jsetzer

I am more worried about it breaking up on the top end than the low numbers, but both suck.

GM847, mild head work.
2.0/1.55 valves
3 angle valve job and I know material was removed from around the valve guides... don't know much more
12.1:1 forged bottom end
mildly ported intake
autozone cone filter in place of factory air box
2.5 duals with 40 series flowmasters and h pipe
hooker long tubes
stock TB
36# fms injectors

A/F was a little lean down low, but up top looks about right. However,,, this was with a decent amount of timing pulled, she still was pulling a few degrees @ wot....

Datamaster if anyone cares,
Log

My current tune,
Tune.lt1

Got code 42 day of dyno: EST Grounded,
Next day got 41, EST OPEN
Today no codes

What now?

DarkHorse

Start with all of the small things - plugs, wires, etc.... tuneup.


Grease made 412 with the 847 and ported AI heads with a 6 speed so i'm not sure exactly what you are expecting in terms of power. For the miss i'd check the basic tune and swap the MAF if you have someone you can trade with to test. That miss should be felt on the street/highway as well as the dyno so try that first before looking into other, more in depth areas.

T/A KID

Who did the head work?? From what I have seen it is easier to mess a good head up than to improve one in the hands of a non professional. I have seen simliar dyno numbers with cam only 847 cars with around stock compression.
Like Darkhorse stated start with the small things first.

jsetzer

Plugs are all new, and just double checked to be good gap
Wires pass a visual inspection, but I will prob swap them eventually just to be safe
put a new coil on, no help
Not much to tune up, almost everything on the motor has less than a 2k on it.
fuel filter is pretty new
pump is new, holding good psi

I will swap a maf to see, that could be it... but the readings from the maf on my logs are normal.

Power wise.... I was expecting very close to 400hp, even not reaching that my tq numbers are low. Should be in the 370 area.

Allen at Folks here in Norman did the head work, they are reputable for a local shop.

Javier97Z28

Not knowing much about your heads there's not much to say about the power level... why didn't ya go with a proven setup? At least LE1 heads..

How much experience do you actually have with tuning? Or did someone else do it?

jsetzer

pcm4less mail order tune, plus a little playing on my own.

Didn't go with better heads because I didn't have the money. Spun 2 rod bearings and had to build a motor. I got a valve job and some minor port work for @ $300.

94IMPALASS

You have no break up, the spikes at the end are from the inductive pickup on the dyno not getting a good spark plug reading. The curves are nice and smooth. The air fuel is perfect (the down low lean is the transition from part throttle to WOT and the delay back to the sniffer, especially if their filter is dirty). If it really was lean the torque would be down and then come up, but it looks nice and flat.
Code 41 and 42 I often see with opti failure, or Coil/ignition module failure and will lead to false knock very often. I would work on fixing these first.
Glad to see I got another air/fuel almost perfect on a mail order tune.
I also have a feeling the heads are very poorly done. LT1 heads port differently than normal chevy 350 heads and I have seen many heads messed up by "the local guys". HP is all in the heads my friends......
Bryan

Javier97Z28

Hey Bryan, rare to see ya on the boards

jsetzer

The spike is a missfire, the you can feel it very much so in the car on they dyno. Could also feel it on the street, but it hasn't been doing it the past few days

Everyone tells me my dcr is fine, I should run fine on pump gas, etc, but @ 3k it was pulling 10 degrees of timing, as it got richer 4-5k it pulled less, then pulled more again @ 5-5.5k and then dropped off to about 1 degree at 6k+

I am trying to find another 95 locally so I can swap icms with them, hate to blow $80 if I am going to need another opti. Already replaced the coil.

Every old graph I have, the car/dyno takes @ 500rpms to go from reading 14.7 to reading the actual WOT a/f. This graph takes nearly 2k, so I have a hard time believing my a/f down low is right.

TQdrivenws6

Figure out what is causing the knock first, put some race gas (try not to mix it with much normal gas if at all possible) in it and see if the KR goes away. If it's real knock it should go away with the higher octane stuff. I also saw code 42 when my opti went south (it was only 1000 miles old and a GM unit to boot) so look into those issues before you chase down other possible problems.

jsetzer

I know its not false knock. If I add in the timing back to where PCM4less set it, I can't drive it. Pings all over the place.

Thanks guys, after I rule out the ICM Ill start chasing other things.

350pride

I had the same problem when I did my hotcam install a couple of weeks ago. Guy said that it was opti going out. I could feel it on the street too. My dyno sheet looks almost identical to yours. If you if out whats the matter let me know; im thinking about switching the opti out. I just did the coil, and all the wires are good.

WS Sick

Did you bore the block? is it zero decked? whats the specs? With a static of 12:1 you have to have all your Ps and Qs lined up.
With an undecked block and a 58 cc cylender head and around a 5 cc dome with a felpro gasket (wich gets a static of 12:1) I figure your dynamic with the GM 847 to be right around an 8.5:1. Really on the edge so the tune is really gonna matter.
Is it getting hot at all? A bad opti will really throw in a monkey wrench as well.

jsetzer

Chambers are all 51-52cc (lt1 heads)
Zero decked (well actually .005 in the hole)
5 cc dish
3.5 stroke (not 3.48 factory)
.039 gasket

WS Sick

Nice work, really got that quench down pretty good.

With that and the GM 847 I get 8.3 Dynamic compression ratio.

I responded to your PM.