Fox Split Block Register

FastDriver · Jun 23, 2024

TheTurboForums.com has something called the stock block chronicles where they listed a few examples of guys' combos that broke. It's the right idea, but they only have a few samples. I think I'm going to turn this thread into that. I'm going to grab comments from anywhere I can find them and repost here.

If you'd like to post your combo and how it broke with pics and any/all of the following information, that would be appreciated:

Block: Year/Original vehicle or code. Roller/non-roller, etc...
Bore/ Stroke/Rod length
How used: Street/Strip/Auto-X/Road Racing
Machine work: Specifically was it ever balanced.
Rotating Assembly weights: If you know the Crank/rod/piston/balancer/flywheel weights, bob weights if it was balanced by a machine shop, or just have the part # or names for any of them.
Balance: 50/28/0
Max RPM
Dyno'd power or Track Trap speed & weight
Forced Induction Type: Blower/Turbo/N20/NA
Gridled? Brand?
Block damage: Did it crack from mains to lifter valley or go in some other way? what was damaged?
Other Notes: Any other details.

Those are about all of the relevant things I can think of.

FastDriver · Jun 23, 2024

Block: stock 302
Bore/ Stroke/Rod length: 4.030/3.4
Balance: 50oz
How used: Strip
Machine work:
Rotating Assembly & weights: eagle crank/rods/je pistons
Max RPM:
Dyno'd power or Track Trap speed & weight: 420-470 rwhp
Forced Induction Type: Nitrous 100-150 shots
Giridled?: Yes.
Block damage: 1st center 3 mains cracked. 2nd: "1/8" split down the front of the block, broken crank, two busted rods/pistons, all intake valves bent, timing chain, etc... toast, hole in oil pan."
Story:

When I cracked two stock 302 roller blocks, I did it the exact same way each time.
Stock block 347, old school 50 oz balance, eagle crank/rods/je pistons, all with a main stud girdle. Twisted Wedges, Systemax II intake, Lunat 544/560 232/242 112 lsa cam.
Motor put down like 300-310 rwhp on a chassis dyno through the 4000 rpm stalled C4 and 424 rwhp on an NX 100 shot jet setting with 1000 psi bottle. Sad thing was, at the time I was thinking that the 100 shot recommended jetting was actually a 125 shot setting and the power it showed at the wheels indicated so. Back to this in a minute...

I think at the time it was in the neighborhood of 11.80s on motor and 10.70s on nitrous. Well, I got a little greedy at an event and upped the jetting to NX recommended 150 shot. Still thinking what I had in there was a 125 shot, not 100 shot and not looking at my jets when I pulled them. So upped the jetting, dropped the timing a couple more degrees and went to town. I don't remember the ET, but what I do remember is getting 5 passes before I lost oil pressure and the car slowed down.

Loaded it up, took it home and tore it down. Hairline crack down the center of the lifter valley. Flipped it over, cracks down the center 3 mains. Pulled the cam, center 3 cam bearings fell out onto the camshaft. Luckily nothing else was hurt!

1 year later I'm back on the track and get greedy again. 150 shot. 5 passes and bam, this time I wasn't so lucky. 1/8" split down the front of the block, broken crank, two busted rods/pistons, all intake valves bent, timing chain, etc... toast, hole in oil pan. Yep, catastrophic!

Now back to the whole jetting thing. I bought the kit used and was told it had 125 hp jets in it (NX Shark nozzle). I never checked the jets, went off what the guy said and pulled appropriate timing. Car loved it and ran better than it ever did on the 5115 dry kit. After two blown up motors I finally realized that the jets that I was running were indeed 100 shot jets as per NX website/jet card. So I went from 424 rwhp on a 100 shot jet to possibly 470ish rwhp on the 150 shot jets (no reason to believe it didn't pick up that much). Bye bye stock block!!!

Bought me another 347 shortblock used and never hit it with more than a 75, still ran 10.70s on the little shot.

