greatwhitez

alright i got my 95 lt1 dynotuned on a dyno jet. comb is a fully forged 396 w/ 12:1 compression, ported lt1 cylinder heads 2.00/1.56 valves, gm 847 cam, 1.6 comp rr's, dynatech longtubes to 3" xpipe true dual exhaust, 4.10 gears, 42# injectors, slp cold air, ile elbow.

my numbers were less than i expected and recently (last nite/2 days after dyno tune) my car has been sputtering and almost like its breakin up, so i pulled the #1 plug and it was white.

on the dyno it made 398.7 rwhp, and 419rwtq, w/ a afr reading of around 12.9-13.0.

i was expecting a lot more out of the car, but the km has been pickin up false knock so i switched to the lt4 km.

what should i look for, i know that there is definatly more power in this combo, i just dotn think these number can be right.

Mystic95Z

Got any flow numbers on the heads? Who did them?

-Tony

greatwhitez

the heads were ported localy 2 years ago, i don't have a flow sheet but seem to remember them flowing around 270 on the intake side at .600". Im confsued because on the dyno chart it shows my car not making any power over 6k rpms, when i know for a fact that the 847 cam pulls and makes power up to at least 6500. Would i possibly benifit from a bigger TB. Also what should i look at, today i'm bringing the tech 2 scan tool home from work and going to hook it up to check the sensors could someone tell me what the sensors should be reading, such as 02's how many mv's and fuel trim, tps, iac, etc..

Spinner

You'd benefit from the biggest TB you can find. IE: monoblade or 58mm. What valve springs are you using? You might be encountering a bad case of valve float as well

greatwhitez

so i'll get a tb then, and as far as valve springs, i'm using the k-800 kmotion valve springs w/ their titanium retainers. w/ the 1.6 rr's and the comp r lifters, they are adjusted but i set them a little on the loose side, and they are pretty noisy.

WS Sick

What kind of knock was the sensor picking up? Was it excessive, I put a knock sensor delete circuit in (can switch back and forth) I suspected I was getting false knock and this confirmed it big time!!

You must must confirm that you are not running too lean first though, because you donot want all that work to go down the drain with excessive detonation.

greatwhitez

ws sick- im not sure as to what you mean what kind of know was it picking up, i have rr's and lt's so i figured it was that, but how do you go about puting a "knock sensor delete circuit" in?

and if you dont mind me asking what kinda numbers did you put down w/ ur setup- it is somewhat similar to mine.

WS Sick

Never had my car on a Dyno, but in the 1/4 mile I ran a 11.92 @ 115.4 in a 3750 pound car (with me).

I mean how much knock is your scanner reporting? I have a toggle interupt which runs one side to the factory knock sensor and the other side to a resistor to ground simulating a knock sensor. If the Dynos A/F says your running good (rich to lean) then shut er down, flip the toggle and run with no knock sensor to see what happens.

Some people here have some other ways to decipher between real and false knock as well.

greatwhitez

ok sounds good, on the dyno i had the lt1 km in, but yesterday i swapped the lt4 in. it ran good all day, but then last nite when i was driving home it was stumbling and seemed to be cutting out, so i pulled over and yanked the #1 plug, and it was white- which would indicate a lean condition, it threw a code on the way home, the ses light came on for about 30 seconds then shut off, so today i'm gunna put it on the tech 2, what should i be looking for?

WS Sick

it should show a knock count, but with stumbling etc you may have some opti pulse issues. (or fueling)

disco192

sounds alot like what my car was doing... turned out to be a bad fuel pump. Check your fuel pressure.

greatwhitez

the fuel pump is a walbro 255 intank pump which was just put in this winter and has the same run time as this motor. What fuel pressure should i be looking for - such as idle w/ vaccum line on/off, wot throttle? I dont think it is the opti because it never did it before the combo went together, and i dont think that it would cause the plugs to look lean.

Dave C. '97 Z28

First of all, because the car is fuel injected you cannot read the plugs on it like you would an old carbuerated car. Well, you might be able to, but you'd have to run it at full throttle and then shut off the engine right as you let out of it. And even then, I still wouldn't put alot into that. Plug reading is shaky at best. The only thing it's really good for on fuel injected cars is to see if there are any aluminum deposits on them.

The other thing is that if you are running forged pistons, they can generate false knock depending on how loose they are. Usually, if the clearance is correct, it will calm down once they warm up. But if you just start the motor and run it, you can get some piston rocking going on that will cause the false knock.

The only way to tell is to scan it while running it to see.

-Dave C. '97 Z28

disco192

Fuel pressure should be around 42-48 psi. A faulty fuel pump will sometimes drop into the 20 psi range as mine did. When i really got on it, it would drop to 15 psi.

And yes, you can read plugs... just not quite like carbed cars. White plugs do mean there is a lean condition. That is prolly what is setting off your knock sensor.

greatwhitez

now is that 42-48 psi w/ the vaccum line on, at wot?