Unbelievable engine survival main cap break

[BigBlockMopar]

Isn't it common to put a very slight camfer on all the cap's edges, or at least sand/round off all the sharp machined edges?

[pamotorman]

back in the days with iron caps I would mill the caps flat and use a cap strap made of CRS and longer studs.

[ZIGGY]

back in the days with iron caps I would mill the caps flat and use a cap strap made of CRS and longer studs.
[/quote
In the middle of the last century, all the mail order speed shops sold strap kits. I bought one without knowing
I didn't need it.

[340king]

Thanks for all the comments. In the end it doesn’t matter how it broke as the block will be repaired and another attempt at destroying it will be made. It’s still on the living side of race engines.

[Krooser]

X2 to Pro's comments about circle track engines though I'm certainly not in his league. Years before cell phone cameras, we broke the center out of a cap while racing. There was enough left to retain the bearing and the engine kept running at race speed. The first indication of trouble was some flame from a small oil fire where the cap chunk holed the pan. Before I could run to the flag stand, a lucky caution slowed things so I could wave the car in.
That claimer engine had about 30 nights on it, which was at our throwaway limit for stock cranks and rods. Monkey dusting showed the crank was cracked. The engine had a stock balancer and ran through an Ernieslide with very small clutch and stock automatic flywheel. I never considered the possible effects of that combination until now.

I wonder how many guys are scratching their heads as to what an "ernieslide" is..

[ZIGGY]

Yep, I should have just said a very low rotating weight clutch & tranny, instead of referring to the cobbled up creation of one Ernie Brookins to circumvent a sanctioning body's prohibition of purpose designed circle track racing transmissions like Brinn and Bert. Its construction evolved as they were hacked out in backyard fashion although with a little care and massaging they served the purpose until they were eventually banned. There was a lawsuit and other drama. He had a similar effort with a Powerglide called of course an Ernieglide.

[Krooser]

Yep, I should have just said a very low rotating weight clutch & tranny, instead of referring to the cobbled up creation of one Ernie Brookins to circumvent a sanctioning body's prohibition of purpose designed circle track racing transmissions like Brinn and Bert. Its construction evolved as they were hacked out in backyard fashion although with a little care and massaging they served the purpose until they were eventually banned. There was a lawsuit and other drama. He had a similar effort with a Powerglide called of course an Ernieglide.

Yep...that pretty much sums it up.

[maxracesoftware]

These photos are from a small block Chevy engine I am advising on. This is the center main of a 4 bolt block. The cap has a ductile fracture just outside of one of the main bolts. There’s absolutely no evidence of fatigue in the fracture mating surfaces.

My working theory is that the cap was fractured during assembly when one side was tightened too much before the other side dropped into the register. The engine raced approximately 70 nights in this configuration as a USRA Bmod. The bearing shows that only part of it was loaded. The last night of competition this engine placed second in the A main!

The interesting part is that one of the adjacent cylinders showed more wear than the others. I assume this was due to less oil spilling out of the top of the bearing since there was this gap at the bottom. The adjacent rod bearings look good enough to put right back into service however.

I never would have imagined that something like this could happen. Please give me other plausible reasons how/why this happened if you have something you have seen like this before.

i've only had this happen 1 time ,
and it was SBC383cid in rear-engine Dragster that my Customer started complaining he's feeling
vibrations and they are getting worse ( Engine in solid-frame Dragster chassis )
so i told him bring the Engine back to me , but he said i have 1 more Race, i'll do it after .

well he made the Race and ran the fastest Run he ever made in 2 Seasons with the Engine
then he brought me the engine , he left my Shop, i started removing the Oil Pan ,
the 3 center Main Caps were all cracked like yours in your Pics

so i hurried up and called him ... turn around come back to my Shop... you gotta see this !!!

in meantime i keep tearing engine down ... happen to turn the Crank counterclockwise,
the Crank is completely cracked in half , in such a way that Clockwise rotation its still able to drive all Pistons up and down .

now this SBC 383cid Engine on its very last pass , ran its fastest ever Run in over 2 years = 8.22 ET in 1430 Lbs Dragster
all broken up like that .

[autogear]

I wonder how many guys are scratching their heads as to what an "ernieslide" is..

The 2 things I noticed in reading this thread; MadBill's wanton destruction of vintage iron; and my jaw dropped AGAIN when I saw an 'Ernieslide' reference

[FC-Pilot]

i've only had this happen 1 time ,
and it was SBC383cid in rear-engine Dragster that my Customer started complaining he's feeling
vibrations and they are getting worse ( Engine in solid-frame Dragster chassis )
so i told him bring the Engine back to me , but he said i have 1 more Race, i'll do it after .

well he made the Race and ran the fastest Run he ever made in 2 Seasons with the Engine
then he brought me the engine , he left my Shop, i started removing the Oil Pan ,
the 3 center Main Caps were all cracked like yours in your Pics

so i hurried up and called him ... turn around come back to my Shop... you gotta see this !!!

in meantime i keep tearing engine down ... happen to turn the Crank counterclockwise,
the Crank is completely cracked in half , in such a way that Clockwise rotation its still able to drive all Pistons up and down .

now this SBC 383cid Engine on its very last pass , ran its fastest ever Run in over 2 years = 8.22 ET in 1430 Lbs Dragster
all broken up like that .

A fellow racer had a similar thing happen in a BBC with the crank. It broke in a main all the way through, but because it was not a clean break it turned the rest of the engine just fine. The only thing that he noticed was after a burnout he could feel some banging from the engine, but all other times seamed fine. LOL The caps in his block were still in tact. It has been said that it always runs its best number just before it lets go.

Paul

[n2omike]

Some older engines only had three mains... I guess they will often run just fine on four. lol
Probably lucky it broke/cracked where it did, and stayed intact enough to route oil to the rod bearings.
Good thing it wasn't a nitrous engine.

[88bluestar]

Byce's Block & Cam 014.JPGThe few broken caps I've personally inspected didn't show classic fatigue indicators; I think the ones in the thread have all happened on the track.

This shot is of a road race 1970 Boss 302" SBF engine making 630 HP*. The only symptom was a sudden 10 psi oil pressure drop. The cap showed no signs of fatigue beach marks. Note the perfect alignment of the cap and block breaks and the immaculate condition of the bearing.

* Yes, I know stock blocks are not supposed to survive with more than 500 HP. This one ran for many years with 485 HP and ~12 hrs. with 630...

Is that a thrust bearing in the middle?

[MadBill]

Byce's Block & Cam 014.JPGThe few broken caps I've personally inspected didn't show classic fatigue indicators; I think the ones in the thread have all happened on the track.

This shot is of a road race 1970 Boss 302" SBF engine making 630 HP*. The only symptom was a sudden 10 psi oil pressure drop. The cap showed no signs of fatigue beach marks. Note the perfect alignment of the cap and block breaks and the immaculate condition of the bearing.

* Yes, I know stock blocks are not supposed to survive with more than 500 HP. This one ran for many years with 485 HP and ~12 hrs. with 630...

Is that a thrust bearing in the middle?

Yes, that's where Ford put it...