TBI Fuel Injector question

[kartoffelpuffer]

Hi all, I'm hoping someone can help me with a question I have. I have a '94 with a 305. I'm getting ready to do a cam upgrade and installing some 081 heads. I know I'll need to get a tune to make it run right. But I'm wondering about injectors. I ended up with a box of various injectors. Some of them are labeled 45, 55 and 65. Which I assume is the PPH flow rate. from looking up the part numbers it looks like the 45 are 4.3l and the others all reference back to 350s. From what I've read I think the 305's are supposed to be around 50pph. So my question is should I try and run the 55pph ones since the engine will be slightly modded. Or should I run the 45pph ones and just crank up the pressure to make them push closer to 50ppm. I'm just not sure if putting in the 55's is going to make it run too rich. I know I could try and reuse my old ones but I'd rather use some that have already been cleaned and tested.

Thanks for any advice you might have.

 

[Dropped88]

I've actually been there done that put a mild TBI 355 in a Nissan hardbody.

Anyways went with a vortec fuel pump and I believe it was a 18lb regulator spring and kept stock injectors

 

[Schurkey]

1. Why modify a 305 when you could drop in a 350? Dicking with a 305 is a waste of a camshaft and cylinder heads, not to mention time, money, effort, and enthusiasm.

2. I suspect you'd need to see fuel trims in actual operation before you'll know how the mods affect fuel demand.

3. Use "Top Tier" fuel, and dump a bottle of Techron in the gas tank now 'n' then, and "clean" injectors aren't an issue. "Tested" injectors might be.

 

[Erik the Awful]

+1. A good running 305 is good how it is, but if you want better performance, don't bother building the 305. It will always be a dog compared to a 350, and you can get 350s for free if you ask around enough. My local Pull-A-Part sells long blocks for $125 every other weekend.

 

[kartoffelpuffer]

+1. A good running 305 is good how it is, but if you want better performance, don't bother building the 305. It will always be a dog compared to a 350, and you can get 350s for free if you ask around enough. My local Pull-A-Part sells long blocks for $125 every other weekend.

You guys definitely live in a different area than I do. My local junk hard wants $350-500 for a 350 "Core" and "running" 350's are around $900-1200. I'm also not the guy who's going to take a junk yard motor and just drop it in and roll the dice. I'm going to pull it apart send it to a machine shop and then rebuild it so, there is another 2-3k.

Anyway, I understand the difference between a 305 and a 350. But I have a 305 and I got remaned 081 heads with 1.92 intake valves for $200. Also, I'm not looking for crazy power. I'm in my 50's and my hot rodding days are behind me. I like the way my truck drives. I just want a little more power for when I pull my 3,500lb camper. Yes I know, 350/383/LS Swap Blah blah blah, wroom wroom.....

 

[kartoffelpuffer]

1. Why modify a 305 when you could drop in a 350? Dicking with a 305 is a waste of a camshaft and cylinder heads, not to mention time, money, effort, and enthusiasm.

Simple answer: Because I want to and I can. Longer answer, see my response to Erik.

2. I suspect you'd need to see fuel trims in actual operation before you'll know how the mods affect fuel demand.

Thanks, I have Tunner Pro and a ALDL cable. I just have not figured out how to actually interpret the data yet.

3. Use "Top Tier" fuel, and dump a bottle of Techron in the gas tank now 'n' then, and "clean" injectors aren't an issue. "Tested" injectors might be.

I've done that, I'm also going to try and clean the injectors myself. I may also try putting together several injector pods with different types of injectors and just swapping them out to see which ones I like the best.

 

[tayto]

keep your injectors, run them at 13 or 14 psi and go from there. once you get over 18 psi you will need a VAFPR, so that is when I would consider going up an injector size or 2. the most common 350 injectors are 61# from my experience. i would recommend getting your oem injectors professionally cleaned & flowed.

as far as cylinder heads, if you are towing I would keep your TBI heads. Pocket port them and maybe go bigger valves if it's in the budget. I am curious what cam you are going with? I ran a 70s era 305 in a 64 impala with a TH200-4R that i daily drove for 5 years, was a great engine for a driver and got decent economy (23/24 mpg on highway trips). Ended up replacing the flat cam with a 327-300HP cam and 3.36 posi that woke it up a good bit. i was in my late teens and didn't know much about tuning so chances are it could have gotten better. Ended up swapping in a 305 TBI from a low milage cop car and converted the car to EFI at that time. Didn't get to drive it much unfortunately. Hit a deer and needed a vehicle inspection which it failed, ended up selling it to my boss at the time. we put a front clip on it and he drove it with dealer plates on it for sometime.

 

[PlayingWithTBI]

Some of them are labeled 45, 55 and 65. Which I assume is the PPH flow rate. from looking up the part numbers it looks like the 45 are 4.3l and the others all reference back to 350s. From what I've read I think the 305's are supposed to be around 50pph. So my question is should I try and run the 55pph ones since the engine will be slightly modded.

The 305 had 54 PPH while the 350 had 61 or 65 (Cop car) PPH. The little bit you're doing, just get an AFPR, and gauge. If your stock spring isn't enough, you can adjust an 18 LB spring from ~15 - 20 PSI.

You must be registered for see images attach

 

[tayto]

if not going to a VAFPR I like to just mod the stock setup to be adjustable. definitely run the TPI or vortec fuel pump regardless of pressure.

 

[kartoffelpuffer]

as far as cylinder heads, if you are towing I would keep your TBI heads. Pocket port them and maybe go bigger valves if it's in the budget.

For now I'm just going to play with what I have. I bought this stuff years ago and never did anything with it. So, I figured I'd just try it and see. I don't really have a particular goal in mind I just want to try it and see what happens.

I am curious what cam you are going with?

It's pretty mild roller cam but should do something.
.447" Intake
.459" Exhaust
201'/208' Int/Ex Duration.