'68 318 to carbed Magnum 5.2: Check my checklist
Now. I'd think your compression w/stock heads should be around 8.2-8.4:1. I've heard of LA rollers having stock oil-thrus before. Magnum heads should bring it to right around 8.8:1.
While the Magnum pistons were different- I think they were functionally the same and without the heads would not improve the CR anyway like the old 318s where the CR bump happened not from same size closed chambers but from new pistons.
Most say they're TTY and not reusable so I can't suggest what I did.
We redrilled my heads for the LA pattern- course ended up going back to a Magnum intake in the end.
Out of curiosity, which specs gave you those much nicer numbers? 0.040 in the hole? At any rate, it would be very nice if these specs are indeed correct.
I see your point about the Mag pistons (particularly as they're dished - just with the dish spread side-to-side as opposed to circular), but are they really as deep as those in this 360? Somewhere I read that the heavy-duty 360s had slightly lower compression to prevent predetonation from harsh acceleration with a heavy load.
I don't know how accurate this is, but it might explain the difference between our numbers.
I thought about suggesting you buy a set of EQs, but I'm under the impression you're trying to save pennies where you can. Keep in mind, many magnums (as you've found already from searing on google) suffer from head cracks...I'm pretty sure the heads on my 5.2 are, since the donor '98 Dakota had over 200K miles on it
True, saving as much as possible is preferable, but sometimes the sensible decision may be to spend a bit more.
I could wind up spending over half the cost of a pair of loaded EQ heads ($504/ea @ JEGS) trying to get a pair of junkyard units presentable, and still not get away from the factory crack issue (I know it's a non-issue, but still), nor have ports that are cast as nice as the EQ's.
Plus, if I do the CH318B heads, I get the LA bolt pattern with no further effort required. Thus, no need to go through another intake sale and purchase.
Perfect example: This LA 360 looks as if it'll wind up costing me the same as a Magnum 5.9 longblock at the end of the day, even though it seemed cheaper to begin with. Yet, I could have gone the route of a $1,700 Mag block and saved myself some effort for a better result. But I'm in the soup now, and I'm going to stick with it.
-Kurt