Here is my demise. 79 F-150 Custom. 2wd w, 4 speed w/od. 38,000 miles. Thrust bearing supposedly went out on my 79 f-150 with 302. I suspect the cause of the problem was pos tranny. Way to high geared! Had to really feather clutch to get it to move. Burt out clutch. All the feathering really messed with the thrust of the crank. I am in process of fixing problem. I have since bought a NP435 to replace it. I am in process of fixing it but I have a few questions. I hope you guys can help me out.

I took it apart. Here is what i found. There was between 1/8 - 1/4 end play in Crank. Crank was pushed far enough ahead to wear trust surface of crank had a grove cut in it from thrust surface of the thrust bearing. The trust bearing fits in it perfectly. When crank it pushed ahead you can't see thrust bearing cause it is hidding within grove on crank. Crank is shot I know. Why did it grind the crank and not the thrust bearing? Wouldn't crank be tougher metal?

The grove had wore down so much that the crank was pushed far enough ahead it was hitting the block which i'm sure was making the horrible knocking sound. It sanded off a little of the crank and the block. I am curious to if my block is shot also? It shouldn't be should it since really it is not a moving part and the part that is sanded off shouldn't have any contact with anything, correct?

My other concern is that with all that endplay could my connecting rods be bent or do will they allow for the much endplay? When i was moving crank back and forth to see wear it was hitting on some of the piston the the connecting rod slide on the pins like it was suppose to but on some the piston actually twisted in the cylinder. Is that normal? I also had a hell of a time training to get the rod caps off. They were really tight. Are they suppose to be? It was almost like they were binding or the bolts on the rod were bend. They didn't want to come straight off.

What do you guys think? There is only 38,000 on it. My idea was the just replace crank. It still runs like new with exception of the knock. I don't see any need to replace anything else or to a complete overhaul. My other conern was how much metal from that ground down crank has been circulating throughout that engine. I hate to fix it just to have somethign else go wrong down the road.

If I were to just fix crank what would be best, new crank or old one from junker and would I have to grind either of them down?

If I get junker, what 302s will work, any/or all of them or only certain years/models etc.?

There is a little grove on block cause from crank hitting it just on outside edge of thrust bearing, will this be a problem? I don't think so because nothing should touch it, correct?

Also. How does a thrust bearing work and when you seat it, how does it seat, as in what it he bearing doing when you knock crank back and forth when putting caps back on. I never have figured that out.

One more. Can i ripe out the air pump and smog stuff? There is a lot of vaccum lines running to it and from it to other places. If i take it out and hoses off, won't it effect how it runs.

Thanks,

flyhound

 

I would just find another motor for it.

 

I agree with mark, unless you have an engine building machinist look at everything with all those problems you are just asking for trouble by replacing only what you see is wrong, i would go as far as to say to look for another truck with a mated 302 and 4 speed (you might need clutch parts and linkage anyhow for the different tranny) that is wrecked or just rusted out, but running, but i dont know how much you want to spend, how in love with your truck you are, and if where you live you can even find a donor truck sitting behind someones barn or something......this comes from many years of seeing people spend a $1000 in the long run trying to save $500 in the beginning. good luck

 

you cant go wrong with a 460

 

Moved to proper forum.

 

You guys aren't telling me what i want to here. I already have 460 in my other truck. Never would be able to find bellhousing, clutch parts, etc for 460 for that year anyway. They simply don't exsist. Truck body is mint! Not going to get different truck to put in a worse off motor than I already have. If nothing else i could just get away with new crank and connecting rods. Don't matter if it is SROD or a NP435. All the clutch and linkage is the same.

 

From racing my 302 now 347! after 500 to 600 runs the thrust bearing failed! I have seen this on a 79 302 also! from your discription the block is most likely ok! On the 347 I could move the crank 1/4 inch and I would still rev like a chainsaw! The crank moving did put a odd wear pattern on the rod bearings, but no big deal these are expendable! I think a lot of the wear you have is from the low mileage and starting up dry! Please tell us how everything goes