As far as the 351 blocks power capabilities. I had cracks in an 84 block with a main girdle using a 4.17 stroke crank, 28 oz balance and only revving to 6400 for a year.

FastDriver · Jun 23, 2024

Woody from fordstrokers wrote about this one, though not as much build detail as I'd like in this thread:
Block: stock 302
Bore/ Stroke/Rod length: Unk, but a stroker
Balance: Unk
How used: Strip
Machine work: Unk
Rotating Assembly & weights: Unk
Max RPM: 6,700 on a data logger
Dyno'd power or Track Trap speed & weight: 475-500
Forced Induction Type: Unk
Giridled?: Unk
Block damage: 3 center mains cracked
Other Notes: customer reported continual drops in oil pressure and nothing was showing up in the oil filter

Woody states that cap walk "is very hard to prevent, the only real prevention is sticking with a stock stroke 3.00 inch crank, and thats no fun " I note from this he did NOT specify balance, but rather stroke. Another clue to me that even the best balanced cranks still aren't balanced at the off-angles, and with longer throws, stroker cranks are going to put more lateral load on the mains.

Another gem from him: "Once the cap goes oval under load it allows the cap to become sloppy in the registers and its down hill quick. When the cap goes slightly oval it sucks the cap ends in and there is no longer any press on the cap in the register" My takeaway here is that this is why bigger thicker caps, like those on the 289 HiPo, Mexican 302, and B50 blocks can mitigate this issue. Stock roller blocks have much thinner caps.

Pics:
Center Mains cracked and working towards cam journals

Cap-walk/chatter:

FastDriver · Jun 23, 2024

MFE is another guy that comes to mind. His case is special because you don't hear about a lot of guys that crack their blocks on a 302, or at only 300rwhp, or at less than 6,500 RPM.

Block: stock 302
Bore/ Stroke/Rod length: 4"/3"/5.090"
Balance: 50oz
How used: Road Racing
Machine work: Dont think so (@MFE92 )
Rotating Assembly & weights: Stock
Max RPM: 6,500
Dyno'd power or Track Trap speed & weight: <300rwhp GT40 combo
Forced Induction Type: NA
Giridled?: Unk
Block damage: Mains cracked on fist block. Crank snapped on 2nd.
Other Notes: He primarily suspects his balancer. Woody has echoes this to me when he advised me on a build to stick with a light balancer to help the cast stock crank out as much as possible. If you've been in the game a long time, you've seen stock cranks snapped due to blower belt tension. This doesn't just pull a crank until it snaps, it causes crank flexion which beats up the mains when spinning. Once the front main gives up, it all comes apart quickly.

My thoughts are that this is a guy who spent a lot of time at high RPM due to the nature of road course racing. I also doubt if he ever had the rotating assembly balanced after swapping dampners. 6.5k is pretty safe for the normal DD or street/strip warrior, but not necessarily for the guy hanging out there frequently for minutes at a time.

His description:

My old block cracked like that at less than 6500 RPM and less than 300 RWHP. The oil pressure gauge acted like a vacuum gauge, when I stepped on the gas and loaded the engine, the pressure would drop. I can only imagine that when I loaded the engine it was opening up the clearances. The car still got me 180 miles home, around town for a few more weeks before I tore it down and found the cam bearings walking their way out of it. Closer inspection showed cracks from the thress center cam bores to mains just like Woody points out. What you can't tell from the pictures is just how thin the walls are, the material between cam and main bores is probably .0125 thick.

Separately, he has explained his suspicions:

maybe a large part of the blame lies with running a heavy-ass SFI damper on it. Sure, it might have the same imbalance as a factory balancer, but they're HEAVY, and not only do I blame it for breaking the crank on my next engine, I think there's a lot of crank "whip" involved. Other people mention rod cap movement/chatter as well. Bottom line is, the castings are pretty damned thin and not well supported above the mains, and things just move too much.

