Heres the deal boys....
I got a 78 Ford Bronco, 429 SCJ engine. I just had it all rebuilt about 3 years ago and have only put on about 12,000 miles. My engine started having some serious issuse which no one could figure out. I finally took it to a shop my buddy refrenced me to go to. They had my truck for 3 and a half weeks before I got it back and 2,000 dollars later. The truck ran fine, it had some issues with it, like it had developed electralysis, and they had to put on a nev harmonic balancer because it spun the rubber and made timming impossible. They also put 429 timing gears in it since the guys whe built my engine swapped in 460 timming components.
OK, so i dont live in the stae anymore and its been like 2 weeks since I got it back fromt hem. The truck ran fine for awhile, but now it backfires through the exhaust and the carb and has a hard time holding an idle when I am warming it up, but after driving down the road for a little bit, it seems to solve itself and run ok. Any ideas? Could the timming have slipped a little? Any help on this would eb great.
~Jason

 

OK for the bill to be 2Grand this is what they replaced: Water Pump, Thermostat, Coolant, Wateroutlet Gasket, Timing chain gear set, spark plug, timing cover, timing cover set, v-belt, oil filter, oil, high preasure steerign hose, cleaner, paint, coil wire, heater hose, silicone gasket, water pump plate, harmonic balancer assembly, and a complete bracket set from a 429 (because the bracket set up I hate wasnt right.) See what had happened before was my engine would run, but then out of the blue the timing would go off and start a real bad spark knock noise while driving, and when it was idling, the engine seemed to advance itself, and then drop back donw. I had taken it to many shops and no one knew what it was. One shop put a new distributor in it and said my MSD off0-raod ignition went bad and told me to put high octane gas in my truck, which I already do since the engine is high performance and runs crappy with anything else but supreme.
Anyway, in the report, they said the timing components havent jumped, but they were from a 460 which advanced my timing by 6 degrees always, so they replaced that. They had to put a new timing cover and water pump on since the electrolysis had eaten through them. This was new I had never run into this problem before and yes, I run coolant in there, but they told me to buy s zinc tablet and drop it in the radiator once a year to keep that from happening. As for the new harmonic balancer, it says the outer gasket shell shell had spun on rubber gasket making the timing marks incorrect.
Ok, as for your questions in order that you asked. I havent opened it up to see if it backfires flames out the carb or just pops, but nomally if it shoots out flames I will see smoke come out, so I am pretty sure its just popping. And black smoke, only when I step on the gas while I let it idle in the driveway, when I get on it a little bit.They didnt put a new cam in it since its all new stuff with only 12 thousand miles on it, they just replaced the timing stuff.There is a new distributor in it now too, and as for the pin in the gears it does have that and the guy who worked on it told me it would pretty much have to break to get it to set the timming that far off.
This problem happened all of a sudden like, the truck ran great when I got it out of the shop and drove it back to Oregon from Washington, it ran extremely well actually, and it ran fine while it was doen here. Then one day I let it idle with the choke on, and when I turned the choke off and the idle dropped, it would barely keep itself running. After I drive it down the street for a bit it seems to stop itself, but the idle it has at a stop light doesnt sound all that great. I havent really gotten on it after it warms up by sticking the pedal tot he flor, btu I get on it a little bit and it seems to run fine and no backfireing when it get off the gas either.
Like I said before, I had never heard of this electrolysis probelm before, but the mechanic told me it happens from time to time in the older engines.
So I hope that is some good info for ya, I know its a lengthy letter, but I am just getting tired of dumping money into this engine. I love it to death, but it has been a major pain in the *** since I dont have anymore money to put into it and I need it to be reliable. Any informations you have to help me out would be awesome. Thanks Paul and anyone else with input.
~Jason

 

Jason,
Two very limited comments concerning your problems. First, I have seen the aluminum timing covers on 429s/460s develop a hole (happened to my 429). Mine had a corrosion-hole on the top of the cover. I have heard of others having the problem as well, so I don't think it's odd that this happened to you.
Second, it's never easy to diagnose problems from a distance, but I noticed that they did not replace your ignition wires (only the coil wire). How are your ignition wires? When they get old, moisture can infiltrate the wires and make the engine run rough until it warms up. It's hard to tell the condition of ignition wires by eye-balling them, and sometimes pulling some of the wires can create tiny cracks which will radically affect them (don't ask me how I know this, but I ended up stranded in Kentucky b/c I performed a tuneup and did not replace the wires. Everything was fine until it started to rain). Does the engine run rougher when it's damp or rainy? Might be your problem, but this is just a thought...
Hope this helps, good luck with your truck.
Ohio Bill
1972 F100 360 4v 4 speed
1968 Torino GT 429 4v 5 speed

 

I dont rightly know why they replaced the coil wire, all the wire in the engine are fairly new. They came along when I had the engine rebiult 3 years ago and since them, I have only put on 12,000 miles. The wires are MSD 8.5mm wires and I wouldnt think I would have a problem with them just yet. I havent noticed the truck runs rough in either rainy or sunny weather, havent really taken the time to notice that. Anyway, thatnks for you help, and I will keep on working on this problem.
However, I did call the mechanic who just did allt he work on the truck, and he said he thinks its a carb problem. He told me to check the butterfly valve and make sure it was staying open after I kicked the choke off. Seems to be looking good from what I saw.
~Jason

 

Pull one of your plugs and look at it.It sounds like your carb flooded out and gas fouled your plugs.Also your timing might be to low.Loosen your distributor hold down and rev motor to around 2000 rpm.Get someone to hold it there.Turn distributor till motor starts to shake like it skipping now move distributor till motor smoothes out.Tighten hold down drive truck and take wrench that fits hold down.Move distributor a little at time till you get spark knock out. Also motor should not drag and should crank right up. When you get a ford right you just hit key and she fires up when shes good and hot. Timing lights are good but some times a ford will not run on factory specs.What kind of carb do you have . Holley is notorious for flooding out.There good carbs they just dont hold up well when they set up and the gaskets get hard.Hope this helps Wes Tanner

 

Jason , Check the wires. I am going threw a couple problems myself . On my 360 powered F250 I had a problem with my choke sticking. I found it when i stopped up at work and the thing backfired when i turned it off, here the choke was stuck on. ( It is currently back at Barry grant inc for repairs). I also develop a popping noise at idle , checked the basics, timing compression, intake leaks, sprayed wires down to no affect. So i then went to the Fe forum for help and they recommended a couple of things, so along with the recommendation i went out in the dark and sprayed my wires and lo and behold they were arcing like crazy ( Couldnt see the arc in the daylight, even with wetting them down. My wires were Msd 8.5 super conductors and were only 6 months old. I wont know if the wires help out till i get my carb back though. And i believe when it backfires threw the exhaust it usally means you have a rich condition? and that applies to blowing out smoke during acceleration. What do your spark plugs look like ? Are they fouled. Maybe the choke is sticking causing it to load up at idle ? Hope some of this helps
David

 

Thanks Guys for getting back to me on this. I am going to take a look at things once again tomorrow when I start it up and see if this problme has gone away since I monkey'd around with it today and it ran perfect. I am not sure if thats cause it was already wram out, or because I actually fixed the problem.
Wes, I have a Carter AFB for a card, I am not sure what the cfm is, its something between the 650 and 750 range i think, i dont have my paperwork on the build readily available. But both of you seem to have some pretty good idea on where to look and what to do, so I will try them both out. Once again, thanks for the help, its good to know there are people out there like you fellas.
~Jason