Hate to be the black sheep on the board, BUT - I am speaking from experience - I had 16lbs, 4lb lower, 2lb upper on my '03 with a KB and holy ***** she rocked (but that had more to do with the KB in my humble opinion!).

I now own a '99 and before I did anything I asked each supporting Vendor what was the biggest bang for the buck with a relatively (and I say that with no certainty) safe boost level. Those that responded said 5lb lower, 90 mm (as 80mm are on the stock '99's), filter and most importantly a relatively (there's that word again) safe tune - as in stock shift points, 11.1 a/f, no or very little change in timing (especially down here in the ever so hot Florida area).

So, that's what I did and I am very happy for the street. Remember I am comparing to a asphalt ripping 496/562 in the 16lb KB street beast I had with the '03.

I have no proof, but I have heard that at 14lbs boost the Eaton falls on it's face at the top end? Again no proof, but that is what "some" 14lb Eaton L owners have told me at the track. "I was pulling really stong until 3/4's of the track and it lost power." - Not something most want to admit, but a street application may be a different story - depends on what you want to do?

I hate to bring this aspect into the picture, but since I am at it I would debate that boost isn't the be-all-end-all to performance on the road. I feel that your tune has a hell-of-a-lot-more to do with it. The key is understanding the limitations where performance peaks and falls and maximizing your tune to your expectations in combination with the mods package that you build. You are on the right road with this question.

Good Luck in what ever you choose!

D-Day

 

That is my thoughts exactly Fowl, is it REALLY worth the move. I've also heard nightmare stories of people making the move and then 3 months later scattering the bottom end all over the interstate. Then again, I guess that's where a good tune comes in. If adding a 2.8 upper to the 4lb lower gives the same result, well then I'm all for the easy intstall of the upper vs the install of the lower.

 

Thanks Dan for the info, it really helps. Question for you, when you ran the KB and the pulley combo you described was this on a stock bottom end? I also assume you were running a dependable tune with the KB as well. I have debated the change from the "fall on its face Eaton" to the Mighty KB, but I still have major reservations as to whether the bottom will hold up. By the way I own a 2000 model.

 

Yes hearing those stories about blowing hole through the block is scary. However there are quite a few persons here that have their 6lb pulley that have thousands of miles on them. I just like you was just wondering if the power gains are worth the effort. On a different note I (think) that the lower pulley might be a safe move than the upper, I have heard that changing the upper pulley may damage the Eaton snout.

Dan_03Lightning: I thought that the cold weather was more dangerous with more boost than hotter weather. Please clarify? Where I live the weather is similar to florida. We have low temps of about 68-72 at nights and between 82-90.

 

Same here. I had the 4# lower with belt slip so I saw 11#'s now I get a solid 14 and love it. I need to go fill up, again.

 

No problem, my '03 was a stock block L. Yes the tune was as follows, 12.1 af, stock shift points, 14 degrees timing. She was hot out of the gate with 15.1 and immediately dropped to 12.1 and leveled through the rpms at 12.1. I ran her hard for 12,000 miles before selling (and regretting every minute of it the day after selling, but hey that's life and that is why I have a '99). Not one problem, mind you I did not stomp on her at 80 mph and hold it till 120mph where we hear horror stories about the big boom (that common sense thing). And in the winter months I watched my foot as the boost gauge would read up to 18lbs with the cooler temps (another common sense thing).

Hope that answers the question.

Dan

 

I would "suggest" that there are two weather related enemies in relation to performance, maybe not a threat to keeping the lower end together, though. Yes, the colder denser (spelling ?) air will increase boost, create ideal conditions for the big boom in leaning your a/f.

In the southern states or hot climates there are challenges, too. Number one we are robbed of power in the 90 degrees and 100% humidity. Evidence of that all day long in climate comparisons and two "in my opinion" - I stress that "my opinion" - when you consider that air moving through our Eaton superchargers increases in temperature to 300+ degrees (Truckin Mag in Oct. '02 in a KB Eaton comparison article) and then streams through our intercooler reducing temps to an amazing 117 degrees (same source article) we are still forcing through pretty damn hot air - that test was done in 70 degrees, drier air than our hotter humid air. Not that I have a formula, but you send air that is on average 20 - 25 degrees hotter - spool it through our Eaton's and send it through the intercooler - the question remains - How effective then is the intercooler (I am talking about stock, no improvements in heat exchanger or cooler tanks etc, just stock) - I don't have an answer. But, I mentioned to my local tuner (who has been in this business for over 15 years) and he said no sense in increasing boost or increasing timing to take further risks, especially considering how hot it gets in the summer and you are running stock cooling. I am willing to bet, unless someone can prove me wrong that our intercoolers have a threshhold in the temperature that is being fed through them and their ability to cool to 117 degrees. Thus hotter air being fed into the Eaton means hotter air being fed into each cylinder.

Just my theory and 2 cents for what it is worth. Boy was that long winded or what You hear of the big boom down here, too. It is most often blamed on user error or aggressive lean tunes - I just think the 90 + degree weather has a factor, too, maybe it is just a performance issue.

D-Day

 

so all that being said, 4 lb, 6 lb, or upper/lower for a DD getting the most power without dangering your truck

 

if you are gonna do long tubes, just go to the 6.

I went 12.71 with my 4lb lower and ported eaton.

When i finally changed to a 6, i went 12.45, and back it up a couple times.

I would say that shows a significant difference.

Whether it's a 4 or a 6, if you motor is gonna blow, it's gonna blow.

 

I wouldn't worry about a 6# blowing up your block, I think a majority of the people who have problems do not perform simple maintainence on their trucks.

What causes the block to break? Detonation is a widely accepted culprit. What is detonation? Premature ignition of the a'f mixture in the combustion chamber.
What causes that? Lower octane fuel, too aggressive timing.
Oil from the PCV system will lower the octane rating substantially.
An extra 2# of boost is highly unlikely to cause rods to break.



Also, I don't think a 90mm MAF is required! In fact a lot of the mustang crowd looks for 80mm MAF from lightnings. Something about there is more range or flexibility in the sensor itself over a 90mm maf sensor.

 

I've run my 4lb lower for almost 4 years with zero issues so thats what I would recommend, I made 444hp with a stock Eaton, 4lb lower and basic bolt ons so power can be made.

 

i have researched the issue myself, talked to tuners, reconsidered, researched ad naseum. I am sticking with the 4lb pulley until i install long tubes. just too much boost on a stock block to be "safe". I think they are pretty amazing engines to survive so well even with the 4lbers. Mine isn't a daily driver but I bracket race about every weekend during season and I want it to hold together as long as possible. it is undenialbe that a 6 is more likely to scatter your internals than a 4. if you don't mind having more risk of blowing it up and spending 5-12k for a new/better motor then by all means I would say throw on the 6er. another thing to consider is you never know what kind of gas you're putting in. heck, even with my safe dyno tune i still run a (10:1 = 95 octane) toluene mix at the track.

 

Your statement above is quite interesting. Is the tuning on a L for a 4lb pulley substantially different from that of a 6lb. It is only 2 lbs of boost extra. If you add a 2 lb pulley on a stock truck you do not need a tune. So it may be possible to not need a tune to move from a 4 lb to a 6lb. What do you guys think?

 

I think you're looking at a minimal difference between 4lb and 6lb tune. I would dyno check it though to be sure, then adjust if necessary. HOWEVER, if you are going to a 6 lb you need a MAF extender, and that does require a retune.

 

so a 4 lb pulley is fine with a 80mm but a 6 lb pulley needs a 90 mm? how much horsepower difference between the first set and the second set?