No 2 main failures

Jac Mac

Active Member
Being a bit frugal with info Frank.. Brg failure or block web or both. Then how many RPM, 50/28/ 0 or other balance factors, wet sump or dry, steel or iron crank, block year, balancer& flywheel clutch size/weight, who balanced it, bob-weight used, type of Bob Weight...................................
I like to entice worldwide comments before getting into individual details. How many others have had similar failures, more common on race engines using standard or semi standard two bolt mains ? This one is a two bolt main, steel crank and 10.5 to 1 compression on pop up pistons machined back. Appears to be only a cap failure, but I wouldn't trust the webs so I think its scrap. Will go for a Dart SHP with 4 bolt caps if the owner will afford it.

Mike Pass

Gold Supporter
Hi Frank.

Hard to comment properly without the full story of what the spec is and how hard it has been used in terms of revs etc. External balance cranks still give the mains a severe beating at high revs because even though the engine is balanced overall the crank is not and this can knock out main bearings etc. This repeated severe vibration can also fatigue the caps and block.
I would not want to re use that block. The Dart will be plenty strong but I would still go the (accurately done) neutral balance route as it is a far better solution from a basic engineering viewpoint.
Time for someone to dig out the credit card!

In years past I had experienced two crankshaft failures:
-a 271hp 289 4v catastrophic forward journal breakage; and
-a 306hp 289 4v (SAI original) nascent cracking filet area detected during magnaflux.

Both engines (then) external balanced (accurately FWIW) 10:5 CR C7FE camshafts, headwork etc.

Although the usual episodic reasons are usually causitive for the drama, I believe the cumulative effect of the original firing order set both of these failures up. (no kidding)


Randy V

Ford’s Mexican blocks are reported to be stronger, but I have no hands on evidence that this is true.
We bought one of the first BOSS blocks that ford was offering back in 2008 or so. It was rough bored both in cylinders as well as main bearing saddles. Once we took care of that and decking the block to bring it to spec, we would have been better off buying a Dart block that was already finished save for honing of cylinders. I am not aware if Ford is prepping the Boss block to a higher spec or not -but worth asking I guess.
#11 and Valley Girdle Pro

This is installed on the 289 that was in my first TS40. Some folks think they are a was inexpensive, so to me, NBD. I think this damage happens most with late model 5.0 blocks as they are very light. A combination of a “heavy”car that can really hook places the block under more twisting force than it can stand reliably. Like a drag car with a good suspension and slicks. My engine inertia dynoed @ 385 HP and the car ready to drive only weighed 2120 lbs, so excessive “block loading” was probably not a factor.
Eddy, the engine has standard 1 - 5 - firing order. The block has now been repaired by installing new caps and line bored, now got to rebuild with new 40th pistons and a rebalance. ( Customer choice to stay with old block ) .
For peace of mind check with the guy that did your line bore, find out how much, if any, they cut from No. 1 web. I'v seen it stretch without showing cracks. and if your in the mood go with a cam and 351 order