Just have a question, possibly covered already but i havent found it in my seraching so a quick yes or no, possibly an explanation as to your answer would be appreciated.

I have a 350 with the TBI setup. Plan on installing headers. Car just dies between 3500 and 4000 RPMs, and i think that possibly my car is starving for fuel, thinking it's most likely air. anyways, by installing the headers will i lean the car out even more than it may already be?

 

Yes.

Easy out (headers) = Easy in (induction)

By installing headers (as well as an entire free-flowing exhaust) you're going to increase the flow of how much air can be pulled into the cylinders. If you don't do something to add more fuel, it will run lean.

You might be able to get away with increasing your FP. The O2 sensor tells the ECM if you're running lean and the higher FP will make it easier for the injectors to flow enought fuel at a lower duty-cycle.

Does it pull OK above 4000 RPMs?

 

thank you for the reply and explanantion. i figured thats what was going to happen if i put them on. Answer to your question is NO the car does not pull above 4000 rpms. In fact it dies before 4000, well actually more around 3700 to 4100. 5th gear is decent in that car, in fact i think it pulls harder than fourth, it wouldnt be so bad if it died more gradually but it just falls flat on it's face you start to get above 3700.

 

Do you think maybe getting a custom chip would help? I know that you can tweak it some so it will confuse the computer thinking that more air is coming through and in response push out more fuel right? It's probably a cheap and easy way that could possibly help your problem.

 

I'm sure getting a custom chip would help alot. It's a 355 with a .440/.454 lift cam. I just dont think it's getting the fuel it needs.

I had a 450/460 lift cam in it when i first did the motor swap. Felt like a much much stronger car but it would stall, flood itself out, and over heat like crazy. I would love to get that cam back in the car but it's a daily driver for now and i need reliability. I'm sure a custom chip would allow me to install this as well but i dont have the time for a hit and miss right now.

 

OK. Wait a second.

I assuming you did a swap, but did you change ALL the things you're supposed to?

Are you running injectors off a 350 (at least 55pph)?

Did you change the chip or the entire ECM for a 350, or is it for the stock 305?

Did you change the knock sensor?

Those are 3 major things you need to change when dropping in a 350. Each one of those could be causing the problem.

 

Well, to correct a previous response.....
You need the knock sensor and knock module from a 350 (L05 truck)
You also need at the very least, the 55lb injectors from a L05 truck. If you have heads, cam and other performance mods, then 65lb injectors from a 9C1 TBI Caprice would be better.
You can keep your stock computer, but you will definitely need a chip to atleast change the injector constant for the larger injectors.

 

To correct?

It's just that I don't assume that someone DIDN'T do those. I'd rather ask them first.

 

wait a second, before I go on I'd like to say: Don't make this a flame thread on me. I hate reading responses where all it is is bickering between different people. I appreciate the help though.

Now, the knock sensor and module I used are those for a '91 Silverado TBI, LO5 or not i haven't a clue.

The injectors i havent done yet because yes i do have a cam, ported heads, and am planning headers(reason for this thread in the first place), but wasnt sure of the injectors i should get.

Would 55lb injectors work with an AFPR?

 

The 55pph's might work but you'd probably have to crank up the fuel pressure quite a bit with the AFPR, but at that point your fuel pump may no longer be able to supply the kind of psi the injectors may require to run right. If you have a 350 with ported heads, cam, and headers you are definitely going to need a custom Prom for it. You say you don't have the time for it, try looking here http://www.tbichips.com .

Also, what intake manifold are you running right now and is the whole TBI unit the stock one from your 305?

 

I wasnt trying to step on anybody's toes, but I wasnt sure why you would even mention swapping computers as most guys who replace their 305 with a 350 usually leave most of the stock hardware (i.e. computer, prom,injectors, knock sensor and module). Its when they leave all the stock pieces that problems occur. I dont know why you were getting bent anyways? Are you not ever wrong?

 

Well sure I'm wrong sometimes. But that's not the point. The point is that it's RUDE for you to say "To correct a previous post"!!! That's just out right RUDE!!

And you're assuming that I told him to change the ECM. I didn't. I just asked if he did. A LOT of people that swap to the LO5 use the ECM out of a truck, OR swap the chip. I just asked if he did either.

That's why I guess I took offense. You assumed that I TOLD him to do something, and I didn't. I asked him IF he did.

Just a suggestion. If you have an alternative way of doing something than another person on this message board (like swapping a chip instead of an ECM), point it out by showing it as an alternative. Don't do it by starting out "To correct the idiot that has no idea what he's talking about".

 

yeah, the TBI is the stock unit off the 305, didnt change the knock sensor and module over to 350 until lately and havent driven it because I'm working at dropping dual electric fans in it. I haven't put the headers on just yet becuase i was afraid it would lean the system out to much. same intake manifold as well. I'm starting school up in the summer and moving to a place where im not sure if i can find a job right off the bat so I'm not trying to spend alot of money on it currently, just trying to work with what i already have. I know a guy just north of where i live just got all the software and equipment to do chip burning so i may go see him before i leave for school(only a week left). thanks for all the help though.

 

hey guys

I'm planning on putting in a lo5 in my maro. why do you uyou need to get the knock sensor and module from the truck.

when the stock one will work with the stock computer.

just wonder why is there a diffrence

 

The knock sensor is tuned to listen for a certain "sound" or frequency. The smaller diameter of the 305 cylinders and pistons causes them to "ping" at different frequencies than a 350 with larger diameters.

Kind of like the difference between and snare drum and a bass drum. The larger head on the bass drum causes it to ring at a different frequency (lower) than a snare drum. If the microphone (knock sensor) isn't set to pick up the lower frequencies, then you'd never hear it in a studio (ECM) while making a recording.

 

What a excellent analogy ...

 

:rockon: :rockon: :rockon: :rockon: