360 Block Question

I've got a 360 block that came out of an E58 1975 Dart Sport. Was cast on the night shift 11.27.1974. What are the chances it has thicker cylinder walls? Can you tell by how much it weighs? Let me know. thx matt

It is cast after the 340 production ended, the theory goes the 340 and concurent 360s used the same cylinder walls. After that they all went thin so it is well into the thinwall production time frame. That being said even if it was in the "340 wall" era I would not want to go more than .030 over without sonic testing.

How big are you going with it. Being the budget racer I am up to .030 over I don't even bother checking them, but that's me. If it keeps you awake at night have it sonic checked

X2

Early block casting number is 3418496. These are supposed to have the same water jacket as the 340 so theoretically they could go .070 or .080 over. Core shift being what it is, I would have one sonic tested before going crazy with it.

10.10.73 date Casting No. 3418496-360-10 block for mine too. Seems .060" over is no problem according to my machinist. He's seen plenty of those blocks.

My blocks casting # is 4006830-360-5. I've also got a 340 block casting # 2780930-340-6 but that block has been punched .040 already.

4006830 is the late thin wall casting. Probably should be checked at anything more than 030 over.

There was a magazine article a while back where they sonic checked several 360's from early 70's to early 90's and the readings where all over the place. I believe the thickest one they had was cast in 1978.

The block in question is too late to be a 340 core.

RE: 360 wall thickness article?: Is there an online copy that I can read? I know AndyF's article on bigblocks. Didn't know about any smallblock article.
R.

My Challenger has the original 360 from my 76 Volare. Been .060 over 20 years don't remember the exact numbers but it was plenty thick.
Doug

I have 3 "E58 motors, all out of 79 300's. Two I had sonic checked and all had thick walls ( around .200"). The E58 motor had a bunch of special parts in it. The block should be stamped 360HP with serial #. Fifth digit of the VIN should be "L" for E58 engine car. Body code plate should have "E58" stamped on it. E 58 engines also came with a windage tray ( same as early HP 340's and 360's), specially selected ( what ever that means )cast iron crank, Larger cast iron exhaust manifolds, "360 Premium engine" sticker on the valve covers. Not sure on the last item on California package cars though. Engine ID is located just below left cylinder head. Example: 9W 360HP 6345. Translates to: 9=1979, W= Windsor plant, 360HP = displacement, 6345 = date code ( Dec. 11, 1979) Above info came from printed Chrysler data. Got a problem, take it up with them.

Anything from the '70s is suspect. Quality was all over the place. Core shift is possible on any of this stuff, regardless what it's supposed to be.

I have had early blocks thin and late blocks thick, and the opposite more common. If you are spending money on a good rotating assembly I would spend the money and have your block sonic checked.

for sure, and that holds true for ANY stock block, regardless of year. IMO, 500 HP or more for any stock block is a good rule of thumb for sonic testing.

My W9 360 Dakota project block is cast January 13 1971 3418496-4-360

It was sonic checked and all 8 bores ranged from .230"-.210" on the thrust side.

We bored this block .030" over and did a fill of Hard Block up to the freeze plugs before machining.

Awesome. You should be good to go. I had a 1971 360 block out of a motor home that checked like that.

Lets say you a had a block that was .250 everywhere. What would be the maximum bore size that would be considered safe?

I would think .060 would not be a problem. Again, what kind of HP you want to push through it has a bearing on wall thickness / block rigidity.

Say 600hp

Cylinder wall thickness is not the only concern on the OE LA blocks. High RPM and/or 550+ HP, bulkheads and block webbing become areas of potential issues also.

LOTS a fast stock block small blocks out there and I can't remember seeing or hearing of any block failures. And some of these guys are RPM crazy.

What's everyone's opinion on Magnum verses LA blocks regarding strength? Heard Magnums are a better ( stronger ) block?