FastDriver · Jun 23, 2024

Marc Arnold's Cobra

I'll just throw this one in here because it's interesting to me. This guy spun the hell out of a stock block, a 347 sportsman block, and eventually an R302. He never did split the block, from what I can tell, but he did have main cap walk on the 347 that finally convinced him to up his block game to a 4-bolt. The coolest part is that he always did it NA, and stayed Hydraulic Roller all the way up to his 359build that went deep 9s in the 1/4. He finally sent SR on the same block and drove it into the 8s.

In any case his stock block, stock crank & rods high-compression 306 made over 400rwhp and regularly spun 7.5k RPM. But, in his words:

I was still using the stock block but we couldn't keep main bearings in it for very long at 7,500 rpm

After going to a B50 sportsman block and building an internally balanced 347 that he spun to 8k RPM and made 498rwhp. Damn! But, spinning this led to:

When I brought the shortblock up to JDC Engineering for a refresh, we noticed a bit of main cap walk.

Finally, he built an R302.

I thought this was semi-relevant in this thread because Marc spun his 2-bolt roller blocks regularly to 7.5-8k RPM and while it worked for a limited time in a race only car, they were on the path to destruction.

FastDriver · Jun 24, 2024

Here's an interesting one. I had to piece things together and I wish he was still around to ask questions of, but this guy killed a mexican block

Block: Mexican 302 block
Bore/ Stroke/Rod length: 4.045" bore/3" stroke/ 5.090"
How used: Unk
Machine work: Unk
Rotating Assembly & weights: Zero balanced done with mallory, Eagle ESP Forged Crank 3.00, Eagle H-beam Rods 5.09, D.S.S GSX 4.045 pistons -11cc
Balance: 0oz - neutral
Max RPM: Claimed he normally kept it under 6,250, but also referenced hitting a limiter. Possibly the stock limiter, but did not clarify. Elsewhere a couple years later he claimed he was shifting at 6.5k.
Dyno'd power or Track Trap speed & weight: 548 through an AOD (maybe closer to 600 through a manual) & "a tad over 600 on race fuel" on a mustang dyno.
Forced Induction Type: Novi2000
Giridled?: Yes. DSS
Block damage: Lost oil pressure. Pics appear to me to show cracks in one of the journals, guessing the cam.
Other Notes: Had main studs.

This was in 2013. Another poster speculated that 600 on a mustang dyno through an AOD would be more like 700rwhp with a manual on a DynoJet.

He thinks it happened went he bounced off of the limiter, but didn't specify the RPM.

"200 or so miles.......there was some cap walk,i think it happened when it bounced the limiter" Also claimed he only made 3 passes on it.

86 GT 308,Novi 2000,TEA 205's,Freezy cam,AOD silverfox valvebody w/transbrake, non-lockup 3500 stall, 3.55's,548rwhp on Mustang Dyno,

This is the first time I'd say the split was more about power than RPM. Though that may have been a factor, most would argue that the neutral balance, forged assembly should've been up to well more than the RPM claimed. On the other hand, it was making BIG power for a 2-bolt 302. Over 600rwhp on a mustang dyno, through an AOD & add to that it was with a blower. Blower motors run with a BSFC in the .6 range, while NA can be closer to .45. Add to that the drivetrain losses of an auto, and even negating any conservative mustang dyno effect, this car would have made 700+, possibly 800 rwhp through a manual.

HotFox · Jun 26, 2024

I broke my 331, 1992 Thunderbird block cryo treated entire short block after maching but prior to assembly, 4.030x3.25, #2 main bolt hole split, eagle Forged crank was also cracked in #2 main radius. Mains were studded, Machine shop said typical on a V8 #2 or #4 at high rpm.
28oz balanced, 8400rpm max, 470rwhp, max trap speed was 129mph at 3200lbs, best ET was 11.11 on DOT tire. Lasted from 2009-2021. Under 10K miles, approx 250+ trips down the drag strip over 50% over 8K rpm.

