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Spark knock/detonation with Holley Sniper under acceleration

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This is what I have:
258 with 4.0 conversion performance 7120 head from Odessa cylinder head (ebay)
Comp cam 68-231-4 206/214 [email protected] 462/485 lift 111 degrees lobe separation
985 autolite plugs gapped at .035
4.0 stainless header with universal cat and Flowmaster Flowfx muffler 2.25 inch exhaust
Holley 2300 Sniper EFI in tank fuel pump, Hyperspark distributor, CD box
TF 999 auto, 4.10 gears, 35" tires
It defaults to 36 degrees total timing and I am set at 32 degrees at WOT. 15 degrees initial timing .
I have been running 93 Octane.
so while accelerating I have been getting spark knock/ pinging from the engine.Being that I have a hyperspark distributor everything is adjustable
Will adjusting the total timing down or the WOT timing get rid of the spark knock. What about a colder spark plug? IIt would be nice to run 87 octane also.
I don't know what the compression ratio of the engine is.
I will take any suggestions.
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1984 CJ-7
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This is what I have:
258 with 4.0 conversion performance 7120 head from Odessa cylinder head (ebay)
Comp cam 68-231-4 206/214 [email protected] 462/485 lift 111 degrees lobe separation
985 autolite plugs gapped at .035
4.0 stainless header with universal cat and Flowmaster Flowfx muffler 2.25 inch exhaust
Holley 2300 Sniper EFI in tank fuel pump, Hyperspark distributor, CD box
TF 999 auto, 4.10 gears, 35" tires
It defaults to 36 degrees total timing and I am set at 32 degrees at WOT. 15 degrees initial timing .
I have been running 93 Octane.
so while accelerating I have been getting spark knock/ pinging from the engine.Being that I have a hyperspark distributor everything is adjustable
Will adjusting the total timing down or the WOT timing get rid of the spark knock. What about a colder spark plug? IIt would be nice to run 87 octane also.
I don't know what the compression ratio of the engine is.
I will take any suggestions. View attachment 4172428 View attachment 4172428
A) like your overall setup
B) EGR delete? Typically helps the cylinders run cooler
C) .035 plug gap seems a bit tight for your setup, maybe try .045
D) generally speaking for the 258, 15° sounds very advanced on the timing...is this what Holley recommends for their Sniper setup?

Sounds like your motor is "wound tight" and although built to handle it not designed to run quite that "hopped up"?

Just my $0.02, I'm sure others will chime in, especially those with more Sniper experience.
 

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Discussion Starter · #3 ·
A) like your overall setup
B) EGR delete? Typically helps the cylinders run cooler
C) .035 plug gap seems a bit tight for your setup, maybe try .045
D) generally speaking for the 258, 15° sounds very advanced on the timing...is this what Holley recommends for their Sniper setup?

Sounds like your motor is "wound tight" and although built to handle it not designed to run quite that "hopped up"?

Just my $0.02, I'm sure others will chime in, especially those with more Sniper experience.
Yes, No EGR. .035 is the factory plug gap for the 258 and a 1995 4.0 liter engine. 15 degrees is a default on the sniper. I may be able to change it. Not sure. My original 258 was stock with a motorcraft 2150. It didn't have any freeway power like 65mph was all it had. Great off idle torque. After modding the motor it can fly down the highway, just got to get the detonation under acceleration sorted out so I'm still experimenting/ learning about timing and the Sniper.
 

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I've been out of it a little while now but why 32* at WOT?
If you are under load you would have initial + centrifugal so most setups would be 8* +18* total of 26*. It might be better. No vacuum advance while under load.

Of course there are plenty of other things to look at like AFR and stuff.

Have you thought of taking it to a tuner?

Nice setup by the way. I never saw a 2300 Sniper before.
 

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Discussion Starter · #5 ·
I've been out of it a little while now but why 32* at WOT?
If you are under load you would have initial + centrifugal so most setups would be 8* +18* total of 26*. It might be better. No vacuum advance while under load.

Of course there are plenty of other things to look at like AFR and stuff.

Have you thought of taking it to a tuner?

Nice setup by the way. I never saw a 2300 Sniper before.
I will try the 26 degrees at WOT. I don't know of any tuners local to me. I figured I just needed to change some settings, just hoping I could get some advice from people with more knowledge.
 

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Discussion Starter · #6 ·
I've been out of it a little while now but why 32* at WOT?
If you are under load you would have initial + centrifugal so most setups would be 8* +18* total of 26*. It might be better. No vacuum advance while under load.

Of course there are plenty of other things to look at like AFR and stuff.