Wait for HotRodDave.. he'll school you on the Magnum

The guys that preach this never provide any proof. 3-2-1.

Yep never showed any evidence for it.

https://board.moparts.org/ubbthreads/ubbt...tml#Post1711743

All you got to do is look at the pics I didn't post, the block weights I didn't post, the personal experience grinding on blocks I didn't post...

What? Weights? And guestimates that a magnum block can handle 100 more HP then LA blocks? Strange way to show proof.

How many cracked Magnum heads are out there? 1 in 4? 3?

Plenty of LA blocks running 600+ and living a long happy life.

Anyways.. it's all about prep.

There is extra meat where it counts, I posted pics. The iron is clearly harder, try grinding one block then the other. Cylinder walls though thinner on average are very much more consistant and the bad spots are not as bad as the older stuff and remember a chain is only as strong as it's weekest link, if you have one thin spot in a block with 1/2 inch thick bores it can wreck the entire thing. 9 out of 10 magnum heads are cracked... SO WHAT? How many does it cause a problem on? I never seen one and have worked with 100s of magnum powered trucks, if it was an issue you would see steam coming out the exhaust on most 92-03 dodge trucks. No stock head LA or Magnum makes enough power to bust any block (unless you get one with a thin spot of course) so who cares. Add on top of all that the 45 years of poor coolant maintnance corroding them up. I am not saying a LA block is a ticking time bomb but if you are really pushing the limits the mag block is stronger, how much I don't know but to deny it is stronger is foolish or in-experienced. As fer a 340 block, so what if you got .020 more clearance on 1/4 of the intake valve, .040 bore barely makes a measurable flow increase if any. Sure I would love to get a 4.25 siamese bore but for most heads out there it won't make any HP difference only more TQ but so will a dirt cheap roller cam. You can sell a 340 block buy a magnum, regrind the cam core bore and square deck it with the money.

I forgot about that other post. Thanks Dave. I am aware of your opinion on the Magnums, and your points are well taken IMO. Looking for any others that might chime in. Doesn't appear to be any big advantage ether way if you are making under 500 HP - except weight maybe?

Probably the only advantage under 600 hp is the cheap roller cam, I don't think the small weight difference matters in most builds.

According to race bulletin #8, July 1982:

"The early 360 ('71-'76) blocks are a special case. They use a 4.00" bore (340 was 4.04") but the block was made with the 340 water-jacket core. This means that these blocks can be bored to the same actual bore size as any 340 and have the same borewall thickness. This is NOT true of the newer 360's"

Basically there's enough "meat on the bone" to go to a 4.10" bore.

Cool.

I believe the "late" block began with 74. The casting numbers are different. Regardless, I wouldn't trust QC from the 70's and would have everything sonic checked for core shift, etc., before going crazy with one.

I know the 71-74's are 3418496 and use the 340 water-jackets. Maybe the 75-76 also. When did the start casting the 360 in MEXICO?

That quote is worthless. It's from the same source of the "thinwall 400s/440s" myth that was in every Mopar publication for years and years. The first I heard of this was in the very early '70s and back then it was considered gospel that the 496 block was the only 360 with the 340 core walls. As years went by it changed by, I think, wishful thinking.

RE: this quote, "all had thick walls ( around .200")".
Sorry, Charlie, the only place 0.200 is considered thick is in Moparland and some Ford circles.

Actually 0.200" is what's considered minimum for a major thrust in the rest of the old stuff. For Mopar engines if you can get 0.170" on a major thrust it's going to work. And the non-thrust parts of the block can go all the way to 0.120" and some won't even make that, and I mean virgin blocks! If you have 0.170" or more on all thrusts you go out and buy lottery tickets!

As for the thousands of 600hp 360s out there, I think they're all out racing those fabled 383 Hemis that Gramps had in his Road Runner. Put another way I don't believe it. If there are 100 360s making 600hp I'd be surprised.

