340 or 360 engine block. Have you ever hurt one

I’m not talking about after you broke a rod or crank I’m talking about cracking up thru the middle of the mains like the big blocks commonly do. I personally never have knock on wood and my junk goes without concrete and I always stick to the stock main caps. Let’s hear some nightmare stories.

Following! There’s a lot of talk about a stock block not handling xxx horsepower but I don’t hear of many failures. I also hear of some that have split cylinder walls. But what about the earlier 360 blocks that are thicker. Im curious what those commonly handle without failure as I have one with 360-1 heads.

I split a 2bbl 273 block, but the rod was already knocking and I just wanted to see at that point how much abuse it could take so I raced it till it blew.

I have a nice april 1970 360 block if someone wants to try and break it thats for sale.

Yup. 14:1 on alcohol. 8000 RPM. Made it...damn I think it made it 20 hard passes. Maybe a few more. That was 1985. I was sneaking up on it for a few years and the bearings always looked like crap because the block was moving around. Had to use .0035 on the mains to keep it from snagging a bearing. That was on 20w50 in the dog days of summer and 10w40 in the spring and fall. To get the rings seal with alcohol with the limited oil choices back then, that's what you did.

Then when we put the W2 heads on it was over. IIRC it broke in the number 2 bulk head. It bent a stock 340 crank but never broke it. That's how I knew something went [censored] up.

After that, I found a reasonable T/A block that needed 8 sleeves, snatched it up. Sleeved it, used some block filler and never broke another block. Knocked some rods out, but that a whole 'nother story

Edit: That had to be 1987 as I got out of the army in early 1984 and started the project. So I killed the block in 87 and bought the T/A block right after that.

Have not broken one, or seen one get broke in person.

I do know people who have broken cast 4" stroker cranks, but it's been after several seasons on full time racing.

Nope never broke a LA small block. Have blown many head gaskets, because they only have 4 bolts for each cylinder. Had a stock 70 340 4 speed dart and the clip broke on the wrist pin, cut a big groove in the cylinder, put a sleeve in it and ran it for several more years, until I blew a clutch and broke off the corner of the block when the flywheel came apart.

Broke a first year “magnum” motor with n2o. (Talking modern era magnum) Ran ok but lost oil pressure. Put new bearings in it, still bad oil pressure. Looked at it with more detail. Found the block was cracked through the 3 center mains, from the caps to the cam bearings along the oiling holes.
“Not a carefully tuned” would be an understatement.

I have broke 3 cyl walls.. 2 of them on the same hole which was sleeved
and 1 on another engine... all been on 340 blocks.. thats all I run

John, I have ran both 340 & 360 blocks with lots of nitrous and never hurt one. I even ran a MP cast 3.58 stroke crank in 71 360 block, stock caps, aluminum rods and a good nitrous piston for a couple seasons early in my KOS days.

A very long time ago we took apart a AHRA Stock Eliminator type engine and the #1 main cap came off in two parts. Started running four bolt mains mostly and never saw it a again.

Once we got up to higher horsepower and high compression we started spiting cylinder walls even with "filled" blocks.

No problems to date with R blocks.

I never ran a SBM , my youngest son had a 93 360 Magnum block break #1&3 cylinders split and #2 Main cap pulled from the webbing, the top of the main stud on driverside still had part of the block around it. 392 (4.00X3.90) Ci 360 with 3 plates NOS I think the heads were edelbrock...I think it was a bad casted block,he thinks it was the power level... The 340 block(I think it was a 68) had the mains walk around a few times.but he never broke that one. that was a 392ci(4.06X3.79) with Shady Dell Brodix and 2 plates of NOS

My last Stock block ran 9.74@2860 pounds. That block was rebuilt 3 times and in need of its 4th when it grabbed a bearing and broke a rod damaging the bottom of the block. .030 (360) from day one the bores were so bad I wore out 2 new sets of stones and most of the 3rd set just to get the bores to where I would assemble it. If I thought it was worth saving I would do some bring and have a new sleeve installed but it served me well and will be going on my scrap pile.

