Backfire........need advice - please help

[69 air cab]

I just removed the 305 engine from my 84 Silverado and replaced with a new 350. Had the carb. professionally rebuilt, installed new compoents in the top end of the distributor. Tried to crank it and it backfires only.........will not start. Even caught fire for a sec.

I believe I have the spark plugs wires routed correctly.
Carb should not be the problem.
I may have some vac lines incorrectly routed - could that be it?
When I installed the dist. I found top dead center of Number 1 plug, marked the dist and faced the mark toward the #1.
I have tried turning the dist a bit to see if it stops backfiring.

Can you tell me what some of the things are that I need to check? I'm into my third afternoon (after work) and ready to call a professional.

[us111]

sounds to me like the timing is off,,at TDC #1 cylinder, your rotor button should be pointing almost directly at #1 cylinder.that is very close to being right,if your timing is only off just a little it won't cause what you are saying as far as i know....

[69 air cab]

Ok........that's a big help. Currently the end of the rotor button is pointed exactly opposite #1. As you know the botton won't fit on the dist. but one way.............so, I must have installed the dist. backwards (opposite #1).
So, I will need to pull my dist, reset the balancer to "0" and reinstall the dist. with the button pointing #1............correct?
Thanks for you help.

[corn]

That should fix it for you. There is a cheat you can do it but I dont suggest it. You can move all of your plug wires on the cap until #1 wire is where # 1 is on the dist...corn

[PHOENIX]

I agree I would guess the timing is wrong.
One time I had the distr. installed 180 degrees off and it would back fire if you tried to crank it. Found out that was the problem, pulled the distr., turned 180, stabbed it, and it started right up.

[jimfulco]

Swap each wire with the one exactly opposite from it on the cap.

[us111]

Originally Posted by 69 air cab

Ok........that's a big help. Currently the end of the rotor button is pointed exactly opposite #1. As you know the botton won't fit on the dist. but one way.............so, I must have installed the dist. backwards (opposite #1).
So, I will need to pull my dist, reset the balancer to "0" and reinstall the dist. with the button pointing #1............correct?
Thanks for you help.

yep,that's the problem,get that rotor button pointing at #1 cylinder at TDC and she outta start right up...

[rockman20]

Everyone has forgot one important thing. You want TDC compression stroke! This is how I have always done distributers.

First I put plugs in every hole except for #1. Then I take one of those disposable blue shop towels (the kind you buy in a paper towel type roll) and I rip a strip off from that and create something that resembles an ear plug. This I take and push into the #1 spark plug hole. (Make sure that you don't push it ALL the way in and make sure that it fits snug enough to make a good seal in the hole) Then I tap the key.....tap the key......tap the key.....until you hear a POP. This will be your home made plug popping out of the hole. At this stage I know that I am close so I grab my socket and I turn the engine by hand to the TDC mark. I now know that I am on TDC compression.

Then I take my dist. and I point the rotor towards #1 cylinder and then I look at how the keyway is pointing on the underside of the dist. (the oil pump drive.) I then take a small mag light and I look down my dist. hole (DO NOT drop the small mag light at this time........I have done it!) and see how the oil pump drive is positioned. If need be, I grab a LONG flat headed screwdriver and I turn the pump so that it will mate up with the notch on the dist. Then I take the dist, turn the rotor so that it is pointing a bit more counter clockwise then I want (the rotor will turn clockwise due to the cut of the gears) and then wiggle and set it in.

One thing to watch out for is make sure that you give yourself enough room for the vacuum advance. I have done this a few times where I get everything lined up and then find that I have no room to adjust the timing because the vacuum advance hits the block or the firewall.

After that it is all simple. Make the terminal on the cap that the rotor is pointing to as #1 and then follow the timing order around the cap and you are done. Doing it this way I have NEVER had a problem with an engine starting unless I had carb settings way off or no fuel or something stupid like that.

[us111]

rockman20 is 100% right,, sorry i forgot to explain farther,,