I had my vette dyno'd on saturday and it put down 505hp/430tq but on the last pull it started a ticking sound after they let off. It sounded like upper engine noise and it was similar to a valve train tick that I am familiar with. Unfortunately , after I pulled the valve covers, I found no valvetrain damage, the springs are still one piece and the rockers/pushrods are all tight and undamaged. However, my oil changed to milkshake.
I was thinking of pulling spark plugs next to look for a specific cylinder with a bad (wet) plug? Also since this is my first LS motor I have opened up, any particular ideas that would cause the noise? It is too high pitched for a lower-end knock. When I drove it home the 30 miles from the dyno shop, the tick went away at about 2000-2500 rpm if that matters at all?

I also suppose a compression test would not be a bad idea?

 

Sounds like a bad head gasket if you have coolant in the oil now. Either that or a cracked head, which sounds unlikely.
BTW...what engine mods do you have to put out those numbers?

 

Just a well tuned vortech supercharger on all stock motor

 

With a bigger cam more noise is normal. Also, if you have headers, that thin pipe will transit a lot more noise than a cast iron exh manifold. Cast iron is very effective at damping sound and vibration. Thin steel tube are not good at daamping sound

The ticking may be normal. If you built it right is should be right

 

The milk is a bad sign, the previous posts is probably right, blown head. Gasket

 

That sucks.

 

How many miles are on the engine? A blown head gasket can cause milky oil. Most often it will cause combustion pressure to leak into the cooling system. Do you have signs of that? Did you change the oil before you drove it home? In my opinion, the oil and filter should have been changed immediately. The engine should have been test run no load 5-10 minutes, and the oil checked for contamination. When an engine is run/driven with coolant in the crankcase, it will spin a bearing.
What did the tuner say when this happened? Did he know you had a 30 mile drive home?

 

Did you discover the milkshake before you left or after you got home?

How bad of a milk shake?
You can run it and watch for bubbles or pressure in the coolant tank.

Ron

 

Just rolled over 32k miles on motor. I checked the oil at the shop and it was fine. We assumed the ticking was valvetrain as it centered somewhere over on the drivers side. The tuner, who I worked with and is well respected here in cali, called me out saying there was a tick, so I went outside and heard it and we decided to call it done and take it home after inspection. The oil isnt terribly soaked with coolant but its very noticable. I dont think any bearing damage would have occured. The ticking never got worse or better.

Like I said above, its very noticable with the dipstick pulled but there is also much oil that is still 'clear' on the stick, so its not like the coolant completely gushed into the oil. The oil was clear before I drove it home.

I dont really plan to start the motor any more since I have the covers off already. I will stick my compression tester on the motor and do some cranking to see how that responds.

Any more input is greatly appreciated.

I believe now that the ticking sound was an exhaust leak. Probably blew the gasket between the cylinder and the exhaust manifold, allowing exhaust gasses to escape to atmosphere. This explains the different pitch in noise with rpm and load on the engine.

 

On other news, I pulled the plugs and cylinder #7 looked grimey and wet, no doubt this is the cylinder with the head gasket breach.
I went ahead and skipped all the tests and started tearing down the motor. I got the intake off today along with the valvetrain and loosened all the exhaust manifold bolts.

I have the vortech supercharger and I need to look at the instructions on how this dumb bracket is best removed from the drivers side head.

Lastly, Since the passenger plugs looked all normal, should I bother switching out that head gasket as well or is this drivers side head gasket blowing out potentially a fluke? If I have to pull both heads I might as well look at swapping to 317 heads with LS9 gaskets, eh? If I can just get away safely with removing and replacing the drivers side head gasket only, that will save me a lot of time and a bit of money, but mostly time.

 

If your not to deep into it yet and have access to a compressor, you can remove the Schrader valve from a compression tester and fill the cylinder with air. With the rockers off, you should see bubbles in the expansion tank to confirm the breech.
Plan b would be put a cooling system pressure tester on the expansion tank. Pump it to 16 psi and bump the engine over and see if it pukes coolant from that spark plug hole. Better yet, remove all plugs to see if any other cylinders are affected. The same applies to the 1st test.
How much boost were you pumping threw the motor? I believe 7-8 psi on a stock engine is common without problems. How much timing under boost? Air fuel ratio should be graphed across the bottom of the Dyno sheet.
What is the overall condition of the cooling system? Any signs of rust or corrosion?
Is the shop you used known for tuning boosted engines?

 

Stock vortech psi on the motor, I think 6.5-7 is what vortech claims. Not sure what the timing was at after the tune, I will have to ask my tuner. AFR was 11:1 all the way across the dyno sheet. Cooling system looks perfectly fine. The shop I used was only used for their dyno and my Tuner works out of their shop. The tuner is well known and respected. I do not blame him.

 

I'm not trying to place blame on anyone. It's always good to know why any part failed. Boosted engines want and need different fuel and timing than NA engines to make safe reliable power.

 

Prob best to change both gaskets as long as you are in that deep. Either the std LS1 MLS or the LS9 MLS gaskets.
Guys like the latter for big boost.

If the budget allows, head studs too. Not trying to spend your money for you. :-)

8 psi is just getting warmed up!

Ron

 

I think I am going for a stock rebuild and have the tune looked over. My tuner said the afr was perfect. The timing showed no detonation but the max retard was moved from -10 to -3 degrees.

He also mentioned that it appears my duty cycle was at 100% and my MAF was maxed as well.

Any input on this information? Could the maxed duty cycle and maxed maf give false information and somehow cause detonation without knock sensors picking it up?




It appears my intake is bent as well. I removed the spring and spinning the valve by hand I can see a slight wobble to it against the valve seat.

The drill method looked fine on the intake valve. The exhaust valve had an obvious wobble to the naked eye and even more so on the drill.

Both will get replaced as well.