85k mile stock engine, stock turbo, i/c etc.. Installed Cottons 2.5 exhaust, 65lb injectors, tt chip setup for 24psi and alky, alky kit, hot wire, cold air kit, adjustable waste gate, 3 bar map, put boost at 20psi in small increments while monitering scanmaster, everything was xtra safe. Alky was set high, o2 volts staying in the 750-800 range, knock stayed 0.0 for all runs, boost was set below what the chip was designed for, felt strong on all pulls, slowly getting in to it in 2nd and 3rd gears, then I floored it in first, followed by a backfire thru the intake and plumes of oil smoke.. You can hear combustion in the valvecovers. Head gasket? Or worse?
Engine gurus step inside...
- Thread starter 55thunder
- Start date
83ttypecooled
Active Member
- Joined
- Sep 14, 2003
Hi,
How's the engine sound when you spin it over? Several low cylinders,maybe? I think you are right. Unfortunately correct. I am not sure why this happened, except to say that MASSIVE detonation must have occured. Cyls 3 and 6 hit me when this happened. The plug electrodes were burnt right off. I did a wet and dry compression check,under 100 psi on those two. Guess what? When I disassembled the motor,#3 and 6 pistons and rings were bruised a bit,but still fully functional. However, the cam was wiped out. Low compression fooled me, and don't let it fool you into a rebuild. These motors can take a lot of heat before they fail. So be aware that the cam can screw you bigtime!
How's the engine sound when you spin it over? Several low cylinders,maybe? I think you are right. Unfortunately correct. I am not sure why this happened, except to say that MASSIVE detonation must have occured. Cyls 3 and 6 hit me when this happened. The plug electrodes were burnt right off. I did a wet and dry compression check,under 100 psi on those two. Guess what? When I disassembled the motor,#3 and 6 pistons and rings were bruised a bit,but still fully functional. However, the cam was wiped out. Low compression fooled me, and don't let it fool you into a rebuild. These motors can take a lot of heat before they fail. So be aware that the cam can screw you bigtime!
Has the SM ever reported knock?
If not.... it's possible the knock sensor isn't working properly.
83ttypecooled
Active Member
- Joined
- Sep 14, 2003
Hi,
Personally, I would be suspicious of NO knock noise. It's too good to be true,as there is always a rattle going on.
Personally, I would be suspicious of NO knock noise. It's too good to be true,as there is always a rattle going on.
TURBOPOWERED68
David
- Joined
- Jan 31, 2006
- Joined
- Feb 18, 2006
Doesn't always take detonation to push a head gasket out.
Pull the intake and see if the head gasket pushed into the valley.
Pull the intake and see if the head gasket pushed into the valley.
Can't wait to tear into it in the a.m. Goal is to have a true 10.50 car without having to beat its brains out, should I leave the bottom as is if its ok, or freshen with piston, rings, bearings, cam etc.. adding champion heads and intake package for sure while I'm at it...
This article has been referred to before in other posts but just in case you did not read it here it is. Good reading.
Engine Basics: Detonation and Pre-Ignition by Allen W. Cline
Engine Basics: Detonation and Pre-Ignition by Allen W. Cline
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