Okay guys needing some help with my 1986 full size Bronco. Bought it as a wheeler and did not plan on needing it as a daily driver untill my '02 Ranger took a crap. I was in the middle of a leiserly engine swap on the Bronco, Taking out the existing 300i6 because of blow-by and compression and well, a ton of reasons, to swap with a stock 300i6. The motor I was running had MSD ignition and coil, as well as headman headers and a 4 barrel offenhauser intake manifold with a 500 cfm eddy and had the same gettup as my John Deer. When I put the stock motor in I switched over the headers because I did not have the stock exhaust. The intake manifold had several places where the stock exhaust manifold connected to it and I plugged them all up. The electric choke I replaced with a cable one, and had to remove the pulley fan so my bigger alluminum radiator would fit with it's slimmer electric fan. I hooked the MSD up to the stock coil and Distibutor, fired it up and drove to the store. I came home and the Bronco Died in the driveway. Every time I can get it to start now the Blow-By steams out of the dipstick tube, manual fuel pump, and breather at exceptional volume. I know it's a 300i6 out of an 84 f-series and some Blow-By is expected. When I try to drive it, it dies within minutes. My brother-in-law came over and we douched the carb with cleaner, changed and gapped the plugs (with diagram to ensure proper firing order) and changed the fuel filter. It ran horrible after that so we assumed timing was an issue...even though it drove fine to the store and back. He adjusted the timing to factory spec 10* and it when it died we could not restart it. He advanced the disributer another 2 or 3 degrees and still no start. Any Ideas what to check or do next?

 

I noticed just how much stuff was hooked up to the factory 1bbl and manifold...does anyone know if throwing an offenhauser and 4bbl on a stock 300 is effective. already has headers... any help would be nice.

 

Check compression, to make sure pistons,valves,& head gasket are ok. Is the coolant hose plate under carb/manifold in place and not leaking? Possible egr stuck open?

 

compression test good...coolant plate? there was a 2x3 inch hole on the bottom of the stock intake manifold. my gasket kit came with a gasket so I made a plate and sealed it up. The egr seems fine but wouldnt that not matter after it warms?

 

egr is currently closed...

 

So right now after swapping the motor, you have the stock intake and carb with headers on it?
The hole on the underside doesn't do anything if you don't have the stock exhaust connected. That hole serves two purposes. The first is to allow hot exhaust from the exhaust manifold to heat the underside of the intake. If the bottom of the intake floor gets cold, the fuel can puddle and cause bogging on acceleration. The second is to allow air from the Smog Pump to pass through the intake and into the exhaust stream, which helps the cat work better. I know you said you capped it off, but there's absolutely no reason to. If it's open, nothing happens.
The coolant hose plate is a custom piece many make to re-create the heat to the bottom of the intake. It wouldn't have one unless someone made one for it.



The vacuum tree thing above the water pump is a Ported Vacuum Switch and it's screwed into the thermostat housing. You can remove it and your temperature sensor and just put a plug into it. That's not the temperature sensor for your gauge, but for the engine's computer and since you have an aftermarket ignition, your computer's not doing anything right now anyway. The stock computer used signals from around the engine to set the mixture on the carb and to set the timing on the distributor. From the sound of it, none of that stuff's hooked up, and the computer's not doing anything right now. The temperature sensor for the gauge is near the back of the engine below the #6 runner on the intake manifold.

Have you checked the compression on the engine? I don't know why you'd be getting so much blow-by.

If I were you, I'd put the Offenhauser intake and Edelbrock back on. Then, I'd get a distributor from a DuraSpark II era ('76 - '83). You can get them new for around $50 - $60. The advance in that distributor works off engine vacuum. If you have the '86 one in there right now, it's probably not advancing (since no computer's telling it what to do), which will make the engine weak.

Normally, people use the whole ignition from a DuraSpark II setup, but you may be able to use your MSD.

Another thing to consider is that your harmonic balancer has slipped. The vulcanized rubber loses it's strength after a while and the outer ring of the balancer will move, which means your timing mark can be pointing in ANY random direction. If you time based off of that, it won't run.
To check your balancer, pull the #1 spark plug (closest to the radiator), and turn the engine until the piston comes to the highest point (pulling the spark plug lets you look down the hole with a flashlight). Look at the timing mark on the balancer and see if it's pointing to the 0° mark. It's okay if it's a few degrees off, but if it's not even close, then your balancer has slipped and you'll need a new one. In the mean time, you can reset your timing to 0°, get it running, and then time it using a vacuum gauge.

 

Well as embarrassing as it is to admit it. The only problem I had was an overheating engine. My altenator belt cut into my lower radiator hose and drained the whole coolant system...because my temp gauge was hooked up on the goose neck above the water pump the temp never got high...no water to run past it. The truck would run fine cold, but once warmed up it would expell burned oil through every orifice, and stutter then die. As if the timing was off and it was starving for fuel. The gauges looked good and the Radiator was just topped off the day before. Had I slowed down and checked ALL my fluids I could have saved myself a ton of time/effort. The timing was adjusted correctly using the marks on the PASSENGER side of the motor not driver side. Seems to be running better with water in it. Tomorrow on my 30 mile commute to work I'll get a real good Idea how this engine is doing. Thanks all for your help....

 

Heh, we've all been there. But hey, it's always better to be able to owe up to something like that than legitimately have an expensive repair on your hands. Hopefully it didn't get damaged by overheating though.

The timing marks on the passenger and driver's side both work the same, as long as the timing marks (there are two on the balancer) both line up correctly.

Again though, the sensor on the gooseneck on the thermostat housing is NOT for the temperature gauge. That sensor is underneath the #6 intake runner. The one on the thermostat housing is for the computer only.

Let us know how your commute goes.

 

I got to work without a hitch. Temp never got above 190.

The tranny has no pulldown attached yet (old one was linkage, currently have a cable going nowhere next to throttle cable.) so I have to shift manually to make it up some of the hills around here, however the tranny is slow to shift down as well??? It is full of fluid. The vaccume is hooked up for the tranny right next to where the breakbooster is hooked up under the carb on a vaccume tree on the intake manifold. The breaks work fine and I did a leak test with starter fluid and found no vaccume leaks. It was the same tranny/torque converter from the last engine and worked fine then. I did not even remove the transmission or torque converter so the Engine is the only thing thats different.

Anyway, back to my commute. I parked at work and shut the Bronco off to discover water pouring onto the ground. A quick inspection showed me it was coming from behind the fan pulley..."water pump." Had my girlfriend meet me at work after my shift, she had picked up a replacement pump/gasket for 20$ at O'reilly's. 30 minutes later I had em switched and topped her off with water. Made it home with no problems aside a constant temp of 220 and no heater.

I previously changed the thermostat and my heater was working this morning.

Im gonna wait till after she cools down then I'll make sure I got enough water in there.

 

"Again though, the sensor on the gooseneck on the thermostat housing is NOT for the temperature gauge. That sensor is underneath the #6 intake runner. The one on the thermostat housing is for the computer only." -AbondonedBronco

I understand what you mean. However when I bought the Bronco, the previous owner had installed aftermarket temp/Oil pressure gauges. The temp gauge he had installed on the thermostat housing. So when I did the swap I coppied what he had. Can't honestly tell you if the sensor under the #6 intake is still there or if it's a plug. I'll update after I go check fluids again later.