Engine mysteriously died, need suggestions please
The engine in my car has been rock solid reliable up to this point, with the exception of minor tuning issues, and only has 20,000 kms on it (about 12,000 miles). Yesterday morning I was driving into town on the highway and after about ten minutes of cruising I instantly lost power to the engine, almost as though it was shut off. There was no prior power loss, irregular operation, or any kind of warning that it was about to croak. Once I coasted to the side of the road, I tried to get it started again but it was completely dead. After getting it towed home, I tried a bunch of things to figure out what was wrong with it but I'm completely stumped. Here's what I tried so far:
- I made sure there was fuel being delivered to the engine, and I've determined that there is nothing wrong with the fuel system. I can pump fuel out of the carb with the throttle, I can smell raw fuel out of the exhaust as I turn it over, and I even checked to see if the pump was working and it shoots fuel out after disconnecting the line to the carb (this made a mess, lol).
- I checked to see if I was getting a spark, and I had no problems with any of the plugs. I took each one out and cranked the engine and I could see a spark as it turned over.
- I took apart the distributor and cleaned all the contact points, made sure there was a good connection to the coil ( I hate the way HEI units are set up), and I checked to see if the rotor turned properly with the engine cranking.
- I checked the timing using a redneck method I came up with because my timing light didn't seem to work. I put my finger over the spark plug hole with the plug out, rested the plug on the header to ground it, and then got my dad to crank the engine. I could feel the shot of air from the compression stroke right about when the spark would fire, so it didn't appear that the timing chain jumped or something went wrong with the cam.
- I'm still getting full power to the car, and I checked all fuses to see if something blew, but they were all fine.
So given what I have tried, here's what I just don't get... Since I am getting fuel and spark, why hasn't there even been some partial ignitions, some sputtering, or anything besides just plain cranking? Even if the timing was out or the spark was weak for some reason, wouldn't I at least get a few pops or a backfire or something? Also, what could possibly just make it die for no reason on the highway during a steady cruise? The biggest thing that confuses me is that I have air, fuel, and a properly timed spark and nothing is happening.
A couple of things that seem odd that might signal something: About a couple of weeks before this happened I noticed my tach gauge bouncing around a bit whereas before it operated smoothly. I assumed it was a loose connection and didn't really pay attention to it. Also, my timing light worked on my brother's truck, but didn't work on my car after it died. I never had a problem with that light working on my car before this happened, is it possible the spark is too weak for it to pick up? Is there some way to check this? Oh and here's a wierd one... When I opened the hood on the side of the highway to have a look at things just after it died, I noticed the #8 spark plug wire was disconnected from the plug. I would have definitely noticed it missing if I was driving with it like that, and it ran totally fine until it died. Could it have been blown off by something? This is just really wierd.
I'm totally at my wit's end as to what's wrong with it. I'm hoping I can get a few suggestions from this forum, because I'll probably start buying new parts if I can't get it working. Any pointers would be greatly appreciated, thank you.
Oh and here is my engine specs:
355 SBC, 10.5:1 CR
Holley 650 DP
Comp Cams XE268 cam (224/230, .477/.480)
Aluminum heads comparable to AFR 180
Edelbrock RPM air gap manifold
700R4 tranny with stock stall
Mallory HEI ignition with Accel 8mm plug wires
Bosch platinum spark plugs gapped at .045"
Stock mechanical fuel pump