Anything over 500 seems to be playing with fire, the 5.0 blocks less than that. We spin them up a little, that doesn’t do them any favors. Last time I had mine apart (Mexican block) there was evidence of main cap walk. Dart block is in my future

 

The blocks that split are almost always nitrous injected or boosted, and something went wrong (obviously). Usually lean/timing/wrong plug heat range etc

 

I have also searched widely for the answer to this question. My 331 is built in a F1SE BB Thunderbird block which legend has it that it is a bit stronger than the E7 but I don't know. I have read that the early 302 blocks are the best assuming they haven't rotted out on the inside. I didn't specifically look for this block. It is what a friend of mine had that was a standard bore that I could use.

I'm well over 400 and just being a bit paranoid or not I have ARP main cap studs in mine and I also a main cap girdle(it is relieved so it doesn't hit the top of the arch in the main caps. My heads are also installed with ARP studs. I also switched to the Ron Morris engine mounts which are not as twist prone as stock mounts are. My block also was align honed on the mains and the engine was very well balanced.

Richard Holdener has built and tested a lot of Ford engines and he did went over this question. Part of the answer depends how well the engine has been built. I also think part of it is how is the thing driven. I found the actual video where he went through this.

 

It's not the HP, but the harmonics that split them. Balance is key. Short filling the block diminishes harmonics and David Vizard talks about this in one of his videos.

 

Lots of things to consider here, but history shows us about 500 hp would be the limits of a stock 289-302 original cast block.

 

The "splitting" is caused by "crank walk", or the failure of the main journals and caps to keep the crankshaft from "swaying in the saddle". Heavier, or 4-bolt splayed main caps, drilling for 1/2" fasteners, stud girdles, lightweight rods and pistons and, of course, precision balancing of the rotating assembly all can help "keep it together" at high rpm. On the other hand, from a perspective of machine work, etc., to keep the OE block, the price of an aftermarket one doesn't look so bad, does it?

 

I've seen a few split, usually forced induction and usually somewhere just over 500 hp. As Woodchuck stated the issue seems to be the crank moving around and rpm certainly makes that worse. The few NA engines I've heard of splitting were actually at a lower power level, simply because of how many rpm it takes to make that power level NA.

 

After watching Richards video, I am much less concerned about splitting it. Those were 5.0 blocks too...supposedly less robust.

 

I've got a 347 crate motor with 500 hp that is built from a stock block that I've never had any issues with...

347 Small Block Ford - Prestige Motorsports

Nevermind all those old-school naysayers. The 347 Ford Small Block Stroker is the only way to go if you are looking for a street engine upgrade for your 302 Ford. 425, 440 and 500HP options available. This would be an excellent addition to a Cobra Kit Car! Everything available from a short block...

www.prestigemoto.com

 

My old 331 (5.0 block) boosted setup was dyno's at 585hp and lasted years before I went with a Dart block because I wanted a 363. The 331 (5.0) was well built and fortified with good hardware.

As mentioned above, the stability of the crank and its supporting hardware will promote a block to stay together.

 

All the failures I can remember were stock blocks and stock or cast cranks. A better crank buys you some room as does a stronger block. With the stock parts they both have the strength of cooked spaghetti.

 

302 blocks are weak and very light compared to the other brand..and the cyd walls are thin and hang out the bottom of the casting..if you can swing it go with a Dart block if your going to make serious power..I would not go more than 4 to max 450 HP..and honestly that’s pushing it..I’m going to build one about that much power but I’m not going to beat on it to much

 

I don’t know if it’s still in publication, Muscle Mustang and Fast Fords. They had a article on the 5.0 block splitting. The shop they were working with said or their thoughts, the problem was the main caps walking. They said the main bolts don’t fit snugly in the caps. I think what they did was to use a larger bolt and machined the cap for a tight fit on the shoulder of the bolt.

I have a bunch of old Super Ford magazines. They did a story on blocks. On the 289/302 the 65-67 289 blocks are the strongest and as the years progress, they get weaker. I believe Ford took like 10 pounds out of the 5.0 block.

 

Are you planning on tracking the car with the new engine?

 

i would like to know how many people blowing 289/302 blocks were with the 289/302 firing order (versus the better 351W firing order). the 302 firing order hits the two front cylinders consecutively where there is almost no support (versus the rear where it doesn't have the oil filter path and does have the extra support of the bellhousing and mass of the flywheel/clutch or torque converter on the crank to keep it from whipping). Also, people pushing higher power are probably not using the typical motor mounts (use engine plates).

 

Also, people pushing higher power are probably not using the typical motor mounts (use engine plates).

A few days ago I saw a pic of a 302 block that had just started to crack. A raced 347" with turbo boost. The cracks were at the driver side main studs, bearing 2-3-4. Looking at where the engine mount is bolted to the block it made me wonder if there's some connection between type of engine mount and how much power the block will handle.

