Sniper efi on Vortec 350 timing questions

[HeavvyChevvy]

Hello.

Been browsing through the forums and noticed some guys running higher timing on Vortec headed engines than I thought was normal. My setup feels kind of flat. I’m currently at 15 degrees base with 28 degrees at WOT all in by 3000rpm and 32 degrees at cruise. Before I had WOT at 32 and cruise at 36. Either way, it feels a bit flat. I tried clicking links to a few tables, but they were dead.

My my setup is as follows:

I own a K30 square body. I recently installed a new L31-R Vortec 350. It has a Weiand street warrior intake with a Holley sniper. The sniper controls my timing with a Holley dual sync distributor, msd blaster ss coil and msd 6efi cdi box. Exhaust is a pair of hedman black maxx ceramic truck headers, 2-1/2” pipes, h-pipe and dual borla proXS mufflers. Trans is a th400 with a Hughes xtm converter and 3.73 gears with metric 33” tires.

i have a steady idle, pulls decent vacuum (~30kpa at 750 rpm idle) and it starts easily. Throttle stabs in neutral are without hesitation and it revs freely.

What would y’all recommend?

Thanks in advance!

[dave w]

Does Holley offer data logging and flash hardware / software for the Sniper EFI?

I think most gearhead-efi members here use factory EFI systems or "Hacked Versions" of factory EFI systems on their engines. Most of the tuning information on gearhead-efi is related to factory EFI systems.

dave w

[HeavvyChevvy]

Thanks for the response Dave. I appreciate you taking the time.

There is data logging software. I see that most on here are running factory type setups. I was hoping to find a close baseline of what the guys on here with bolt on performance mods were running for timing as a comparison. My other thought was to time based on kpa values.

More simply, what are y’all running for base, wot, and cruise? Also, any timing tables I can open and read to copy and paste into my timing table? For some reason, the ones I’ve found have a big photobucket watermark over them or when I attempt to zoom in, they become too blurry.

[Fast355]

I am attaching the advance curve in the 5.7 Marine module. The distributor times at 8*BTDC and all values in the table are without the 8* base added to them. So basically add 8* across the board. As for vacuum advance, a good high performance advance curve mimics the old delco vacuum advance on the L79 327, LT1 350 and L82 350. 10* @ 10 in/hg with 0* until 5 in/hg. Should work out a bit better. At WOT you would get
23* @ 1,000 rpm,
24.5 @ 1,500,
26.5 @ 2,000,
28.5 @ 2,500
30* by 2,800 rpm.
At idle the timing would be 30.5 @ 750 rpm.
2,000 rpm cruise 36.5
3,000 rpm cruise would give 40* advance.

That should get you fairly close, then make slow changes from there. The advance curve on my L31 Express van was very similar to what I said above. With the CNP 5.3 coils I ran up to 48-50* timing at cruise though for best fuel economy and throttle response.

[HeavvyChevvy]

I am attaching the advance curve in the 5.7 Marine module. The distributor times at 8*BTDC and all values in the table are without the 8* base added to them. So basically add 8* across the board. As for vacuum advance, a good high performance advance curve mimics the old delco vacuum advance on the L79 327, LT1 350 and L82 350. 10* @ 10 in/hg with 0* until 5 in/hg. Should work out a bit better. At WOT you would get
23* @ 1,000 rpm,
24.5 @ 1,500,
26.5 @ 2,000,
28.5 @ 2,500
30* by 2,800 rpm.
At idle the timing would be 30.5 @ 750 rpm.
2,000 rpm cruise 36.5
3,000 rpm cruise would give 40* advance.

That should get you fairly close, then make slow changes from there. The advance curve on my L31 Express van was very similar to what I said above. With the CNP 5.3 coils I ran up to 48-50* timing at cruise though for best fuel economy and throttle response.

Thanks for your response fast355.

Oh wow, that’s wild! I would’ve never guess that high for a vortec.

I’ll give that a go and report back with my findings. Since my distributor has no mechanical or vacuum advance (all electronic) I must’ve really been missing the mark. Hopefully this will wake it up.

Quick question, why do so many engine ‘gurus’ claim the vortec engines like really low total timing? Say 30* or so... or am I again missing the mark?

I’ll post a picture of my timing tables and graphs before and after when I get to my laptop.

Thanks again guys!

Btw, I like to support forums that help me. Is there a paid membership to help the people who manage the board?

[Fast355]

Thanks for your response fast355.

Oh wow, that’s wild! I would’ve never guess that high for a vortec.

I’ll give that a go and report back with my findings. Since my distributor has no mechanical or vacuum advance (all electronic) I must’ve really been missing the mark. Hopefully this will wake it up.

Quick question, why do so many engine ‘gurus’ claim the vortec engines like really low total timing? Say 30* or so... or am I again missing the mark?

I’ll post a picture of my timing tables and graphs before and after when I get to my laptop.

Thanks again guys!

Btw, I like to support forums that help me. Is there a paid membership to help the people who manage the board?

I have found 29-32° advance to work well as a WOT timing total. Cruise timing at part throttle can be substantially higher.