Hilborn Shot Gun Injected 468 Big Block Chevy Setup

Old 05-07-2015, 12:53 PM
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aabad508
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Default Hilborn Shot Gun Injected 468 Big Block Chevy Setup

I have a 468 Big Block Chevy Im seting it up with a Hilborn Shotgun hat injector 80A Pump I need to no what Nozzles To start with I plan on puting a high speed bypas also it is in a Altered Bantum with a B&J 3 speed Hays two disk clutch & 456 gearsI also need to no where to start with a barrel valve leek down & pill size & timing im at 4400 feet
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Old 06-18-2015, 04:51 PM
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sandegj
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You didn't state what fuel you are using, and didn't complete the pump information, as 80A-0 -.5 or -1. Make a big difference. Call or Email Hilborn, and they will give you a ball park starting point, just convert your Enderle pump size to Hilborn pump size. They will give you a "on the rich" side cal, because they really don't know the exact flow rate of your pump, just a ball park figure. My guess would be 9A nozzles for gas, or 20A nozzles for Alcohol. Don't know what barrel valve you have, gas alky or nitro, I use a nitro barrel valve on alcohol with a injected motor, with 18% to 22% leakdown. If gas is the fuel then 9% to 10% leakdown. the return pill size depends on the pump size. Don't worry about a high speed by-pass until you get the basic fuel cal worked out, then you will richen it up a little and work with a high speed by-pass. Since your system wasn't tuned on a flow bench, your will be spending a lot of track time tuning it. I have put a pressure gauge in the system and found out what pressure was at around 6500 to 6800 rpm's then set up a high speed for that pressure with the main jet richened for the high speed install to the system. Just make sure you keep a eye on your oil for fuel contamination. If I remember right on a Big Block Chevy, Number 2 cylinder is the one that has a tendency to run lean. Jerry
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Old 07-22-2015, 08:10 AM
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oldandtired
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Mike Chilando has helped me with my stack ingection set up.
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Old 12-13-2020, 10:24 AM
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bobszabo
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Default jetting recommendations

Hi aabad508,
I wrote a lot of books about this subject. Here is some info specific to your setup that I checked out on our procalc jetting calculator:

For 4400 foot elevation on a typical summer day with 83% air density, moderate enrichment on methanol, an 0.030" dia nozzle (nozzle diameter not nozzle number).

The main bypass depends on the size of the fuel pump, independent of the proper nozzle.
For an 80A-0 at 4 GPM, a main of 0.077" dia is good for moderate enrichment.
For an 80A-1/2 at 5.2 GPM, a main of 0.099" dia is good for moderate enrichment.
For an 80A-1, at 7 GPM, a main of of o.125" dia is is good for moderate enrichment.

Small changes to nozzle or main bypass put the engine into a different setup and it may or may not run well.

Going to a different altitude may need different nozzles as well as a different main.

A smaller set of nozzles and main are needed for a high pressure setup that usually runs better. But that needs to be worked out with a high speed.

Introducing a high speed into the setup is complex. Recommend not starting out with a high speed until the car runs good without it. As stated above, you have to know what fuel pressure is at the RPM you want to open the high speed. That is 500 to 800 RPM above the torque peak, so you have to have an idea where the torque peak is.

Trial-and-error is tough on an NA engine. Too many things to coordinate.

Bob Szabo
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