Magnum-LA parts interchange ?s

[mguner]

I am about to embark on the stroker 318 project. I have access to both magnum block or late 80's roller cam block. Are there any advantages to either? Will timing covers interchange? Will early hyd roller lifters oil magnum valve train? I have magnum and 360 "J" heads, preference?

 

[Coyote Jack]

The magnum heads being a closed chamber design will raise you compression ratio. The limiting factor on the magnum heads is the total lift of the cam. You can't go any higher than .525 total lift and personally I wouldn't push it past .515. Also the magnum heads use 1.6 rockers so you have to use that in the equation. The stock springs in the magnum heads are only good to about .480 of total lift. If your build is going to stay within those limits, I would definitly go with the magnum heads. Remember that the magnum rockers are oiled through the pushrod so you have to use the proper lifters and measure for your pushrod length.

Jack

 

[dgc333]

The magnum heads are a much better design than the J heads. Besides the compresion increase that Jack mentioned you can achieve a proper quench are with these heads that allows the high compresion without worrying about detonation.

You can use the magnum heads on either block but you can't use the J heads on the magnum block because there are no provisions to provide oiling to the rocker shaft on the mgnum block (unless it's a very early one).

The timing covers will swap between blocks and you need to use the LA cover if you plane to use a mechanical fuel pump. The water pumps do not swap between timing covers (the magnum rotates the opposite direction).

The magnum heads will require an intake that is drilled for the vertical mounting bolts used by the magnum or you will need to have the magnum heads redrilled.

Don't know if the LA roller lifters will oil through the push rods. If there is a hole in th ebottom of the cup where the push rod seats they likely due.

You can use LA valve covers on the magnum head, you just don't use all the holes.

 

[blk00rt]

if you run a magnum block you can go more than .525 lift with magnum heads. I know guys that are running stock blocks with .544 lift on them. You need to run the better .600 springs. I personally run a .528/.536 cam on my magnum motor with no problems, when it was in stock configuration.

 

[dgc333]

The .525 lift limit is in the magnum head. You can go well beyond that if you have the guides cut down but .525 is the limit with a stock valve guide height.

 

[MopaR&D]

If you don't mind me chiming in, what about the stock Magnum rockers? How much can they handle?