390 Dilemma
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390 Dilemma
I have a '78 F150 with a 390,Np435,Np205 in her and recently I had to put a new clutch in , and while I had the engine out i decided to change mains and rods ,oil pump and gaskets ,minus heads. Well everything is back together now and she will not start. It's backfiring through the carb. Now I've gone through the basics like lining the timing marks up TDC and #1 piston is where it's supposed to be along with the rotor. She cranks fine like she wants to start but spits stuff out of the carb.This truck ran beautifully the day I took the engine out and now I am stumped. Any advice would be gratfully appreciated.
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Joined: Feb 2001
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390 Dilemma
Don't mean to be condescending but are you sure you set the distributor up at TDC when #1 was on the power stroke? Sounds like you're 180* off, the pistons at TDC but the exhaust valve is open. Just a thought.
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From: Ozarks
390 Dilemma
I've built several engines and no matter how carefully you check for TDC compression, it's still possible to get it 180 off. (360 crank degrees). Done it at least once myself. That backfire made my ears ring from inside the car!
Now, before I let any fuel enter the manifold, I put a compression tester in #1 cylinder, hook up a timing light, point it at the gauge face, and hit the starter. If the timing is right (or at least close), the light flashes when the needle kicks. Could save a carb fire, sore ears, etc.
Now, before I let any fuel enter the manifold, I put a compression tester in #1 cylinder, hook up a timing light, point it at the gauge face, and hit the starter. If the timing is right (or at least close), the light flashes when the needle kicks. Could save a carb fire, sore ears, etc.
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390 Dilemma
Should be pretty simple to check. Put #1 on TDC mark on the dampener. Now check the valves, don't worry about the rotor yet. If the rockers are pretty much level, both valves are closed and this means you're on the power stroke. Now go in the distributor and make sure the rotor is on or very close to the #1 wire position. If the valves are not equal (the exhaust rocker will be "lower") and the rotor is at #1, then it is 180* off. Hope this helps.
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