Yes, I broke a rod on my old backup 340 awhile back and it took out the block. Ran good 11.30s with a 557 lift cam, 9 1/2 to 1 compression and ported "J" heads , Didn't owe me anything as it served me well and already had a few rebuilds on it. Been running a 360 Magnum block and presently an R3 block every since.

That wasn’t the blocks fault. Like I stated I’m looking for block failures like big block Mopars are known for.

I have never seen a block broken on its own. Take all the rotating assembly failures out and no never seen one. I’m not sure you can take all the rotating failures out though, if the caps walk because the block is moving and takes a bearing out isn’t the block “failing”

Yes. That means the block was seeing more load than it could handle.

Again, the only question this really answers is how long did it take you to FIND the crack. If you went 100 runs and found the crack, did it happen on run 99? Nope. Sure didn't. That fracture started long before it was found.

I say these cracks show up very early and then just keep growing until the expose an issue.

So no one really knows how many runs before a fracture happens. Same when you mag a crank, or rods.

Sorry I guess I misread it , forgot who posted , I would have never answered.

OK JOHN......ILL SAY IT

YOU DONT SEE SMALL BLOCKS FAIL LIKE BIG BLOCKS.....BECAUSE THEY DONT MAKE BIG BLOCK POWER....
HA HA HA HA HA HA HA HA HA HA HA HA HA

I didn't break it but feel it would've broken eventually. 360 block with a 4" crank, I ran it for five years, best was 6.57 @ 104 in a 3260# Dart. When I took it apart to freshen it up the cam and main bearings were worn odd from the back to the front. Luckily a member here called me with a R1 engine that he no longer needed.

Several years ago there were photos posted of a small block that busted a couple cylinders from top to bottom that wasn't caused by rotating assembly failure. I don't remember what site it was posted on.

Looks like a pretty good track record to me.

Hit the ignore user button if I hurt your little feelings. Cheese and rice. Lol.

Just curious, would you speculate at all on the primary cause? RPM related load or peak cylinder pressure?

I ask because I am putting a 5.9 magnum in my 69 Coronet and am planning on E85 & 11-15 psi boost (no intercooler) I was planning shifting at 5500 rpm and the limiter set at 5800

I want to believe that holding the RPM down will help keep it together.

I'm pretty sure it was a weak area in the block.. I do run high rpm but that
has never been a issue.. I didnt measure those blocks but it might have
been core shift.. for yours just measure the thickness... now days I measure
all my stuff
EDIT
all these blocks were/are 340 .030 over

Thanks going to do that, you didn't hurt my feelings. I broke a rod and took out a cylinder wall I would think that was a " hurt". You jumped on and said that's not what you wanted to know. Fine , I'll take the cheese don't care for rice unless it's shrimp fried. Have a nice day!

Here's my VERY first sentence. "I’m not talking about after you broke a rod or crank I’m talking about cracking up thru the middle of the mains like the big blocks commonly do."

Got it!!!

I didn’t mean to come across like a dic but I hope to do a fresh build with a 4 inch K1 crank I got off of Dan at Performance Only and a set of K1 rods. (Chevy sized) I have a new set of Diamond Flat top pistons and a set of domed Wiseco Pistons. I went 9.74@2860 pounds and around a 10.04@3200 pounds in my sons car with stock location pushrod position. Next set of Edelbrock heads will get a set of Harland sharp .350 offset rockers, more cam, more compression, and more carb. That should give us an idea how good a stock block is.

hmmmm...

Does this mean that 5.9 magnum with stock heads, block, crank, rods, pistons, camshaft, lifters, pushrods, valves, intake manifold, exhaust manifolds, head bolts, rod bolts, main bolts, timing chain isn't going to go 9.99@ 3500 lbs with a 78 mm turbo @ 15 psi?

Couldn’t tell you honestly. I’ve always been a NA guy but may change that one of these days. If I do it better be a 7 second ride though, and big block. Lol

One of my best friends has a gremlin with a 472 hemi , 18 spline 833, 345/40R18 tires...

I have a fake full weight 69 super bee with a stock 360+boost, a good 727 w/brake & bump box, 325/50R15 Nitto drag radials

I think I am going to need to be way out on him at the 1/8th