Magnum vs LA compatibility

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matt030305

matt030305

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Hey FABO techs, I was wondering on the part compatibility on magnum engines vs LA engines. I recently had a 340 block crack on me and now have a bunch of top end parts made specifically for an LA block. I’m contemplating if I should build a 340 based 416 Stroker or a 360 based 408 Stroker. 360s are more abundant and I’ve heard that the magnum blocks can handle more power as well. Since I have a bunch of top end parts made specifically for my LA block, Here is the list of parts:

-trickflow 190 heads with hydraulic roller springs (supports lift up to .680)
-edelbrock air gap intake for LA block
-morrel hydraulic roller lifters
-Harland sharp 1.6 roller rockers made to support LA block oil thru pushrods

I know I have change the intake since the bolt pattern for the magnum block is different, lifters since magnum blocks came standard with roller lifters.

My question is: should I return my roller rockers since Magnum blocks have a different oiling system? And is there anything else I need to replace? Thanks!
 
The intake has to match the heads, not the block, so if you have Trick flow heads and an LA pattern intake those match and can be used on a Magnum block.

Double check your rocker arm part numbers. If they have the oil through pushrods provision they can be used with your Trick Flow heads on a Magnum block. If they were LA style without the oil through pushrod provisions you need different rocker arms.

You can run the factory Magnum hydraulic roller lifters with a new hydraulic roller camshaft for either LA or Magnum.

I do not know if the LA retrofit hydraulic roller lifters will fit a Magnum block because I never tried it yet. The top of the lifter bores on a Magnum block are a little taller than an LA block.
 
Personally, I love the 340 as is and would never stroke that one. I'd put the stroker in a 360 or a magnum 360. If I wanted to use roller lifters I'd use the magnum. I'm in the same situation and have a couple 340's and a 360 police motor and a magnum and that's the plan I came up with.
 
If your just using the magnum block only the main difference is the rocker oiling, magnums oil through the roller lifters, some have the LA style oiling holes too on the deck most don't but probably could get a machine shop drill them if you wished. And the Deck height is slightly shorter from what I hear. Other than that it's basically a roller LA 360 block.

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Like has allready been pointed out before, AND in your other thread, with the parts you have, you can put your top end on the magnum block, zero issues
 
NC Engine Builder said:
Like has allready been pointed out before, AND in your other thread, with the parts you have, you can put your top end on the magnum block, zero issues
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...and you can put the LA front end on the Magnum. I wanted my 5.9 to look as much like an LA as possible so I used my LA timing cover, water pump, v-belt pulleys, and fan.
 
Bobzilla said:
The intake has to match the heads, not the block, so if you have Trick flow heads and an LA pattern intake those match and can be used on a Magnum block.

Double check your rocker arm part numbers. If they have the oil through pushrods provision they can be used with your Trick Flow heads on a Magnum block. If they were LA style without the oil through pushrod provisions you need different rocker arms.

You can run the factory Magnum hydraulic roller lifters with a new hydraulic roller camshaft for either LA or Magnum.

I do not know if the LA retrofit hydraulic roller lifters will fit a Magnum block because I never tried it yet. The top of the lifter bores on a Magnum block are a little taller than an LA block.
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The rocker arm number is the Harland sharp S70026K, it seems that they have the LA style oil through pushrods provisions.
 
LO23M8B said:
Personally, I love the 340 as is and would never stroke that one. I'd put the stroker in a 360 or a magnum 360. If I wanted to use roller lifters I'd use the magnum. I'm in the same situation and have a couple 340's and a 360 police motor and a magnum and that's the plan I came up with.
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The only thing I’m worried about the power handling capabilities. The 340 block I had in my duster cracked. I just don’t want the same thing to happen again, hence why I’m looking for a later magnum block
 
If your making enough power to break blocks you probably need aftermarket one.

If not you might of just had a faulty one, highly doubt there’s a huge power capability difference between factory blocks.
 
273 said:
If your making enough power to break blocks you probably need aftermarket one.

