Ever see this issue with Cometic head gaskets??

[Chuck Leeper]

Is that the aftermarket feedback system that uses the GM flex fuel sender to tell the ECU what % of alky is in the fuel?
I've heard of it but never saw one. Who makes it? How does it work in our application?
TIMINATOR

Not sure on this one. I saw it posted on a forum and copied the pic.
AIRC, it was on LS1 tech.
That's the GM sensor.
It will go in the return line. AIRC, Powerlogger and many of the aftermkt ecms will have the ability to log such info.
Here's one such discussion.

Using the GM flex fuel sensor on an Fbody - LS1TECH - Camaro and Firebird Forum Discussion

PCM Diagnostics & Tuning - Using the GM flex fuel sensor on an Fbody - So when i stumbled across this: http://forums.corvetteforum.com/c6-tech-performance/3266340-flex-fuel-a-complete-guide-to-adding-it-to-your-c6.html It got me thinking about how to make this work in an Fbody. I know that our...

ls1tech.com

 

[Pronto]

Very common to use the GM flex fuel sensor for aftermarket ecu's. They seem to work just fine.

 

[Mr.Spool]

GM Chuck, Dowel pins are in block. I took the angle pic so you can zoom in and see the broken seam , if I take a pic from top you see nothing due how small the cut is. Also, I have 5 dyno pulls and about 500 miles on this E85 setup, I am surprised how much carbon is on the piston tops and how different they look from one another.

That's a problem.
And it's not the fuel alky percentage.
As suggested
The heads and block need to be prepared for cometics gaskets.
As the cylinder pressure rises you quickly find out how good the engine builder,fuel system,tuner are and we are all human.
I would pull the block and have it checked and I would look at the ignition system,fresh wires,and the type of plug you are using.
If 1 cylinder loads up with fuel its game over.
If 1 cylinder goes lean it creates hot spots in the piston and will pre ignite.
Egts in each cylinder would show this and you may want to consider doing that untill you find the smoking gun.
Cold and hot compression tests and leakdown will be your best friend especially after dyno or any kind of tuning session.

 

[gnfanatic]

I purchased the shortblock already assembled, they probably did not clean up the deck for a cometic gasket which is my fault for not finding out. Otto has been tuning my car's forever, it made 636 to the wheels. My compression on all cylinders was only 125 cold, I will do it again once I out everything back together. Why did e85 turn my oil brown?

 

[TIMINATOR]

If block and heads are milled with CBN cutters, the surfaces look almost like chrome, and trying to scratch with a fingernail, will feel like chrome, perfectly smooth. No texture, scratches, roughness or apparent machine marks. Also make sure the shop has BHJ fixtures to make sure the decks are perfectly 90 degrees to each other, 45 degrees to the cam/crank centerline, and exactly the same height. The line hone must be DONE FIRST, or verified to provide the correct datum points for the BHJ fixture.
At this HP level, nothing else is acceptable, or you will be doing it again.
Oh yeah, you are... Sorry
Now you KNOW how to do everything correctly, as per the folks that have gone before you.
I tried to nurse my new to me car with the new motor for a while while I accumulated the parts to do it correctly.
Mine lasted under 15 street miles at 11 lbs. boost. I own a perf. machine shop and know better, but I hoped I could get away with it. I didn't either.
I feel your pain.
TIMINATOR

 

[TIMINATOR]

Look near the top of the pic where the cut trails off, and you can see the smoothness of the CBN cut and the rougher texture of the old broached previous cut. Also notice how far off the deck was from the new BHJ fixtured cut. This is on my motor, and it took, as I remember about .014" to get the decks flat and equal in height to each other.
I have seen factory decks off as far as .019" front to back, and .034" from one deck to the other deck! On that engine, the calculated compression ratio was around .5 different, 9.2 to 9.7! on a 440 MOPAR, 6 pak engine, and you would have thought the factory would do better on a "performance" engine!
Without professional machinework, you have dick! JMHO
TIMINATOR

 

[Mr.Spool]

I purchased the shortblock already assembled, they probably did not clean up the deck for a cometic gasket which is my fault for not finding out. Otto has been tuning my car's forever, it made 636 to the wheels. My compression on all cylinders was only 125 cold, I will do it again once I out everything back together. Why did e85 turn my oil brown?

Why do you think it did?
You could always send the oil out to see what's going on.
Also I would leak it down cold and hot

 

[1KWIKSIX]

Why do you think it did?
You could always send the oil out to see what's going on.
Also I would leak it down cold and hot

X2
I bet A hot engine compression test will yield significantly higher pressure readings

 

[gnfanatic]

Guys btw, the it has a 224/224 cam that is a "custom Grind" with 4 degrees adv built in. I am looking to buy new valve springs since the heads are apart. Any recommendations?

 

[BEATAV8]

Guys btw, the it has a 224/224 cam that is a "custom Grind" with 4 degrees adv built in. I am looking to buy new valve springs since the heads are apart. Any recommendations?

Try to find something that can get you around 200 seat with a 420-440 rate. For me that’s been a pac 1222X. Beehives would be a different story.

 

[TIMINATOR]

What spark plugs and gap? Black on the pistons could mean yer blowing the spark out at high cylinder pressures/load. How old are the wires?
Check everything before reassembly. You have several issues going on here, do your best to find them all.
With the hack job build on my ride I kept finding things it seems like forever. I went over every single part and checked all of the machinework too. When finished, there was not a single part not left remachined. And many parts replaced....
Mine was a fresh build too.
TIMINATOR

 

[gnfanatic]

Autolite 103 gapped at .028

 

[gnfanatic]

I have a distributor setup and has custom wires made years ago. Will you get accurate results if you ohm them to see if they are still good??

 

[TIMINATOR]

Since I am unfamiliar with autolite plugs, and they don't use a straightforward heat range numbering system as most others use, are the 103s a projected nose? How hot, like a stock plug?
Colder?
How much?
.028 seems big. Depending on the ign box.
I had thought about going to a distributor system myself.
Post a plug pic, from the side and straight down on the insulator so we can see what u have.
TIMINATOR

 

[TIMINATOR]

Spiral Core wires run about 40 ohms per foot of length. What brand and type wires? Carbon cores can run 1000 ohms per foot.
TIMINATOR

 

[gnfanatic]

 

[gnfanatic]

 

[TIMINATOR]

PROJECTED NOSE PLUGS! WITH A TURBO? AAAAAARRRRRGGGGHHHHH!
TIMINATOR

 

[gnfanatic]

??

 

[Chuck Leeper]

Back off on the Never Seize. Way too much on those threads.
And what Tim said about the projected tip plugs. Too far into the chamber.