Magnum 360 heads "best" for my build?
Well, with that cam, I think 3.55's is what I'd look at and possibly 235/60/15 on the back. At Hwy speed, (Somewhere in the 65-70 mph range I assume) you should be cruiseing right in the power band, which cam manufactures recomend doing, at about 3000 - 3200 rpm.
I am running 245/60/14s in the back. I have calculated highway speeds 65mph & 80mph respectively as follows:
2.94 - 2714 @ 65mph, 3340 @ 80mph
3.21 - 2963 @ 65mph, 3647 @ 80mph
3.55 - 3227 @ 65mph, 4033 @ 80mph - nice launch, but ouch on the fwy
My other option is the 3.91 gear set in the SG equipped 741 I have for my 8.75 - if only the car were 100% strip I'd run those...
The Magnum heads will work fine as cast, a good valve job and back cut of the valves is more than enuff. I don't think porting is needed. The heads, as cast, delivered 400+ HP on the create engines. So, IMO, the ponential (SP) is there for you without extra work. Stock as cast OE valve sizes will work fine.
Good news there, just got them back from surfacing, seals, seats and stems - aside from springs they are ready to bolt on
The cam your looking at, the Comp cam is alot smaller than the MoPar roller cam in the create engines.
I am not "sold" on this cam, but it does seem like a good compromise in power with mild lift. Not sure if I wll run 1.6 or 1.5 ratio rockers yet... I am open to other cam choices, comp suggested a custom grind, waiting to hear back from them as to why they suggest it over the 20-223-3 XE268H, here are the specs they sent me:
265/273 adv dur (@ .006)
216/224 dur @ .050
.3170/.3170 lobe lift
.4755 valve lift with 1.5s
.5072 valve lift with 1.6s
110 LSA
-install dot to dot for a 106 IC (4 deg adv ground in)
Would love to know what the logic in suggesting this cam is...
Powerwise, headers win hands down. However, they really suck to install. There worth the power. The exhaust manifolds are great for installing and lasting halfway to forever without issues later on.
I'll see if the struggle with the headers is worth it. I have the coveted 340 manifolds now...
The down side? The Magnum head valve train is not as stable as the "LA" system and the attaching bolts are weak, but can be upgraded to a larger size and use Chevy rockers for an inexpensive upgrade. 1.7 rockers are also available.
Then again, your not stressing the engine/valve train enuff to care about it.
I was looking at a set of stud-mounted self-aligning roller rockers, SBC in origin, as long as the length and geometry were correct; no guideplates. Obviously the pushrods are of concern too
Keep the head cool to avoid cracks in between the valves.
Cooling was my next concern. I have a 22" radiator on the 318 now, not sure if it will be sufficient for the 360 - but I was probably going to go to an electric fan/shroud/relay as I really like this setup on my '59
Thanks for the advice!