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Author Topic: 360 Magnum block and 360 LA Heads  (Read 1776 times)

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Offline George46

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360 Magnum block and 360 LA Heads
« on: July 27, 2005, 11:12:48 PM »
How can I correct this?  It's in a 91 RC. Long story but engine rebuilder who can't be located botched this up - can I change to magnum heads, alter TBI intake to fit?  I need a cheap way out of this!  Thanks for any advice!!

Offline leftymopar

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Re: 360 Magnum block and 360 LA Heads
« Reply #1 on: July 28, 2005, 07:28:56 PM »
I don't know when they made the change but I just got a 360 from a '99 and found that the bolts for the intake manifold are facing straight up instead of at an angle.

gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #2 on: July 28, 2005, 09:02:55 PM »
Unless I'm the only one on the planet with this situation, you'll see that the LA (pre-Magnum) intake is not wide enough to fit properly on the Magnum. Then there's the intake bolt issue. So, since it's a Magnum block, if you want to use this engine, get Magnum heads. You'll need a Magnum intake (Mopar makes a dual-plane carb intake). Then you'll need.......you know what? It'd be easiest to sell the Magnum shortblock, get an LA shortblock and use the LA heads that came on the Magnum block.

gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #3 on: July 28, 2005, 10:54:22 PM »
Actually, the intake width issue comes into play when trying to adapt an LA intake to Magnum heads. On a Magnum block, with Magnum heads, the LA intake isn't wide enough. On an LA block with Magnum heads, an LA intake fits. I remember reading about using LA heads and intake on replacement blocks, and using the LA heads and LA intake together will work (and I'm not talking about the intake bolt arrangement being a factor). The LA intake bolts to the LA heads as before, no problem, so you could use the stock TBI and intake. However, the issues come into play after this are another matter.
1. Rocker are ratio. The LA rocker arms are rated at 1.52:1. Production units are usually closer to 1.46:1, give or take. The 360 Magnum cam is ground to produce .410" gross valve lift (just like the 360LA), but on the Magnum, this is with 1.6:1 rockers. So, the 360 Magnum cam, with LA rockers will actually put you with less lift, etc......more like the 318 LA cam, and that's just plain bad. Solution? 1.6:1 rockers for the LA, or a new roller cam with the lower ratio LA rockers in mind.
2. Rocker lube. The LA's lubed via the #2 and #4 cam journals through the block, and up into the heads, finally into the rocker shafts. The Magnum blocks have these oil passages, but they are not drilled for use, so the quick solution is to lube like the Magnums do.....through the pushrods. They must be hollow, and I'm thinking you'll need to use the LA roller cam pushrods---the length is close, but not the same as the Magnum pushrods. Just make sure that whatever rockers you use, they have oil holes in the pushrod cup so oil can get through to oil the rocker shafts. The other solution is to tap the oil passages so the LA rockers can lube as designed. You will also need to get a roller LA cam (for the oil holes), or have the Magnum cam drilled to match the LA setup.
3. Use the ignition system for the RC, including the distributor.
4. The 360 Magnum is externally balanced, just like the 360 LA, but the weight is a little less on the Magnum, so your flywheel or torque converter will need to be rebalanced.
4. Use the RC belts and pulleys......less of a headache.

That's the bulk of it. Less difficult would be to use Magnum heads and thrash out some sort of setup for induction. Easiest is to do like I said in the first reply.

Offline George46

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Re: 360 Magnum block and 360 LA Heads
« Reply #4 on: July 30, 2005, 09:30:16 PM »
Thanks to all for the responses.  I'm now not so sure its the wrong block since according to the factory shop manual a 91 RC would have had a roller cam and lifters.  The only way for me to be sure is to check casting numbers, I guess.  Does anyone have a source for this.  All the references I've seen for casting numbers are pre-magnum 360s.

If it turns out that the block is correct, then there is the issue of why the pushrods are rubbing against the slots in the heads and why the lifters don't appear to be making adequate contact. The Dodge boys told me they could move the lifters slightly up and down in the bores.   I can surmise that maybe the wrong pushrods were installed?

gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #5 on: July 31, 2005, 08:13:36 PM »
May have heads from a pre-roller era 360. Once the rollers came along, the pushrod holes were enlarged.  The roller lifters used in the pre-Magnum engines are very similar, but not exactly the same as the ones used in Magnums. Could very well have the wrong pushrods, maybe even the wrong lifters. Your missing engine builder seems to have not known the differences. The engine serial number is stamped on the left fron pad on the block, however, a surefire, easy way to see if it's an LA or Magnum block is to look at either side of the engine block. Look along the lower edge just above the oilpan. On an LA, it's essentially smooth, but a Magnum has tapped holes in the lower center section for the engine mount "triad" used in most newer vehicles. The LA block only has the engine mount "ears" at the upper forward section of the block.  

