At what point do you need to upgrade the factory injectors. Does heads and cam warrant an increase of injector size? Any help is appreciated.

 

All depends. I would suggest you find other setups running similiar components and find the successful ones and base your decision on them.

There are LOTS of opinions out there on this and other subjects. The one thing that is tough to argue with are results.

Most of us running big inch motors with success on here are running 24-30 pound injectors. Most around 24 pound, since they are a nice upgrade off stock and are still not too large. These motors are making around 500-650 hp. So logic says if your at 350-500 hp you should be absolutely fine on the lower end of the injector size range.

I think there is a fundamental misunderstanding which people inadvertantly think if they have "bigger" its going to make them go better/faster. A motor can only consume so much fuel, which is a function of how much air is coming in. Obviously a motor with big inch, good intake and great heads and exhaust is going to consume more air than a smaller inch motor. Anything extra in the way of fuel supply is a waste and going to slow you down if that extra fuel is entering the cumbustion chamber. A loose analogy would be me thinking I need a fuel system capable of supplying the volume of fuel a TOP FUEL dragster is capable of. Yeah I could put that sorta system on my car and trim it back to control the volume to an acceptable level(not really), but it would be gross overkill and a waste. And chances are your going to experience other problems introduced by trying to control an over-sized system.

But as I said, there will be other opinions...so as I said, choose the size that is in other comparable setups that are runnig well. No sense in re-inventing the wheel with his stuff. Its hard enough to get good results following other examples. Go out on a limb, don't be surprised if you fall.

 

I definately wouldn't put 24's in it as GM put 28lbers stock in the higher performance LT4 (which I'm guessing you have from your name) You should be able to go quite far with those stock injectors.

Bottom line when it comes to upgrading your injectors. Ask your tuner.

 

This has been a hotly debated question. I believe injector sizing is proportant to hp to a degree. Look at what the professionals are using. GM put 23.8 lb injectors in the 300hp LT1. and then put 28 lb injectors in the LT4. I noticed that TJWONG converted a 620hp 572 to fuel injection and used 42lb injectors. My tuner (Alvin at www.pcmforless.com ) recommend that I get 30 lb injectors due to my dyno pulls going lean at the high rpm end of a dyno pull. I have not done it yet but I will and I made 362rwhp.
One other source to look at is a supporting vender on this site, Racetronics. I found this post which has some info on what they recommend for different hp levels. http://forums.corvetteforum.com/show...90&forum_id=55
Its more then just making power, its how safe are the smaller injectors running at max. capacity etc. GM and all these others go up in size and they may be thinking more then just hp or how fast a car can run the 1/4 mile.
But most importantly, has your tuner what he wants to work with.

 

Thanks for all the help guys. I will check with my tuner (can't say that I've been that happy with him- but not alot to choose from in Austin TX area), but think it would be safe to hold off until I have the bottom end stroked and forged.

 

You might consider Alvin as mentioned in a previous post -- I live in Nor. Calif. and will be using his services once my rebuild is done. He is extremely helpful and very sharp. Prices are fair, too.