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Cant and wont say, use at your own peril. I give them to my scrap guy, I cant and wont chance it for my customers.

Look at it this way, the crack developed with 200hp
I can't read, either.
 

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There is a cracking problem that is becoming an epidemic, and its only among the 351 roller blocks, the F4TE. We are averaging 2-3 cracked blocks for every 10 we get in. The crack is in the same spot every single time.

The cracks are noticed easily by eye when you remove the number 2 and number 4 cam bearing. Its not a coincidence that this is the same area that is used for the spider tray hold down. You can clearly see the cracks in the picture.

A problem will arise if this crack runs, the cam bearing will lose press and the bearing will walk out quickly and its all down hill from there.

I can guarantee alot of shops will use the block, whether they overlook it or think its not a big deal. I do NOT use these blocks. If you are having your roller windsor block machined, tell your machinist you want to see this area, protect yourself.

I will answer all questions should you have any :)



woody thanks' for the look out I was going to use the 351w I have for my new build and this is the block I have. It is still a long block should I just get a later block or just inspect this one? and use if all check's out good. What would you do if you had a choice?
 

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as important and informitive as this post is I think the concern has been overblown and a little perspecitive would help.

There are two separate issues here. The first is if you are building a high power engine than this block cracked or not is not your best choice. I totally agree that Strokeme totally made the correct decision in not rebuilding these blocks. For my business personally I would never let anything but the best go out to a customer as its my reputation on the line. I also think that letting people know about this crack is good info to get out there so those building a performance 351 know what to look for.

With that said I think this post has become more than was intended. In this thread Strokeme states that he has never seen one of these fail, in other words all the engine blocks he has seen like this came into the shop had nothing more than a crack. Also Strokeme made the statement that a lot of builders probably wouldn't even notice the crack as it is not a normal place to check so there are probably a lot of 351s out there built up that have that crack. I spent a lot of time on-line looking, and I could not find a singe instance where this crack ran and caused issues, not one. People talk about 302s coming apart and most of those cases can be attributed to boring the block out further than they should, the 302 is also a much weaker block than the 351 from the factory and is being pushed higher than it should be IMHO.

Another way to look at it two things cause cracks on a running engine the first is heat/thermal cycle and the second is stress from combustion. Being in the center of the block heat is obviously not the cause as the center of the engine will cool slower than any other part of the engine and the hottest parts will be at the cylinders and especially at the top of the block and the heads. As far as combustion stress again the stress points are going to be at the mains and the cylinder walls not the top of the cam journal where the lifter valley and the cam journals meet. In fact that part of the block probably has a better strength to stress ratio than anywhere else in the block. I do not see any way that either of these causes would apply in this case.

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth"

That leaves the obvious cause being related to the machining, so it happened at the factory. An EFI engine can easily last 200K to 300K miles. Just to be safe lets say 200K miles per engine. That means for every 5 of these engines that are cracked thats a million miles of engine life. Strokeme said 1/10 blocks have this crack. I don't know the production numbers but at 1 out of only 10 only 50,000 of these blocks would need to be produced to have over a billion miles on cracked blocks. Again I could not find one instance of a a failure.

I think this crack is something to be aware of especially if you are building a performance 351 but based on real world data I do not believe this crack is much to worry about in most applications.

I ran into a similar situation when researching Jag IRS for my Mustang. The upright hubs are cast aluminum and quite a few hubs were showing up with a crack in the lower webbing. It was always in the same spot and had a lot people worried about the parts. After a lot of research and panic from the Jaguar community (like the 351 not one failure documented) the general consensus was that the crack happened at the factory and was not a big deal, something to be aware of so you could make an informed decision. I was thankfull that neither of my hubs were cracked and I don't think I would have risked it had there been a crack given th performance nature of my appliation, but the same thing happened there that has happened in regards to the 351 crack, a lot of concern for a minimal issue.

The info is here so people can make an educated decision that will best suit their needs, but unfortunately IMHO it has become a a decision forced upon them due to fear and panic.
 

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People talk about 302s coming apart and most of those cases can be attributed to boring the block out further than they should, the 302 is also a much weaker block than the 351 from the factory and is being pushed higher than it should be IMHO.
Bore size has nothing to do with it. RPM and/or cylinder pressures are what kill factory 302 blocks. And yes, it's blatantly obvious that the 302 is being pushed higher than it should when they break. That's usually why engines break: they were pushed harder than they were designed to go.

Strokeme said 1/10 blocks have this crack.
mmmmmmmmm no he actually said 2-3 blocks for every ten.

We are averaging 2-3 cracked blocks for every 10 we get in.
The whats and whys of the cracks forming is irrelevant. They're there, and it's not recommended that they be used.

But hey, it's your customer's motor, I'm sure they won't mind when you tell them. I mean, you'd tell them, right? What with all that real-world data to back up your claims.
 

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If my engine builder used an engine with cracks in it....ANY WHERE....and took my money I would want to straight up murder his ass.
 

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if yall even need to question if your builder would use a block that was cracked you need to find a new builder.

as some one who is building an F4TE blocked 408 thats going to be pushing near 1kHP the first thing my builder said was we need to check the cam bearing area for cracks. everything checked out with my block so we kept going. we are using a lot of tricks from the X275 race motor program to help keep the block happy and together at this level
 

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Well piss.... I guess I need to pull the cam out of my 96 before I get any deeper into this project. I guess if it's cracked, I'm staying 302 for a while.
 

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Anyone can use the block if its cracked. I just made a note of it, since I saw so many of them. Life is all about choices
I'm just going mild compared to some of the numbers I've seen here.... planning on 400-450 hp. Even though it's not going to be a strip only car (it's mostly a garage queen), I don't know if I can sleep at night if those are there, LOL. Hopefully I'm lucky.

Thanks for the PSA though, I'm glad you brought this to light.
 

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408whp and 440tk 65 Mustang.. Have a true trac 8 inch to put in and a T5z but the stock axels and the junk yard T5 have stayed together so far. This is a stock block 70’s 302 though so not sure it’s very relative to the post.
 

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what I've seen in the 351w is locked up distributors most of the time with an oem setup. Due to the distributor shaft being longer than a 302 think maybe an oiling issue for the distributor. When buying a 351w for a core to build.
 
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