Ford Mustang Forums banner
1 - 20 of 85 Posts

· Registered
Joined
·
456 Posts
Discussion Starter · #1 ·
So my Fordstrokers 347 decided to spit the crank out. I have no idea why. It was dynoed at 350 to the tires, not commonly revved past 6000, never been to a track, and had around 3500 miles. So a very conservative build. It could have been block failure or the crank, will probably never know for sure, now.It pretty much took everything with it. At least 1 bent valve, and 2 others that touched the pistons. I still need to get the bottom end out and the pan off but figured it's time to figure out my next move.

Now I'm scared to run another stock block 347 with a cast crank, but yet don't feel like I need more. Did I just have bad luck or was I that close to the ragged edge? Is there any chance of anything being salvaged? Only 1 piston broke and it looks like the rod on that one is bent, could I maybe reuse the other stuff, or should I just write it all off. What about the cam, it seems to still be turning smoothly and I can't see any marks on it yet..



 

· Registered
Joined
·
5,357 Posts
It seems to happen a lot. And the builder's got nothing to do with it, nor the brand of crank.

Gilroy's:


Blacktop's:


Flyin'FoxBody's:


Etc, etc.

They all have one thing in common - stock blocks. My stock block cracked in a bunch of places, but I caught it before catastrophic failure happened (and I had a girdle - probably helped keep everything in one place). No more stock 8.2" deck blocks for me.
 

· Registered
Joined
·
456 Posts
Discussion Starter · #5 ·
Well this definitely sucks. I purposefully left it a little weak on power , to what I thought would be a safe level with the stock block, 350 ain't a lot. Though when it was on the dyno it was 100 degrees and raining. It was during a dyno days when everyone was complaining about how low the dyno was reading. It very well could have been more like 400.. and ran very strong.

If a stock block simply can't hold up to this power, I guess I'm down to few options. Either drop the power more, and keep a stock block, go to a 408 stock block, which still could be problems, or go aftermarket block and 363 it, then hope no other part fails and takes a $2000 block...
 
  • Like
Reactions: cab0154

· Registered
Joined
·
1,149 Posts
the last one with a cast 347 crank i saw with the main caps off (didnt break) in an early block had a lot of cap walk etching. i just think they are a time bomb. i would bet the block failed before the crank.
 

· Registered
Joined
·
6,822 Posts
Scat cast crank here, DSS level 20 block half hard filled. 347 street car. Puts down 400 both sides to the tire. 10,000 miles and I beat on it.

Had an another 347 and 331 neither had block or internals failure. It's more uncommon than common for stock 302 roller blocks.
 
  • Like
Reactions: 2camsam

· Registered
Joined
·
37,878 Posts
If a stock block simply can't hold up to this power, I guess I'm down to few options. Either drop the power more, and keep a stock block, go to a 408 stock block, which still could be problems, or go aftermarket block and 363 it, then hope no other part fails and takes a $2000 block...
There's a reason they don't build the stock blocks any longer. And according to Woody, it's getting tougher and tougher to find 9.5" stock blocks that aren't cracked around the #5 head bolt. Many modified thin cast 8.2's are time bombs. No way to predict and no way to strengthen. Of the options you stated - I think Dart is the one I'd pick. But there are other ways..... ;)
 

· Registered
Joined
·
456 Posts
Discussion Starter · #10 ·
But there are other ways.....
Sorry can't do an ls motor....... ;)

I guess I have to look at this realistically, I won't be happy with less power then what I had before, even though technically it would be enough. So stock block out. To go 408 I'd end up spending as much on new parts as the upgraded block will cost me, and I'd still have a stock block. So that's out.
I'm leaning toward a Dart 363 from ADp..
 

· US Army Retired
Joined
·
5,807 Posts
Probably a million or so 302's were cast and put into vehicles, thousands upon thousands have been stroked to 347 and pictures of four or five busted stock blocks and its fact. I don't think so. I ran a 347 stock block with the 5.4 rod combination at the power level the op posted for seven years and 7K+ plus miles with zero issues and have seen many exceed that number hp wise.
 

· Registered
Joined
·
5,015 Posts
Probably a million or so 302's were cast and put into vehicles, thousands upon thousands have been stroked to 347 and pictures of four or five busted stock blocks and its fact. I don't think so. I ran a 347 stock block with the 5.4 rod combination at the power level the op posted for seven years and 7K+ plus miles with zero issues and have seen many exceed that number hp wise.

