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360 magnum education

Posted By: zrxkawboy

360 magnum education - 07/13/10 11:05 PM

Please educate me on magnum engines. I am considering building a 360 magnum in the future for my 67 Belvedere.

I am quite familiar with LA small blocks. What are the differences I need to know about? What do I need to look for if shopping for a junkyard magnum (which years are best)?

Thanks in advance for your help!
Posted By: Neil

Re: 360 magnum education - 07/13/10 11:27 PM

Not sure if they really changed much over the years.

These engines are famous for the heads cracking between the valves. Not sure if there are certain years of heads that are less prone to cracking?

Other stuff I can recall reading on here over the years:

No provision for a mechanical fuel pump.

Valve covers are double ugly (imo) and while older LA covers do fit the magnum heads the gaskets don't have a lot of sealing surface on the ends.

The small ends of the rods are different width so certain aftermarket pistons don't fit on the stock magnum rods, iirc.

At one time adding a carbureted LA intake to a magnum meant you had to redrill/slot the intake bolt holes. I'd imagine you can just buy a carbureted 5.9 intake that works by now.
Posted By: Andrewh

Re: 360 magnum education - 07/13/10 11:42 PM

depends on what you want to do.
the early one's are easier to retain the efi on. Around 93-94 era.

Anything else, the newer the better. The big changes occured 98 and up, but that is mostly computers and sensors.

They do make a couple of different carb intake's now for the mag.

They also make a bolt on thing to run a mech fuel pump, but you have to run the LA front end.
I prefer the serpentine belt setup.

LA 360 pan and gasket will work on any mag to put it in a car.

if you run a 727 neutral balanced converter, B&m makes a flex plate so you don't need to add weights or anything to make it bolt up and run.
Posted By: gdonovan

Re: 360 magnum education - 07/14/10 12:29 AM



1) These engines are famous for the heads cracking between the valves.

So I'm told but in 25 years as a mopar dealer tech I have never seen a set. Don't be afraid to use the stock heads. I have three sets here that are perfect.

2) No provision for a mechanical fuel pump.

Correct unless you swap to a flat slider or use one or two of the odd roller cams with long snout or get the adapter from Hughes.

LA covers fit with no problem, I have them on mine or you can run the factory covers or MP ones.

Lots of intakes you can buy or redrill the heads or even buy enginequest magnum heads with LA intake pattern from Hughes.

Balance is different, have to use 5.9 magnum flexplate or get a flywheel balanced.

Front is the same, I have an early cover on mine.
Posted By: HotRodDave

Re: 360 magnum education - 07/14/10 01:35 AM

If you have not seen a crack in a magnum head you have not looked close enough. It is VERY hard to find a set that is not cracked, I have pulled tons of those motors apart and have found mabey 6 heads that I could not find a crack between valve seats, probably %90 of them are cracked, I have even seen NOS castings that were cracked. Now you got to think to yourself, do you see magnum powered trucks blowing steam out the tail pipe all the time? Neither do I. I have pulled heads off motors that ran great with low miles and no sludge(evidance of overheating) and found cracks in them If you do find cracks get them preasure tested, they are probably fine, I have never seen a set that leaked from the crack. The cracks are not huge, you need the valve seat very clean to see them, I use a wire brush in a drill, polish the crap out of the seat and get a bright light on them and you will see the cracks

On the other hand if you don't clean them up and find the cracks you can just pretend they are not there and live happily ever after.
Posted By: Magnum

Re: 360 magnum education - 07/14/10 04:06 AM

Quote:

If you have not seen a crack in a magnum head you have not looked close enough. It is VERY hard to find a set that is not cracked, I have pulled tons of those motors apart and have found mabey 6 heads that I could not find a crack between valve seats, probably %90 of them are cracked, I have even seen NOS castings that were cracked. Now you got to think to yourself, do you see magnum powered trucks blowing steam out the tail pipe all the time? Neither do I. I have pulled heads off motors that ran great with low miles and no sludge(evidance of overheating) and found cracks in them If you do find cracks get them preasure tested, they are probably fine, I have never seen a set that leaked from the crack. The cracks are not huge, you need the valve seat very clean to see them, I use a wire brush in a drill, polish the crap out of the seat and get a bright light on them and you will see the cracks

On the other hand if you don't clean them up and find the cracks you can just pretend they are not there and live happily ever after.




