1991 Z-28

We set the timing at about 8 degrees. The fuel pressure is set at 44psi. This thing is pulling 12 inchs of vaccumn at idle and even my own 388 pulls 16 inchs at idle. I change the plugs on it switched out the ignition coil. I've reset the valves incase they were not set properly even though its a crate motor and you should have to. I played around with the PROM, and when i try to give it more fuel in the VE tables, it just runs terrible. The plug readings are jet white, which means its running way too lean, but it doesn't like to run any richer than it is now. The car is extremely jerky fuel if added to it in the PROM. What other suggestions to run on the checklist to get this thing going properly before nationals?

cam is 208/221 LSA 112

Free Bird

iTrader: (1)

Try adding a $hit load of fuel to the initial shot. Some refer to it as the "pump shot". It helped my lean condition a lot and made it easier to drive around town. Try to do a search on the prom boards. They're getting pretty good at tuning these HSR motors.

Free Bird

iTrader: (1)

Is that Jeremy's (Poorboy8) car in the bottom right?

Steve86TA

iTrader: (57)

Yes it is.That was last year at a meet we had in So. MD.Did he get any paint on that thing yet?

Matt87GTA

Is it going into closed loop? Got any scantool data (BLMs, knock counts, etc)?

V8Astro Captain

iTrader: (1)

Uhhh, it idles with 12"Hg and you want to put MORE fuel in it?!? You're going the wrong way. You need to lean out the VE table in the idle area. I'd also crank the timing up in the same area. That should get you driving so you can tune it.

Der91Z

iTrader: (1)

The car is running super lean, the plugs are jet white. There is alot of timing in it, so much that i was afraid it might hurt it because of how lean the car was running, so i backed it down a little. I'm going to check the firing order on it when the weather breaks, but i would assume thirdgen resource got that right, I mean 1991 Z-28 did pay a fair chunk of change for this job. then again, we all know what happens with assumptions.

330hp_91RS

I really don't know anything about tuning cars with proms and all but... with these Stealth Rams and such can't you tune the car with a lap top in the car? If so then couldn't you set the base timing to 10 or 12 degrees, then alter the fuel mixture to get the most vacuum?

I would also get an air/fuel gauge....it always helps me out. If the plugs are white, then yes it's lean....but are the plugs looking like this when you let it idle for like 5 mins then pull them out? The a/f gauge would really help you out cause all you would have to do is set the a/f mix to 14 or so on the gauge and you are set, comp. controlled cars ecm's will usually make up the rest of the driving range...well stock ones anyway....shoot I better get off this post before I say something retarded.

330hp_91RS

What do you mean..." The car doesn't LIKE the fuel mixture to be any richer than it is now"

Clarify....

Der91Z

iTrader: (1)

When more fuel is added in the VE tables, the car runs really bad and is extremely jerky. It almost stalls at part throttle and when you crack the throttle it just flat out dies out.

330hp_91RS

That's really strange. What kind of air intake/filter assembly is on it?

Der91Z

iTrader: (1)

Same as factory, tpi boot with y snorkel with two paper filters.

330hp_91RS

i know it's a long shot, but sounds to me like you r are choking the motor, then when you richen the mixture, it richens even more rapidly because you are already at a standpoint with the amount of air entering the engine. Just a thought, but why in the heck do you have a Stealth Ram with factory intake? I don't get it. At least some K&n's and maybe a ram air setup later.

Kingtal0n

vacuum leaks.

that cam should pull more than that at idle. whats the idle speed? my 218/224 Pulls 15" at 800 Rpms. My 234/244 pulls 10" at 800 Rpms. if your only pulling 12" at 800 rpms somthing is wrong. it would explain the super lean looking plugs, and the jerkiness.

are you using a MAF? vacuum leaks play hell with mafs because the computer doesnt see the extra air and wants to pull fuel out.

Der91Z

iTrader: (1)

Not a single vaccumn leak, and it is Speed Density so no MAF sensor. I'm leaning towards the firing order being off since thats the one thing i haven't checked yet.