Where did you happen to find replacement parts cheap? I could use some myself as you already know.

 

True.... unlesssss I happen to work at an engine building shop that happens to have a $35,000 CNC machine

 

Dammm so lower than 2.7" is unsafe i guess. Can you list all the mods you had? Wat exactly was wrong wit the motor?

 

hmmmm

 

Nice vid, very fast cobalt. My best friend just bought an 06 black SS and we plan to start modding it really soon. Hes got some money to throw around and wants to make it faster than my SRT but watching this video will scare the crap out of him. How common is it for these engines to blow, any mods to really stay away from for reliabilitys sake?

 

It seems to be a problem with the heavily modded cars. The ringlands don't care for the boost of the 2.6" and smaller pulleys. Upgrading internals seem to be the only solution.

 

Just gotta keep the pressure down as low as you can. Anything you can do to increase the flow rate of the engine so it doesn't build up as much PSI in the manifold will both increase your power and reduce the stress on your engine.

 

well sometimes a 2.7" too, tityrous thats on here, blew his motor running a 2.7.

 

Damn too many blown engine!!!

 

wouldnt a tune limiting the engine to 20 psi fix this problem??? It seems to me 21+ psi is the breaking point of our engines. Not to mention, I think havine the SC ported is a bad idea because it allows even more air into the engine, creating greater psi build.

I full on exhaust wil help lower the PSI.

 

I'm runnin 20 psi with a pacesetter header and full 3" catless exhaust.

 

i think both guys that ran tweve's had forged pistons

 

Rob was on stock internals with a 12.8xx.

 

Yea, but Rob is also a tuning god. He did a lot of the initial work that was used for most LSJ tunes now'a'days.

Just something for everyone to think about. With the LSJ and a roots supercharger (like the M62), pushing anything past 18~18.5psi is bad. Roots types all have a very sharp downhill plunge about that point. Plus, if your hitting that high of boost, your feeding your engine far more air than it can use.

So when you get to this point, start thinking of valve work, porting, cams, and anything else that will help air flow through your engine better. If you can, you want to get your PSI down to 15 or lower. Remember, heat produced and SC efficiency loss is directly tied to your manifolds internal psi. I don't have a efficiency map for the M62 handy, since I can't pull one up here at work, but you want to find a high S/C RPM cross linked to PSI point where efficiency is high.

Roots Efficiency map

For any given roots blower running under given conditions, a single point will fall on the map. This point will rise with increasing boost and will move to the right with increasing blower speed. It can be seen that at moderate speed and low boost the efficiency can be over 90%. This is the area in which roots blowers were originally intended to operate and they are very good at it.

Boost is given in terms of pressure ratio which is the ratio of absolute air pressure before the blower to the absolute air pressure after compression by the blower. If no boost is present the pressure ratio will be 1.0 (meaning 1:1) as the outlet pressure equals the inlet pressure. 15 psi boost is marked for reference (slightly above a pressure ratio of 2.0 compared to atmospheric pressure). At 15 psi boost Roots blowers hover between 50% to 58%. Replacing a smaller blower with a larger blower moves the point to the left. In most cases, as the map shows, this will moves it into higher efficiency areas on the left as the smaller blower likely will have been running fast on the right of the chart. Usually, using a larger blower and running it slower to achieve the same boost will give an increase in compressor efficiency.

The volumetric efficiency of the roots type blower is very good. Usually staying above 90% at all but the lowest blower speeds. Because of this, even a blower running at low efficiency will still mechanically deliver the intended volume of air to the engine but that air will be hotter. In drag racing applications where large volumes of fuel are injected with that hot air, vaporizing the fuel absorbs the heat. This functions as a kind of liquid after cooler system.

 

yeah I really don't think the M62 likes to go much above 15 psi... but I"ve also been running a 2.55 pulley for a few thousand miles now with no issues at all. But I am building up a spare motor for when the inevitable happens. but new motor will have a CNC head and forged pistons. Still waiting for my head to get back and once thats in.... I"ll ba able to finish the other motor, than its time to push the stocker to destruction. MMMMM nitrous..lol