MSteezy

Okay, I have been reading on this forum for years. Still trying to completely grasp all that's happening with a Heads and Cam swap. A little about myself, I have a 95 Impala I went with Le2's 226/232 le cam on a 110 Lsa. Stock block, long tubes, new opti, oil pump, 3 inch exhaust, le ported intake, 30 lbs accel injectors. Magnaflow cats to dynomax 18 inch bullets. Pcm tune from pcmforless. All of that and the car doesn't accelerate any faster than it did initially. So I am trying to figure out where to look to see where power is being robbed. I just checked fuel pressure it goes up to 44 when the car is off but will dip down to about 34 during revving. I have been data logging but I'm still researching to find out exactly what I am looking at. Nobody tunes lt1's in Austin Texas... So there is not a shop I could take the car to that I know of.

Here is picture of what the pcm shows at WOT

Is there anyone that look this info and see what's wrong? Any help would be greatly appreciated

jakemussman

iTrader: (1)

Did you change gears and converter?

MSteezy

The gears were changed prior to the heads and cam swap. I went with 3.73s. I have a 2800 stall yank converter that I was going to put in once it was running right. I did have the pcm programmed for the yank but since it doesn't seem to run right I have been stuck where I am.

ahritchie

iTrader: (1)

If your fuel pressure is not staying minimum of 40psi, your pump is weak and needs replaced. You really should tape the gauge to your windshield and see what the pressure is under WOT under load driving. Factory specs are 41-47psi. For hardly any more money than a stock replacement, I'd go straight for a Racetronix Walbro 255L/hr pump with hotwire kit if I were you.

Once it's running good with factory spec fuel pressure, you could always take it to a shop with a dyno just to do a few runs to see the HP # and make sure it's healthy (or take it to the track and check the trap speed), PCM for less here in NC only charges $75 for 3 runs on the dyno (no tuning).

fbody_brian

Intake restriction? shouldn't map be closer to atmospheric pressure at wot?

Also your knock counts are pretty high, and it's pulling timing. Are you getting any detonation?

MSteezy

It's got a k&n cone filter on it. I do still have the stock 3 inch intake pipe could possibly not be enough air? I haven't notice an odd sounds coming from the car. I doesn't start right up when cold it take about 3 tries or you have pump the gas like it has a carb on it to get it to catch on. Once it's warm it fires right up.

I am going to try to install a fuel pump this next week to see if that helps.

Here is a snapshot while cruising. Does this give you more of a idea of what's happening?

I'm still trying figure out how to decipher the data from these scans...

ahritchie

iTrader: (1)

Sounds pretty obvious to me by what you are saying: hard starting, having to pump the gas, 35psi low fuel pressure, it's a fuel related issue. You have to see what the pressure is with the car under load while driving as mentioned to get an accurate reading....the PCM is not going to tell you the fuel pressure. Also, consider upgrading to a LT4 knock module...much less sensitive to the noise roller rockers make so you don't get false knock.

4K+Converter

What stands out to me is the knock retard and retard count. Having the PCM juggle your timing around isn't doing you any favors. The LT1 knock modual is really sensitive to anything that sounds like knock. Get a LT4 knock modual, which is made to be less sensitive. Factory LT4 cars had roller rocker arms and that can set off the LT1 knock modual. Headers can do it too, and a lumpy cam can do it too.

If that doesn't help, you can have your tuner program the knock sensor off, but that can be dangerous as well.

On a different note, I doubt an aging stock fuel pump has the juice to power a h/c car. Get a fuel pressure gauge and test it at WOT to make sure it's good or bad. If bad, throw a 255 and a Hotwire kit at it.

MSteezy

Thanks a lot. I was thinking fuel pump should be next. I will try to get one and put it in within the next week. Just didn't know if there was something else that was there that's obvious the I don't know. I'll tape it to the window first and open it up to see what the pressure is like.

ahritchie

iTrader: (1)

Let us know what happens! I'd call around your local GM dealerships and see if they still have a LT4 knock module GM part 16214681 in stock, it plugs into the bottom of the PCM and takes all of 10 minutes. They don't make them anymore...if not, you have to hunt around for someone to sell one second hand.

myltwon

iTrader: (1)

If car is hard to start and lacking power I would lean towards a vacuum leak, bad valve adjustment, or possibly the aforementioned fuel pump. Especially the valve adjustment considering it seems worse off than before the HC swap.

MSteezy

Ok here we go again. New Racetronix fuel pump, constant fuel pressure under throttle and LT4 knock sensor and the same problem. It is easier to start however and it doesn't take so long to idle at same speed so the pump did change so things. The power feels down, there is still knock retard and the BLMs get maxed out a lot. Any other suggestions on what could be wrong with this picture?

MSteezy

Can anybody look at these two attachments in the post above and notice what may be wrong?

Puck

iTrader: (17)

First thing to do is to run race gas mix to see if the knock goes down or not.

You need to determine whether it is false knock from noisy valvetrain, true knock from detonation, or worse case scenario knock from physical damage. If the race gas has no effect whatsoever, it is most likely valvetrain noise or the motor is damaged. If it is false knock, it is easy to desensitize the sensor through the tune.

BLM issues are a separate problem due to the tune, vacuum leak, TB, etc.

draggin97s10

iTrader: (2)

Knock count at 37000 that is what is wrong

SS RRR

iTrader: (2)

Yeah, is that a high knock count? I have no idea, but I had a faulty KS at one point and it caused lack of power issues. Plus it's pulling 7* of timing? I know nothing about tuning, but this seems like it may be a timing issue?

Shownomercy

iTrader: (1)

So you are driving round with a 226/230 cam and stock torque converter?

SS RRR

iTrader: (2)

Sum Ting Wong?

Shownomercy

iTrader: (1)

Nope, nothing at all. Typical LT1 owner.

MSteezy

Yes... I have a 2800 stall yank that I have held up installing because I wanted to have the car right first. It's not a daily driver so while I'm figuring out what's wrong it sits in the garage.