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351W backfiring

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Old Jun 6, 2007 | 10:48 PM
  #1  
strokermotor91's Avatar
strokermotor91
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351W backfiring

So i just replaced the headgaskets and intake manifold gaskets, got it all put back together, dropped the distributor in pointing towards #1. now when i try and start it, it kinda just gurgles, and once in awhile it backfires out the exhaust really LOUD! exhaust smoked for about 2 minutes. i had the key turned to on, and with the remote starter tried to start it and no luck. Withoug touching anything else i moved the distributor by hand and it backfired again. I have no clue. Maybe you can help?
 
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Old Jun 6, 2007 | 11:04 PM
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Put a timing light on it and make sure that you are in time.
Depending on how long you let it set, the fuel injectors may not be working properaly either.
 
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Old Jun 6, 2007 | 11:38 PM
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F150xlt
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From: Baltimore
Sounds like you have the distributor installed 180 degrees out.

With the ignition key off.

Remove the number one spark plug.
Put your finger over the hole.

With your remote starter. Slowly crank the engine.
When you feel the compressed air coming out of the spark plug hole stop
cranking. Look at the front damper and crank or manually move the damper till it lines up with the zero mark on the timing marker.

Install the distributor so the rotor is under the number 1 plug on the distributor cap. Install the distributor hold down bolt but leave it loose enough so you can still turn the distributor base.

That should allow you to start the engine and set the timing. Make sure you unplug the spout connector while setting the timing. When done tighten the hold down bolt and reinstall the spout plug.
 

Last edited by F150xlt; Jun 6, 2007 at 11:49 PM.
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Old Jun 7, 2007 | 12:22 AM
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Originally Posted by Dean88
Put a timing light on it and make sure that you are in time.
Depending on how long you let it set, the fuel injectors may not be working properaly either.
I cant even get the engine to run to use a timing light. It wont even start
I set the #1 at TDC and dropped the dist. in so the rotor points at the number one cylinder. I put an MSD cap and rotor on so it doesnt say which one is number one. So long as you put the number one wire where the rotor is, right?

I cant even find the spout wire either. its an 88 250
 
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Old Jun 7, 2007 | 11:51 AM
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F150xlt
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On a four stroke engine, the number one cylinder piston will be at top dead center two times per complete cycle.

Once on the compression stroke and once on the exhaust stroke.

You have the distributor rotor pointing to the number one spark plug wire on the exhaust stroke. That's why the engine doesn't start and you're getting back fire in the exhaust. The spark plug is being fired with the exhaust valve open on the exhaust stroke.

Here's the sequence.

Intake stroke. The intake valve is open exhaust valve closed. Piston moves down drawing air into the cylinder.

Compression stroke. Both intake and exhaust valves close. Piston moves up to the top of cylinder compressing the air. (TDC on compression stroke)

Power stroke. Both intake and exhaust valves closed. Spark plug fires. Piston moves down to the bottom of the cylinder.

Exhaust stroke. Exhaust valve opens. Piston moves to the top of the cylinder and exhaust gases are pushed out of the cylinder. (TDC on exhaust stroke).

So you need to install the distribtor with the rotor pointing under the number one plug on the distributor cap at TDC on the compression stroke.

If you had the valve cover off you could just look at the valve springs to see if the valve is open or closed while the engine is rotating.

As I mentioned you can also place your finger over the number one spark plug hole and feel the air coming out of the spark plug hole on the compression stroke.

I don't know how the MSD ignition box is wired. The factory distributor which used the TFI module is bolted on the side of the distributor, you should see I think it's a six wire harness, the spout connector should be plugged into a yellow/light green wire. It's a plug that jumpers the two yellow/light green wires together.
 

Last edited by F150xlt; Jun 7, 2007 at 11:56 AM.
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Old Jun 7, 2007 | 12:36 PM
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From: Eastern Washington
I agree. I just did the same thing to my truck, new heads and all new gaskets. Thought that I had set #1 cyl. to TDC, but was actually 180 out. I couldn't even get the engine start, and it was mis-firing. I pulled the distributer and set it 180 degrees out, and it fired right up. I had to set the timing to make it run smooth, but I was happy that it started!
 
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Old Jun 7, 2007 | 01:36 PM
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Agree also. The key here is to have #1 at top dead center (Compression stroke) The timing mark will be aligned and the rotor will be at #1
 
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Old Jun 7, 2007 | 05:23 PM
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this is the first ford engine i've built. i've built numerous chevys small and big block from the ground up. I'm pretty sure its at tdc, but tonight im gonna double check, and double check the wires also. this is my buddies truck im just helping him with. I'm gonna look again but i couldnt find the spout for it either. This is why i'll always have carbureted engines. too many wires
 
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Old Jun 7, 2007 | 11:25 PM
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well took everything back out and re set it to #1 tdc, and i guess i was at #1 bdc. I thought i had it right the first time. It started up and runs pretty good at 10 deg. BTC, but now it still smokes out the exhaust. Just put new head gaskets and intake manifold gaskets in. Changed it to right at TDC and it smokes a little less. Doesnt really smell like antifreeze, but it burns my eyes, like its running really rich.
 
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