[macstang]

Yeah, I know. Probably beating the dead horse again on this. However, being the analytical type of person that I am and considering I've been offered one of these blocks(complete short block in fact) and also seeing that I'm considering another horsepower jump beyond badda boom, I thought I would research this a bit.

One obvious thing I found is people running superchargers and snapping the front area of the cranks off. That one is fairly obvious as to the cause if the crank is a stock crank. Obvious answer to that would be to upgrade the crank beyond the stock cast and the rods and pistons would need it as well. It probably needs a full 4 bolt main block as well so the stock block is probably going to fail under any significant super charger sooner or later.

These blocks, 85/6 to 95 I guess, were apparently cast a bit lighter than the early 70's 302 blocks and they are said to be specifically a bit thinner in the main cap to cam webbing areas. I don't have one to examine just yet so I can only take people's word for this. It makes no sense to me though considering that these blocks were built to run roller cams. I would have thought they would strengthen the area around the cam and lifters due to the roller cam.

So, the question is still all over the map regarding how much power you can push through one. I've read everything from around 400 horsepower max to 600 and everything in between. 500 came up as something of a general consensus from a lot of posts. My 72 302 block would probably have handled more than that but it is now cracked from the blunt end of a rod comeing out and will be sent to the corn field,,,,from which,,,,there is,,,,no return.

The most common crack is down the lifter valley and second most common is around the main caps which got me thinking. I also saw a write up on the last of the 351W blocks which were rollers and an engine rebuilder said 2 out of 10 that he gets are found to be cracked around one of the middle mains.

Well I came up with a list of some things that I think are part of the cause or things to avoid to prevent these blocks from cracking;

1. don't run big roller cams in the stock blocks. Sounds strange perhaps since they are roller blocks but I think the spider and dog bones put additional stress on the lifter valley area of the casting and around the lifter bores. The bigger you go with the cam and the higher rpm you push it the more stress that causes also. I think this is one of the main reasons these blocks split.

2. run internal balance if at all possible - for a lower rpm engine 28 external might be ok but avoid 50 oz external if you are going to significantly increase the horsepower limits of the block

3. install ARP main cap studs on even a stock rebuild and everything beyond that

4. have the rotating assembly performance high speed balanced if you are going to push the engine beyond the stock build and it will help a stock rebuild also

5. Cryo. This is known to improve the strength of parts like this but it costs a bit to ship the block back and forth across a state or 2. The cryo process itself for a block runs $225 to $250 which does not look that bad to me. If you can find a cryo automotive place within driving limits it is a lot cheaper than buying an aftermarket block. It will only increase the strength of the block by maybe 20 percent though so if you plan to go beyond some magical horsepower/rpm limit like maybe 500 and 7000(just a guess), get an aftermarket block.

6. run a lighter rotating assembly. This goes along somewhat with internal balance. There are aluminum rods, feather light cranks and I've seen machine shops taking material off pistons to lighten them. It is probably not wise to lighten rods.

I still have some questions. Do the thicker 2,3,4 main caps that are available help any. I have been told that it is not worth a lot to install the 4 bolt caps because the area of the block where the outer bolt holes are drilled is not very strong to begin with and drilling a bolt hole might make this worse. Would something like the DSS main girdle help to extend the limits of these blocks a bit? How much would a bit be? Partially filling the blocks does not fix this splitting problem.

What else is there that you can do to one of these blocks to make it stronger?

 

[cmefly]

Nothing is going to help the stock 289/302 block. The only thing a main girdle will do is hold all the parts together when the block does crack. For me if you are going over the 500 Hp mark then just step up to a 8.2 dart block and build a 363 or go with a stock 351W block.

 

[zray]

Nothing is going to help the stock 289/302 block. The only thing a main girdle will do is hold all the parts together when the block does crack. For me if you are going over the 500 Hp mark then just step up to a 8.2 dart block and build a 363 or go with a stock 351W block.

^^^^^ YES.

The OP characterizes his own post as "beating a dead horse" and that sums it up nicely as Cmefly points out. Every solution mentioned is a bandaid, and not applicable outside the race track where reliability means lasting all weekend. There's a right tool for every job, and the 289/302/5.0 blocks work well for the power they were designed for and then some. But for the over 400 HP crowd it doesn't make financial sense to try and make a silk purse out of a sows ear.

Z

 

[stephen_wilson]

I agree. The "entry fee" may cost a pretty penny, but how much does a grenaded engine cost you? There's two theories: 1) build it once to last 2) build "cheaply"- expecting to lose one now and then.

