ktmrider

I finally had a chance to dyno the 383 iron stroker in my signature. I was hoping to see 350/350 wheel hp/trq.
Final numbers were very disappointing. Torque was there, 365, but the HP was tops at 280. The dyno curves were very wavy thru the RPM band and you can feel the truck fall flat above 3500 rpm.
I have been tuning with the stock O2 narrow band charts. The dyno shop thinks it is running very rich, and the HPT shows 4000+ to have -5 to -7 cells. I thought this indicated a lean condition?!? I am also concerned that the head work I had done might also be to blame ( 6.0 valves, 3 angle, slight polish work ).
Anyway, any feedback is appreciated.

GMC SKI

What are you 02 voltages at wot ?
How much timing are you running with your setup ?
Are you seeing and KR while logging
I would shoot for near 28-30 degrees of timing if you have decent gas
Wow i see your running a tiny cam with your setup
Are you going to keep it N/A of planning some sort of power adder?

tdogg5.3

iTrader: (6)

i think the z06 cam is way to small for this set up. i think you need someting in the 230 duration range.

DietCoke

iTrader: (13)

Post the graph, you have a serious problem somewhere.

sfj

1 yes that cam is way too small
2 yes you have a problem and should probably post the graph
3 you would be able to see 350 to the ground with a stock 6.0 and a mild cam so with a 383 you should be expecting way more than that
4 so far i am as stumped as everybody else

ktmrider

Thanks everyone. I will post the graphs shortly. Initial graph ramp is good but levels out at the 3500rpm area like I mentioned. Just seems to be running out of juice very quickly. Bottom end is awesome, lights up the tires from a standstill ( this with 32" BFG's and 5000ft altitude ).
I stayed with a mild cam for emission purposes, figuring I would not give up too much with the Z06 cam at higher RPM. But I also figured it would be at the same or higher power levels as the 01 Z06.
There is a little KR ( 4 deg ) at WOT above 4000rpm. Most of the timing is around 30 deg but my brother does not run good gas all the time. Sometimes the timing hits 35+ but I'll review the graphs again as I was concentrating on the retard and O2 levels.

greentahoe

iTrader: (2)

Some things that have caused this with other members
1. Incorrect cam install.
2. Exhaust restriction
3. Bad tuning. I would think some changes to the VE table would be needed, but Im no expert. You definately need to get that thing on a wideband. Are you getting knock? Oh, you beat me to it.
I dont think a bad head job would make you lose power, at least not much.

ktmrider

Still waiting for the dyno charts, they are on x-mas break and I forgot to get a printout.
I did one VE +3% adjustment to all the cells at 4000rpm and up. The KR cells dropped from 8 to 4 with that but my bro thinks the power was cut even further. He is kinda on the lam with money issues and I don't have much time to tune on his ride these days.
We are also on the ethanol blend plan around here thru the end of February. Not sure if this is what caused the KR to drop earlier but I have no tuning experience with the corn fuels or what their impact is.
Thanks again everyone for adding your 2 cents, more to come.

Stroker 1500

iTrader: (1)

Wouldn't the engine run like shat if it was a incorrect cam install?

ktmrider

You know, one thing I totally forgot about was that I bought a "used" ASA timing assembly from eBay ( 2 dyno pulls of use ). I wonder if I used the wrong keyway ( it is keyed for +/- 3 degrees ) and am advancing the timing too much?!? That would explain the top end falloff and excellent low end torque, plus some of the KR at high rpm's. Coulda swore I used the center key but it was 1000P at the time and I was running from the oven to the crank snout after heating it up.
Too bad it will take a total teardown to verify. Maybe an excuse to swap the cam?!? A good excuse at that....