Holley Sniper Tuning 500hp 383 Stroker

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Have some questions for the tuning wizards out there. I have a fairly worthy monster under the hood. Nothing insane by any means. 383 n.a at 512hp and 500tq being fed by a holley sniper 4150. It seems to run okay, wont idle below 1k without dying once warm. Hard for me to know 100 percent as ive never dealt with a performance motor before. It rips pretty good but im having some problems at WOT. It seems to bog out when i put it to the wood. Also sounds like it chirps a little but not at the tires, from the engine bay, when i mash the throttle as well. Belt slipping under the power? Clutch slipping?

I went through the snipers wizard a second time, updated the ECU firmware to current, and i downloaded the tune that it generates into my computer and grabbed the holley software from the website. I have never done any fuel mapping or engine tuning of any kind before but id like to dive right in. I have been told i should be running 13.5 to 14.5 AFR at idle, around 13 at cruise, and 12 or 12.5 at WOT. So i made those adjustment on the handheld and it didnt make any difference when driving. The changes were also only slightly off the defaults.

Anyhow because i am sure someone is bound to ask for some of my engine specifics heres a list of what im using:

Holley Sniper 4150 w/ 3/8 feed and return line, built in pressure regulator on unit, 10 micron inline filter, holley pump in factory sending unit

MSD Streetfire HEI dist, no timing adjusment at all just set at 16-BTDC

383 w/ 5.7in rod length, 4.03in bore, 3.75in stroke

Liberty Heads - 110cc, 180psi crank compression, 200cc intake, 140cc exhaust

Weiand Intake rated @ 850cfm

Taylor Wires...... i have a set of Accel 9020c ceramic wires incase my taylors melt. They are EXTREMELY close to my shorty headers. I dont know if the Taylors are spiral wound or not, although i dont think that should make much of a difference in my scenario. The Accel wires are, however.



Lunati Cam - INTAKE: Ratio- 1.5:1
Valve Diameter: 2.02 inches
Seat pressure: 125psi
Open pressure: 395psi
Lift: 0.560 inches
Duration: 295 degrees

Exhaust: Ratio- 1.5:1
Valve Diameter: 1.6 inches
Seat Pressure: 125psi
Open Pressure: 395psi
Lift: 0.565 inches
Duration: 303 degrees

So that might all be TOO much information, but better than not enough lol

I dont know where to start making adjustments. Im comfortable poking around in the software with some guidance but the videos I am able to find on youtube are situation specific and nothing that really glosses over the general theory of computer tuning.

Help would be greatly appreciated. I am open to phone calls, discord chat, video calls or whatever as i realize some things might be difficult to explain long hand in a forum, i just want to get this thing running ****.

Thank you
 

LC2NLS6

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I'm no expert, but I have Holley HP on the race car and Sniper the old Suburban.

The key is to let it learn, take it on 3-4 different drives, key off between drives. That seemed to help mine just figure it self out to get close. However, verify everything in the physical install, like fuel pressure.

The biggest thing about tuning is, logging where is it now and then finding out where do we need to make changes. Log what it does now when it misbehaves. Pull that up on the laptop. See if there is anything standing out, like, AFR pegs 18:1 or goes 9.6 :1 etc. I wish they would have included an electric fuel pressure gauge on the snipers. That is one of the best diagnostic tools other than AFR in tuning, at least for me to see what is happening at WOT etc. If you are losing fuel pressure, all you can see is symptoms of it, not the actual cause. Adding base fueling won't help if the pump can't keep up.

Double check static timing, use the 15* in the Holley videos to set that up.

Could be you are running open loop? When my O2 sensor went bad, it ran just fine off the tune without correcting for the indicated 35.6:1 AFR, actually wasn't bad at all just ran real rich.

Holley now sells the can bus Y connector so I can have my laptop usb cable in the car sometimes and leave the handheld on all the time.

Could be RFI? I haven't had that issue. Did you install wires per the manual? IE - direct to battery. I even went so far as relay for my switched ign sources to get fed right off the battery via relay as well, and not the factory fuse block switched ign.
 

