Cracked 4.6 Block.....AGAIN

[stkjock]

huh


I thought I saw it in a different spot

 

[weather man]

I see a crack from arrow to arrow.

 

[06gtmustang]

Yup that runs all the way across.

 

[stkjock]

what's the bolted to the block other than the motor mounts?

 

[kepsus]

maybe stupid question, but is it standard mount, and what about bolt lenght

 

[stkjock]

I asked Mike at L&M about this here's his comment about the midplae

All those items must be square and not preloading the block with stress.
If the crack was closer to the mount I would say that is the issue, but it DOES NOT rule that out.
These brackets/plate must align without using a “BOLT TO PULL IT UP”

 

[ethic1]

Is there a reason you are running a motor plate? I have not seen many doing this....

 

[19COBRA93]

Any pics of the plate you're running?

 

[05moneypit]

My last block was a WAP. I ran steel mounts with a 1/2" urethane bushing between the mount and the K member. That motor ran almost 2 seasons and it cracked at the bottom of number 4 cylinder right below the rear mount hole. Our thinking was the stiff mounts and the weakness of the WAP caused that problem but didn't have any real data to prove it other than a few other guys that have tried putting big power to a WAP and ended up with broken blocks.

So with this build we used a NVH block. We made a .090 mid plate for this build and are using the stock motor mounts with the stock bolts and the correct isolators for the BMR K member. We mocked everything up with a bare block to get the mid plate aligned correctly. The trans mount is also very soft. Most people will tell you not to even run a trans mount with a mid plate but we still made one.

As much as I hate to admit this is my own doing I believe that 19COBRA93 may have hit on the root cause with the head torque comment. We had problems getting the first head (this side that the block cracked on) to torque when we put this engine together, the head studs were from the last motor. We had a few studs that felt like they were starting to yield before they reached torque so we tried it again and got the same result. We took the head back off and I called ARP and talked with tech. Al's very first question was "did you use regular moly lube or ARP lube?" He said some regular moly is to slippery and can cause over torque. He told me the studs should measure no longer than 9.520 and we had some that were .080 to long. We got a complete new set of studs from ARP along with a bottle of their lube. We chased the threads in the block and torqued the head up with the new studs with no problems.....but I think the damage was already done. It just didn't show up till we got some heat in the motor and put some boost to it.

This is just a theory but out of any of the possibilities this makes the most sense.

Engine is out and on the stand. Here are a couple more pictures.


Lee

 

[19COBRA93]

I really think that's the cause. That crack is about at the bottom of where the head bolts reach. An over torque of the head bolts would cause a crack like that in that area. On aluminum blocks proper head bolt torque is VERY important, and one reason to stick with TTY bolts (not to start any sort of debate about TTY vs ARP). That's an unfortunate failure. Sorry to see.

 

[05moneypit]

what's the bolted to the block other than the motor mounts?

It's the power steering pump. I deleted the AC years ago and changed the belt routing around to get rid of belt slip.

Lee

 

[05moneypit]

I really think that's the cause. That crack is about at the bottom of where the head bolts reach. An over torque of the head bolts would cause a crack like that in that area. On aluminum blocks proper head bolt torque is VERY important, and one reason to stick with TTY bolts (not to start any sort of debate about TTY vs ARP). That's an unfortunate failure. Sorry to see.

I can't argue with you on the TTY.....right now I have more belief in the TTY than I did a year ago.

 

[BruceH]

The whole situation sucks. Any plans for the replacement motor yet?

 

[DILYSI Dave]

Uhg. I think that is right about the head studs though. It takes a shit-ton of load to stretch an ARP stud like that. I love ARP's, but I also only use the moly with their logo on it. Sorry for the loss.

 

[05moneypit]

My rotating assembly is fine, hell the rings probably are not even close to be seated yet. I've got a line on a few Teksid blocks but would rather stick with an NVH or maybe go to iron this time. We have a race on June 1st that I really want to be ready for. I will make a decission this weekend on what the plan of attack will be.

 

[19COBRA93]

I've got a brand new iron block here if you're interested. Shipping wouldn't be real cheap, but I'd sell it to you at dead cost. PM me if you're interested.

 

[05stroker]

With the new ARP studs, did you "strech" them when installed?

 

[DiMora]

Just so I can learn something here...TTY (Torque To Yield) - for those that prefer them - are we talking factory head-bolts...use once and discard? (vs. re-usable ARP head studs)?

 

[BruceH]

Ford designed the mod motorto use tty. The bolt cannot be overtorqued. It is very easy to not have consistent torques with regular hardware. This can lead to warping, uneven sealing, and additional stress. With a head it can also cause cylinder bore distortion.

There are a few whitepapers out there about the mod motor design. Dry reading but informative. Ford engineering designed a small, efficient, and very strong motor using modern technology and close machining.

 

[19COBRA93]

Just so I can learn something here...TTY (Torque To Yield) - for those that prefer them - are we talking factory head-bolts...use once and discard? (vs. re-usable ARP head studs)?

Yes, factory torque to yield bolts. Use once, discard. They're very effective and hard to mess up. ARP's are great for high boost, high HP builds, but you've got to be very meticulous when torquing them down, especially on aluminum blocks.