LS2 heads on LS1 - spark map?

[Mud]

Probably a stupid question, but I'm running LS2 heads (unported) on an LS1 engine, and I notice the LS2 monaro/GTO runs a bunch less advance...assumedly due to more efficient heads. The spark map is something I've really neglected as I just haven't had my car on a dyno, but is there any harm in trying out the LS2 high octane spark map? I'm assuming not unless I'm missing some effect from a different table since detonation should be less likely. I notice it is a slightly larger table, but the relevant bit fits perfectly. The LS2 doesn't seem to have a base spark table, so I would massage that (and the idle region) to check there's nothing too disjointed there.

I realise I really should pay to get the spark map done on a dyno, but it's hard to justify at the moment, and I'm tempted to one day get better heads...

X-air OTRCAI, no MAF
102mm Nick Williams TB
FAST LSXR
AAS medium-length 1.75" headers into dual 2.5" Wortec cat-back (no cats)
222/226-115+3 .6"/.6" EPS cam

[Jetmech442]

The ls2 heads are essentially the ls6 design. For a better fit spark map, I would try the map from a 2002 C5Z06. I did this on my 6.0L lq9 and I didn't have donation issues.

[Mud]

Good point - the 2004 Z06 spark maps look very similar to what I had, typically 1-2 degrees less advance.

I'm off my game, so (rightfully) second-guessing myself. I did find follower was causing my idle hang though :)

[Jetmech442]

Cool, I found my idle hang was a combination of follower and spark. I pulled like 15 degrees out of the low map/ mid-high rpm range and now it drops like my old big block. 😀😀

[Mud]

There may have been a bit of spark in there too - I wasn't being completely scientific and pulled some out first ;)

[joecar]

Try it (2002 Z06/LS6 spark tables as said by Jetmech), see how it goes.

[Mud]

Any reason for 2002 specifically? It's a little different to the 2004 tables I had lined up.

edit: actually, scratch that, getting muddled on little tablet...

[joecar]

2002 thru 2004 LS6 should have the same tables (let me check).

[Mud]

You're right, my mistake. The Surface Pro 3 is very good for ad-hoc EFI live use, just not so much screen real-estate for comparing things!

[joecar]

Yeah, no display is ever big enough :)

[MyM8V8]

Hi Ben,

Let me know if you get this sorted as I'm putting a similar combo into the GTS. Basically swapping the blower motor into the Ro and the LS1 stuff into the GTS. I'll then put the LS2 heads off the VZ Maloo onto the Ls1 with my 224-232. Why? Don't ask - I must be nuts.

[Mud]

Hi Gareth, the non-scientific butt-dyno seemed to approve...I'm sure it's safe to play with as after all it's just retarding the advance a couple of degrees. It felt effortless through 3rd and 4th (up a steep hill at that), but it would be good to get it on a proper dyno to confirm :)

Worth noting I have retained my old tweaked spark timing around idle (more advance), and I tweaked the injector timing which I think made the idle more stable with the new cam - I'll send you my tune file if you want a look.

Sounds like you're trying to keep up with G's build ;)

Aside, my slight idle hang issue is still there on a cold engine, but behaves pretty-well exactly as I want warm. Not sure what the modifier is there, but it's a minor issue.