Sniper efi on Vortec 350 timing questions

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!

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

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.

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.

Quote:

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Originally Posted by 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.

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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?

Quote:

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Originally Posted by HeavvyChevvy

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?

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

Quote:

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Originally Posted by Fast355

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

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Attachment 14507
Attachment 14508

here's what I came up with. it's a holley v5 efi base calc with a few degrees pulled evenly from the whole table. pretty much matches what you listed except no where near the 30 degrees at idle. i'll see how this works out for me.

thanks!

Look here for how to build a spark table: https://www.thirdgen.org/forums/diy-...ml#post6301288