 

[Huskinhano]

Correct me if I'm wrong but I seem to recall that Ford took something like 10 pounds of cast iron out of the 5.0 block. Back in the later 70's and 80's they were all making engine blocks light as possible. Remember the Pontiac 301? I remember many years ago a guy made a post as to how strong is a set of cheap $85 cast piston set is. The guy built a turbines 5.0 making around the 500 hp Mark with the pistons. The block cracked down the middle but the cheap cast piston were fine.

 

[Woodchuck]

Yeah, I know. Probably beating the dead horse again on this. However, being the analytical type of person that I am and considering I've been offered one of these blocks(complete short block in fact) and also seeing that I'm considering another horsepower jump beyond badda boom, I thought I would research this a bit. :deadhorse:

One obvious thing I found is people running superchargers and snapping the front area of the cranks off. That one is fairly obvious as to the cause if the crank is a stock crank. Obvious answer to that would be to upgrade the crank beyond the stock cast and the rods and pistons would need it as well. It probably needs a full 4 bolt main block as well so the stock block is probably going to fail under any significant super charger sooner or later.

The factory steel cranks are pretty stout, considering. I think the issue with longevity can be mitigated with proper balance and firing order. There's a reason Ford put a bob-weight on the front of HiPo's...

These blocks, 85/6 to 95 I guess, were apparently cast a bit lighter than the early 70's 302 blocks and they are said to be specifically a bit thinner in the main cap to cam webbing areas. I don't have one to examine just yet so I can only take people's word for this. It makes no sense to me though considering that these blocks were built to run roller cams. I would have thought they would strengthen the area around the cam and lifters due to the roller cam.

Most of the weight (about 10 lbs.) was taken out of the area around the main webbing. The affected blocks would be those between '81-2 and '01 with the one-piece rear main seal. There is much less lifter loading due to a) the longer bores and b) the roller lifters than a flat-tappet motor and the lifter spider adds no extra stress to the block. The stress imparted on this area comes from the crank, not the cam.

So, the question is still all over the map regarding how much power you can push through one. I've read everything from around 400 horsepower max to 600 and everything in between. 500 came up as something of a general consensus from a lot of posts. My 72 302 block would probably have handled more than that but it is now cracked from the blunt end of a rod comeing out and will be sent to the corn field,,,,from which,,,,there is,,,,no return.

I think the number I would feel comfortable with, as far as a 5.0 block, would be around 425 HP. IMHO, any more than that is a crap-shoot, depending on the individual casting.

The most common crack is down the lifter valley and second most common is around the main caps which got me thinking. I also saw a write up on the last of the 351W blocks which were rollers and an engine rebuilder said 2 out of 10 that he gets are found to be cracked around one of the middle mains.

Well I came up with a list of some things that I think are part of the cause or things to avoid to prevent these blocks from cracking;

1. don't run big roller cams in the stock blocks. Sounds strange perhaps since they are roller blocks but I think the spider and dog bones put additional stress on the lifter valley area of the casting and around the lifter bores. The bigger you go with the cam and the higher rpm you push it the more stress that causes also. I think this is one of the main reasons these blocks split.

Disagree. The roller lifters are much easier to move than flat tappets. The cracks here are precipitated by stresses imparted by the crankshaft.

2. run internal balance if at all possible - for a lower rpm engine 28 external might be ok but avoid 50 oz external if you are going to significantly increase the horsepower limits of the block.

I think there are some advantages to internally balancing to zero as far as not having to re-balance the entire rotating assembly upon replacement of the harmonic balancer or flywheel/flexplate. As far as external balancing is concerned, I believe the key is to use an appropriately-sized balancer for the application. After all, the purpose of the balancer is to provide a mass to absorb the torque twist of the crank. That's why 351W balancers are bigger than 302's, to counter the effects of a longer stroke and more torque. If I was building a 289/302 with 28oz imbalance I'd use a 351W balancer. Using a lightweight balancer would be asking for failure of the crank. Keeping the pistons, rods and pins light would also be beneficial as it's the forces of those working perpendicular to the crank are always trying to push and pull the crank throws away from the crank centerline.

3. install ARP main cap studs on even a stock rebuild and everything beyond that.

I question this. I don't perceive a big problem with main caps "walking" or if this would have any effect on the blocks, themselves, failing. It's a definite, though, if you are running a main cap girdle which is another subject for contention.

