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Holley EFI VS OEM conversion

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Old 06-12-2016, 12:36 PM
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Default Holley EFI VS OEM conversion

What would you folks who have been in this game for a while consider to be the best route to take..

I already have a Holley Terminator throttle body that was on my 455 Olds and I can convert it to work with an LS and also have it run the ignition, ( I have a dual plane manifold and holley wiring for this)

I also have a complete new LS6 manifold assembly (minus wiring) that I can use.

I am looking for a nice combination of gas mileage and reasonable performance out of my LS327 GMPP engine. (And reliability especially)

Do I use the Holley Throttle body?, Convert to Holley LS1 wiring and use the LS6 stuff or should I dump the Holley altogether and use an original/new LS1 harness conversion with a reflashed GM ECU... Holley is easier to program but is it reliable over a long period of heavy use?

Indecision equals $$$

Argh... Spending too much money going in too many directions....
Old 06-12-2016, 03:30 PM
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If fuel economy is important, then consider going the OEM route. The Holley system is great and can be tuned well and easily, but it takes a lot of tuning knowledge to really get optimal fuel economy. I have gone both routes so I speak from experience.

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Old 06-12-2016, 05:13 PM
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Ok that's one for OEM . Anyone else?
Old 06-12-2016, 05:57 PM
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Default Holley or OEM

If you are running a 4L60E trans then you must control it. The OEM system will handle both but I think the aftermarket systems will not. For set it and forget it I vote OEM.
Old 06-12-2016, 09:54 PM
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Hmmm 2 for OEM
Old 06-13-2016, 04:03 AM
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i had the oem stuff on my mustang then converted to holley ,, still wondering why it took me so long!
its a lot easier to work with tuning wise , very flexible in terms of growth , gives you a lot more options than oem , and you have the benefit of self learning and setting up warnings and fail safes in case something happens . it also gives you the possibility of controlling your transmission ( in my opinion in in a much better way than the oem system )

if you do the wiring the correct way and not cut any corners , you should be fine with the holley.
Old 06-13-2016, 09:18 AM
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2-1 OEM in the lead
Old 06-14-2016, 05:27 AM
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I vote Holley. I'm running Holley HP EFI in my swap and love it. I did read last week in the forced induction section that the terminator system uses the dominator ecu. If so that would be great if you could just get the LS wiring harness cause that ecu will control the transmission.
Old 06-14-2016, 08:43 AM
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That settles it for me... I will try out my Holley first and keep the oem idea as a backup.. Now to decide if the throttle body I already own is best or go with the LS6 setup...



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