Holley HP EFI conversion
#1
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I thought I would start a thread chronicling my conversion from carburetors to EFI. I never had a plan to go EFI it kind of just happened. I found some good deals here and there, purchased couple Holley HP units, EFI intakes, found throttle bodies and then Smitty (articfriends) hooked me up a great deal for injectors and EFI fuel pressure regulators. I am going to be replacing 2 flawless carburetor/intake setups that I have ran for almost 20 yrs. Custom Barry Grant that flow almost 900CFM and have spot on AFR reading throughout all throttle postions.
This might be a slow conversion so bear with me. This will be my first Holley EFI experience and might need to rely on the board for a little guidance. I've only worked with Haltech FX10 and the Fast EZ EFI 2.0. I'm just going to start out running multi port injection. I run Crane HI-6M ignitions currently and eventually would like to have the Holley unit control the timing.
![](https://cimg3.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/636x847/20190712_140650_resized_ad1d01dff19ef22d57077f600587a3ab1839f78a.jpg)
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I bought 2-36" universal fuel rails and made injector bung holes. This was a 3 step drill process. Initial hole for fuel needed to be drilled, then hole for injector and O'ring to seat into, then a chamfer.
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Tapped the end of the rails for 1/2"NPT and a 1/4"NPT port for fuel pressure.
![](https://cimg7.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/360x640/20200410_145614_resized_4e0365359cf911146598e5c4fc656f2bda059f84.jpg)
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This might be a slow conversion so bear with me. This will be my first Holley EFI experience and might need to rely on the board for a little guidance. I've only worked with Haltech FX10 and the Fast EZ EFI 2.0. I'm just going to start out running multi port injection. I run Crane HI-6M ignitions currently and eventually would like to have the Holley unit control the timing.
![](https://cimg3.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/636x847/20190712_140650_resized_ad1d01dff19ef22d57077f600587a3ab1839f78a.jpg)
.
I bought 2-36" universal fuel rails and made injector bung holes. This was a 3 step drill process. Initial hole for fuel needed to be drilled, then hole for injector and O'ring to seat into, then a chamfer.
.
![](https://cimg3.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/876x403/20200410_123232_resized_6818c26d7f1a1cb7be797601853afaa232bafdfb.jpg)
![](https://cimg9.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/720x1280/20200410_123348_resized_e76d4d4a0d583ee11fb05b99eb29f321a0b52f95.jpg)
![](https://cimg4.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/2000x1124/20200410_123425_9f6e368660b2cf69e9517c244b31ca50a4f9ab2a.jpg)
.
Tapped the end of the rails for 1/2"NPT and a 1/4"NPT port for fuel pressure.
![](https://cimg7.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/360x640/20200410_145614_resized_4e0365359cf911146598e5c4fc656f2bda059f84.jpg)
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Last edited by Rookie; 04-14-2020 at 09:07 PM.
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#3
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Are you tying the two rails together or feeding them separately, nice work
#4
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Very nice work! EFI when done right is so nice.
#6
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Oh, BTW the drill bit for the injectors is a 17/32" bit, not really off the shelf at your Home Depot.
![](https://cimg4.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/587x274/fuel_system_d34bdc2ca3eec7cf162791dd23e61b0ad69f507e.jpg)
Last edited by Rookie; 04-15-2020 at 05:53 PM.
#7
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The EFI is going in the other... "junk"
![](https://cimg2.ibsrv.net/gimg/www.offshoreonly.com-vbulletin/675x847/resized_20190902_122657_700_d7aa314c4050666d83f07216a7b28c9c887059ea.jpeg)
Last edited by Rookie; 04-15-2020 at 07:36 PM.
#8
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Well today we shut down my plant due to a possible (+) Covid19 employee so I had half the day to work on my injection/manifold fuel system. I'm using taller injectors so I can not use the pre-drilled/tapped hole in the manifold. I 3D printed mounts that will connect to the base of the rail and side of the manifold. (carbon fiber reinforced material) All went well until I mounted the rail. I didn't realize the rail location was on a 10° angle to the mounting boss. There is a gap between the mount and where the screw would fasten to the manifold. If I tighten it down there I will push the injector rail forward and the injectors won't sit parallel in their holes. I'm going to have to print new mounts with matching 10° dog leg to match the manifold.
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#9
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Next I spent a couple hours trying to figure out how to plumb the manifold. This did not go well, apparently everything is bigger than planned and took up a lot of space. The regulator will not fit on the back with a distributor inserted. After trying 30 different combinations I came up with mounting the regulator on the back rail and running the connecting fuel line through the middle of the manifold. I looked up my regulator and the spec's say 2 INs and 1 return OUT. (Smitty, can this regulator be used as 1 IN, 1 OUT and 1 Return OUT???) It would make a lot easier to mount the regulator next to the pump and filter.
https://www.racetronix.biz/product.asp?ic=reg-fi886bs
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https://www.racetronix.biz/product.asp?ic=reg-fi886bs
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