4. have the rotating assembly performance high speed balanced if you are going to push the engine beyond the stock build and it will help a stock rebuild also.

Can't say I disagree with this although I don't think it's a necessity on a stock rebuild. I think QUALITY COMPONENTS are more of an issue. I recall quite a bit of conversation on Summit balancers and somebody's flywheels being quite a bit out of spec. There's no excuse for this.


5. Cryo. This is known to improve the strength of parts like this but it costs a bit to ship the block back and forth across a state or 2. The cryo process itself for a block runs $225 to $250 which does not look that bad to me. If you can find a cryo automotive place within driving limits it is a lot cheaper than buying an aftermarket block. It will only increase the strength of the block by maybe 20 percent though so if you plan to go beyond some magical horsepower/rpm limit like maybe 500 and 7000(just a guess), get an aftermarket block.

Before I ever got to this point, the stock block would be long gone and a Dart would be in its place.

6. run a lighter rotating assembly. This goes along somewhat with internal balance. There are aluminum rods, feather light cranks and I've seen machine shops taking material off pistons to lighten them. It is probably not wise to lighten rods.

Like anything, too much can be detrimental. Lightening reciprocating and rotating parts can aid the speed of acceleration in the motor but at the expense of reliability. During the build you have to ask yourself... "Do I run I-beam or H-beam rods?". "Do I run deep skirts or short ones?". I think the individual application dictates what you do and to what point.

I still have some questions. Do the thicker 2,3,4 main caps that are available help any. I have been told that it is not worth a lot to install the 4 bolt caps because the area of the block where the outer bolt holes are drilled is not very strong to begin with and drilling a bolt hole might make this worse. Would something like the DSS main girdle help to extend the limits of these blocks a bit? How much would a bit be? Partially filling the blocks does not fix this splitting problem.

Do thicker main caps help? Sure. They have more surface area at the parting line to transfer load to the block. IMHO, you are correct about 4-bolt caps as far as Windsor blocks are concerned. Main girdle? Depends on how much energy you're going to ask the crank to absorb. If you're asking the crank to deal with a power-adder it might be a good idea.

What else is there that you can do to one of these blocks to make it stronger?

You're not going to make the block any stronger than it already is. If you have the ability to look at a bunch of cores and inspect the main web area and pick one that looks best that's about all you can do. The rest lies in what you can do to keep everything together. To be honest, if you're wanting more than 400 HP you shouldn't be looking at a 8.2 inch block anyway.

 

[sportsroof69]

While there are some 302 blocks surviving at higher numbers, you're still gambling if you're making over 400. A guy that used to own a performance shop in OKC has one with a blower that made over 700, and he's had it for 6-7 years, and never hurt it. The kicker is that he never races it.

You can put any of the band aids you want on it, but make over 400, and its on borrowed time. A Dart or Boss block would save you money in the long run, or you could hate life by stuffing a stock 351 block in it. For what you do wih the car, I wouldn't build a stock 302 block motor.

 

[Lemondrop]

I agree the roller lifters won't add stress. They should reduce it by the lifters not side loading as badly in the bore. The only thing that might cause any trouble would be where the spider attaches at the bolt bosses but if the bolt holes truly could cause any cracking, I'd suspect the oil drain holes in the block would crack first.

That said, the cracks would be from the block moving and not from anything related to the lifters. I agree with everyone else, if going for the high HP, move on to an aftermarket block.

Does anyone make a lower block plate that bolts on the oil pan rail for small blocks? I don't know what strength that would add but in large Diesel engines they are used to stop the bottom of the block from bellowing.

 

[macstang]

Thanks for all the thoughts on this. I guess the short answer to the question is that these blocks or any block for that matter will start to flex at some point under both higher horsepower than it was made to handle and/or higher rpms than it was made to handle. Once it flexes enough it comes apart regardless of how well built or assembled it was.

I found another discussion somewhere about the possibility of a bottom block plate that would catch all the oil pan bolt holes. These main girdles just free float inside there so how much is that really good for? I don't have a clue.

I talked with the balance shop that did my engine and the guy said they just built and dyno'd a customer's 289 at 485 at some rpm he wouldn't specify. They used the Dart block and a whole bunch of other parts.

At one time I had an early 80's 351W that came out of a pick up. It was std everything but in need of a rebuild. Unfortunately I let it get away from me.

 

[jdub]

Here's a question, what's less likely to crack?