Hipster

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What's the duration on that cam @ .050? 245+? A 383 cammed up to make 500hp/tq is probably going to need to idle around 1k. Maybe a little less but probably not going to see 750rpm. 500hp 383 is pretty stout
 

CNRED

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You didn't say whether standard tranny or auto? Dying in gear or neutral. If auto and in gear converter may need higher stall speed on a 500 hp.
 

arrg

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The most important thing I've found with tuning any efi system is to make 100% sure you have no exhaust leaks and no vacuum leaks. The primary inputs into those systems are manifold pressure, RPM, and AFR from the wideband oxygen sensor. Like any computer system garbage in=garbage out. LC2NLS6 is right on the money about letting it learn though. Drive it, a lot. Drive it on varied routes at varied speeds. It needs to see as many areas of the fuel table as you can make it see or your tune is just a guess. On to your specific concerns:

It seems to run okay, wont idle below 1k without dying once warm.
Do you have the vacuum advance hooked up? Your engine is going to want way more than 16 degrees of timing at idle. Hooking up the vacuum advance to full manifold vacuum is how you get it. Based off what you spec'd out above, it still won't happily idle much below 1000 rpm.
It seems to bog out when i put it to the wood
Once you have put more miles on it and the Sniper dials in the fuel table better, this could get better. That bog is usually a lack of acceleration enrichment fuel. Here's a post on the Holley forum about those settings: https://forums.holley.com/showthread.php?46501-Acceleration...
 
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Awesome insight guys. I will definitely drive it some more and do logs for each drive.

@arrg @LC2NLS6 As far as the vacuum advance goes, the shop that built the engine said not to hook that up and leave it set at the timing they dialed in. That being said, i have no problem giving it a shot, it just hadnt crossed my mind. One issue with that is you said full manifold vacuum which means the largest of the 3 vac ports? I have my brake booster hooked to that one currently because the other 2 are far to small to connect it. I find it strange that the booster uses such a large vac hose. Also because of that I have the PCV hose just sitting next to the air cleaner because it is also too large to connect to either of the other ports on the throttle body. I dont like it, but i suppose the worst that could happen is a little oil getting on the valve cover now and again.

This is my first new engine. I know my way around to a fair degree, and i have the aptitude to learn for sure, but i dont have anyone to help me out that knows much at all. Im generally the guy my friends and family come to when they themselves have issues. So any bit of hand holding from any of you will be greatly appreciated. I wont be offended if you explain to me something i already know as learning often means getting another perspective from another mind to analyze your own knowledge and build upon it.

So I will check my plugs for foul but not until i take it on a few more drives and let the ECU do its thing. Worth noting is that my headers have an O2 bung on the drivers set right at the collector just before the Y pipe flange. I have installed it there in hopes that it would suffice, i am wondering if i should move it to just after the y pipe merging point to have the snesor get data coming from all 8 ports rather than 4. I checked with some carb cleaner and didnt find any vacuum leaks, however i will check again. I dont notice any exhaust leaks yet, but after another drive or 2 I will re torque the header bolts to be sure its all up to *****. I did notice today that i had a tiny bit of coolant leaking from the intake at the front most passenger bolt. I am going to re torque those as well being that the heads and intake are aluminum on an iron block. (TINY little seep, not enough to pool up and drip anywhere)

@CNRED it is a 5 spd nv35, it died at idle when i tried to lower the basic idle to 750, I was able to get it to idle at 850 for a good while but it started to stutter so i gassed it a little and set it back to 1k.

@Hipster I dont know that answer. I will find out though. I do think your right though.
 

LC2NLS6

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And make one change at a time. That way you know each change either makes it better or worse and can put it back.

New engine should not seep. Vortec style heads? Could be leaking into the engine - check oil. Might need sealer on the threads if they aren't blind.

My O2 is after the Y.
 
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@LC2NLS6 I'm not sure about the heads being vortec, but the seep is coming from the intake just left of the thermostat housing. I reached out to the builder and he said to check torque on the bolts in sequence. That because of the iron to aluminum mix they could loosen after a few heat cycles. tighten down in 5 lb increments as needed not to exceed 35 lbs and at that point if the seep persists then I may need to pull the intake and re seal it. Fingers crossed
 
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Well I pulled the fuel pressure regulator off the return line end of the throttle body, it had some slime in the screen so I cleaned it as best I could. I installed the progressive linkage, a throttle return spring to grunted a zero out on the TPS, and made the necessary adjustments in my configuration file and uploaded it to the ECU. I decided to start completely fresh after this so im going to have to let it learn again.

I took it on an EXTREMELY short drive, maybe 2 minutes, and data logged it for the hell of it. When I pulled back in my IAC was hovering between 35 and 40. Thought that was a bit strange. First chance I get to head into town I'm gonna get some hose and hook up the vacuum advance as well. Gonna try to drive it for 10 or more minutes once or twice a day hopefully hit the highway and let it cruise at 65/70 for a bit as well. Will update.
 

Erik the Awful

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As I re-learned in the last week, with your coolant temp over 160*, you should see an IAC of 5-10% at idle. That fixed a lot of my drivability issues. With an IAC of 35-40%, you need to tighten the throttle adjustment a hair and re-check.
 
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