Have you thought of taking it to a tuner?

Nice setup by the way. I never saw a 2300 Sniper before.
The Sniper 2300 matched the Gronk Motorcraft 2100 carb setup I had. I wanted to retain the factory carb/trans linkage setup I had.
 

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You will want to take a log file at the condition you are hearing the knock. Then if you download your config to the SD card, you can then bring the SD card to your computer and open it with the free Holley app. You will find a table for the timing at RPM and MAP similar to the AFR and fuel mapping tables. You will also want to open the log file at the same time. Put your cursor on the log file graph where you hear the knock and then move to the timing table and there will be an indicator showing that point. You can the retard your timing in the areas of the knock. The other thing to keep in mind is that that AFR has an influence on how fast detonation occurs. Rich mixtures (lower AFR values <14.6] detonate faster than lean (AFR > 14.6) so you need less advance with a rich mixture than a lean one at a given RPM.

You should also be updating the learned values to you base fuel mapping. Acceleration is one of those those times that it may go into open loop and revert to the base fuel table and ignore the learned values.
 

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You can do my a compression test. My compression is high because i had the block decked. And mine spark knocks if dont run premium.
 

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Might not be relevant to the issue raised but our totally stock 1998 Grand Cherokee 4.0 has always pinged on 87 octane fuel so we have used 89 most of the time we’ve had it. 15* initial timing seems too far advanced to me.
 
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Might not be relevant to the issue raised but our totally stock 1998 Grand Cherokee 4.0 has always pinged on 87 octane fuel so we have used 89 most of the time we’ve had it. 15* initial timing seems too far advanced to me.
15 is what the Holley sniper install video sets it at, not saying it’s correct or incorrect
 

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15 is what the Holley sniper install video sets it at, not saying it’s correct or incorrect
I do not have a Sniper, interested, but pretty happy with my hopped up Weber 38. I personally AFR Logged it and did some custom stuff to it, so have a bond to it now, lol.

What spark plugs are you running? Supposedly, you are supposed to run the cooler spark plug for the 4.0 head, 4.0 head=4.0 sparks.

And 15° does sound a bit advanced. Was this Holley video specifically about a Jeep 258? I have a Nutter Bypass, DUI Dizzy, and am at 13° with Vac advance plugged, 7120 head (stock intake besides some smoothing out the carb outlet and stock 4.0 headers with the expansion coil things). No idea about timing Im at, at WOT or 2,500 RPM (IIRC that's when it's supposed to be at 35°? Correct me if wrong).

The 4.0 head was from Autozone, I run 89, and haven't had any issue. I know it's been decked, as I saw the milling marks, and I needed shorter rods than what was in there. Dunno how much, though. I have no pinging, and I run my stuff hard, lol. Not in the woods at low RPM, either. I run it like it's a stolen Porsche in the city, if there was pinging, it would probably be destroyed by now.

Compression mixed with timing doesn't add as much as many think, from what I've read. I've gotten away with up to 15° with my 258 head, no pinging that I heard, but I backed it down some, to 13°. Not worth the 5 extra HP. And with the 258 head, with Weber 38 and 30's, Dyno'ed at 103 HP and 188 TQ at 13°, didn't feel a need to push it, personally. And my 10-40 MPH time dropped by about 1.5 seconds, IIRC. Point is, if not needed, no reason to push your timing, maybe back off to 13/14 and see what it does?
 

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I do not have a Sniper, interested, but pretty happy with my hopped up Weber 38. I personally AFR Logged it and did some custom stuff to it, so have a bond to it now, lol.

What spark plugs are you running? Supposedly, you are supposed to run the cooler spark plug for the 4.0 head, 4.0 head=4.0 sparks.

And 15° does sound a bit advanced. Was this Holley video specifically about a Jeep 258? I have a Nutter Bypass, DUI Dizzy, and am at 13° with Vac advance plugged, 7120 head (stock intake besides some smoothing out the carb outlet and stock 4.0 headers with the expansion coil things). No idea about timing Im at, at WOT or 2,500 RPM (IIRC that's when it's supposed to be at 35°? Correct me if wrong).

The 4.0 head was from Autozone, I run 89, and haven't had any issue. I know it's been decked, as I saw the milling marks, and I needed shorter rods than what was in there. Dunno how much, though. I have no pinging, and I run my stuff hard, lol. Not in the woods at low RPM, either. I run it like it's a stolen Porsche in the city, if there was pinging, it would probably be destroyed by now.

