Guest47904

Too high for me. Especially on a NEW set of heads. Every published document I ever read said you should not be over 10% with anything close to new. Can't comment on the fact that #2 was higher than 15% other than it may not be from ex. valve.

So what happened when you listened to the tail pipe on the side you were testing?

Remember, you will hear air out the tail pipe with ex. valve problems. Air out the intake with in. valve problems and air out the oil fill cap with bad rings. BUT you must couple this with the readings you got. If you hear air but the gage says 8%, no problem. But if the gage reads 17% and you hear air. Ding ding ding we have a winner.

I want to say that in the case of the #4 & 6 your valves were probably not seated properly and are leaking slightly. BUT again, I want you to listen to the tail pipe for air to be sure your problem is the ex valves on those 2 cylinders.

There are those who simply install valves but do NOT lap them in. I always lap valves in. Just something to consider.


You're almost there buddy. Keep going.

ericcer

The puzzling thing about all of this is that the problem existed with the old engine too. I have had 3 different machine shops do the heads. The first was the well known CNC Cylinder Heads which here locally.

I know we have just got deal with the present right now to see where it leads us. Hopefully it is just the heads and not the rings.

Thanks for the help.

ericcer

I did a better job this time finding the sweet spot for valve closure. Again interesting...

#2 indicated 10%, air escaping through oil filler cap
#4 indicated 12%, I hear bubbling from the radiator cap
#6 indicated 12%, air escaping through oil filler cap
#8 indicated 16%, air escaping through oil filler cap

I hope I don't have a cracked block because the head gaskets have about 1000 miles on them and the heads were resurfaced. I would not be surprised if the engine shop did not check for that.

Guest47904

Your fine with ring quality. You will always hear air at the oil fill cap. Stop worrying about that.

As far as hearing bubbles at the radiator cap. Don't just go by ear, look to see if there are bubbles.

So your problem isn't valve closure unless you have a problem with lobe timing on just 2 valves. Obviously unlikely.

So now it's time to go back to the drawing board on the glowing problem. And if that weren't enough, now you have to figure out if your leaking between the cylinder and the water jacket. Obvious next step is to pump up the radiator and see if it holds.

ericcer

I might be able to get 1 and 7 lower if I tried a few times more.

#1 indicated 15%, air escaping through crankcase
#3 indicated 12%, air escaping through crankcase
#5 indicated 13%, air escaping through crankcase
#7 indicated 16%, air escaping through crankcase

Mystery still remains... This is basically what I have been running into for a long time. I try something and it leads nowhere. No reason for glowing headers on those 5, 2 and 4 cylinders. I did discover #4 leaking gases into the coolant and I did see the bubbles today doing a retest. Fortunately the passenger side head is the easy one to replace a head gasket and hopefully that is all it is.

Do you see a need to pressurize the radiator for a test?

Guest47904

No, no need to pump up the radiator. I'm just **** that way in that I test, test, test every which way to sunday before I tear into anything. But I do have the tools so it's easy.

I would be suspect of something causing the head gasket to go since you don't have a lot of miles on the engine. Could be the heating(glowing) problem led to the gasket issue but I would check several things including deck flatness while you're there.

BTW, just FYI. When you do the leakdown test, you want the piston at TDC.

I also found out something interesting while hunting for a misfiring cylinder on Saturday. The way I do it is let the engine cool. Start er up and measure header pipe temperature with an IR Thermometer. What I found was that the header temp will go ballistic and then settle down lower. I didn't check to see if it lowered after it went into CL but that's the most reasonable explanation.

Point is, it seems as though when it's running rich, as in open loop, it runs much hotter at the exhaust. I know you checked the AFR before but that is for an entire bank of cylinders. Is it possible just the cylinders in question are running richer than normal? I know you swapped injectors. Is it possible the injector pulse for those cylinders is goofed up? I know, not likely.

Got to get the problem you know with the head gasket fixed before going on to anything else first though.

Good luck. Better you than me. It's cold here.

ericcer

I have a IR gun and those glowing cylinders have always been hotter. I will be taking most of the engine apart because of leaks the engine shop cannot fix (long story). I suppose sometime in January I will have it back assembled to continue hunting down the mystery. My feeling is that the injector signal to those cylinders is somehow getting messed up and I have heard that that can happen with a bad PCM. However, the condition exists with both of my PCMs. I had a shop with an electronic engine analizer check out the car and they found nothing. I assume that equipment can verify that the injectors and signal are OK.

I think I may try a 95 PCM from a friend and let him give it a try on the tuning to see what happens. He tunes Impalas and I don't know if those PCMs with work with mine. I know that the CCM (specific to Corvettes) won't work. A mechanic friend says the 96 PCMs are tough to tune.

ericcer

Next, I will swap out the injector wires at the PCM to see if the problem follows. I think there is enough wire length on a pair of injectors connectors to get away with the test.