1) 50oz 347 making 500hp at 8000rpm, competition drag car
2) Internal balance 347, 10psi of boost, making 550hp at 6000rpms, my dad's street car that scares him

 

[macstang]

Umm, the one that wants to go to Heaven first? LOL. Oh wait. Less likely. The one that refuses to go into the light.

Look what I found. It was a dirt track 74 302 block / Eagle stroker taching somewhere between 7200 and 7400. I wasn't sure which because I saw both numbers.

By some strange miracle, one of the main webs actually wanted to stay in the block.

The lifter valley didn't crack on a count of because it split horizontally instead of vertically.
It has t he valley bars but it was probably the red paint the kept it glued together there.

Maybe we should turn this into a block carnage thread, LOL.

 

[stephen_wilson]

You can really see how thin the webs that support the Mains are in that picture. That's why girdles or anything on the pan rail won't work, the problem area is above them !

 

[jdub]

It'd be cool to see a 351w block and 5.0 block sectioned so we can see the difference. Cleveland too for that matter.

 

[turbo2256b]

The first 3 years of the 351W are the strongest of that breed. They then reduced materal around the main webing.

 

[Huskinhano]

Back in the early 90's "Super Ford"magazine (remember them?) they did a great article on blocks. the 65-66 289 was the strongest of all SBF blocks. Next up 67-69. The 70's weren't that good.

They also did a sonic test on a NOS 427 side oiler block, never used. With it's standard bore, the major thrust side was already too thin, below factory specs.

351W were pretty good. Check on Corral, there's a sticky about 80's 351W blocks cracking in the cam journals.

I was saving a standard bore '65 289 block but sold it to a friend who kept bugging me for it.

 

[macstang]

My ex-wife rolled my original 289 block out by the garage, it rained in it and then froze and cracked the block big time. I couldn't get back up there to get it in time.

So I went on a scout about and may have found myself an alternate plan B.

I found a mid 70's 460/C6 that looks in pretty decent shape actually at a shop owned by a friend of mine. Even has headers. Its in a F250 extended cab truck. Well, the 302 in my F150 is up around 75,000 miles on it now, lot of them hard miles pulling a trailer it will barely pull and it won't rebuild again(.060 over, .020 on the crank). If I get the 460/C6 I can put that in my pick up and then the fresh Cleveland short block I have along with a bunch of other parts in boxes could go into the mustang. I found a Crane cam(don't remember the spec's), 1.6 roller rockers, block plates, baffled pan, valve covers, even has headers but doesn't look like those would fit my car, Mallory Comp distributor even. Lotta stuff there but the heads are bare 2v's. Performer intake which I don't know if that would keep or not. 600 vacuum carb. It is an option at least and it sort of wacks 2 ducks with the same rock sort of.

 

[GT_Rich]

I agree with others that cracks down the lifter valley have nothing at all to do with the cam. However, I mostly disagree with putting hard limits on these 5.0 blocks and I'd like to bring up a new factor that has not been addressed. That factor is knock and detonation. This is what kills a 5.0 block...especially the supercharged motors that you read about grenading. The pressure pulses that happen during knock (typically due to too much timing mixed with boost) will send significant shock waves through the block. Repeated knock will crack a block. Many guys running blowers can easily put down 500 hp below 6,000 rpm. If there tune isn't perfect, they could see very small amounts of detonation on every pull they make, and never know it. The supercharged blocks making 5-700 hp that you see live are well tuned and not running on the ragged edge of fuel and spark curves. Keeping a very wet AFR under boost will limit the likely hood of detonation. It provides a buffer and doesn't sacrifice that much power. This same theory holds true for high RPM N/A motors.

87 to early 92 5.0 blocks came from the factory with TRW forged pistons. In my opinion, when properly tuned, these short blocks can live while putting down really good power if the tune is correct and the RPMs are kept below ~6300 RPM. Above that RPM the rods, specifically the rod bolts, will become the weak link. Upgrade the rod bolts and push it farther....I'm not sure how much.

 

[sportsroof69]

Here's a question, what's less likely to crack?

1) 50oz 347 making 500hp at 8000rpm, competition drag car
2) Internal balance 347, 10psi of boost, making 550hp at 6000rpms, my dad's street car that scares him

Engine 2.

 

[Woodchuck]

Engine 2.

^^^ This.

 

[Huskinhano]

Or just keep a stock pile of 5.0 short blocks from the pick n pull on half price day.