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Discussion Starter · #1 ·
I know I may be opening a can of worms but from the last post I read 450 rwhp (500+ crank hp) was considered beyond the safe limits of a 5.0/302 roller block. For a street/strip car with a turbo or supercharger shifted at 5800-6000 rpm, what are the safe limits of the 5.0 block? 450 crank hp? 375 crank hp? Apparently 500 is over the safe limit.
 

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Roush racing is selling 2 yr 24,000mile warrented engines using the production block with a main stud girdle ,and stating 450hp 420tq. From what ive heard 500 is about the limit even with a girdle. And of course you have the issues of a weak block here or there that might skew it farther below that.
Some have boasted of 600 hp and lasting forever while others say 500 and it split. So for my money if I was trying to make that kind of hp id get at least a sportsman block. Or if i was starting from scratch a roush engine looks mighty sweet complete, and with a 2yr warrenty.
 

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On 2006-05-10 19:02, rkite wrote:

I know I may be opening a can of worms but from the last post I read 450 rwhp (500+ crank hp) was considered beyond the safe limits of a 5.0/302 roller block. For a street/strip car with a turbo or supercharger shifted at 5800-6000 rpm, what are the safe limits of the 5.0 block? 450 crank hp? 375 crank hp? Apparently 500 is over the safe limit.
After 500, especially with power adders, its a case of "when" will the block fail, not "if". They don't usually go out in a blaze of glory. It usually is a case of unexplained dropping oil pressure that doesn't go away.

When the block fails, it does it through the center of the block, there are no water jacket passaged. the only thing that get compromised is the main oil galley..since that is inside the crankcase - you'll never notice it. Plus, the manifold, bellhousing and front cover will keep things in order until it finally lets go.


There was a story on the web of a guy that had a loss of oil pressure that he couldn't explain. He finally decided to pull the engine and check - he thought that maybe he had spun a bearing or something. When he took off the intake he first saw the crack...it went thru the middle of the block, right down the valley. When he took off the front cover and oil pan...the block openned up like a book. I think that picture is still floating around the internet.

The 289/302 short throw crank is near bullet-proof. The issue is the thin wall block. They made it even lighter when they went to the roller lifter blocks, by removing even more metal. Early blocks are better, even better are sports man blocks, then, SVO, A-4, R blocks and finally the newest crop of after market blocks.

It's not all bad. You can just run one until it pukes...then get another block and do it again. The "pocket rocket" guys do tat all the time. Get a honda or prelude engine, strap a turbo to it, crank it to "11"...then when it blows, just steal a car, get the block and do it again. There a gazillion Honda's out there so they have a lot of years of "slash n' burn" to go thru.

The point is...this question has been asked and answered way too many times. The "safe" point is somewhere around 500 hp with factory roller lifter blocks. There are exceptions and there are people that lie about how much horsepower they are actually pulling. With power adder (turbo, supercharger, nitrous) you can do more at the risk of accelerating when it will start to give. The "killer" is detonation, if you keep the fuel, ignition in line and watch the effective compression, it'll last longer.

As always - Your mileage may vary.


_________________
"Your role may be thankless, but if you are willing to give it your all ... You just may bring happiness to those that outlast you."-- Sacrifice

<font size=-1>[ This Message was edited by: Beoweolf on 5/11/06 1:43pm ]</font>
 

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Discussion Starter · #4 ·
I guess 400rwhp (470) is near the limit with no girdle. Many say the girdle does not make the block handle any more power. It just keeps things together when they blow.

<font size=-1>[ This Message was edited by: rkite on 5/11/06 11:05pm ]</font>
 

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In my humble opinion and from what I have read and gathered from builders, about 400hp at the flywheel. Between 5800-6000rpm you run into valve float on rollers unless you upgrade the springs. I would think 500+hp in a street 302 isn't going to last long. The folks at this web site are very helpful and they build both street and racing engines. http://www.tandlengines.com/

Ed
 

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Good hydraulic rollers with properly matched components will spin to the 6800-7100 range. I have seen blocks live at the 500-550 range for quite some time and as far as stud girdles / valley reinforcing are concerned save your money the only effective way to stop cap walk and make the bottom end stronger is 4 bolt mains / aftermarket blocks
 

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Early block and a turbo is going to hold up much better than a late block and a supercharger.
 

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Early blocks do not have as much metal around the main bearings so I don't know how people can say they are stronger. I have a 71 block and 82 block and a 91 block all bare in my garage. Looking at the blocks if I were building a 500HP engine I would take the 91 block over the others. I have seen blocks split from 500HP and less NA. So if you are concidering high pressure from boost, well, GOOD LUCK. Like someone already said it's not IF it will split it's WHEN.
 

