Mr_Asa GRM+ Memberand PowerDork
4/9/22 9:40 p.m.

With my intake reaching 85% completion, its time to work on that last 15%.
In that 15% is injector placement, injector sizing, and various other items.

My goal is kinda arbitrary, but I figure double the flywheel HP of the original engine at the wheels is worth shooting for?  Means 330HP at the wheels, this is behind a Ford E4OD trans.  This video has an EFI system, cam, headers and an original style head and is hitting 270HP at the crank so I figure that with a much better flowing head I should be able to get there.

Based on various flow calculators that I've played with, at 80% duty cycle and ~44psi it appears that I want ~38lbs/hr?  Does that sound accurate?


Lastly, my neighbor was redoing the engine on an early 2000s Tahoe, it came with new injectors and he only had to return a long block and manifolds.  As they weren't called out on his return sheet I snagged the injectors from it.  From some light googling they appear to be ~33lbs/hr?  They won't meet my goal HP, but I figure they'd be a decent starting point for free. 

I have some aluminum roundstock ready to be chucked up in my lathe, is it worth cutting injector bungs for this style injector, or should I look for another common injector?


Mr_Asa GRM+ Memberand PowerDork
4/10/22 2:25 p.m.

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RXBeetle Reader
4/10/22 3:18 p.m.

a 33lb injector is a 38lb injector at 58psi instead of 43.5psi, just need an adjustable regulator and a pump that can keep the flow at the higher pressure. 

More injector info:

Target the spray at the back of the valve. Wall wetting sucks for transients. It helps these injectors you have are for a 2 valve head, any injector a for a 4 valve head will likely have a dual cone spray pattern targeting 2 intake valves. 

GM Superchaged 3800 or RX8 secondary injectors would be other good options. I would still have whatever you use cleaned and flow tested. 

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