318/ Magnum Head Conversion

[MOPARJ]

I am thinking about dropping some Magnum heads onto my 318.

My motor currently has 2,000 miles on its rebuild and has a performer intake, Comp XE268 cam, stock compression slugs, stock rods, reworked stock heads, and the block was not decked when rebuilt.

What all do I need to complete this swap? What pushrod will work with this cams rocker ratio? I currently have the comp lifters with my cam, which should have the necessary oil holes, correct? Also, will the valvesprings that are accompanied with the Magnum heads be suitable for my cam?

I guess another question is about my cam. Is the lift and duration on this cam going to be too much with the different rocker ratio, or do I need to be looking for a single pattern cam? Also, do the new magnum heads come fully prepped with valves, seals, retainers, ect?

 

[needsaresto]

I am thinking about dropping some Magnum heads onto my 318.

My motor currently has 2,000 miles on its rebuild and has a performer intake, Comp XE268 cam, stock compression slugs, stock rods, reworked stock heads, and the block was not decked when rebuilt.

What all do I need to complete this swap? What pushrod will work with this cams rocker ratio? I currently have the comp lifters with my cam, which should have the necessary oil holes, correct? Also, will the valvesprings that are accompanied with the Magnum heads be suitable for my cam?

I guess another question is about my cam. Is the lift and duration on this cam going to be too much with the different rocker ratio, or do I need to be looking for a single pattern cam? Also, do the new magnum heads come fully prepped with valves, seals, retainers, ect?

Are you asking about the eq mags?I think they can be had bare or complete but dont quote me on it.Maybe someone else knows.

The magnums use 1.6 rockers so lift will increase.They are good to about .520 before you run into problems.Looks like your just under that but check for interference at the retainer/guide anyways.

Comp lifters should have the oiling hole you need for oiling thru pushrods.

Heres a list.You wont need everything.

http://www.moparts.com/Tech/Archive/smallblock/7.html

 

[dgc333]

The XE268 with the magnum rocker is .509/.512 lift. I am using it on my LA360/magnum hybred. I didn't need to cut the guiides but do check.

If your deck is stock and the magnum heads have not been cut down the MP conversion push rods that are 7.625" long will be OK but it's another area to check to make sure you have enough preload.

You shouldn't have to do anything regarding lifters since I am assuing you got new after market ones to go with the new cam.

The performer intake will not bolt to the magnum heads unless you have the heads redrilled to the LA bolt pattern. But, the small ports of the performer will not give you the full benefit of the heads. MP, Edelbrock and Professional Products have intakes that bolt to magnum heads the PP intake has both LA and magnum bolting provisions.

Your LA valve covers will work fine even though the mgnum heads have 10 bolt holes. I would recommend the MP composite LA valve cover gaskets though.

You can use either LA or magnum head gaskets but the intake gaskets must match the bolting (redrilled heads use LA gaskets). You will need new head bolts, the magnum heads use two lengths and they are different than the LA bolts.

The stock magnum valve springs are not acceptable for the XE268 cam. When I did this with the XE268 Comp didn't have a drop in spring and they recommended the MP R/T spring. This spring is a straight spring with a damper and won't work with the magnum retainer. The 2.2/2.5 mopar 4cyl retainer is the same as the one MP sells and is easily available at the local bone yard. Use the magnum locks though. There are other spring options now but you will still likely need new retainers.