Magnum Shortblock VS. Non-Magnum

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cactuscarl

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Can anyone tell me the difference between a Magnum shortblock (P4876906) versus a non-magnum shortblock (P4876907) from Mopar Performance?

Would Edelbrock Performer RPM Chrysler Magnum Heads work on either shortblock?

-Jeff
 
cactuscarl said:
Can anyone tell me the difference between a Magnum shortblock (P4876906) versus a non-magnum shortblock (P4876907) from Mopar Performance?

Would Edelbrock Performer RPM Chrysler Magnum Heads work on either shortblock?

-Jeff
Click to expand...

I believe the Magnum's oil the rockers throught the pushrods, the non-Magnum's ( LA series....) oil the shafts throught the cylinder heads directly. There may also be an extra cylinder head bolt too. I know you can swap Magnum heads onto the old LA block, so it can't be much difference. I'd also check motor mount pad location.

BTW: I'm going through a living hell with a MP non-Magnum short block thats killing me.... It ate the cam in 20 miles and I'm on rebuild # 2. Have fun..... :salut:
 
Wow, what happened to the CAM? Was it something MP did?

Just curious, what heads and intake did you put on your shortblock?

FYI: I just found out today from MP that Cummins is the company that builds these motors...go figure.

-Jeff
 
cactuscarl said:
Wow, what happened to the CAM? Was it something MP did?

Just curious, what heads and intake did you put on your shortblock?

FYI: I just found out today from MP that Cummins is the company that builds these motors...go figure.

-Jeff
Click to expand...

In all honesty I think it was a combination of incorrect valvetrain geometry and a crappy cam. I had a set of X heads with a six barrel on it. Now I'm going with a set of Edelbrock heads and keeping the six barrel.
 
I havent bought one, but what I'm pretty sure of it is this: Magnums do have provisions for hyd roller cams, they do not have provisions for rocker shaft oiling, they do not have a machined fuel pump boss. The head bolt count and pattern is the same as a non-Magnum. The Non-Magnum does have provisions for hyd roller cams, does have the fuel pump boss and eccentric, and does have thru-the-shaft rocker oiling. The Non Magnum can be fitted with Magnum heads, by using AMC lifters, and Magnum pushrods. For intakes, you can either use the few available for Magnum heads, or have your heads re-drilled for the earlier style intakes, and run anything. Something to keep in mind also, the Magnum heads use 1.6:1 rocker ratio, so if you are choosing your own cam, or putting Magnum heads on the earlier blocks, the cam's effective size is larger with 1.6s.
 
Magnum short blocks have a different
bore.... (.020 over)
hydraulic roller camshaft
oil through pushrods
different lifter type
different balance than normal 360


Edelbrock heads will work but you will have to use standard Small Block Chevy rocker arms... this is cheaper to just use SBC roller rockers
 
According to the Mancini site, they are all bored +.020 over..I thought they may be more than that, depending on what condition the block was in originally, but not according to the website. There is definately a balance difference, I forgot about that one..lol I dont know about using the GM arms tho..That's a new one to me. I guess at that point, you can use any ratio you want. I would have thought the heads would have had the rockers on them, just not rollers.
 
Mopar is right, They all are bored .020" over unless they need more. Theres a guy on another site that bought one that came .020" over on one bank and .030" over on the other.
 
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