[QUOTE
could this be a symtom of my low compression/over cammed set up?
.[/QUOTE]
Most likely yes. But remember you can detonate a low comp build just as easily as one with higher compression.

 

i am not sure But the cam I requested from my rebuilder was the stock w30 cam. So if the stock carb needed 8-10 degrees at idle I dont see why it would need much more than 12-15 with todays gas

i run 10-12 in my GMC motorhome with a Olds 455 up from the OEM 8 degrees. When I had it smogged I had to detune back to 8 to pass.

 

I tried running it at 20* and 40*, the higher the advance the more vacuum it makes and less air/fuel it demands (iac valve letting more air in)

I dont seem to run into any detonation until I start getting into 15:1 or 50*+

I do plan on setting up my lock up converter soon so im thinking I might run into issues there.


this is it at 40*

This is it at 20*

455+.030 over l2323 pistons.
ported big valve c heads. Air gap dual plane intake
9:1 compression, 155psi cranking pressure
.520/.520 240/240@.050 292/292 adv 108 lobe sep, installed at 106. Solid flat tap, .018 lash.

 

So you actually see a lower KPA when you go from say 35 to 40* at idle?

 

yes a small average lower, all the way to 50* degrees as well. The iac and duty cycle #s go lower as well.

35*

40*

50*

 

But your pulse width doesn’t go down any after 40 and only a little after 35. I think you’re playing with fire there but.......

 

what would you recommend?
its a 72 cutlass, 3.73 rear, 2004r with 2600 stall, (soon to have lock up) 26.5" tire
68 toronado 455 .030 over, l2323 pistons, 9:1 compression, ported big valve C heads, air gap dual plane intake, 1 3/4" 3" headers, 3" dual exhaust with x pipe.
clay smith solid flat tappet cam 520/520 lift 292/292 adv 240/240 @050 108 lobe installed at 106,
i would like to run 87 octane e10 gas, (i already have been)
i am running the base configuration street/strip that came pre programmed, (race seems the same)
it seems to transition from idle to cruise at 2000 rpms.
it seems to like 14.0-14.5 a/f and more timing.
I am not racing it, its just a street car.

thanks,

 

50 degrees timing seems kind of high to me. I thought most Olds 455 curves topped out around 38-40?

 

It looks like he's running 50* at idle.

 

I had the whole system too. Had problems with the distributor not holding timing, so I put my Mallory unilite back in and it ran like a charm. Just saying.

 

I had some hiccups getting my Sniper to work properly as well, but overall it's been great.

When you show 50* timing at idle on the handheld display, does your timing light agree?

 

As you read on in the manual, the sniper does not advance timing it can only retard timing that is why they say to drop the distributor in at 50.

 

I just checked it with my timing light, its pretty spot on, I used the dial at 50 and balancer at 0, and balancer at 50 dial at 0, both ways show its maybe 1* retarded.

on another note I do notice quite a difference in idle quality, the more I advance it, the lope becomes less and less audible and idles smoother.

I also tried different settings for starting, 0 to 50, all of them started the same, this is while it was warm already.

 

it said no such thing in the installation Manual for the Hyperspark! It said drop it in at 0! Not sure where anyone saw 50.

Maybe there is something different for the MSD distributor?

 

There’s a another, better reason why they have you drop it in at 50 but for this application it really doesn’t matter.

 

Where did you mount your CTS for the Sniper?

 

Walden Automotive in Atlanta (really good hot rod shop) just put a new rebuilt 455 in it w a Sniper. Rob is the owner. They did all the work. They have done tons of them.

 

FWIW,

Spent a year tuning in my Sniper 4150 controlling the timing with a Holley Dual Synch Distributor (Hyperspark was not available at the time) on my Olds 455. Learned a few things through experience about the handheld monitor vice the PC-based Holley Sniper software (the good, the bad, and the ugly). The default template for the 4150 that is used for the initial setup has very little timing curve. You must use the Smooth function or edit the table's individual cells within the PC-based software to develop a timing curve. See following photos:

 

One more tidbit about Holley Sniper software info I learned. The RPM scale can be reduced from 8000 to 5000 so normal daily drivers can have finer fidelity of the timing curve. Once again, this is adjusted in the PC-based Sniper software. See examples in the following photos. Note the bottom axis which is RPMs:




P.S. Worked high tech world for 48 years so know a little about software/firmware-based systems.

 

This is what I made for mine, it seems to run better then it did, but I seem to get lean/rich spikes when its below operating temperature, do i just need to let it self learn then transfer learned to base fuel?

 

Again I’ve mentioned this before, your timing table is going to get you in trouble. You don’t want 30 something degrees of timing in it at low rpm and high load. That’s a recipe for disaster.

 

what would you recommend? I idle around 60kpa, cruise around 40-50kpa 2000rpm, never hear any pinging...

Thank you,

 

I believe I sent you a spark map already didn’t I?

 

Here is a Holley Sniper Software tuning manual link https://documents.holley.com/techlibrary_199r11259.pdf . Pages 6 thru 15 discuss Fuel and pages 24 thru 25 discuss Timing. Temperature Enrichment and Startup Enrichment will affect AFRs before self learning operating temperature is reached (160 degrees).

 

no, you did to the original post author, then I started asking questions...

 

Hope this helps. The following photos depict the fuel settings on my Holley Sniper 4150. The caveat is that I live at 3300 feet and have to go over 5000-6000 foot mountain passes with grades that are 6-7 miles long at 6-8 degrees. Once over the passes, usually travel at 500 to 2400 foot elevations. Timing is limited to 12.0 idle, 33.5 cruise, and 32.0 WOT to avoid pinging on the mountain passes. At this time, the spark plugs are burning a golden brown and highway mileage is 14-15 MPG.

Target Air Fuel Ratio (AFR) Table - What the Closed Loop and Self learning uses to establish Fuel Tables

Target Air Fuel Ratio (AFR) graphical representation

Base Fueling Table with RPMs limited to 5000

Base Fueling Table graphical representation


MAP pressure before starting is 92.5 kPa because of the elevation. My engine idles at 40-42 kPa. A handy Elevation and Atmospheric Pressure chart follows:

 

You do know that stoich on today’s E10 is no longer 14.7 right?
At altitude I’m surprised you have a detonation problem. What does your timing table look like?

 

your base fuel table makes allot more sense then mine, im guessing it should be a smooth transition like yours, mine seems to dip lower where the learned values would be.
I think ill look for a similar table with #s close to my learned #s.

kinda odd my #s are so much lower then yours tho...

Thanks,

 

I'm having my car remote tuned. I was able to get the car much better than "learning" could alone, but the tuner has done a great job of getting the transitional stuff smooth as silk. Almost makes me wish I had a bigger cam!

This is his 3rd revision, we still think there is some timing that could be added. Mark - I'm curious what you think about low RPM cruise timing? I often cruise around 1,800 - 2,200 RPM and 45 kPa and I only have about 28-32* of timing in that range.

 

Nick, try to find a long flat road and make changes while running in that part of the table. If you add timing and your KPA comes down then you’re headed in the right direction. Vice versa if the opposite is true.

 

Good to know, looks like I'm taking my wife for a cruise this weekend!

Thanks Mark.

 

👍 np.

 

Why is that?

 

Too much timing for high load low rpm. It’ll detonate.

 

here is my latest learn table, I dont think Im ever above 80kpa at low rpm, what would you consider high load? I'm at 102kpa when not running.