[AIR RAM]

Originally Posted by Steve C.

When I converted to fuel injection on my current 505 we used a Holley HP EFI Universal kit, p/n 550-500

https://www.holley.com/products/fuel.../parts/550-500

Holley p/n 522-488 48 lb/hr fuel injectors
Holley p/n 565-107 Dual Sync distributor

For the intake manifold we used a old style 4500 Victor intake that I had on hand. It was previously runner blended and port matched to my cylinder heads. We outsourced the intake to have bungs welded on for the fuel injectors and the FI rails mounted. In order to fit the 4150 style throttle body to the intake we used a Brodix HV300 4500 to 4150 carburetor adapter. However the adapter was modified, it was cut down and blended for a smooth transition into the intake plenum/runners. With the adapter modified and the shorter throttle body there was no reduction in hood clearance. I use a small diameter K&N air filter that fits up inside the shaker scoop molded onto my fiberglass hood.

The previous 4150 Victor intake with the carb pad milled 0.650" was not used for the FI project. Our dyno testing indicated by milling the intake it lost about 8-10 hp at peak power rpm. With it and my modified HP950 carb the engine made 660 hp at 5900/7000 rpm. No testing was done after the change to fuel injection but I suggest there was no significant loss in power.


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It would be interesting to see how an set up would react to the same intake both before and after milling and fuel injection all else equal.

I guess the test would need to be (and unlikely to ever happen)

Intake un-milled - CARB vs Fuel injected
Intake Milled - Carb vs Fuel injected.


I would think that the fuel injection set up would not be as finicky to the placement height of the throttle body vs a carburetor which operation is in direct relation to the air flow passing through it and the air+fuel within the intake.... The Carb will respond with changes in spacing however I dont believe a "throttle body" which only flows air is as responsive to the throttle body height as it is to velocity within the intake runners.

So I personally feel that a fuel injected engine can get away with a lower profile single plane intake manifold (and fit under lower hoods) than a Carb engine and make the same if not more power than a carb with ideal spacing that needs a taller hood to run.

I ended up going with the Northwind intake for its lower profile and EDL fuel rails... Hopefully it will work well.

And I could be way off on the mark as well...Ive been wrong on occasion.

[Steve C.]

"I would think that the fuel injection set up would not be as finicky to the placement height of the throttle body vs a carburetor which operation is in direct relation to the air flow passing through it and the air+fuel within the intake.... The Carb will respond with changes in spacing however I dont believe a "throttle body" which only flows air is as responsive to the throttle body height as it is to velocity within the intake runners."

I had a discussion with the the fellow who did the work on my intake regarding the modification with the Brodix carburetor adapter. In short, he felt the same as your statement. It's air and not air/fuel mixture and the F.I. set up would be less sensitive to the impact.

Almost all my different engine combinations have been tested on a engine dyno but I've never had my car on a chassis dyno. I hope to do so soon with the current 505 and the now converted fuel injection set up. For interest, plus I want to know if my small air cleaner assy has a significant impact on the performance. My Trans Am does not have a functional shaker assembly. The car has the saftory shaker scoop molded to a fiberglass hood. The air cleaner assy sits up inside the scoop, thus I cannot go larger. What I have is a K&N filter that measures 2.875" high x 9" diameter, with their 9" dia X-Stream filter top. When I talked with K&N tech they stated those two items used together would flow approximately 710 CFM and suggested my 505 / 650 hp engine needs approximately 1100 CFM for operating at 6000 rpm where it made peak power on the engine dyno with the carb set up. I then asked at what lower RPM will the above 710 cfm be adequate for ? The answer, based on their calculations, a 505ci engine at 4000 RPM would require approximately 710 CFM. WHAT ! I'm having a HARD time understanding this and now want to test on the chassis dyno with and without the current air filter assy.

I'm curious how the K&N numbers differs so much based on my dyno sheet with the carb set up that indicates 866 scfm at the 6000 rpm. Then the formula below that suggests 867.9 cfm. Note, almost the same as my dyno sheet

( For the calculation I used 0.99 for the volumetric efficiency. However at 6000 rpm on my dyno sheet it indicated 106.9 VE)

6000 x 505 = 3030000
3030000 divided by 3456 = 876.73
876.73 times .99 = 867.9 cfm

https://itstillruns.com/calculate-en...e-6393767.html





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