Crankshaft End-Play

[Jordanlu]

Hey guys,

Had my 69 Bronco in for some clutch work today (throwout bearing shot), and after dropping the parts, the mechanic found I've got about .125" of endplay on the crankshaft. The top end sounds fine, compression on all cylinders etc. I had him stop the work so I could decide which direction to take from here.

It's apparent I'm going to need a rebuild - but I'm not sure it's worth the cost of rebuilding the original 302. I've got a new carb, and switched out the points for an electric ignition, new plugs/wires, and new starter. If you're in my situation, do you yank the 302 and go searching for a 351? Or yank the 302 and hit it with a rebuild? Keeping in mind that I have yet to see if there has been any damage inside the case....

I'd like to do this as inexpensively as possible, as I'm getting married this fall and weddings are effin expensive!

 

[Jordanlu]

Follow up:

I already have a raised cowl hood, so the clearance on a 351 is not an issue.

 

[Broncobowsher]

See if other agree...
Drive it!

Yes, the bottom end is shot. You can either drive it now or replace the short block now. It will need a short block now or later, not going to save anything by rebuilding it now. Damage is already done. Drive it with the knoweledge that it will need a short block eventually. Don't plan any long trips with it and keep the towing insurance.

No to see how many agree and how many think I am nuts and how many think I am wrong (I guess there are 3 choices?)

 

[chuck]

What other than the thrust bearing could cause this? you might put a set of main bearings in and drive it until you get your EFI 351 built. Or you might just leave it alone and drive it while you are building your EFI 351. Oh, did I mention I wouldn't put any money in a 302? Go EFI, either 5.0 or 351 my choice is the 351.

 

[Jordanlu]

Not sure what else besides a fouled thrust bearing would let the crank move fore/aft.

The 302 doesn't owe me anything, so I'll put it back together and keep my eyes open for 351 that I can build up.

Any year better than another for the 351W with EFI?

 

[bax]

I am thinking, change the thrust /main bearing. Or at least drop the pan and look at it. Sometimes it's the crank that is worn, can't fix that. Sometimes a new set of bearings will really help things.

 

[Wyflyer]

I'd like to do this as inexpensively as possible, as I'm getting married this fall and weddings are effin expensive!

Have him put the clutch back together and drive it. Endplay is required, and you can live with quite a bit (obviously). Think about it like this: we've all seen engines with more endplay than we'd like to see, but I have never seen an engine blow up or come apart due to 'thrust bearing' wear or excessive endplay.
Save your money and spend it on the 5.8L that's out there.

 

[av bronco]

If you have good oil press. just drive it.

 

[Pedestrian]

Put it back together and drive it. It will last way longer than you think. 94 and up 351 has the roller cam, these blocks are a dime a dozen so don't worry you will be able to get one even after the wedding. Congratulations by the way.

 

[bmc69]

Not sure what else besides a fouled thrust bearing would let the crank move fore/aft.

?

Actually..more often than not its the thrust face of the crank that is gone when you see that much end play. By gone, I don't mean as in anything 'bad' will happen if you keep driving it as is..I mean gone as in the crank cannot be recovered by a regrind and would have to be replaced. I see that a lot in 302's that had a manual trany behind them for a long period. I tossed one not long ago where the thrust face was worn in to the crank well over .125" and the overall end play was nearly .25"..but the darned thing still ran OK before it was torn down.

You don't see that problem with the 351W or 400 engines because the thrust bearing, and hence, thrust surface area, are huge in comparison to the 302 yet the clutch loads on all are quite similar.

 

[Jordanlu]

Thank you for the peace of mind guys. I've put a few feelers out for a 351 that I can get started on while I keep driving the sloppy 302. You're a great bunch of guys, and I'm glad to have this resource for when things go wrong.

 

[Hal9000]

My bronco has the same exact problem. I was worried at first, but it runs perfect. I'm just going to run it till either it dies or until I do my efi swap.

BTW, do the 5.0's have the same weakness, or was it remedied in the newer generation engines like it was in the 351/400 engines?

 

[357Bronco]

I'd roll some bearings in it, new gaskets and run the wee out of it. New thrust bearings will get you probably down to half of what you have know, still way beyond specs, but would buy some more time. And bearing set are cheap.

 

[Pa PITT]

I SAY JUST DRIVE IT..it last longer than you think..

 

[Viperwolf1]

A new thrust bearing is not going to help for long if the crankshaft thrust surface is worn. You would also need to remove the crankshaft to put the thrust bearing in. Why take a bad crank out just to put it back in? At that point you've already removed the engine to get the crank out. Might as well put a good engine in. If the old engine runs good for you now keep driving it and just know that at some point it's going to die and not come back to life.

 

[bmc69]

BTW, do the 5.0's have the same weakness, or was it remedied in the newer generation engines like it was in the 351/400 engines?

Same. It wasn't really 'remedied by design' so to speak..its just that the 351W, 400, 460 etc have much larger journals than the 302 and 351c.

 

[Hal9000]

Thanks for the info. I guess it's not the end of the world for people like me who don't want anything more aggressive than a stock 5.0 efi motor. But it would have been nice if Ford had fixed the problem. This seems like one of the most common failures for the 302/5.0...

 

[bmc69]

Thanks for the info. I guess it's not the end of the world for people like me who don't want anything more aggressive than a stock 5.0 efi motor. But it would have been nice if Ford had fixed the problem. This seems like one of the most common failures for the 302/5.0...

It is certainly no 'uncommon' yes..but then again its not common when you figure that the extreem crank wear is limited to 'some' very high-mileage engines that were standard tranny. The lack of main bearing oiling that goes along with the usual low oil pressure due to worn cam bearings trait is a contributing factor too, because, unlike the pressurized oil feed on the rods and circular mains..the thrust face receives only what 'spills out' the side of #3 main after its delivered.

 

[Hal9000]

The lack of main bearing oiling that goes along with the usual low oil pressure due to worn cam bearings trait is a contributing factor too, because, unlike the pressurized oil feed on the rods and circular mains..the thrust face receives only what 'spills out' the side of #3 main after its delivered.

Now we're getting somewhere. I hate to threadjack (well, thread kidnap anyway), but has anybody ever tried an oiling modification to fix the issue? Drilling extra oil passages isn't that tough if there's a supply line nearby As a matter of fact, oiling mods are almost common on some other engines I've dealt with...