I am going to be building my engine here in about a month. Mild cam, flat top pistons, crank, exhaust, porting heads. It will be mild but should be a certifiable street killer. I am thinking of running 30# injectors on her. Can the stock fuel pump feed those?

 

I'm doing the same general setup but only running 24 lb injectors. 30 might be overkill. I've been told that its alot harder to tune for oversized injectors vs smaller injectors... But then again I'm no expert lol so I'm sure someone else can explain in better detail.

 

Those are some big injectors. You might want to read this article.

http://www.megamanual.com/v22manual/minj.htm

 

Unless you're planning on making 500+ HP, I would advise against 30# injectors. Blade 09 is correct that it is much easier to increase the output of small injectors than to decrease the output of large injectors. The key is fuel pressure. The effect of pressure on injector output is linear. Injectors are generally rated at 40psi. Raising pressure to 60 psi raises output by 50%. Tuning of either the VE map or base fuel map, depending on the engine management system used, allows fine tuning of the air fuel mixture. Higher fuel pressure also improves atomization, improving combustion efficiency. The main point in choosing injector size and setting fuel pressure is to achieve injector output that allows the injector to operate within it's mechanical limits while providing the engine's fuel requirements in all operating conditions.

Running too large injectors, will leave you needing to lower fuel pressure to compensate for the too large nozzles. This will reduce efficiency and since you can't really go below 30psi on a port injected engine without affecting drivability, you are limited in how much you can tune by pressure.

 

Okay I have slightly educated myself on fuel injectors now. I'll be going 24#. Can the stock pump handle those?

 

The stock pump will be adequate to about 300HP. I would not trust it past that point, especially at higher than OE pressures. When you have invested time and money into building a motor, you don't want to risk starving it for fuel with an inadequate fuel pump. There are many choices available for upgrading the stock pump, from an in tank upgrade to a external pump. One popular choice is the Walbro high output pump. Aeromotive offers many options as well.

 

I have an AC Delco "stock replacement" pump in my IROC and I have absolutely no lean conditions anywhere in the RPM range with my 24lb SVO injectors at the stock fuel pressure. In fact, it ran pig rich until I dialed my injector constant way up in the BIN file. That said, I don't know whether the AC Delco replacement pump is exactly the same as the stock one or slightly more robust. My car made 250RWHP (300 crank) and my fuel pump is more than up to the task.

For the amount of effort it takes to replace a fuel pump, I'd stick with the stock one for now. If you're finding that you're lean during high fuel demand conditions, then drop your tank to replace it. That said, if you do replace it, make sure you get a good 255lb/hr Walbro or equivalent pump. It's way too much work to put in a cheap pump. If I'd known how much of a job it was prior to doing it all those years ago, I would have installed a better one!

 

Awesome. Thanks for all the info

 

Stock pump is good to around 450 hp or so. I am assuming you are keeping the TPI intake? 24 pounders will be your best bet.

 

Yes the TPI is staying. For now. I see a carb in my future though

 

Maybe on someone else's engine. Not mine. In my opinion, in order to assure the safe operation of a motor, a fuel system should be capable of flowing
50% more than the engine's maximum requirement at the system's actual pressure. One thing to remember is that as pressure increases, a pump's flow decreases. If you need to run 60psi, you will want a pump that at 60 psi, can flow half again what your engine requires at max power. I would never trust a factory stock TPI pump to do that. This is only my opinion, not everyone will agree with me.

 

I run 30#ers on mine @ 50psi and had no problems dialing it in with my custom tune. but let me stress you have to change the parameters in the prom for it to work correctly.

 

I am building a 383 with around 450 horse going to keep it tpi, will the tunercat products do the job making a chip for the ecm . also should i switch to the elderbrock high flow base and runners?

 

Yeah if you get the hardware you need to burn roms Either Tunercat or Tunerpro will do the job. You will be hard pressed to make anywhere near 450 horse even with a 383 using the stock base and runners. I wouldnt go with the edelbrock base if i was to do it again I would get myself a FIRST TPI setup.

 

No to sound dumb . What do u mean first tpi setup. This is going on 85 z28. I also have a tpi from 87 z28 and computer .this is my first fuel inj build. So It's a learning process . Have always build carb motors

 

to clarify, First, is an aftermarket intake that looks very similar to the stock TPI but with larger runners, base etc.

 

Thank u, where u find it?

 

http://www.firstfuelinjection.com/