Late night romp = motor missing please help

[GNDriven]

I went street racing this weekend on a freshly built 109. At the end of a race with a LS1 Cadillac, NOS nasty, I lifted the pedal and the car popped through the exhaust two loud times. Missing badly and not revving past 2500 rpm I limped it home, but I did pull the Caddy. I immediately thought it was a head gasket, but I am not convinced. I replaced all spark plugs and the o2 sensor. It idles well, but when I raise the rpm to about 2000 it starts shaking and shuddering, it is a rocking motion like a rev limiter. I am running a GEN2 and have a LS-1 MAF. I also have a power logger which I can view sensors. The engine light is not on. I am not sure if it is electronic related or in the valve train. Tomorrow I am taking the valve covers off and checking for a broken spring. It has the Fullthrottle roller cam kit. I would appreciate advice on some things I can check that would help to rule out possibilities. I do not have the funds to start replacing items.

I am guessing it would be good to start with electronics, because I do not want to spend precious hours tearing the motor apart just to find nothing and the problem be in the electronics. I can do a cylinder pressure check to let me know if it is a head gasket or a burnt valve right ? If that reveals no indication what could I focus on? Also, could I have blown off a vacuum line will that make one shake and refuse to rev. Thanks

 

[TurboBuRick]

Any recordings?

Post a log.

 

[49-blues]

Old maf?

 

[GNDriven]

OK I can get a log tonight of me revving the motor until it starts sputtering.

I have not ruled out the MAF, but an event happened that took something out. I am thinking this way over... that some electronics went bad at the instance of racing it.

 

[83ttypecooled]

runs bad

Hi,
I am hoping you have an fuel or ignition problem,as the symptoms don't seem to be indicative of head gasket failure.Mechanically, I guess cam timing should also be checked,but even the stock chains don't tend to jump until the very end of cam sprocket lifetime,and I'm pretty sure you aren't running a stock setup.
Just as information, I have been using shop air to check for blown head gaskets and cracked castings.So far, this seems to be a pretty good indicator of a problem.My method pressurizes the cylinder with shop air pressure,and is non invasive, to use a medical term. Here's how I do it:
* Be sure the cooling system is FULL.
* Remove the radiator cap.
* Remove the sparkplugs.
* Using the hose from a compression gauge with a quick connect and multiple accessory hoses, remove the schrader valve from the applicable hose.
* Install the hose in cyl.#1, connect shop air to hose, and, using a breaker bar on the alternator pulley nut, bring the cylinder to tdc compression stroke while observing the filler neck of the radiator.
* Bubbles are what you are looking for. A really bad problem will spout a geyser, so wear safety glasses, or stand aside.
* Repeat the process with each cylinder, following the engine's firing order of 165432,to save rotating time.

This process has worked pretty well for me. Again, this is pretty much just info, but thought I would share it, as a lot of had gaskets fail when hard pressed, and you were apparently pressing it!
Good luck with your problem, hope it's something simple.

 

[johnnyttype]

do u have a cat. converter on the car still, could be clogged? it kinda sounds like an ignition problem to me, like a bad ign. module or coil? what do u guys think? i was just tryin to think of things that would affect how high an engine will rev.

 

[jasjamz]

Cam sensor should be checked. My tab that aligns the window on the shaft sheared off and simulated a rev limiter. Would idle and go into boost! but 2000-3000rpm did that rev limiter shaking thing. So if all else fails try this.

 

[Junior Samples]

Diagnostic Vacuum gauge will eliminate most head scratching