Holley 4160 questions.

cool, at least you'll have an accurate plug color to read and not be fooled by the previous tune.

18 initial sounds kinda high for your combo, but it's really a trial and error deal. My combo listed below likes 16 initial, 32 total and no vacuum advance. At 12 and 14 initial it idles good but at 16 it feels it's strongest right off idle and idle is stable as rock in or out of gear. At 18 idle quality starts to degrade some and is not as stable.

At 34 or 36 total I get some ping on premium gas around my torque peak but this particular engine is in a very heavy vehicle (5600 lbs) with 3.55 gears and 33x12.5 tires.

Your idle mixture screws being set at 2 turns is not a big deal. 1 1/2 turns is just a baseline. If you had to be at 1/2 a turn or 2 1/2 turns with your combo, something would be wrong.

Here's my combo:

LA heads, 2.02 intakes, 1.60 exhaust
1.6 ratio Crane roller rockers
213/220 .454/.475 lift. 112 LSA cam
10.2:1 Comp Ratio
Weiand Action + intake manifold and a 650 dbl pumper. The manifold is choking it though and a open 1" spacer added at least 25 hp.

Keep in mind my altitude is over a mile high so I can run high comp ratios with small cams. This combo probably wouldn't work at sea level without running a larger cam.

1wild&crazyguy said:

jmo go 1-2 sizes bigger on the primary jetting and try and get it so you have 3/4-1 1/2 turns and even amount on both mixture screws.

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Main jets have very little effect on the idle mixture.

That plug looks pretty good. Pull them all though and check them. Some intake manifolds have pretty crappy fuel distribution (like my Weiand before I put the spacer on).

Plugs will clean up some after a good full throttle blast to 90 or so. As long as it's not oil fouled. Hence the term "Itailian Tune Up", lol! I do agree that changing the plugs is the best way to go though.

ramcharger said:

Main jets have very little effect on the idle mixture.

That plug looks pretty good. Pull them all though and check them. Some intake manifolds have pretty crappy fuel distribution (like my Weiand before I put the spacer on).

Plugs will clean up some after a good full throttle blast to 90 or so. As long as it's not oil fouled. Hence the term "Itailian Tune Up", lol! I do agree that changing the plugs is the best way to go though.

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I've seen people compensate for a lean jet by choking it out with a rich idle mixture, thats where I was going with that.

Really, I'd be shocked if that plug cold clean itself much.

His timing looks about right though by the color change on the tangs bend.

No big.

if after changing the plugs they end up looking like this again, besides a step back in jetting try the next hotter plug.jmo

1wild&crazyguy said:

I've seen people compensate for a lean jet by choking it out with a rich idle mixture, thats where I was going with that.

Ah yes, I see now what you meant.

Really, I'd be shocked if that plug cold clean itself much.

That plug does look cold judging by where the discoloration is on the threads. No evidence of detonation from what I can see either.

His timing looks about right though by the color change on the tangs bend.

Agreed! You should some NGKs I pulled while I was doing some ignition tuning. The bands are clearly visible as I kept reducing my total timing.

No big.

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No worries man. 8) I was just bringing stuff up for discussion, I like a good intelligent debate every now and again. Other people here can benefit from free exchange of ideas too. As is much said, "There's more than one way to skin a cat".

Thanks for the input. I hope this helps someone else with the same issue.

Hey Ramcharger. Ya think your combo would be better at sealevel with a narrower centerline cam on a 110 or 108? Just thinking out loud here.

rumblefish360 said:

Hey Ramcharger. Ya think your combo would be better at sealevel with a narrower centerline cam on a 110 or 108? Just thinking out loud here.

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Hey Rumble!

If I were run a narrower centerline I'd build too much cylinder pressure and run into detonation problems. I think a good way to run this combo at sea level would be with the same cam but Eddy alum heads as they have a quench pad. I'm set up for it, @ .005 below deck with KB 107's, but there's really no quench area on a open chamber LA head and the aluminum will dissapate some combustion chamber heat. This would be the "safe" way to go.

Another way would be to have BJR fit some 1.88 intakes in a 302 head and port it. Nice quench pad to qwell detonation too and no loss of power via aluminum, but it take some very careful advance curve tuning.

Plan C would be Magnum R/T or EQ Magnum heads.

Now here's a plan D, lol. Take this exact build to sea level and swap in a 114 LSA hyd. roller cam in the 212 to 216 range. This would work with fuel injection, have boatloads of torque and should haul *** with a shot of nitrous.

Here in Colorado, we'll use narrower centerlines like a 108 or 106 to make up for an engine that was built for sea level. I'm planning a B build and finding out that I'm going to have to run 13.5 to 1 with a 106 LSA cam to even come close in HP to a build at sea level with 11:1. And it'll should still run on pump premium!

The reasons I went with the 112 here on my build was for the option to run fuel injection on this gas gulper and to extend my top end a bit while still having excellent torque charasteristics right off idle and plenty of vacuum for power brakes. I had visions of running a 100 shot just in case I come across a Porche Cayenne in the mountains. I want to blow their minds, lol. Plus, it bleeds off a bit of pressure so I can run crap gas if I have to.

In summary, 10:2:1 is too high to run at sea level with cam under 220@.050 with open chamber iron heads on a 5600 lb truck with full time 4wd. I get buttloads of torque here though and no domestic or foreign (Toyota) 8 cylinder truck can keep up with me as it sits. I haven't run a Dakota R/T yet though, lol. In a lighter vehicle, detonation may not be as much as a problem. Another deal here at high altitude is we only have 92 octane vs. the 94 you get down there. That could well make up the difference too.

Just some food for thought, every combo I mentioned will need to be put against the true use of the vehicle, converter stall (I'm using a Hughes 4x4 convertor that stalls around 1800 if I flash it), gearing and vehicle weight.

BTW, the gas mileage isn't all that bad. Well over 10 if I keep my foot out of it which is really good for these trucks.