Rebuilt motor not starting

[72Jesse]

Trying to start my rebuilt 302 for my 72 Bronco and it's not starting. It's getting fuel and spark and is popping and backfired so I thought the distibutor was off. Went through and pulled it and put it back with the motor at TDC on the crank and still popping and not starting. Also checked the plug wires and they are correct. Seems like a timing thing, but not sure what else to check? What else can I check?

 

[fishinman78]

Pull #1 plug and make sure you are at top dead center on the compression stroke. Then double check your rotor is pointing at #1

Have you verified the firing order of your camshaft?

 

[72Jesse]

That was it! Guess I got to excited missed being TDC on the compression stroke. Fixed and fired right up! Thanks

 

[73azbronco]

popping? double check plug wire routing to dizzy/plus based on firing order for camshaft

 

[DirtDonk]

And don’t neglect the cam break-in!
Assuming it’s a flat tappet type of cam that is? Or is it roller?

 

[72Jesse]

Sorry got busy and didn't get back to this. Roller cam so no break in needed.

 

[72Jesse]

So now it starts but runs like garbage and is missing. Looks like cylinders 3, 4, and 5 aren't firing. Verified that they are getting spark, but not firing - headers are barely getting warm? The cam I installed is standard firing order and rechecked the plug wires too. I rotated the motor till #1 was at TDC and then installed the distributor with the rotor point at #1 on the distributor cap. Any thoughts?

 

[DirtDonk]

And this is without changing anything from when it was running good? Did not move the distributor, or change any more plug wires?
By "standard" firing order, do you mean the old 154 version for your original 302, or the 137 of the later 302's and 351 engines?
Assuming you meant for your old engine, with the 1,5,4,2,6,3,7,8. But had to ask... Mainly because not many roller cams utilize the old firing order.

Which distributor are you running? Does it have the correct gear material for the roller cam?
Older plug wires? You mentioned changing a plug wire before, so curious what you're running in the new-vs-old equipment category.

If you did more wires, a double check is in order:
1. #1 spark plug on passenger side front.
2. Distributor rotor rotates counter-clockwise while the engine turns clockwise.
3. "Standard" firing order for a 351 or HO302 13726548
4. Good pressure feel on all cylinders? Whether using your finger over the plug hole (this is also used to verify firing order) or a compression tester.
The tester is an accurate way to gauge how things are working, but testing the rotational order of pressure on each plug hole with a finger is a tried-and-true method of verifying firing order. If the #3 cylinder comes up right after the #1 pressure buildup, then you know.

What other ignition components are you running.
And I didn't see where you said, but is this carbureted or fuel-injected?

Paul

 

[72Jesse]

Just did a full rebuild with new bearings, Roller cam, and AFR heads. So hasn't ran since the rebuild. The cam card just says standard for the firing order so assuming 1,5,4,2,6,3,7,8, but I will do some looking at this. Running a brand new MSD distributor with correct gear and with new wires. This is a propane motor.

 

[ba123]

and you're sure you went the proper direction with those wires and know which way the distributor turns?

Wouldn't be the first time...simple mistake.

 

[72Jesse]

I just checked the cam specs online ant the firing order that they list as standard is 1,3,7,2,6,5,4,8. Switched the wires to that and fired right up on all 8 cylinders and idled just fine. Thanks for the ideas.

 

[DirtDonk]

That’s great! Yeah, their “standard“ was certainly standard for Ford engines. Just not those from before the 80s.
But we can give them that. After all, 40 years is a long time to be running something not by now considered standard.