If not you might of just had a faulty one, highly doubt there’s a huge power capability difference between factory blocks.
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What aftermarket blocks are available these days.
 
matt030305 said:
Hey FABO techs, I was wondering on the part compatibility on magnum engines vs LA engines. I recently had a 340 block crack on me and now have a bunch of top end parts made specifically for an LA block. I’m contemplating if I should build a 340 based 416 Stroker or a 360 based 408 Stroker. 360s are more abundant and I’ve heard that the magnum blocks can handle more power as well. Since I have a bunch of top end parts made specifically for my LA block, Here is the list of parts:

-trickflow 190 heads with hydraulic roller springs (supports lift up to .680)
-edelbrock air gap intake for LA block
-morrel hydraulic roller lifters
-Harland sharp 1.6 roller rockers made to support LA block oil thru pushrods

I know I have change the intake since the bolt pattern for the magnum block is different, lifters since magnum blocks came standard with roller lifters.

My question is: should I return my roller rockers since Magnum blocks have a different oiling system? And is there anything else I need to replace? Thanks!
Click to expand...
Use the trick flow heads and the Harland Sharp rocker arms for pushrod oiling and any LA intake.

Otherwise, there are way to make the LA stuff work on a Magnum block.
 
matt030305 said:
The rocker arm number is the Harland sharp S70026K, it seems that they have the LA style oil through pushrods provisions.
Click to expand...
That part number is NOT supposed to be for oil through pushrod. You keep saying "LA style oil through pushrod provisions" but you must look carefully at the part numbers. Your part number is LA oiling through the head, into the rocker shaft, and then to the rocker arms. There is a different part number for the oil through pushrod rockers, but it is only different by one digit.

Part number S72026K is for oiling through the pushrods. Notice the third digit is a two, not a zero.
 
matt030305 said:
Can I still run a mechanical fuel pump?
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Yes. If you run an LA style timing cover and accessory belts you can run the fuel pump eccentric and a mechanical fuel pump.

A Magnum camshaft with a short snout will require an adapter from Mancini Racing or Hughes Engines to mount the fuel pump eccentric.

An LA style long snout camshaft will mount the fuel pump eccentric with the bolt and washer setup from your old LA engine.

If you found an early Magnum block that is drilled for LA oiling you can use the rocker arms you already have, and you can install LA cam bearings and an LA camshaft drilled for LA oiling and with a long snout, which reduces all special considerations.
 
matt030305 said:
Can I still run a mechanical fuel pump?
Click to expand...

@Bobzilla. Explained everything expertly.

I used a 1970 timing cover that has provision for mechanical fuel pump and has the timing marks on the passenger side (not that it's easy to see with the LA power steering pump, lol).

I started with an electric fuel pump but discovered my autistic grandson couldn't ride in the back with the buzz of the pump ) I even used rubber mounts). So I bought the cam snout extension from Hughes Engines and switched to a mechanical pump. The cam snout extension is a little tricky, but if you take your time and use Loctite, you'll be fine. It's been probably 1.5 years and no problem and I drive it nearly every week.

Just today, I replaced the fuel line so now I just have rubber on the two ends.
 
Bobzilla said:
That part number is NOT supposed to be for oil through pushrod. You keep saying "LA style oil through pushrod provisions" but you must look carefully at the part numbers. Your part number is LA oiling through the head, into the rocker shaft, and then to the rocker arms. There is a different part number for the oil through pushrod rockers, but it is only different by one digit.

Part number S72026K is for oiling through the pushrods. Notice the third digit is a two, not a zero.
Click to expand...
I apologize on that part. I thought that the oil through pushrods was an LA specific trait. Didn’t know that it was magnum specific. If that’s the case, I’ll just purchase a 340 bare block.
 
NC Engine Builder said:
It didn't crack because of power.
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Right. My question now is: since I plan on making some decent power (around 550-600 hp), what’s the N.A. limit on an LA block? I’ve heard from people that the magnum blocks have better castings, more accurate machining, etc.. There are future plans on a Paxton supercharger. So I’m trying to figure out what will be the best for longevity and durability.
 
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