Center main blowout
 

I helped a friend pull his motor to see why it was rapping. We knew there was a main bolt that had fallen out but that's it. The motor was still on the hoist when we pulled the pan and that is as far as we got. Half the cap was in the pan with a broken bolt. When we tried to loosen the other bolt it broke off the same way. I have never seen anything like this but my experience is limited. I think the bolts never got fully torqued to the cap due to bottoming out. That is just a thought.
It's out of warranty and don't ask who put it together. Mistakes happen, he's not doing them any more and he's a good guy.

Re: Center main blowout
 

They dont look like ford bolts.
Lawrie

Re: Center main blowout
 

wrong bolts, no split washer or wrong bolt (too long) and bottomed out in block and when torqued wrung them off. second block I have seen do this the other was a NOS from Carpenter

Re: Center main blowout
 

https://www.fordbarn.com/forum/attac...p;d=1615942473
Doesn't look good ?

Re: Center main blowout
 

I had this same thing happen on my '51 Ford in 1959. The only difference was that the bolt had not broken. As I remember it, the chunk of the main cap laying in the pan was an almost exact duplicate of the large piece you show. Back in those days, I needed the car to drive back and forth to school, so my main objective was to get it fixed and not wonder what happened. I went to the local Junk Yard and got three random center main caps and fitted them up with some plasti-gage from the local auto parts store. The first one I tried (with the original main bearing shell!) provided the proper clearances, so I put it back together, torqued the main caps, and went down the road. The engine ran fine in that car (and a subsequent '52 I put it into).

Another difference is that what ever happened put a slight hole in the pan that I brazed shut. The engine in this car had been "rebuilt" to the tune of $185 about a year earlier. Seeing this, and looking back, I have to believe that improper torque on the main bearing bolts was the cause. As I said above, the similarity of the broken cap pictured to the piece I recovered from the pan 52 years ago is eerie.

EDIT : After thinking about this overnight, my memory became clearer and what happened to me was not the same. When I dropped the pan, The large chunk was still where it should have been (bolted onto the block with one bolt),and the remainder of that cap had disintegrated, putting the hole in the pan, leaving several chunks in the pan. The other bolt was still screwed into the block, just that there was nothing there to hold anymore. The remaining chunk of the bearing cap was almost identical to what the O/P has shown.

Re: Center main blowout
 

I had the same thing happen to me on my 8ba merc. The main broke in half along with both bolts. Lucky for me I came a cross another main that worked without having to line bore

Re: Center main blowout
 

thanks guys. I did not notice the lock washer missing. That could be it.
The next question is, how best to get the broken bolts out?

Re: Center main blowout
 

"if" they are both bottomed out it will be a challenge. I would take a short bolt of same size , drill a center hole all the way thru it and use that bolt as a guide to drill the ones in the block, looks like enough threads to do this, start with about 1/8" and work your way up. did not say what engine , if you need a center cap or a few to work with and can't find them around you let me know I will send you a few.

Re: Center main blowout
 

I take responsibility for this engine, as I built it for a fellow about 15 years ago. It's a 258, max#1 cam, and that all I can remember. Not sure where the original block assy came from, but it was bored cleaned valve job with rotators and reassembled. Plaed on the dyno and broken in. OIl pressure and temp were OK and engine was picked up buy the new owner. I bought the original engine from him and just put it in the stash with the rest of them..
Did I make a mistake?? Not sure. I was building allot of engines back then, and from the bottom they all look the same. But, when installing the crank you have to take special attention to details. I have no idea how many miles were put on the engine before this happened and the owner isn't really sure either. I'm sending him a box full of center mains, hope one fits, have no idea on how to remove the broken bolts, nothing to weld to, easyouts??. hope for the best.
Gramps

Re: Center main blowout
 

My guess is that the cap broke first - then the bolts were taken out.

Re: Center main blowout
 

Re: Center main blowout
 

I’m not gonna blame Ron .
15 years is a while,,,,,and who said the bolts were not tight?
We don’t know that,,,,,I’m not blaming anyone.
Some times parts just fail !
Also,,,,these are cast main caps,,,,which failed first,,,,,the cap or the bolt ?
There can be defects in castings that arise later,,,,or a stress riser that can appear over time .
Also,,,,,detonation can play havoc with the mains,,,,,not just the bearings.

I have witnessed it first hand,,,,,,a perfectly good bolt being screwed back in,,,,,with hardly any pressure,,,,,and bink !
I was just glad it failed then and not later.
I am sorry that it happened,,,,,,but,,,,15 years is quite some time,,,,,who can say what really happened ?

Tommy

Re: Center main blowout
 

When I have a blind hole and the broken bolt , I first try left hand drills . Start small but expect to go to 3/8 and hope a 3/8 will catch and work the broken piece out . Set the clutch on the drill so you dont break small drills . On old Jaguars i start with 1/4 and then 3/8 . Let the piece cool , if it hasnt snagged the piece a little dry ice in the 3/8 hole with a propane torch ready . Get the appropriate easy out ready , warm the block and try to remove . Atthis point they usually can be removed . I hope the jag procedure can work on the flathead .
Good luck .

Re: Center main blowout
 

How much have you fiddled with it Frank? Can they spin as they are? I'd try a transmission pick. If you're very lucky they will turn.

If they are bottomed into the block the tension is still there and plan B, C and D are in play.

I like the idea of using a hollowed out bolt(s) as a pilot for drilling. You've got access to a lathe to get that bolt centered up.

Re: Center main blowout
 

by the time this "see if this works" get thru the thread we should have the process down pat--so let us know what was done and the outcome. good luck!

Re: Center main blowout
 

I think the hollowed out bolt for a pilot is an excellent idea. I’m gonna remember that. Yes, let us know how you progress...... Mark

Re: Center main blowout
 

Yes sire!

Re: Center main blowout
 

Not that it matters, but the bolts in my engine spun out easily with my fingers. Still, I think that if you can get anything to "catch" on the broken portion (left hand drill, a slot ground in the bolt for a screwdriver, or the last choice, an "EZ-Out"), they should come out.

Re: Center main blowout
 

Put some 50.50 mix on them and let it soak in for a while. I too like the pioleted drill method something to remember. I'll have thse caps shippedm out tomorrow.
Ron

Re: Center main blowout
 

Can you take some pics of the face of the fractures? On the bolts and the cap? Might get an idea what happened first and how fast it happened.