If you had a 4.00" bore and 0.300" thick cylinder walls it'd be a Siamese block and you could go 0.200" over. It's being done with aftermarket smallblock chevy blocks right now. The largest area of concern is the head gasket between the cylinders.

R.

My 496 block

I have a 1971 360 block that has been run bored .060 over since the early 90's. and has many NOS passes on it.

Man I hope so. I have a block that is already .030 over and on its 3rd rebuild. Its gone 9.70's already but the block is worn out and needs bored. I picked up 2 sets of .060 over pistons that are standing by to be put to work.

Jason over at Shady Dell speed shop seems to think .060 is alright on a 360.

Agreed & I think the first number went from a (3) to a (4).

650 ponies here in my 360....been beating it for 3 years now....

1967 barracuda
1.30, 6.40 1/8 mile....

mine was cast 10/10/73.. 496 block. What do you mean 3 to a 4?

Truck is almost done, I will see how much and how long a stock magnum block can last

The thing is, that's only 20-thousandths on the radius even if it is true. That's just not really significant if you start measuring and see how much the numbers vary place to place. I can't see how they'd even bother to have a different set of water jacket cores for such a small difference.

You people a scaring me to death, my 340 is .060 now with no fill and about to be raced after 10 years on the road like that. Of course it was babied all its life, cam had no lobes and a Holly one barrel carb.

I have a 360 block that's .250" minimum on all thrusts at standard bore but my lottery tickets aren't so good. It's from '82, or '84 I believe. I also have a 440 block with similar numbers from '76 or '77 I think.



A friend had one last year until an H-beam snapped in half. Block was probably still usable, heads were fine, crank was repairable, camshaft even survived!

[/quote]

This is the block I have been racing the last few years. 1979 E58 motor originally. Sonic checked around .2 on the average. Lifter bore pic shows the holes located in the middle of the bosses. Block is about a 1/2 fill and 4 blt Milodon caps. Blower motor making about 650 HP. No problems so far. 4" stroke and .040" over.

Ma changed the first number from a 3 to a 4 to denote the (so called) thin wall change which we now know from Andys work was hit or miss or something not the same across the board but there definitely was a change somewhere that was denoted by the first number changeing

Well my count is up to three 600+ hp 360s.

Blazin' Bob, any new casting gets a new casting number. Even if it is a little tiny change. Or maybe the mold cores are starting to flake.

The only time a significant casting change was made without a casting number change was the last half of the run of 451 heads for bigblocks. Engineering corrected some thin areas to make them safer to port but because the bigblocks were already planned to be out of production they didn't dare give it a new casting number. So they instead put the number "1" on the end of the head.

Casting numbers increase with time as more and more castings are designed. So for example a casting number with a 1 in front is probably from the '50s, 2 would be '60s, 3 would be late '60s, etc. I think the casting numbers are in the 5s nowadays.


In the early '80s you could buy a bare 452 casting for something like $59.00.

R.

And? Point being it can be done and those blocks live no problem.
Dude came down to sonic my 496 block. 24pts every cylinder all .2+.
$100 well spent.

I'm not going to say that there aren't 600 HP stock 360 blocks out there running but how about posting up your average ET's at the track, weight, and track and corrected altitude. Let us do some number crunching.

I use to have a guy doing my sonic checking that
did 64 reading per cyl... charged $75 at that time..
he was well worth it... he was a old hard core guy
that did a lot of machine work also... very nice guy
and his prices on everything was on the cheap side compared
to most shops... I watched him do my mega block so I
knew he wasnt BSing on the numbers... guys that get a
small hand full of readings have no idea what the block
is really like... a 1/2" away it could be paper thin..
plus if he found a area that was iffy he would do a dozen
readings just in that area... no charge

I had a 318 block sonic tested and when it spilt 3 bores I measured the busted parts and none of them were what he told me, not even close so watch it done if possible and listen to what p body said, a chain is only as strong as it's weakest link or in other words a cylinder is only as strong as it's thinnest point.