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Discussion Starter · #9 ·
I am just kicking ideas around. On www.turbomustangs.com people are getting up to 500rwhp on stock 5.0 motors with 1 or 2 turbos. Apparently 2 T3 rebuilt junkyard turbos from various 4 cylinder cars are enough for 450rwhp on a stock long block. It looks like an interesting project assuming you have a car with enough room for the turbos and the plumbing. It appears if done right to be another path to decent horsepower.
 

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Stock blocks are for daily driven passenger cars.

Even with a decent tune up, the stocker can and will crack at the 350 hp. level.

I have 2 to prove it.
 

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...The point is...this question has been asked and answered way too many times. The "safe" point is somewhere around 500 hp with factory roller lifter blocks. There are exceptions and there are people that lie about how much horsepower they are actually pulling. With power adder (turbo, supercharger, nitrous) you can do more at the risk of accelerating when it will start to give. The "killer" is detonation, if you keep the fuel, ignition in line and watch the effective compression, it'll last longer.
the issue with turbos is detonation and fuel delivery. Most of the ones that survive use some sort of inter-cooler and ignition retard based on boost. this is especially important in the 93-95 blocks as their compression was raised. The 8.1 - 5 cr stock blocks will take more boost, but there are other problems. of course, there is always the "Slash 'n Burn" technique....turn up the boost - Replace as necessary!

The question originally was posed as Safe horsepower, wasn't it?
_________________
"Your role may be thankless, but if you are willing to give it your all ... You just may bring happiness to those that outlast you."-- Sacrifice

<font size=-1>[ This Message was edited by: Beoweolf on 5/13/06 12:56am ]</font>
 

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Discussion Starter · #12 ·
Yep safe horsepower. Many of the guys on turbomustangs are running intercoolers and ignition retard or some other method to control detonation. It seems like an interesting project to get 2 small rebuilt turbos and keep the boost on the low side ~5 - 9 psi. The motor itself would need nothing more that a stock rebuild with forged pistons. I am not talking about a high boost application. There are several low and high boost JY Turbo (Junk Yard Turbo) owners on the forum.

<font size=-1>[ This Message was edited by: rkite on 5/13/06 1:47am ]</font>
 

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I think we can all agree a in tune (No detonation) motor is going to last alot longer than one that is improperly tuned !!
 

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OKAYY NOW this ought to stir up this post some more.
"Valley Girdles" The idea sounds good. Its supposed to reduce the block twisting thus leading to block cracking. (?)
Hmm something id like to try if i ever go power adder, and a hell of alot cheaper and eaiser to install than a dart block etc.

http://www.nmraracing.com/forums/showthread.php?t=47626
and
http://www.horsepowersales.net/main.html
The second site is from the company that makes the 'valley girdle'.
They have a video from being on Horspower TV on the main page.
 

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This will prob. start a whole different conversation,but if the motor is race balanced (I know that all motors are balanced from the factory) it would prob. last longer than a stock motor.
 

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I say about 500 is all it takes and then its gonna happen. Ive seen a few blown up 302s and its usaully when they are/over 425 rwhp horsepower. My friend had a 302 wit the normals. int,carb,cam,holley heads on the bottle. engine sawN20 from 150-200shot for about 2yrs. then about 2 months ago KABOOM!! block split right in half. pull the intake and u could damn near pull out the cam from the top of the engine.Turbomustangs is a really good site.thinkin about puttin myT3s on my lincoln mark7.They do get there cars very fast but it still happens. Here is an example from the site.

"So, I've had all the elements I need for a 9 second pass - a 1.4x 60', 135-136mph trap speed well, it should go a 9.9x still using the stock fuel system, stock rear end, stock computer with no tuning aid, and stock hypereutectic shortblock. We'll see...
Update 12-29-03: Barry just split his stock block in half. Every other part of the engine was fine, other than the split block!"



<font size=-1>[ This Message was edited by: fiercej on 5/14/06 5:50am ]</font>

<font size=-1>[ This Message was edited by: fiercej on 5/14/06 5:52am ]</font>
 

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Yesterday my sportsman block let go. It looks like the main bearing caps went. The front of the crank is out of the block an inch and at an angle. I haven't pulled it out yet. Ballpark 500 engine hp with Vortech supercharger at 10#, trick flow twisted wedge heads and GT40 intake. FRPP says in their literature that the sportsman block is good up to 450hp. John
 

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Discussion Starter · #20 ·
I know someone with that exact combo with #12 pulley and TF Stage 1 cam. He is making 446 at the rear wheels. His ignition timing is fixed at 20 degrees.
 
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