hirdlej

iTrader: (31)

Ok, so I built a 6L for my 2004 Silverado and I don't know if I should be pleased with my dyno results. The combo in a nutshell is:

'04 Silverado
Regular Cab, Short Box 2wd 5-Speed Manual
'05 6L Lq4
Stock truck intake manifold
44 lb/hr injectors
ported 243 heads
10.6:1 comp
comp 218/224 cam
OBX long tube headers with magnaflow catback


So the engine idles great, truck drives great, feels nice on the street, etc but for the life of me I cannot figure out why the power falls off so aggressivly on the dyno. I've never seen an LSx engine have power fall off so fast 5400 RPM. Where in the world did I go wrong? I like the torque curve but can someone help provide some intelligent insight as to why the power falls off so quickly up top?






Also my friend brought his stock '08 LS3 vette the same day. Here's my torque and HP curve laid over his vettes curves:




Can anyone provide me with some intelligent insight? I can answer just about any questions you have. I am wondering if the cam sprocket is off a tooth perhaps? Perhaps I got the wrong camshaft? I have a smoking deal lined up on a 222/224 duration comp XR275 cam. Would this be worth stuffing into the truck?

hirdlej

iTrader: (31)

Wow, no one?

1989GTA

Was the cam degreed in? Looks like you are running out of air to soon for some reason.

hirdlej

iTrader: (31)

Just dot to dot. I was thinking of taking everything apart to degree it and verify that everything is on. Someone I know is selling a 222/224 comp XR275HR cam so I might upgrade and try that out at the same time.

1989GTA

Even though your cam is small in todays world it is not that small. I don't think you cam is the problem if degreed in correctly. If advanced to much than yes.

Old Geezer

iTrader: (3)

"Stock truck intake manifold",is one item I'd be looking at.
Our dyno tests show that a 5.3 w/ truck intake, runs out of power @ about 53-5400. I'd bet you R seeing the same thing, on your combo.
That intake is tuned for low end grunt... exactly what you are getting.

RsSean

iTrader: (27)

Switch manifolds ^ I would say that is your problem. Those trucks are made for low end power which you have. GM did not make a Silve to do high hualing. Does anyone make a Intake to clear the front acc. on those truck. Cause I have heard that the F-body manifold won't fit.

Old Geezer

iTrader: (3)

right now.
We have a mock up w/ an LS1 intake, on a blk w/ the 04 truck accessories on it. The idler will have to be relocated, and it also looks like the alt brkt will need to be trimmed.
The 07 truck wp appears to be more "space friendly", but may also be in need of a relo of the outlet..Not sure yet.

hirdlej

iTrader: (31)

The LS6 intake isn't an option nor is an aftermarket one. A lot of guys are making power higher than myself with similar or larger cams with similar combo's. I'm starting to wonder if the cam was ground improperly. I found a smoking deal on a XR275HR new in the box, I may try that.

njc.corp

my honest view is to say that dont focus too much on what other peoples combo are doing as thats the main thing

everyone's combo is different wether the engine builder did it one makes 405 and the other makes 410 hp-

no biggy and u say others have the same cam and some have bigger ones

thats not a apple to apple example-

after viewing a lot of dyno sheets over the years it seems to be a typical graph of a intake that cant keep up

this is the internet so do some testing before taking anyone's word for it-

Hope it get's sorted out

Thanks

1989GTA

Saw this post regarding the truck intake manifold. I don't know how many versions there are of the truck intake. Here is the post.

"thats what they say about the truck intake and i pulled mine to 6900...switched from the truck intake to the LS6 intake and pulled to 6900 and gained absolutely nothing. ls6 intake was a waste of time for me."