then sat there forever. Still had fuel spray several hrs later when pulling the test gauge off. Still, something is not right in #7....
If the #7 injector nozzle is damaged that would explain the brown spark plug. Again, all 8 inj solenoids check out at 16.9 or 17 ohm.
Today I made a BUNCH of calls looking for someone that had the correct equipment to run a full dianostic on the OBD-1 and engine. No such luck. I'll talk to a couple vette shops tomorrow about that. Everyone else has gone to the simple OBD-2 scan equipment around here and traded in their scopes and gas analyzers yrs ago when the state initiated smog inspections. Lots of places can do a scan, but all they're doing is running the DTC's. If there are none stored, they can;t tell me anymore than my flash codes will.
Next step is to test the CAT for function. I almost bought a temp scanner that would handle 700 degrees...but for the money and the fact that I'd use it once and forget that I owned it, I decided to pass. I'll pay someone else to check inlet vs outlet temps on the cat to see if its dead or not. It was a cheap one, and more than one good wrench operator tells me that cats CAN die without plugging.
My nOX levels were very low on both test. If memory serves me, that indicates low combustion temps, does it not? If that is the case, could a mild EGR leak be cooling the combustion too much to get a good clean burn? 7 of 8 cyls have plugs that read perfect, so I'm not leaning toward an EGR issue.
I guess I can pull the plenum and clean the EGR ports too. Check the EGR valve and being sure. Its not like I have to drive to Brazil on Thursday...I'm still trying to comprehend "retirement" and actually having the time to do things. I still feel pressured on weekends to get it done before Monday....old habit.
I also disconnected the o2 sensor and ran it intentionally to see what happened....the ECM did exactly what it should, doing nothing until things were hot enough, and run for the required 2 minutes then it set the code. I'll still replace the o2 sensor as soon as I can get it on a lift where the 4 ft cheater can be applied.
I am curious about the AIR management valves...the AIR sys muffler seems to make a lot of noise when the engine is at 210+ degrees. That tells me that the air is being wasted and not injected into the CAT or manifold fittings. I need to re-read that chaptor on the valves and testing.
Anyone have any thoughts on this latest info? If I can find a real scan I'll get it and post the results, but like I was saying, most places simply don't have the software or the equip to look at an 80's model anything. The vette shops all have a waiting line, but it might come down to having to drop it off for a couple days in order to get some answers.
ad
. Close to E85 strength. That will heat up the burn, lower the HC's, and raise the NOx's. You need to advance timing a few degrees too to heat up combustion. That will raise NOx's, but you had lots of room to spare in your first scan...
