I'm stuck on why this engine is still backfiring. During Idle I am getting a small backfire and, though I haven't moved it in a while I imagine if I did it would stall out. Let me give you some specs.

1979 F150
351C
New Ford HEI Distributor
New Plugs/Wires
New 600 Edelbrock
New Internally regulated Alt

It does not have an Electronic ignition module as I presume I do not need it due to the HEI. The Wiring harness in the truck is from a 76 F350 Dully, there are no additional electronics aside from engine components. All the fuses in my box are good.

I got No.1 cylinder up and installed distributor with the rotor pointed at about 1:15 (This is the only position the truck will start in. Also this is where all of the videos/pictures puts the rotor for the No.1 compression stroke)

My firing order is 13726548 counter clockwise with No.1 being at my Rotor's position. (So just like the Diagram from the haynes Manual. That being 3 at exactly 12:00)

On initial start up the truck starts fine, nearly touch start. However the idle is rough, there is a distinct low backfire and upon shutting the engine off the truck shudders.

With a timing light, I am sitting at about 11 degrees BTC and holding. Advancing to 13 does not help the issue.

As far as engine quality is concerned the engine seems in very good condition. Looking under the covers it is well oiled, clean and looks as though it was rebuilt, but not by me. It has run well in the past before the upgrades.

There are no major vacuum leaks that I'm aware of. However in that area I could be wrong. I halve all my ports hooked up or closed off, and during the install for the carb i cleaned the mounting surface and tightened down in a criss-cross pattern.


I think thats all. Any help or suggests would be great. I am linking to a video as well of someone elses car that is showing similar problems as an example.

 

this is my truck. sorry about vid quality

 

Ok, just to clarify one thing first, are you SURE it's a Cleveland and not an M series? They are very much alike, but different.

I watched your video. You got a problem alright.

The first thing I would do is get a new set of matching plug wires and re route them so they are as clean as possible. Having wires go everywhere, crossing everything, can lead to problems with spark jump.

 

Hold on a second. Does this thing have a big cam?

 

Do you know for certain that the cam timing is correct?

 

What about the carb? Is it new or pulled off something that ran fine before putting on this truck? What is the carb make and size? Have you adjusted idle mixture or anything? When you bump the throttle it dies, right? You can't raise your rpms gradually?

 

Sounds to me like you have a real bad misalignment of the starter and fly wheel...all the grinding noise when turning over, does not sound normal.

As far as the backfire, mis wired, bad spark plug, bad/ill tuned carb, can you hot swap a different to see how it runs? Triple ck all your elec connections, especially with the conversion to HEI and internal regulated alt.

Might have to undo some electronic upgrades and see what when wrong that way.

 

Are you timing it with the vacuum advance disconnected

 

K to try and answer all the questions.
Truck has new carb, 600 edelbrock. Timing is in order, wires are correct. I do need matching wires, i just threw those red ones one to check that side if it was those wires or not. Iv since put matching ones back on. So far, I believe the timing chain maybe the problem at this point. I have done my timing with vac advance off. The reason for thinking its the chain is I turned the crank and there was play in the rotor.

 

Yes im sure. And the wires on it were just setup for some testing. I have put new wires on and routed them as not to cross over.

 

I believe the timing chain is the problem at this point. Someone must have overhauled the engine before i got it. The cam could be off

 

new carb. 600cfm. have not adjusted idle mixture, only throttle position to keep it from dying out. I can increase rpms gradually but it continues to backfire

 

far as i can tell all connections are good. getting 12.6 to dist on run and 14.3ish while in idle, no fluctuations. I did not think of the starter though. I may pull that and re-install, see if i get any changes