 

Another theory that's surfaced (which I think has some merit!) is an issue with firing order. Every firing order for 90 degree V8s ends up with two firing impulses on one end of the crank or the other, so that main cap gets a 'double whammy'. Under low throttle, or with a 'wimpy' engine, it would never be a problem. The 289/302 firing order has the double-tap happen at the front, and the 351 firing order, it happens at the rear.

I don't know, but I suspect that the "early" Windsor firing order transmits a little less vibration to the drivetrain, because the entire length of the crank would better soak that close-together power impulse, working as a spring, and then getting absorbed by the harmonic damper and drivetrain. With the double-impulse happening at the rear, less would get transferred through the crank back to the front (and damper), while more would get sent to the gearbox.

The front main support is not as beefy as the rear main, and that part of the cycle really hits the bearing hard. Typically, cracks start at the front, zip up to the lifter valley, and TADA! The block is now twin 4-bangers, rapidly divesting themselves of a common crank.

A lot of the guys who have experienced this with even a 5.0 engine on the dragstrip are running flat tappet (early firing order) cams from what I've seen.

Edit: Sorry I missed your post, @buckeyedemon ! I bet you've been listening to Ben Alameda, haven't you? lol

 

 

I have a 68 302 block sitting machined awaiting a 347 stroker kit. I plan to shift it at least at 7000 rpms and I hope it will approach 500 horsepower or more. I will put a girdle on it so it will at least not come out the oil pan. Looking at ALL the comments online I feel that it's fine as long as you stay out of detonation. I am adding an aluminum flywheel as I think that may take some stress off the rotating assembly. I think you will be fine as long as you make sure you don't have detonation or run it super hot.

 

I saw this on facebook, an aussie built stock block 347". 623hp at 7500 rpm on the dyno.

 

There is a lot of mention here regarding HP. Is it not the TQ that blows'm up?
Mine is 401 TQ at 4200 in an old 5 bolt block. I've always been cognitive of "if" and "when". But then, I don't stress the ole girl that much either.

 

There is a lot of mention here regarding HP. Is it not the TQ that blows'm up?
Mine is 401 TQ at 4200 in an old 5 bolt block. I've always been cognitive of "if" and "when". But then, I don't stress the ole girl that much either.

I would say yes. Other factors too like balancing, harmonics and such also. But, yea torque is a force and HP is derived from torque to give a value of work over time. Harmonics though can be a killer for any system. If harmonics aren't dampened or if the natural frequency of the short block or just the block itself is reached then bad things happen. If the harmonics is what could destroy a block then adding a main girdle may dampen or change the natural frequency of the block to a higher frequency and the block may be spared. It may not be the strength that a main girdle adds, but instead the effect on damping or natural frequency that the main girdle adds.

I was looking at valve springs the other day and David Vizard did a very good video on different type of valve springs and the pros/cons of each type (traditional, beehive and conical). The harmonic frequency of traditionals is relatively low and fairly constant over rpm while beehive harmonic frequency is higher to begin with stays steady for a while and then increases as rpms get high and conical harmonic frequency starts high and continues to climb over the entire rpm range as rpms increase making it nearly impossible to reach the harmonic frequency of the spring in operation.

 

I’d like to get into the minds that build the Indy blocks for their view of it all.

 

One of the reasons I posted that 623hp 347" is that it was posted by Competition-Engines in Melbourne. They seems to be a fairly serious engine builder that do a lot of high powered Fords. I don't think they would have used an stock block for this build, if not fairly sure the block will handle the combo. The racers down under build Windsor based engines with way more than 600hp. I think I earlier have posted a video of Dandy Engines drag and drive Falcon making 2700hp on the dyno. It's a twin turbo 427" Windsor and the 3900lbs car have run 6s on leaf springs and 275 tires. 🔥

Competition-Engines have also posted pics of a "sleeper" street Cleveland. Looks like an factory stock engine on the outside, but makes 618hp/589tq on the dyno. 😁 👍👍

 

Do not get a main girdle that requires the tops of the main caps to be knocked down. I think a few of those are still floating around on the market. You also want to keep your main cap studs with a girdle. I don't see much point in going to a girdle and then bolting it down with bolts.

 

Bumping this old thread. I have a mildly built ‘68 302 in my GT350 clone which has aluminium heads. The previous owner told me the bottom end was put back together with stock components and balanced. I’m assuming they just replaced the bearings and hardware but used the stock rotating assembly. I expect the motor only makes about 300 crank HP but was wanting to know roughly what I can rev the engine to? He told me 5,000 RPM but I have read 6-6500 rpm elsewhere?

 

The bigger question is where does it make peak power and that is subsequent to the camshaft and heads. If it is making power that high I would agree that you should be fine to 6000 or so rpms. If it made peak around 6000 I would even think 6200 or 6300 would be okay.

 

I would feel safe to 6000. I think on my old 85 5.0 LX the orange started at 6200. I have a stock GT40P with a carb in my 66, I go to 6000.

 

Thanks, that’s good to know. The later model blocks are supposedly weaker too, correct?