+1
Posted By: joedust451

Re: 360 magnum education - 07/14/10 05:07 AM

Quote:

If you have not seen a crack in a magnum head you have not looked close enough. It is VERY hard to find a set that is not cracked, I have pulled tons of those motors apart and have found mabey 6 heads that I could not find a crack between valve seats, probably %90 of them are cracked, I have even seen NOS castings that were cracked. Now you got to think to yourself, do you see magnum powered trucks blowing steam out the tail pipe all the time? Neither do I. I have pulled heads off motors that ran great with low miles and no sludge(evidance of overheating) and found cracks in them If you do find cracks get them preasure tested, they are probably fine, I have never seen a set that leaked from the crack. The cracks are not huge, you need the valve seat very clean to see them, I use a wire brush in a drill, polish the crap out of the seat and get a bright light on them and you will see the cracks

On the other hand if you don't clean them up and find the cracks you can just pretend they are not there and live happily ever after.




+2
Posted By: 360view

Re: 360 magnum education - 07/14/10 10:26 AM

There was a 3 part set of articles beginning in
Sept of 1998 in Hot Rod magazine called
'Magnum Manifesto'
that has a lot of tech info on the 360 Magnum.

Jim Szilagyi's 2004 book
"How to Build Big-Inch Mopar Small Blocks"
is perhaps the best of the books on this engine.

http://www.amazon.com/Build-Big-Inch-Mop...2151&sr=8-1

and is certainly worth the $17

the piston drawings and weights listed in all years of the Ram FSM are incorrect,
and apply to the pre-Magnum piston,
but the iron V10 has the same piston and that section of the FSM has correct numbers.
Compression height is nominally 1.622
but I measured an average of 1.626 inches.
Dish volume is nominally 11.3 cc, but Larry Shepard refers to it as 10 cc
Szilagyi's book has the correct numbers for the stock piston, plus much more for aftermarket pistons.

Combustion chamber volume is nominally 60 cc, and Larry Shepard writes that officially it should not be below 57.2 cc,
but many Magnum chambers have been measured by owners as around 62 cc,
so the range might be a sloppy 57 to 63 cc

the rocker arms are listed as 1.60 ratio nominal,
but nearly always measure higher in the 1.65 to 1.68 range

there is a lot of conflicting info on stock camshaft lift and advertised duration specs for various years

the stock Magnum valve springs have limited ability to handle higher lifts

the stock stamped steel impeller in the 360/5.9 water pump has had problems with 'cavitation corrosion' if the right anti-freeze was not used... it can look like it was 'eaten by termites'

the stock thermostat is a standard grade Robertshaw-Siebe with a steel body and brass arms which are prone to cracking after a few years

The 'belly pan' gasket below the stock intake manifold is prone to blow out near the back, perhaps caused by bolt holes that were not tapped full depth, and made worse by the plate being steel and the rest of the manifold aluminum.

1992-1993 cast iron exhaust manifolds are slightly larger internally than later years

Posted By: gdonovan

Re: 360 magnum education - 07/14/10 08:11 PM

Quote:



On the other hand if you don't clean them up and find the cracks you can just pretend they are not there and live happily ever after.




As a line tech who has worked on thousands of Rams and Dakota I have yet to see a customer bring in a vehicle for cracked heads.

The facts are what they are.

Did I look for them? Of course not, there were never anyone complaining about it!

Except on moparts.

I have looked at the three sets I have here, nothing.
Posted By: feets

Re: 360 magnum education - 07/14/10 09:00 PM

I think they're like the 2.2 turbo heads. The cracks aren't a defect. They're installed on the assembly line.

Posted By: POS Dakota

Re: 360 magnum education - 07/14/10 11:55 PM

Quote:

I think they're like the 2.2 turbo heads. The cracks aren't a defect. They're installed on the assembly line.






HAHA! True!
Posted By: Dartthunder340

Re: 360 magnum education - 07/15/10 03:03 AM

I believe the Magnum blocks have a provision in the rear for the crank trigger sensor or is that in the trans?
Posted By: Andrewh

Re: 360 magnum education - 07/15/10 03:19 AM

there is a boss on the rear of the block to mount the crank sensor. But it is the transmission with the notch in it for the sensor.
Posted By: 360view

Re: 360 magnum education - 07/15/10 10:55 AM

Anyone know how close
the compression height is
of the FORGED 1996-1998
aluminum Viper V10 piston is
compared to the
1.622 inch 1993-1995 360 Magnum piston?

or know a person
or website that would have this info?

Edit: maybe 1.388 inches?
Posted By: 318Bruiser

Re: 360 magnum education - 07/15/10 03:04 PM

Summit says it is 1.605 for a 1997 forge V10 piston.
Posted By: zrxkawboy

Re: 360 magnum education - 07/16/10 12:24 PM

Thanks for all the replies! This is a future project, just in the planning stages, but I'm trying to learn all I can. All the info has been helpful!
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