Dyno results, tuning help needed

[manoa matt]

There is a pretty good thread over on Turbo124.com about wide band O2 sensors. I may pick up one too as I'll be going to duals in the near future. A Gunnison's color tune kit will also let you see whats going on, but you can't drive around with it like a O2 sensor, only for driveway tuning through the rev range, which does not factor in engine load.

[baltobernie]

Exactly. Under very light load at 2,500 RPM, Boogiedude might see 11:1 with a properly-tuned Weber. Not at all ideal, but because his engine is producing very little vacuum due to the big cams, he'd be running rich under those conditions. With a quarter-inch of throttle pedal, that ratio could instantly change to 13:1

If he tuned to optimum under light or no load, the engine could "flash lean" beyond 15:1 under part throttle, high load conditions. Mine did that on ordinary, easy upshifts ... for that split-second at the completion of the shift. Also demonstrated it with a "miss".

If only there were a way to take the output of the O2 sensor and have it constantly adjust the fuel delivery quantity and timing, maybe even adjust the spark event ... wow, wouldn't that be terrific?!

[majicwrench]

Looking at an O2 sensor reading while your shifting "that split second at the completion of the shift" is not giving you any information that should be used for carb adjustment.
Keith

Oh, and that is exactly what modern computers do...adjust everything based on input. And they do it wonderfully

[So Cal Mark]

"modern computers"..... well perhaps with FI but if you can remember the feedback carbs of the 80s and their ecms, they were pretty terrible with major driveability troubles

[majicwrench]

Oh gosh yes I remember. I worked on thousands of those. But for the most part, if everything was set to specs, and all the pieces were there and functioning, they ran OK. The biggest issue with those----they were adjustable, and everybody thought they could "adjust them".
But even carbed, you could pull the PCV hose off to create a huge vacuum leak on a 84 chevy, and the ECM would compensate, richen the mixture, and bring the idle down. Pretty impressive stuff back then.
Keith

[boogiedude]

Well boys and girls, I just blew another head gasket

Currently on the side of the highway waiting for my tow truck.

I was heading up over the mountain like I do everyday to get to work, and as I was passing through the tunnel at the top I started to smell something hot. I glanced down at my gauges and noticed the temperature at about 3/4 and immediately got out of gear and let the car coast hoping the cool air and lack of engine load would bring the temp down. It didn't. The gauge stayed pretty steadily at 3/4 and when I looked out back to check for smoke I got fantastic view of white smoke! I immediately pulled over and popped the hood and found coolant EVERYWHERE. All the hoses appear fine so I don't believe I busted a hose. The overflow was filled almost to the very top and when I activated the pressure relief valve on my radiator cap, the overflow began shooting coolant out of the sides of the cap with a LOT of force, leading me to believe the system was somehow way over pressurized. When I finally got the cap off, I found that the coolant was near half empty. Gave it a few minutes of sitting and decided to try to crank the engine over and it appears to be hydrolocked. Starter can't get the motor to budge.

More details when I get home and can get a good look at everything....

[So Cal Mark]

that's pretty horrible news

[manoa matt]

This quote was taken from SteveC in the headgasket thread in the engine and tuning section, it sounds like what you just experienced:

"A blown headgasket ... well generally oil and water don't mix with a blown headgasket on a twincam... usually it's just combustion pressure into the cooling system when running, and coolant into the combustion chamber when shut down."

Are you still driving around with that 45DCOE?

[baltobernie]

Tough break, boogiedude. I hope you suffered no permanent damage.

I've reviewed your post and was wondering ... what cylinder psi are (were) you reading?

[boogiedude]

Tough break, boogiedude. I hope you suffered no permanent damage.

I've reviewed your post and was wondering ... what cylinder psi are (were) you reading?

I've never done a compression test, I'm definitely going to after this is put back together....again

Pulled the plugs and checked down the holes to see which cylinders had failed and had coolant in them. First thing i noticed that all plugs were whiteish/dirty. Not clean like I would have expected from burning coolant... I only found coolant in cylinder 1 through the spark plug and when I loosened the head bolts coolant came waterfalling down the entire exhaust side of the block and ended up filling all four cylinders. I got the head off the car and what I found is a bit confusing... The pistons and combustion chambers are blackened which seems to indicate that I'm running rich(which I was already aware of) but the head gasket has some blackened areas that I'm assuming are from detonation? Also note that cylinder 1 is dramatically cleaner than the other 3(See pics) There is also some damage to an area of the firing ring near cylinder 1 which appears to have caused the failure(hard to see in the picture)

If I'm running rich enough to deposit this much carbon over the course of a month or so, how could I also be detonating? I was under the impression detonation was caused by a lean condition?


Firing rings cylinder 1&2

WP_000439 by boogiedude, on Flickr

Firing rings 3&4

WP_000442 by boogiedude, on Flickr


Block deck

WP_000454 by boogiedude, on Flickr


Head surface

WP_000453 by boogiedude, on Flickr

Full gasket, head mating surface

WP_000443 by boogiedude, on Flickr

Full gasket, block side

WP_000444 by boogiedude, on Flickr

There are giganto versions on my flick site, feel free to check them for better views, also individual shots of each cylinder

[131]

That gasket was never going to last, none of it has adhered to the block or the head properly. I've got one similar I bought years ago, no crush washers around the oil transfer holes, it was sealed in plastic, no brand name. I refused to use it and bought a good gasket from another vendor. If you're not going to service the head, clean the block and head surfaces scrupulously, use a quality gasket, torque it properly, I always retorque after it's cooled from the first start, regardless if it's a non-retorque gasket. The biggest problem with bolting the head straight back on is oil dripping out of the oil galleries and contaminating the gasket mating surfaces.

[boogiedude]

That gasket was never going to last, none of it has adhered to the block or the head properly. I've got one similar I bought years ago, no crush washers around the oil transfer holes, it was sealed in plastic, no brand name. I refused to use it and bought a good gasket from another vendor. If you're not going to service the head, clean the block and head surfaces scrupulously, use a quality gasket, torque it properly, I always retorque after it's cooled from the first start, regardless if it's a non-retorque gasket. The biggest problem with bolting the head straight back on is oil dripping out of the oil galleries and contaminating the gasket mating surfaces.

what do you mean by adhered properly? if you sticking to the point that it doesn't separate without leaving chunks of gasket behind, the entire block deck has gaket still stuck to it.

And I did re-torque the bolts after the first few heat cycles.

I'm going to have the flatness checked tomorrow and then clean the chamber/pistons/valve surfaces

[131]

Didn't notice the bits out of the gasket for the block side, but the head side appears to have left nothing behind, I've never pulled one off that clean.

[So Cal Mark]

modern gaskets are graphite coated to allow for expansion and contraction between the block and head. They're not supposed to stick, otherwise the scrubbing action of the aluminum head will tear them apart

[majicwrench]

Dotto what Mark said. Block and head expand at diff rates, gasket has to allow some slide. Is not supposed to stick. And use no sealer.
Lean does not cause detonation, although rich can calm it a bit, just due to the cooling effect of too much fuel.
Really no need to clean the piston surfaces, they are gonna look like that right away again anyway.

And cranking compression is not going to tell you much of anything. If you have wild enough cams, the cranking compression is going to be a bit low regardless of the compression ratio.
Keith