Compression mixed with timing doesn't add as much as many think, from what I've read. I've gotten away with up to 15° with my 258 head, no pinging that I heard, but I backed it down some, to 13°. Not worth the 5 extra HP. And with the 258 head, with Weber 38 and 30's, Dyno'ed at 103 HP and 188 TQ at 13°, didn't feel a need to push it, personally. And my 10-40 MPH time dropped by about 1.5 seconds, IIRC. Point is, if not needed, no reason to push your timing, maybe back off to 13/14 and see what it does?
thevideo was for a 258 but not a dui dizzy and the other stuff.
 
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If the Sniper base spark map looks like this Terminator X, OP can definitely tune that out with a laptop. 36* by 2,000 rpm? Yikes!

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I've never seen a Sniper base calcs list, John. They actually give you an AMC 6 to start with? That would come in handy, I'm sure.


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I can appreciate the desire to maintain spec, but there's nothing factory about your setup. The 0.035 is determined by the spark system (coil, distributor, etc), which has been modified from factory. DUI recommends 0.050-0.055 with their setup. I don't know what the hyperspark recommends, but if it's no more than stock gap I'd be very surprised.


Yes, No EGR. .035 is the factory plug gap for the 258 and a 1995 4.0 liter engine. 15 degrees is a default on the sniper. I may be able to change it. Not sure. My original 258 was stock with a motorcraft 2150. It didn't have any freeway power like 65mph was all it had. Great off idle torque. After modding the motor it can fly down the highway, just got to get the detonation under acceleration sorted out so I'm still experimenting/ learning about timing and the Sniper.
 

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I can appreciate the desire to maintain spec, but there's nothing factory about your setup. The 0.035 is determined by the spark system (coil, distributor, etc), which has been modified from factory. DUI recommends 0.050-0.055 with their setup. I don't know what the hyperspark recommends, but if it's no more than stock gap I'd be very surprised.
I don't think it's specifically AMC 258. All they ask is number of cylinders, Displacement and camshaft type.
OK, I don't have a Sniper, but dove DEEP into a Weber 38- custom Emulsion tube, 4.5mm Aux Venturis, etc.

The reason? I found that most people (IMHO even Red Line and Pierce) accept the Weber and jetting more so for a high rev-ing little Porsche motor, or Opel GT, or even a 3.0 V6 on EU. I found the flaws because our engines aren't even close to those, not just in size, either. But our RPM range and power curves. Some of those cars go twice as high in the RPM range. So while the Weber 38 Jetting will work from Redline, etc. It leaves some performance on the table, IMHO. And I have a Dyno Run to back that up. -funny story, got Dyno by a guy that's an LS Specialist, 1k+ HP type builds, he got done, said, "Man, smooth engine!! But it wouldn't break 4.5k RPM'S...." 😳 I showed him the faded red line on the Tach and we both kinda laughed, lol. Anyhow, we got "wierd" engines.

So, Holley may ask size, cylinders, etc. But that would match a stroked/bored Slant 6? A Jaguar 4.0, etc. This may not be the case at all, just sharing what I have ran across, and that's that no one seems to look at Jeep I6's as their own class of tuning, atleast not from the big manufacturers. And.... why would they? Lol, the market is better for SBC, etc.
 

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OK, I don't have a Sniper, but dove DEEP into a Weber 38- custom Emulsion tube, 4.5mm Aux Venturis, etc.

The reason? I found that most people (IMHO even Red Line and Pierce) accept the Weber and jetting more so for a high rev-ing little Porsche motor, or Opel GT, or even a 3.0 V6 on EU. I found the flaws because our engines aren't even close to those, not just in size, either. But our RPM range and power curves. Some of those cars go twice as high in the RPM range. So while the Weber 38 Jetting will work from Redline, etc. It leaves some performance on the table, IMHO. And I have a Dyno Run to back that up. -funny story, got Dyno by a guy that's an LS Specialist, 1k+ HP type builds, he got done, said, "Man, smooth engine!! But it wouldn't break 4.5k RPM'S...." 😳 I showed him the faded red line on the Tach and we both kinda laughed, lol. Anyhow, we got "wierd" engines.

So, Holley may ask size, cylinders, etc. But that would match a stroked/bored Slant 6? A Jaguar 4.0, etc. This may not be the case at all, just sharing what I have ran across, and that's that no one seems to look at Jeep I6's as their own class of tuning, atleast not from the big manufacturers. And.... why would they? Lol, the market is better for SBC, etc.
Could just be the carb jets from what I’m readin - in this thread. I once saw a motor trend article about how stock jets in you’re aftermarket carb may run too rich.
 
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