Offline Dodge 85 RC

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Re: 360 Magnum block and 360 LA Heads
« Reply #6 on: August 1, 2005, 10:07:52 AM »
There is an intake manifold out that will supposivly work on LA and magnum blocks.
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Offline George46

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Re: 360 Magnum block and 360 LA Heads
« Reply #7 on: August 1, 2005, 04:27:09 PM »
gen1dak got it right - when the casting numbers were run by the Dodge boys (stealer, er sorry, dealer) this morning the dates came up as 1989 block and 1980 heads.  Unbelievable, but they still tried to argue that I needed a new long block.  So I now need the correct 89-91 heads to make the engine right.  gen1dak, any way to tell if the lifters and pushrods are correct?  I asked and was told they "look" like the right ones - of course they went on to say they compared them to a 360 magnum engine that was apart right next to my RC.  So how could I believe them, on top of all the other b---s----t they've tried to unload on me.  Just as an FYI - this is Southern States Dodge in Raleigh, NC.  I'll be posting a warning anywhere I can about their service department.

One other question - is there enough material on a 1980 head to open up the pushrod slots - if so I could save some bucks by doing this myself and reassembling the engine.

Thanks for the help - Ramcharger Central is the best!!!!!

gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #8 on: August 1, 2005, 08:44:48 PM »
There is an intake manifold out that will supposivly work on LA and magnum blocks.
Nope. It works on LA blocks with LA heads, or LA blocks with Magnum heads, but not Magnum blocks.

gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #9 on: August 1, 2005, 09:26:08 PM »
gen1dak got it right - when the casting numbers were run by the Dodge boys (stealer, er sorry, dealer) this morning the dates came up as 1989 block and 1980 heads. Unbelievable, but they still tried to argue that I needed a new long block. So I now need the correct 89-91 heads to make the engine right. gen1dak, any way to tell if the lifters and pushrods are correct? I asked and was told they "look" like the right ones - of course they went on to say they compared them to a 360 magnum engine that was apart right next to my RC. So how could I believe them, on top of all the other b---s----t they've tried to unload on me. Just as an FYI - this is Southern States Dodge in Raleigh, NC. I'll be posting a warning anywhere I can about their service department.

One other question - is there enough material on a 1980 head to open up the pushrod slots - if so I could save some bucks by doing this myself and reassembling the engine.

Thanks for the help - Ramcharger Central is the best!!!!!
Yeah, there should be no problem opening up the pushrod holes. On the "roller" heads, it looks like they just essentially doubled the size of the holes. The LA roller pushrods are 6 49/64 inches in length. The LA flat tappet pushrods are 7 31/64 inches in length. Magnum lengths are between 6.915-6.936 inches. On the roller lifters, they do have different part numbers, but I have yet to have a chance to actually look at them side-by-side. It is written that the lifter valley in the LA is identical to the Magnum. Now, the pushrod angle was changed, but since long-style flat jeep lifters can be swapped in, I'm thinking maybe the Magnum rollers are just a little longer than the LA lifters (because on a roller LA, you can use the regular LA flat tappets, long ones aren't necessary---but this is just speculation on my part). Anyway, first thing is to check those pushrod lengths. On the LA roller engine, nothing else as far as rockers, arms, and other valve gear were changed, so once the pushrod holes are enlarged, and pushrods properly seated, you should be on your way at least as far as that goes.

Offline chrysler300le

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Re: 360 Magnum block and 360 LA Heads
« Reply #10 on: August 2, 2005, 02:49:25 AM »
I'm not sure there is enough room to open up the pushrod holes on pre roller heads.  Especially if any porting was done.  Heads designed for roller cams have more of a restriction from the pushrod hole in the intake port.  Pre roller heads have .5" diam. hole and roller heads have .66" holes.  85 up 318 Police engines have 360 heads with larger pushrod holes.  That would be another option if you can't find 308 heads anywhere.
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gen1dak

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Re: 360 Magnum block and 360 LA Heads
« Reply #11 on: August 2, 2005, 10:17:01 PM »
The pushrod intrusions you mention are routinely ground down (within reason) to improve intake port flow. Some of that enlargement in the pushrod hole is excessive to allow for relatively loose assembly line tolerances. George46 could limit the potential intake port issues by focusing on a more oval-type shape to alleviate the restriction where it's most important....less to the left and right, more to the north and south. He would, after all, have the luxury of checking each hole individually for clearance. The reduction in meat would be no different, just done from the opposite side (to enlarge the hole), but it would be easier to snag a set off a wreck if available. Look on eBay too. LA heads (reman.) aren't all that costly, and depending on the amount of work involved, could be considered money well spent.

 

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