Engine is pulled - 273 rebuild or replacement 360 crate?

brodphish said
So today we picked up a 5.2 Magnum from a late 90s Dakota. $300 from the local pick & pull. Also scored a brand new Milodon SBM timing gear set for $50 from the machine shop that’s going to do our work.

So that brings up the 273 block is going to the machine shop to be assessed for the extent of clean up it needs. If it’s minor maybe we can use the 273 block with Egge .060 over pistons and Total seal rings?

One thing we discussed is boring the 273 block out to 3.91 like a 318. The machine shop says it can be done and the block integrity tested before and further work / build is done. I’ve often wondered why these small motors can’t be bored out to 318/340/360 since it’s the same block, it’s all metal, right?

If we go this route can we use the 5.2 heads? Clean & port em’? Will the TTI headers bolt right up?

The advantage to this route is the engine would slide right back into place, tranny, mounts, etc. Keep the bell housing and 7 1/4 at least for now.

Or we could rebuild the 5.2 with performance parts and make the minor modifications necessary.

Smart move on getting the 5.2 Mag. Only possible issues to check for are cracks in the heads between the valve seats and cam bearings. Cylinders and pistons shouldn't need to be touched unless it was severely abused. Stock roller cam can be reground and stock roller lifters can be reused. If heads are cracked (likely) there are a couple routes to go, I lean towards cheap aluminum heads (Speedmaster) checked over by a good machine shop and oil-through-pushrod rockers unless your Magnum block still has the holes drilled for LA-style rocker shaft oiling. Aftermarket LA-based heads also open up many more options for intake manifolds.

You can't just bore a 273 out to 340 size because the cylinders are cast different with generally the same thickness; it's not like they're all cast to the same OD and just bored out different sizes from the factory. You might get lucky with a block that has unusually thick cylinders or core shift in a desirable direction but that's not common and needs to be sonic checked to know for sure.