Bad power wiring to injectors, look for 12 volts on the red injector wire while the engine is running. Bad wiring between the computer & injectors. The computer provides a ground to complete the circuit and fire the injectors. Bad computer, driver transistors inside the computer that do not completely pull the injector signal to ground.
Remember that the computer does not source any power to actuators, relays or injectors, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)
LOL! Seriously man, you do realize that it's called "compression" because it compresses things...such as air and fuel. Compression is crap being squeezed together really tight, the complete opposite of "sucking in".
Ok, I dont want this thread to turn into a pissing contest, evidently he had a brainfart and thats done. That doesnt help my problem.
I need to know why I keep blowing head gaskets over and over even with decked block and milled heads. What the hell is going on? Only thing that makes sense is the back two cylinders getting hot, or running lean to blow the head gasket
# 7, and 8 usually run a tad lean due to the heat of the coolant and lack there of. Its the hottest part of the motor, farthest away from circulating coolant, an closest to the firewall. There have been many stock motor racers who run a slightly larger injector in those two cylinders due to restrictions in their class requirments.
Nah, I dont buy into that whole, "Dont worry because of their location, the 7 and 8 always run lean." If that was the case, then everyone would have this issue. So you just know your head gaskets are blowing, not that you are actually running lean? IF you know for sure its running lean, then I'm going to say its a wiring thing because you said you had the injectors rebuilt. Are you running the correct pump and is your fuel pressure good? Is your computer properly tuned for your combo? Just throwing up ideas but it isnt compression I'll tell you that or that those 2 just naturally run that much hotter.
compression on 7 was 80, 8 seemed to be fine at 145. but as soon as we took out the plug in 7 and did a compression test on 8 at the same time, we got crap results for that cylinder. 8 is blowing oil. 7 is low compression
how do you expect the air and fuel to get to the right cylinder without sucking the air in. when the piston goes down, it sucks the mixture in, then the valve closes and the piston come up on the compression stroke and ignites
so if you take leave the #7 plug out and did the test on #8 then you have a bad head gasket if you didn't know. you coul have a warped head or block or maybe stretched head bolts.
here is a chat with a friend from www.fordtrucks.com. ponder on this thought.
rusty-ford351: you bring up a good point if he has poor compression and oil is getting by the rings real bad then that would create a rich condition which would also be a reason for blown head gaskets, what do you think? a lot of people who set up blowers run them extremely rich and in the process blow head gaskets all the time.
when you get a rich condition, wouldn't the computer try to lean it out or something, i know it does on my 95 when i had a bad intake gasket, the computer made the thing extra rich because it was actually running lean and sucking unmetered air into it. yours could be doing the opposite
the motor has 350 miles on it. blew head gaskets on those two cylinders for the past 3 times. headgaskets put on by different people including me. something is really weird.