Engine backfires...

Hi guys and gals, I have an 84 w150, the truck has had an engine swap to a 78 440. It ran good until I tried to park on a hill. Facing downward, I put the truck in park, then I let off the brake, and what sounded like the transmission slipping. Like gears grinding very slowly. Now when I try to accelerate fast the truck backfires like crazy, but not when I accelerate really slowly? Any help on what this is or what I should do to fix it? Could it be my timing?

hhhmmm sounds like timing to me. Possibly timing chain slipping or distributor gear wore out?

Alrighty, I am completely new to working on trucks, and vehicles for that matter. How would I go about checking my timing and distributor? I believe you helped me out with my ignition problem a while back too, thanks for that.

might want to check for a vacuum leak too

sounds like timing to me. if you are worried that the timing chain slipped....find top dead center.......mark your #1 plug on the distributor then turn the crank with a wrench till the mark on the harmonic balancer aligns with the timing mark at zero on the timing chain cover. pull the dizzy cap off and see if the rotor lines up with the #1 mark you made on the dizzy. if the rotor is 180* out then turn the crank over one complete rotation and see if the rotor lines up with your mark. if its not lined up then the chain slipped.

that grinding noise could very well be the park pin slipping.....but ya, i'd check the timing, make sure its where its supposed to be, then check for TDC, then check for vacuum leaks after that.

Thank you, I might need some more instruction, but I will check it out tomorrow after work.

bring it, i'm sure everyone here is more than willing to help out

x2 on timing/ignition.

Being parked on a hill doesn't help that carb much, either. I've had a couple rigs vapor-lock being parked on hills and going up a steep hill before. Once on a boat launch... Bad day...

Wouldn't hurt to investigate the coil and plugs, either. My Jeep had a plug cable melt and ground-out on an exhaust manifold intermittently. I didn't figure it out for a couple of trips. It had a lot of similar symptoms you are facing...

Backfiring is an igntion-timing and/or fuel-delivery issue.

I park on flat ground. The day I went to park on a hill, I saw about a 200 inch whitetail, put it in park to grab my binos, and then it slipped. I never park on hills, mainly because my park brake doesnt work. I'll do the timing tomorrow after work.

Holy shit, I've been looking at some youtube videos on how to replace a timing chain... am I going to have to take the engine out of my truck to do it? There is no way I am bringing my truck to a shop. I want to do everything on my own. I am just wondering, is it bad for me to be driving my truck with bad timing? Because if it isn't I would rather wait until the spring when I have a bunch of money saved up and a motorcycle to ride, to work on it. I will pull the distributor cap of tomorrow and check my timing chain though. Dam this truck.

you dont have to pull the engine but it's serious work. investigate everything else before considering timing chain. that's the worse case scenario

Could be a bad distributor cap or moisture in the distributor. How long since the cap and rotor have been replaced?

Okay so I checked my timing chain by taking the distributor cap off and watching. It's about 1/16 turn before it starts to move. I will post a pic of my distributor when I get home. Also another thing I might add, someone jacked my gas cap, it's been off for a while now. I made it out of aluminum, I guess thats why they took it. could the backfires be because of moisture on my fuel?

what do you mean by 1/16th turn? water could be the culprit. get a bottle of water dryer and dump it in the tank

you'd probably see a lot more play than a 1/16th of an inch if it was bad. the thing to do is turn the engine, stop, then turn backwards and see how much the crank turns before the rotor turns.

start with the easy stuff first, spark plugs, spark plugs wires, cap, rotor, the water thing, coil. get a vacuum gauge and check to see how much vaccum you are pulling. stuff like that, the simple stuff.

Oh sorry for the confusion. By 1/16, I meant when i took the cap off, turned the motor forward until it started to move, then it took about 1/16 of a turn going backwards for the thing to start moving again. I am going to get a bottle of that water dryer and see what that does. Today coming home from work it didnt back fire once. Almost makes me believe it's the water in my fuel? It seems when I have a fresh tank of gas that my engine runs fine. Still no power, but no backfires as well.

The first one is the distributor and the second is something right beside it. Says msd on it

that's your coil. sends the spark to the distributor. the silver thing on the distributor is called a vacuum actuator, just so you know.

edit: ok i'm going to leave that there...wow my brain is fried. vacuum advance.....not actuator

Another thing, how do I tune my carb? Isn't it something like screw the two adjustment screws in all the way, then back out 1½ turns? Then go from there? And screwing in is leaner right?

Ok, so to check if I have a vacuum leak, I would put a vacuum gauge to the vacuum advance?