302 mains

[simonjrwinter]

If the knocking in my 302 (see earlier post) IS the mains or big ends and IF I can get the sump off without having to take the engine out, what's the procedure for renewing the bearing shells (presuming of course I haven't buggered the crank as well)
Thanks
Simon

[GUMBALL UK]

Hi Simon,

Funny how we communicate here thousands of miles away, yet only live about ten miles apart

Personally, I would pull the motor out from that RAM and Stick in that Stroker you've been building
Seriously though, I think you are best pulling the engine out to work on the mains, I have tried working from underneath before and it is much quicker, in my opinion, to pull it out (ooer!), and work on it out of the car. When laying on your back under a car working above you I find the blood drains out of my arms and you get colder and colder and colder (hope this doesn't mean my heart isn't working right??) - you know how cold it is at the moment. Besides, you need to pull the crank to get to the bearings - this is too much from below.

Sean Graham

[speed220mph]

I wouldn't do this job without pulling the engine. On the other hand, if you don't, it's still possible to change the main-bearing inserts with the engine and crankshaft in place providing you can remove the pan.

The bearing-insert halves in the caps are no problem to change, however you'll have to "roll" out the top inserts. This can be done with a special tool inserted in the main oil hole, a tool that looks similar to a nail. Guess you could use a modified nail with the head bent to lay flat on the main journal.

With this tool in place--doing one main at a time--turn the crank so the nail head butts against the end of the insert that's opposite the tang end. Make sure the head of the nail is low enough that it clears the block as it turns.

Reinstall the new insert in a similar manner after inspecting the main and oiling the insert. Reinstall the cap with a new bearing insert, torque the cap bolts and go to the next main.

Don't forget the rear seal while you're at it. Hope it's not a rope seal, which are hammered into place. Chances are it's a split lip seal, so this job won't be too bad. On the other hand, if the rear-main seal is the later full-circle type, the transmission, clutch and flywheel will have to come out.

Good luck. This will be a neck-bending job, but it's possible.

[Clois Harlan]

I know the thought of pulling your engine is not a pleasant one but just wait until you are on your back trying to change out those bearings and trying to see what you are doing. In all honesty you will probably save a lot of time and feel a lot better about your work when your finished if pull your engine. If you really think you have a bad bearing you really need to have your crank inspected.

Just to NOT have to lay on my back on a cold floor would be enough to make up my mind.

Best wishes Simon.

Clois

[Art Burtt]

I did this once when the shaft on oil pump broke on '81 Ford pick up. The engine ran for about 5 mins. after the oil pump quit. I had to lift engine slightly to get pan off. The crank looked fine so I just put new bearings in with lots of lube on them. I used a really thin screw driver to push top cap around and out. Then check with plastic gauge. It's been two years and 10,000 miles and engine is running strong. Lucky I guess. Oil pump failed due to a piece of plastic getting wedged into it. I had just had oil changed
at a quick lube place,something I always usually do myself,I figure the plastic had to come from oil filter they installed,el
cheapo one I 'd guess. This is what happens when you're too lazy to change your own oil. Live and learn!!

[Excaliber]

Cranks are pretty tough. I'm betting you have NO damage to the crank journal from the undersize main bearing.

Pull the engine? NO WAY!!! Jack that turkey up and get your butt under there. Take a short nail with you to roll out the top bearing. I would probably leave the top rear seal alone and replace only the bottom.

Plastiguage is your friend, USE IT this time. If you used it last time and STILL put in bearings to small, try READ the directions again, lol.

All though I was a Ford and Chrysler dealership mechanic for years I did a lot of "back yard" work in my time. If you were a "customer", oh yeah, I'm pulling the motor! If it were mine and I was doing it "at home", I'm using my creeper, some jack stands and a "nail", underneath the car!

Ernie

[Mr.Fixit]

Every spun bearing I have seen caused enough damage to the crank journal to REQUIRE regrinding the crank. The thumping you hear is the crank getting hammered. That means new bearings, a new balance job. You have to remove the motor to do it correctly. If it were my motor or one of my customer's motors I would pull the motor out and find the problem, before you do any more damage to it. If you could give us a more thorough desription of the symptoms, maybe we could point out a few things to check before you yank it out. It could be piston slap, insufficient deck height, the list goes on. It just depends on how comfortable you are not knowing exactly what is going on. Plastigauge is a waste of time, measure with tools, not a strip of wax.

[cobrashoch]

We are talking about a smallblock Cobra, right? To me it's a no brainer, It should only take about 2 hours max to pull the thing ASSuming you have a hoist. I'm with Mr. Fixit on the plastigauge, not very good. And yes, every engine that has main knock that I've fooled with usially needs crank work. Think of it this way, what if you crawl under there and find a bad crank? You would have to pull the engine anyway.
cobashock

[Excaliber]

Serious builders use plastiguage to CONFIRM their measurments! Like measuring twice. Good chance he didn't spin a bearing, which means good chance there is no substantial crank damage. Re-balance??? If no crank damage I wouldn't go there. Heck, I might not do a balance anyway depending on what kind of "build" I was doing! Drop the pan and see how bad it is before you go to far with it.

If he were one my CUSTOMERS,,,OR,,,,he's building a "race" motor, yeah, different "rules" would apply.

But Simon built this motor himself, my hats off to him!! I think he should keep it simple, unless he's ready to throw in the towel and hire a "proffesional". But heck, that takes all the fun out of it.

Ernie

[cobrashoch]

Ernie - The only time I use Plastigauge is when I use over and under bearings. And even then it's just for a "rough" final check.
Plastigauge is the subject for another thread though.
I would still pull the darn thing, but that not to say that I havn't done things on a cold hard floor though, in the past.
Cobrashock

[Excaliber]

Ha ha,,,I gotta admit, I'm not likely to be over there laying on the cold hard cement floor anytime soon. I been there enough to know you better "measure" four or five times AND plastigauge it (just to double check) because I DONT want to be on that floor when I'm done!

Creepers suck........lol

Ernie

[750hp]

If you can hear knocking, you will be replacing more than just bearings. I'd pull it out and get it onto an engine stand. Bummer!