LA 360 or Magnum 5.9

[SublimeSixpack]

I went with magnum heads (among cam/intake) on my LA build. 411 HP

View attachment 571157

Would you mind giving me an idea approximately of what the gap is/was between your intake and the block (between the heads) front and rear on your engine?

I ask because I recently installed Magnum heads and a Magnum type intake manifold on a rebuilt 318. When I fired it up and ran the cam in I experienced coolant leakage issues in three of the corners where intake, heads and block meet. I'm now trying to determine whether the leakage was at the intake or the heads. I pulled the intake off and found no obvious reason for the leaks. After cleaning surfaces I mocked the intake back up with the used gaskets and only have 1/8" gap front and rear. Seems that the LA engines with LA heads I've done have had more of a gap there. Is a smaller gap normal when using the Magnum heads? I'm wondering about the machine work that was done to the heads. Would appreciate any insight on this.

 

[rumblefish360]

The Magnum block is slightly shorter than a LA block.

 

[SublimeSixpack]

But I wouldn't think that would have any effect when using the Magnum heads on the LA block?

 

[rumblefish360]

But it was proven to you when you bolted it up!
Is a thicker head gasket out of the question?

 

[SublimeSixpack]

The thing is I'm not using a Magnum block.

The holes of the intake and heads line up quite well so I'm thinking the machine work (surfacing) is probably okay.
I don't really want to go with thicker head gaskets, but I do think I'll try a different type of head gasket and intake gasket set and see how it turns out.
Thanks for your input.

 

[rumblefish360]

Sublime, your 318's deck could have been milled?
The "LA" block is slightly taller so it could be, and this I don't know, but are the decks of the heads milled down?
the block heights could have an effect on how the head is cast/made? Seems unlikely.
Are the heads used? Intake used? They could have warped a little bit.

 

[SublimeSixpack]

This 318 short block, the magnum heads and intake were part of a recent acquisition. This is what I know; the short block was Remanufactured by Chrysler in Canada. (I'm quite sure that the block has not been decked). The heads appear to have been fully redone including surfacing of both block and intake sides. (I don't know how much metal was removed. For that matter I don't know who did the head work, although the work that was done looks to be good).
The intake manifold I believe was used for a short period but looks good.
I also have a new unused Chinese copy of Edelbrock's "Air Gap" intake which actually sits lower on this engine than the intake I'm using.

 

[Bobzilla]

SublimeSixpack, this should actually be a new thread of it's own, since it's off subject.
As for the leak, there is nothing wrong with an 1/8" gap at the front and rear. That's actually a very nice gap, easy to seal with silicone only. Do not install the cork or rubber end seals that come with kits. If the coolant passages of the intake line up well with those on the heads, and there are no cracks (I don't expect cracks but check if it's still apart) then just lay a nice smooth bead of gray or black silicone sealer on that front and rear area.
Also, do not over tighten the intake bolts. The vertical Magnum bolts can pull the corners of the heads up, causing a leak at the head gasket.

 

[SublimeSixpack]

Thanks bobzilla, your point that I should have started a new thread is well taken.
FWIW I did use black RTV on the front and rear (I very seldom if ever use the gaskets).
I'm pretty sure I did over tighten the intake bolts and that probably caused the problem (the site I sourced gave an incorrect torque number for the bolts and incorrect procedure in general).
I have retorqued the head bolts and will install new intake gaskets and bolts using what I now believe is the correct tightening sequence. We'll see how it goes. This is the first Magnum head to LA block conversion I've done. I learned something.
Thanks for your input.

 

[Bobzilla]

I should clarify this concern would be the same on a Magnum block; both LA and Magnum are good blocks, just the vertical Magnum intake bolts make it easy to lift the corners and cause a leak.

 

[rumblefish360]

I should clarify this concern would be the same on a Magnum block; both LA and Magnum are good blocks, just the vertical Magnum intake bolts make it easy to lift the corners and cause a leak.

How do you figure? The bolts for pulling the intake manifold down there should be no lifting of the intake manifold. If the intake manifold is lifting you up, or more correctly stated, that seating correctly, and something is in the way. That would be assemblers fault.

 

[SublimeSixpack]

I should clarify this concern would be the same on a Magnum block; both LA and Magnum are good blocks, just the vertical Magnum intake bolts make it easy to lift the corners and cause a leak.

Yes, I knew what you meant.