^^^ truth

My daddy always said "Son, you can take the elevator all your life but you are going to tell everyone the one time you take the shaft".
 

· Registered
Joined
·
456 Posts
Discussion Starter · #14 ·
Probably a million or so 302's were cast and put into vehicles, thousands upon thousands have been stroked to 347 and pictures of four or five busted stock blocks and its fact. I don't think so. I ran a 347 stock block with the 5.4 rod combination at the power level the op posted for seven years and 7K+ plus miles with zero issues and have seen many exceed that number hp wise.
Aren't you kinda doing the same thing? You're saying yours was good, so it must be a myth. 7k really isn't that many miles, I would be very curious to see how many 347 builds lasted to 50k.

Now to be fair, on a Dynojet mine probably would have been around the 400 mark. It was a very healthy running motor.
 

· Registered
Joined
·
37,878 Posts
I've seen the busted block on 260 rwhp motors. It was a thin-wall casting designed to reliably support 170-240HP and around 300 lb-ft of torque all produced below 5000 rpm. If you want an idea just how much metal they took out of the block for their OEM applications - compare weight of a stock 5.0L block, a Dart 8.2 cast iron block and a Dart 8.2 aluminum block. It's predictable that problems begin to show up when people begin to ask MUCH more of it than it was ever designed to accommodate. How many problems? No good answer. How many with no problems? No good answer. At what output and rpm levels do the problems start to show up more often? No reliable answer. My definition of 'reliable' here is - info from something that happened to someone else that I can rely on to predict what's going to happen mine.

What you can rely on is that as you increase output and the rpm at which it occurs, it's more likely that problems will show up -- risk increases. Each individual makes their own choices about how much risk they're willing to take. To try and conclude much more than that is fabrication. Go to Fordstrokers site -- they're not building stock blocks any longer. I'm guessing the failure rate began to fall outside their risk tolerance.
 

· Registered
Joined
·
913 Posts
IF I had your car & was trying to keep it stock looking(as you have done)..I'd go back with either a R302,or Dart blocked 347/352/363. IMO,the way you modded the car was very tasteful & kept the original appearance ;) You can most likely bet on going to a 3-4" cowl hood,drop motor mounts,different intake,headers...ETC if you go 408. A 347/352/363 in any of those blocks(with your top-end parts) will haul a$$ in that lighter car,and be very,very durable..without changing intake/exhaust/hood...ETC!!
 

· Registered
Joined
·
1,679 Posts
I've seen the busted block on 260 rwhp motors.
My '92 stock block broke in a similar manner back in 2000 during a practice auto-x. It only made 273 rwhp, 304 rwtq and was rarely revved above 5700. Crank split in half and came out the front of the block. I always thought it was because of the stock balancer re-clocking itself but the pics in this thread pretty much are identical to what mine looked like after she went kablamy.
 

· Registered
Joined
·
1,149 Posts
Probably a million or so 302's were cast and put into vehicles, thousands upon thousands have been stroked to 347 and pictures of four or five busted stock blocks and its fact. I don't think so. I ran a 347 stock block with the 5.4 rod combination at the power level the op posted for seven years and 7K+ plus miles with zero issues and have seen many exceed that number hp wise.

i have had that didnt break as well. the last one i tore down with the same crank had a #### ton of cap walk, and it was an early block. i assure you that its only a matter of time when the caps are dancing.
 

· Registered
Joined
·
1,670 Posts
Guess I've been lucky. I've owned several fox body cars with stock bottom ends all putting out over 4oo rwhp and not one cracked block. Granted, I keep it under 6000 rpm and don't beat on them regularly. There are also a ton of explorer motors out there that I can use from the JY. A lot cheaper than $6k bottom ends and have worked well for me on swaps.
 

· Registered
Joined
·
37,878 Posts
Guess I've been lucky..... A lot cheaper than $6k bottom ends and have worked well for me on swaps.
Yes, you've been lucky. A lot cheaper unless/until the broken block takes out the expensive top end pieces too -- which many people run and it frequently does. But it's all unpredictable.....it's simply how much are you willing to pay up front to minimize the risk. Each person can only answer that for themselves.
 
1 - 20 of 85 Posts
Top