Well this guy does testing for the 3 major machine shops around here.. so yeah, he's trustworthy.

He also did every cylinder.

What's my point?

You said, "Plenty of LA blocks running 600+ and living a long happy life."

I have now counted three. That's not plenty.

My point is it's super easy to SAY you have a 600hp 360. If you had said there are plenty of claimed 600hp 360s, I would have had to agree.

Way back in the days of smallblock Pro Stock the Mopar guys started having trouble with 2-bolt 340s at around 600hp. They reportedly scrapped T/A or AAR cars for the blocks which had provisions for adding four bolt main caps.

Or maybe that's just a myth.

R.

Nutter..

http://www.hotrod.com/how-to/engine/1606-small-block-big-punch/

Nice article..but did I miss the ET slips?

BINGO!!!!!!!!!!!!!!!!

Kinda reminds me of the kids I used to over-hear talking about their cars at the bar.
Its not that hard people to back up the truth.
Car weight
Corrected altitude or supply barometer reading, temperature, humidity.
And the ET ( MPH) you ran in the quarter mile. (60 foot, 1/8, 100 ft)
We can take it from there. LOL

I'd like to know how many runs qualify for living a long happy life.

And I'd like to see what the main caps look like out of a 600+ horsepower 360 based engine after maybe 120 runs at 7k+ in the lights.

120 runs for me would be over 60 years lol

But would a stock 360 block live well at 500 horse?

I know plenty were killed at 180hp

Yes. It may still want to make the main caps dance around a little and would need some oil system help to keep it happy if you spin it up.

Me too...............

Granted mine is a 340 base 416.. it made 590 hp
525 tq on the dyno.. I had the pan off the other
day and pulled the #5 main so I could check the oil
pump... the bearing looked new...that was about 600
miles on it and just beating on it on the street..
turning 7200rpm.... thats with my W-2s.. I want to
change over to my W-5s or pull the engine and put my
395ci in it... the 395 ran 9.50s in the race car.. but
for a street/strip rod I wanted the extra torque.. but
I didnt even advance the cam for more torque because of
the conv.. its already 5000 stall and I didnt want it any
higher... based on that article those Indy alum heads put
out more power by a lot... I'm running less cubes, less valve
diameter on both, less lift but I run a solid roller...my
heads flow 305 but dont remember if thats at .650 or .700
but I believe its .650.. when dynoed it was with a 850 cfm
and now I run a 1000 cfm throttle body multi ported injection
so I have no idea if its more,less or what on power.. that
was dynoed on 93 octane.. most of the time I run 87 octane
and beat on it pretty good(up to that 7200 rpm)..
I also use chevy rods at 6.125 and Diamond pistons
at 10.6 compression..could be 10.4.. I forget which
gaskets are on it now.. but it runs great on moose pi$$

Never had a problem with a steel crank 340. Stock bottom end except for pistons, 7800RPM. Ran all year with no issues. I started fooling with 360s and it was a different story.

Just over 200 10-second timeslips and thousands of street miles since refresh.
Mid-10's @ 130+ mph at 4190# race weight.
Best mph: 133.65
700+ hp?

Stock '99 Magnum 360 block here.
No fill.
No girdle.
Stock 2-bolt mains with stock bolts.
Forged, internally balanced lower parts with a turbo.
It's all completely happy with a 7,000 rpm rev limiter, 6800 in the lights.

Built it in 2004.
Hurt 2 pistons in 2007. (tune)
All bearings looked great.
Minimal evidence of cap walk - but did spin it to 7500 quite a few times.
Refreshed it and continue to put laps/miles on it.
If it broke tomorrow I'd still say it lived a long and happy life.
Hopefully it doesn't break though. LOL

Always impressed with your truck Duner. Also have many 10 second passes. Best = 10.50 @ 128.38 mph. 3600 lb race weight.