Why is my 408 a dog down low?
Jan 12, 2007 | 09:38 AM
#11
Thread Starter
High on diesel fumes
iTrader: (70)
Joined: Mar 2005
Posts: 12,658
Likes: 3
From: Phoenix, AZ
Originally Posted by 03sierraslt
You are used to supercharger low end torque.
Originally Posted by trever1t
You did the 80e swap at the same time?
Most report that the low end SUCKs on the 80e but I would still think you'd spin 'em at will.
Most report that the low end SUCKs on the 80e but I would still think you'd spin 'em at will.
Originally Posted by slowec
Have someone else eye your tuning. You forgot something 
Originally Posted by hirdlej
Please, take no offense but that is a gargantuan of a camshaft you have there for that 4800lb+ beast my friend. In a motor that's 408 cubic inches in that heavy; lifted truck, I would have shot for something more around the lines of a XR273HR cam with a 220/224 duration and a .530/.534 lift on a 112deg lobe separation with your lower 9.5:1 compression. Whoever recommended that cam to you should be shot. Sure, if you want all out ***** to the wall top end power and a heavy loping cam, what you have is fine. But if you want gas mileage, instant tire busting throttle response and an overall more pleasureable truck to drive, get that monstrosity of a cam out now. I am willing to bet your peak torque doesn't even come on until 4800 RPM's or so with the current camshaft you have installed. Do keep in mind, if you go to a smaller camshaft and someone says "Don't do it man, your power will die past 5200", who gives a flying flipper? Fact of the matter is, you have 408 cubes and regardless of your powercurve tapering off, you still have almost 100 more cubes than the rest of us schmucks with our 4.8's and 5.3's. You'll still vaporize us like we never existed. Design intelligently, match perfectly, do it once and be happy. 
Jan 12, 2007 | 09:40 AM
#12
Thread Starter
High on diesel fumes
iTrader: (70)
Joined: Mar 2005
Posts: 12,658
Likes: 3
From: Phoenix, AZ
Originally Posted by vanillagorilla
What kind of TC do you have? Is it the same one from your 6.0/Radix setup? If so, then the reason why it stalled higher then, is that you were making more torque with the Radix. As for not breaking the tires loose, I'm guessing it could be something with the tune. I don't know what though, it seems you have all the bases covered. Even with the shitiest of tunes my 4.8 N/A could still break the tires loose. It really sounds like you activated TM or something. Which brings me to my next suggestion, and that could be the timing. Maybe it needs some more. 23-24* isn't a whole lot when dealing with a N/A engine. I doubt it's your cam being too big though. That's an oxy-moron! 
It's a Hughes 25-20L towing converter. I guess I can check TM, I don't know how it could have gotten accidentally turned on, but it's worth checking.
I guess that's all I have left to do is try throwing more timing at it....I'm not getting any KR when stalling it up, maybe I should just keep adding until I start to see some.
Jan 12, 2007 | 11:53 AM
#13
TECH Fanatic
Joined: Dec 2005
Posts: 1,932
Likes: 0
From: arkansas
Do you have a problem with going with a like a 3200 perf truck converter like maybe a 10" over your 2800 towing converter. Say at 2800 your making 250rwhp and 275 rwtq. 3200 you maybe making 320rwhp and 350rwtq? Just something to think about.
What about the first gear swap for the 4l80e? Do you still have 3.73's? Maybe 4.10's would help?
What about the first gear swap for the 4l80e? Do you still have 3.73's? Maybe 4.10's would help?
Jan 12, 2007 | 11:56 AM
#15
formerly silverbrick (changed 02/17/2013)
iTrader: (5)
Joined: Mar 2006
Posts: 4,525
Likes: 0
From: Pasadena, Tx
IMO that cam definitely isnt too big for a 408. Since you are going turbo in the future, a looser stall will help you spool more so you could check that out. I Would just keep adding timing until you caught some retard, then back it off a couple degrees and you're set. Also one thing to consider is your compression, I understand its stock but if it was higher then you would have more low end, but since you are going turbo, you have it set up just fine.
Jan 12, 2007 | 11:59 AM
#16
Thread Starter
High on diesel fumes
iTrader: (70)
Joined: Mar 2005
Posts: 12,658
Likes: 3
From: Phoenix, AZ
I won't re-gear the 4wd, too expensive and it's my DD and sees a decent amount of highway miles. I'd rather not do a new TC either, I tow a 6000 lb boat during the summer. I look at both of those as being bandaids for the real problem anyway. I was there before with current hardware, and now I'm not. I think putting some more timing in is a good start. I'll mess with it at the track tonight, assuming it doesn't rain.
Jan 12, 2007 | 12:01 PM
#17
Thread Starter
High on diesel fumes
iTrader: (70)
Joined: Mar 2005
Posts: 12,658
Likes: 3
From: Phoenix, AZ
Originally Posted by onebadrubi
lol I just keep thinking of more and more possibilites. Your the ONLY ONE TO RUN THIS MANIFOLD IN HIGH HP APP. Maybe something with that?
Jan 12, 2007 | 12:07 PM
#18
TECH Fanatic
Joined: Dec 2005
Posts: 1,932
Likes: 0
From: arkansas
How are those a bandaid. Your motor has a powerband of probably 3000-6600(maybe 7k). You only problem is getting 2500k more.
Your just use to your power coming in at 500rpms or sooner. This is what im thinking. Do you have access to dyno? Did you dyno your old setup? This could answer alot of questions.
Im not knowledgeable at all in the tuning department so keep trying their, I dont htink you can ever tune it enough. lol.
Your just use to your power coming in at 500rpms or sooner. This is what im thinking. Do you have access to dyno? Did you dyno your old setup? This could answer alot of questions.
Im not knowledgeable at all in the tuning department so keep trying their, I dont htink you can ever tune it enough. lol.
Jan 12, 2007 | 12:11 PM
#20
Thread Starter
High on diesel fumes
iTrader: (70)
Joined: Mar 2005
Posts: 12,658
Likes: 3
From: Phoenix, AZ
Big cubes are supposed to give lots of good low-end torque, and the cam I got is "small" for the 408, which should also give me good torque. 4* of cam advance is also good for low end torque, as is a truck manifold with the long runners for high velocity. The only thing that isn't that good for it is the 9.5:1 CR, most 408's I see shoot for somewhere in the 10's or low 11's. This leads me to believe that I have a problem somewhere, and the likely culprit is the tune. My cam is spec'd to have about a 2200-6000 RPM powerband, so at 2400 I should be able to rip the tires pretty good. All of this leads me to believe that the answer is in the tune...and with my AFR's spot-on at 13.0:1 the only thing left is timing.