why wont my 91 gmc 350 start just changed head gaskets have spark and gas did tdc?

Answer 1

If all you did was change the head gaskets, I am assuming the motor ran before you did this, there can be a couple of things you didn't do properly when you did the work. Did you set the rocker arms the way the manual says to do or did you just start tightening by feel as you might have set the rockers too high or too low. Too tight would mean the valves would always be open and therefore no compression, but you might get some popping or backfiring through the intake. Too low and you would have no air/fuel entering cylinders so therefore no bang for your buck. The other thing is setting the distributor in. The TDC mark thing you mentioned can be for either cylinder #1 or for its running mate, cylinder #6. Depending on where the motor was when you installed it. If you assumed #1, you might have it 180 degrees out which requires you to remove the distributor and turn the rotor 180 degrees and re-assemble. To be sure, I always rotated the motor and watched the rocker arms on #1 and when the timing mark starts to come up to the TDC area, the rockers should not be moving at all for cylinder #1 which indicates you are on compression stroke and about to fire. That's about all I can tell you without further information about what you are doing. Good luck.

Answer 2

Did you put the wires on right???
The fireing order is 1-8-4-3-6-5-7-2
Did you tighten the lifters down to tight and maby the valves are staying open

Answer 3

i have to agree with goldwing in this case although one other posibility is that there is water in the cylinder from when the head was removed try tow starting the car to ensure that the compression pushes any water residue out also it may be worth doing a compression test to make sure that the engine has full compression as this will cuase the engine not to fire you can get a compresion tester from most autofactors (car parts shops)

Answer 4

Valves adjusted too tight.....distributor a hundred and eighty out......firing order incorrect..... make certain the valves are adjusted precise, then carry #a million as much as tdc on the compression stroke and notice the place your plug wires are in terms of the rotor. additionally word the rotation of the rotor, and make certain the wires shop on with it. you're becoming to be used tdc on the exhaust stroke, no longer the compression, which might particular make it do what you describe. stable success!

Answer 5

Check the timing of the distributor.