Noobz347 · Jun 26, 2024

Just a side note: Fk fotobucket Rank ass amateurs

rednotch · Jun 26, 2024

Lol I wish I had my old desktop HD drive still. Plenty of pics, some completely in two halves after taking off a girdle. They do not like to be rattled at rpm under boost or nitrous, that's for sure. Belt driven blowers just help them get there faster. Even after the b50 came out it wasn't long before ppl started splitting those. Tuning has come a long way to help but there still a giant weak link. Feather weight and a motor plate will give you some extra wiggle room. I did the whole neutral balance, forged light weight in a stock block once, after that high dollar parts go in a good block, cheap junk goes on stock one's..

AeroCoupe · Jun 26, 2024

Dude this has been a great read. I have nothing to add data wise but good info for sure.

I keep harassing BluePrint to sell their four bolt main block (#2, #3, & #4) so I can move my 331 over to that block as my stuff does not warrant a Dart block. I just want to be able to move the shift point up from 6400 to 7200 as it pulls past that. I’d even entertain a 150 shot but not on a stock roller block.

Anyhow, good stuff here guys!

limp · Jun 27, 2024

AeroCoupe said:
Dude this has been a great read. I have nothing to add data wise but good info for sure.

I keep harassing BluePrint to sell their four bolt main block (#2, #3, & #4) so I can move my 331 over to that block as my stuff does not warrant a Dart block. I just want to be able to move the shift point up from 6400 to 7200 as it pulls past that. I’d even entertain a 150 shot but not on a stock roller block.

Anyhow, good stuff here guys!

Blueprint told me that as long as they can sell all the blocks they make as an assembled engine, there will be NO bare blocks sold...

AeroCoupe · Jun 27, 2024

They tell me that too but the more people bug them about it the more they will see another revenue stream. That and if I bug them enough who knows one may just show up at the house.

Noobz347 · Jun 27, 2024

Where did we see that Blueprint engine blocks are 4-bolt main?

AeroCoupe · Jun 27, 2024

2021 SEMA

SEMA 2021: Blueprint Engines Is Casting All-New SBF Windsor Blocks

Windsor blocks are nowhere near as plentiful as they once were. But thanks to BluePrint Engines, there is now a new source.

www.enginelabs.com

If they would sell them for $1,000 I would buy one in a minute.

AeroCoupe · Jun 27, 2024

Group buy anyone or are those done anymore? I am just trying to think of a way to show them there is a lot more interest in buying one of their blocks than a short block or long block for a lot of people.

nickyb · Jun 27, 2024

I'd buy one for a grand.

FastDriver · Jun 27, 2024

Well, B50s were $900 16 years ago. I know China does it cheaper, but $1k is a pipe dream.

rednotch · Jun 27, 2024

Blue print blocks are out of the same foundry as dart, world and edelbrock... If ford wants a budget block some one needs to talk Brodix into doing one, everyone else has a ford tax for parts.

rednotch · Jun 27, 2024

Add to that dart seems to have woken up a bit on pricing...They lowered MAP pricing... Map just means advertised agreements, if they claim they can't sell below it, its because they don't want to, they can, they just can't advertise it. That's why all the damn private equity owned brands started to be exempt for online discounts deals, even if it hid the price in the cart. Blocks still not going to be cheap though, then add in labor for machine work & prep. Buddy picked up the dart shp 205 heads for a good amount less then the afr enforcer retail price after the new map sheets went out, assembled heads are supposedly Pac springs and Manley valves. But old school 11/32 valve train. That's a nice budget casting that went on a stock block, it will probably end up on the list of cracked one's eventually.

Noobz347 · Jun 28, 2024

Noobz347 said:
Where did we see that Blueprint engine blocks are 4-bolt main?

Fox Split Block Register

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

Stangnet Facilities Maint Tech... Er... Janitor

I'd like to remain having one chocolate starfish

lube between the nut and the face. I know my lubes

wrap a little cheese around it and its a done

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

lube between the nut and the face. I know my lubes

I gotta say i never painted my nuts, Never Ever

I was uncomfortably high & wearing a helmet

I'd like to remain having one chocolate starfish

I'd like to remain having one chocolate starfish

Stangnet Facilities Maint Tech... Er... Janitor

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