Almost running , more like walking and coughing

[Rwedoneyet]

I am posting this because I am very frustrated. I have read the threads one by line as my build has been going on, and I have tried to use this site as a troubleshooting guide to solve my roadblock, but with no luck. I am so close to having my truck back on the road. *Any help ideas or comments would be welcome.
Let me start by stating I am not a Motörhead and don't understand *half of the jargon on this forum , *but I can try to explain where I am at with my problem.
I had a old junkyard motor that was old life support so I figured that I would freshen everything up.*I purchased rebuilt short block 302 roller engine which was bored 30 over. A New comp cam was installed(mild) , with other new and recycled parts from a 1995 302. I found 1995 GT 40 heads (donor block) and had them redone with new springs to match cam. Heads were polished or milled to remove rust? Engine and was assembled by a mechanic A. The engine was installed in my truck with new wires, plugs, timing chain and distributor and stuff by builder B. *It has a Howell TBI universal 2 barrel system on it brand new. *When we Turned the key it barely runs, once it starts to warm up*, it pops and backfires out of the carb.*All plugs and wires have spark. *Compression is 120-125 across all. Cant do test when engine is warm because *i cant get engine too run that long.No vacuum leak was detected . Timing chain was off a tooth -4 we thought that was the issue but nothing was different when we changed. *Took covers off valves and they look like they are working properly. It seems to get worse as it starts to warms up.*
Any ideas I am at a loss and could use so guidance.*

 

[Edger6]

Timing, could still be off try rotating the distrubator slowly and see if the problem gets worse or better.
The only other thing is maybe a fuel supply issue, carb not functioning right, spray so ether in the carb when its running and see what happens.

 

[Larry B]

I am really guessing but I would check the fireing order. a 351 has a differing order than a 302 but I think the 351 firing may used by the the 302 depending on what cam was installed. I do not know where you live but would be nice if another Bronco nut would drop by and offer his openion.

 

[bknbronco]

First off welcome to this site. You will never go to another site for bronco information as long as you live!! These guys rock.

Im no motor head either, so ill keep it short. My motor ran like crap for a few weeks after i started it for the first time. Backfired all the time and once it warmed up it wouldnt run until it cooled back down.

It ended of either being the cap and rotor, or the points and condenser. I finally decided to change out the points and condenser even though mine looked like brand new. They were a few bucks each. While i was in the i noticed that the rotor had a rivit holding the brass arm on and that the rivit was loose (brand new rotor) and the arm was crooked and would move easly. I pulled the arm and put a chunk of papertowl around the rivit and pounded back in. Bronco fired right up and has been running ausome since. Because i did the points and condenser at the same time i fixed the rotor i cant say which it was for sure?

Just somthing to look at. I thought for sure it was something way more wrong and was mad at my motor for weeks. Turned out a few bucks and a chunk of papertowl fixed my problem!

GOOD LUCK.

It sounds like you have TBI so im not sure i was any help. Not sure you even have any of the stuff i talked about??

And another thing i noticed is that my valves wernt closing all the way. I had them adjusted per the ford rebuiold manual but the rocker bolts were still too tight. I loostened them to where the rockers were a bit loose and didnt tighten them the extra like i previously did.

 

[zbronco]

I ran into the same issues with my build and my fix was the firing order. I changed to the 351 firing order on my 302 and that fix it..

 

[broncnaz]

X2 on the welcome.
Sounds like a timing issue but I'm going to say its most likely that howell setup that is the issue. well that coupled with the comp cam. Sometimes they dont play well together. I'm not real knowledgeable about howell systems but I believe they usually need all your engine specs so they can tune the computer to your setup.
Might be a good idea to stick a carburetor on the engine to see if it will run or not. If not then you probably have other issues with your build maybe to many hands in the engine and something was overlooked which very well may be the case since you did find that the timing chain was not correct,

 

[DirtDonk]

...Im no motor head either...

Oh I beg to differ. Yes you are!
Look at what you did to figure out your odd running behavior. You pulled removed and replaced points (some POINTS!!!), and literally fixed a defective rotor.
Lots of official motorheads don't even know what points and condensers look like anymore.

So with that little bit of inspiration, and the comment about the valve adjustment, I'd bet the OP gets his issue fixed.

Ok, sorry for the hijack Rwedoneyet, but I just had to comment on that.


In your case, I agree with all of the above. Here's the list.

1. Check your cam card (if you have it) to verify the firing order.
2. Verify that your damper markings and timing pointer line up at the correct TDC position, then check your timing.
3. Is the valvetrain on your heads stock? If aftermarket, then the rockers may be adjusted slightly too tight. If stock, did some years have adjustable valvetrains? Your compression pretty much indicates that this isn't an issue, but I thought I'd ask anyway.
4. The best you can, check for vacuum leaks. Popping through the TB can indicate a too-lean condition, valves not closing completely, something wrong with the TBI programming/function, and probably a few other things as well.
5. If your wiring harness is original, what have you done to add grounding circuits to all the major components (body, frame, engine, battery and more to the body) to make sure that the computer has all the best signals to run with?
6. Check the ignition for proper wiring and a VERY HEALTHY spark at each plug. And I mean a healthy white/blue ZAP when you test it.
I know you checked for spark, but what were they like? How big?

And along those lines, what ignition did you put in?

Good luck. And welcome again too.

Paul

 

[bknbronco]

I also made sure i was not off 180deg on my distributer. I started second guessing my motor rebuuild, compression, timing chain off, got a new coil, etc, and was getting pretty worked up. In the end it was a stupid thing making it not run. Dont start second guesssing right away. Step back and inspect the easy things before you pull the big wrenches out.

AIR-FUEL-SPARK!!!

We assume you have air- but a leak can cause too much in the wrong place? You said you checked. Also valves have to do with air both in and out, and at the correct time.

We assume you have fuel-TBI? Not sure what can be done to check this. On my carb i made sure fuel bowl was full and stayed full. I had carb rebuilt to make sure everything was good inside.

Spark- good spark at the correct time?

 

[bknbronco]

And who put the timing chain on incorectly?? Your mechanic put it on wrong? if so id get a new mechanic! And your sure is on correctly now?

Sounds like the same type of mechanic that leaves the fuel eccentric off%)!

 

[Rwedoneyet]

Wow you guys really jump in too help. I can't tell u how cool it is too have a pit crew that have been there. Thank you!
The firing order needed to be set for a 351 even though it is a 302 motor. Originally both firing orders were tried and the 302 order worked better. But that was before it was discovered that timing chain was off a tooth. The firing order was assumed to be 302. Your collaborative help was great in getting me to think outside what was being tried. Still have some tuning and Plumbing to do but we are over that hurdle .

 

[ilovemaui]

Did you get the rockers and push rods with the GT-40 heads? GT-40 heads use pedestal mount rockers. The stock rockers are not adjustable. Make sure you set it to top dead center when setting the timing. Check all the plug wires and make sure you're using the correct firing order.