Davidgmcman

I got a 5.3 been bored to 5.7 10:9 compression PRC ls6 stage 2 heads vinchi high trucker camshaft, etc cams rated for 1800-6400 we made max power at 5500 rpm... I know the engine has a ton more potential I duno what it is but I figured we would get good power up to 6200 but wasn't the case anyone think the factory intake manifold is fading out with those heads? The cam make great mid range power just Max's out way to low any suggestions? Yes we have plenty of injector.

sbcgenII

iTrader: (1)

I am thinking 216* duration and 41* IVC why it isnt making better power up top.

Davidgmcman

I don't know I ran a TSP 224r cam before on factory heads and it died at 5900 that's y I have the assumption vinchi said should make power all the way to 6600 hey he made the cam I would think his word is pretty good I'm guessing the heads are outflowing the factory manifold that's my only guess

Davidgmcman

Engine made great power till then just just slowly died off right at 5500 even a smaller cam should make power something up to 6k cam can in right at 2300rpm like it was saposed too

thunderstruck507

iTrader: (18)

You can do a scan and compare key on engine off MAP readings to your MAP readings at WOT. If you have more than a couple kPa discrepancy that means it's pulling vacuum and there is an intake restriction.

Is the graph smooth or does it get rough which might indicate valve float?

What exhaust are you running?


Here is my 205/210 cam in an otherwise stock 5.3 with true dual exhaust on factory manifolds:

Davidgmcman

My correction the cam is a vinchi trucker high lift 216 224 285 285 the graph is smooth as a straight edge and just slowly goes down after 5500 I have pacesetter 1 3/4 long tube full 3" exhaust to corsa system no cats Texas speed said change the manifold I was just wondering if anyone else had ever ran into this issue before mayb i just had a shitty design of the factory manifold the truck is a 1999 so mayb it was crappier then I don't know

Davidgmcman

The truck mad power to 5800 factory but with the CNC heads on it it's maxed at 5500 that's y I said I think it's pushing to much air through it by then creating turbulence and losing power up top

thunderstruck507

iTrader: (18)

Very well could be the intake. I don't look at many graphs of trucks honestly. Mine starts to nose over at 5500 too.

It's certainly not your exhaust or heads. So that leaves the intake (or what's in front of the intake) and the cam to dictate the curve. You seem certain it's not the cam after speaking to the cam company so intake might be your best bet.

Forcefed86

iTrader: (4)

Truck intake is making peak power up to 6900 on this 6.0 combo. I think it's the baby cam holding you back.

http://www.hotrod.com/features/1507-...ifolds-tested/

Davidgmcman

I saw that article too witch it crazy to me that's the only thing I found on this subject I wish they showed there gain at each rpm to see what exactly it did I don't know anyone who has ever ran a 5.3 intake to 6900 but hey they did lol I don't know I'm going to put in new springs and a tbss intake and see were that takes me I'll do the tbss intake first just to check but I deff don't think I'm getting valve float

Forcefed86

iTrader: (4)

216/224 .585 lift, LSA 115... thats too small of a cam for your 5.7 IMO if oyu are looking to make power in the upper RPM range.

Toss a cam similar to this in and it will be night/day difference up top. Nothing wrong with that nice flat torque curve though. Throw a $200 gt45 turbo on it at 6-8lbs the way it sits and make another 100hp instead of farting around with cams.

http://www.tickperformance.com/tick-...1-ls6-engines/

Davidgmcman

Yea I could run a bigger cam true but I was looking for a cam that can move this 5000 pound 4x4 tank and the one I got runs awesome I'll post dyno graph soon

Davidgmcman

Here is the graph let me know what yall think remember this truck is 4x4 with 4:10 and 32" tires it loses alot from motor to wheels but see how the horsepower starts droping after 5500 5600<br/>

JoeNova

I don't see the issue. That's an extremely healthy looking dyno graph. It holds power for 1000 RPM up top. No peak and shift happening there.

NEVER spec your build so that it peaks at red-line. Why on earth would you want to shift right at peak power? You want to be able to hold as much power as you can for as long as you can. I also don't understand the desire for a cam that peaks at 6000+ in a 5000 lb 4x4. You should be focused on as much mid-range power/torque as possible.

roastin240

iTrader: (13)

This^^^^

big hammer

What are you running for exhaust