Gents,

It's time to replace the stock injectors on my LT1. I plan to rebuild the engine early next year into a 383 with an LT4-like top end. I have the stock injectors in there now, but figured I would get larger ones to go with the future upgrades. Sooooo, 26 & 30 lb injectors are the next sizes up. Will going to 30 lb injectors cause any problem with a basically stock engine with lots of miles?

Thanks,
E.


P.S. My '93 has 184k miles on the stock original injectors!!!! Never had a problem with the car until ignition woes reared their head 2 years ago. Car is going under the knife this weekend for an opti-heart replacement!

Larger injectors will not hurt you, unless you get ridiculous. Of course your ECM/chip will have to be programmed with the new injector size in order for the engine to run correctly. It would be wise to select an injector large enough to meet your long-range HP goals with the 383. One guideline I've developed for sizing injectors for normally aspirated applications is to simply multiply peak flywheel HP by 0.07

As an example, if you plan to ultimately develop 500 flywheel HP:

500 x 0.07 = 35 #/HR.

The downside of a large injector is the difficulty in turning it down to the small pulse widths required to allow the engine to idle smoothly. The larger the injector, the shorter the pulse widths. You are limited by the injector drivers in the stock ECM, and the response time of the injectors you select. In general, I have not seen anyone get into trouble with idle quality using 36 #/HR injectors on an LT1, and many people seem to do OK with 42 #/HR injectors. If you try to go beyond 42 #/HR, you will either have to select from the limited number of available high-impedance injectors, or use an external converter box to allow your stock ECM to drive low-impedance units.

Thanks!

Stock units are 24# I think, so I was leaning towards the 30# units. I'm not going overboard on the power, prolly 400-420 hp/torque.

Stock Delcos are $89/ea. (!)

I was going to call Fuel Injection Specialties in San Antonio and get their input.

Thanks,
E.

Stock injectors on your 93 are 22 #/HR. The 94-97 LT1's are 24 #/HR (programmed as 24.9 #/HR in stock PCM programming).

You can get injectors much cheaper than the factory parts. Many people opt for the pintle style injectors used in the Fords.... under the name of FMS or SVO. They typically start at about $240 for a set of eight 24's. Maybe up to $300 for a set of the sizes you might be interested in. The Ford injectors are flow rated at 39.15psi (2.7bar), compared to the standard LT1 fuel pressure rating of 43.5psi (3.0bar). Hence, the injectors will flow about 5% above their rated flow, when you use them on an LT1 with stock fuel pressure.

Also check out Racetronix for injectors.

http://www.racetronix.com/