1984 H/O 307 Holley EFI Swap

mashud46

Not-quite-so-new-guy
May 31, 2023
5
3
3
Hey guys,

Anybody here ever swapped a Holley Sniper kit with the Ignition components (distributor, coil, Ignition box) for the Quadrajet on a 307 H/O? I'm aware of the challenges it encompasses ( CCC, Vacuum, TPS, etc.). I'm also aware of the fact that it won't make my 180hp 307 a 350 sbc so please save those comments lol. I know the converter lockup is controlled via the distributor and the trans also uses TPS in the stock Qjet. Curious is anyone has swapped and how they kept everything working properly or how they hooked up a lockup switch for the converter. I'm sure there is a way, just not sure if anyone has done it yet.

Thanks in advance!
 
Oct 14, 2008
8,799
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Melville,Saskatchewan
Basically you have to treat it like a non CCC carb swap. The cruise will need grounded at the black wire on the speed sensor. Also the A/C relay needs grounded, I believe. The Qjet Sniper is plenty big for your 307 and will bolt right on. A toggle switch is easy and lock up kits are available. I would get an in tank pump, inline pumps cause plenty of grief. What is your end goal with the Sniper?
 
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mashud46

Not-quite-so-new-guy
May 31, 2023
5
3
3
Basically you have to treat it like a non CCC carb swap. The cruise will need grounded at the black wire on the speed sensor. Also the A/C relay needs grounded, I believe. The Qjet Sniper is plenty big for your 307 and will bolt right on. A toggle switch is easy and lock up kits are available. I would get an in tank pump, inline pumps cause plenty of grief. What is your end goal with the Sniper?
Thanks for the reply and info. My goal is just to have ease of use over the Qjet and monitor a lot more things via the handheld without having to add lots of gauges. Not really looking for huge power out of the 307, that will come from the LS at some later point.
 
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78Delta88

Royal Smart Person
Supporting Member
May 23, 2022
1,186
1
906
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SW Arizona
I have, 2019 installed the sniper system on a 400 SBC in a 1957 Chevy. 700R4 Trans had the lockup kit not installed yet. Long story but engine was built by someone else And it was a mess. 40 over cylinders with 30 over pistons... You can figure the rest. Engine got pulled and sent to machine shop.

The sniper is straight forward but has some issues. Yes in tank pump has to be min 58 psi to get unit to work. I made the fuel lines custom bent steel line. The kit has the fuel line option for about 300, if I had to do over, I would have just gotten the fuel line kit. In our kit we ordered the new fuel tank with the pump installed, but that is not how it came. The baffles are preset in the tank and absolutely did not work with the supplied pump. Constant modification to get the pump setup, installed and working, took 2 days. Plus we got close with the fuel level but it ended up about 3 to 5 gallons off. The only other way we could have done it was cut the tank and re-weld.

Went through all kinds of crap just getting the engine to start, and then we were told we needed the ignition control box. This was after we were previously told we bought "everything (we) needed". Plus the engine builders had no clue of the cam specs. You need that to setup your base tune.

Talk with tech support make sure you get the dongle. You will need it for the software upgrades and use your laptop. You mount the user interface on the dash. You set the basics and it will self learn from there.
 
Last edited:
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mclellan83

Comic Book Super Hero
Jun 27, 2017
4,126
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Pgh, PA
I have, 2019 installed the sniper system on a 400 SBC in a 1957 Chevy. 700R4 Trans had the lockup kit not installed yet. Long story but engine was built by someone else And it was a mess. 40 over cylinders with 30 over pistons... You can figure the rest. Engine got pulled and sent to machine shop.

The sniper is straight forward but has some issues. Yes in tank pump has to be min 58 psi to get unit to work. I made the fuel lines custom bent steel line. The kit has the fuel line option for about 300, if I had to do over, I would have just gotten the fuel line kit. In our kit we ordered the new fuel tank with the pump installed, but that is not how it came. The baffles are preset in the tank and absolutely did not work with the supplied pump. Constant modification to get the pump setup, installed and working, took 2 days. Plus we got close with the fuel level but it ended up about 3 to 5 gallons off. The only other way we could have done it was cut the tank and re-weld.

Went through all kinds of crap just getting the engine to start, and then we were told we needed the ignition control box. This was after we were previously told we bought "everything (we) needed". Plus the engine builders had no clue of the cam specs. You need that to setup your base tune.

Talk with tech support make sure you get the dongle. You will need it for the software upgrades and use your laptop. You mount the user interface on the dash. You set the basics and it will self learn from there.
Atleast I am not alone
Hey guys,

Anybody here ever swapped a Holley Sniper kit with the Ignition components (distributor, coil, Ignition box) for the Quadrajet on a 307 H/O? I'm aware of the challenges it encompasses ( CCC, Vacuum, TPS, etc.). I'm also aware of the fact that it won't make my 180hp 307 a 350 sbc so please save those comments lol. I know the converter lockup is controlled via the distributor and the trans also uses TPS in the stock Qjet. Curious is anyone has swapped and how they kept everything working properly or how they hooked up a lockup switch for the converter. I'm sure there is a way, just not sure if anyone has done it yet.

Thanks in advance!
Liam Neeson Good Luck GIF

Hope you are very patient, I have gone through quite a lot with mine. I will say when it first got setup it worked fine for a year or 2, but a year or 2 ago it blew a fuse and never seemed to be right after that. Am still trying to work out the kinks after buying all of their stuff separate since they would blame anything they didn't have. Now they don't have an excuse cause its all Holley but still has RFI issues
 
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gearhedjon

Apprentice
Dec 5, 2012
70
25
18
oak forest IL
First, I do not have a Holley sniper system, but I may provide you with a solution for a in tank fuel pump.
I purchased the fuel injection tank kit from G body parts.
You will get a larger baffle that is welded. This will continually feed the pump on acceleration.
Your choice of Walbro pumps based upon your demands.
New tank straps and insulators, and sending unit.
New O ring and lock as well as a filter sock.
I also placed a fuel filter in the same location on the frame as a 4.3 fuel injected Monte Carlo.
Hope this helps.
 
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Ugly1

Royal Smart Person
Oct 26, 2021
1,573
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Lost in the woods of NH
Definitely do an in-tank pump. I do not have the system but a guy at work just went through the fuel pump process of having to put one in due the the external gets to hot and slows down causing lower fuel pressure. He went through about six O2 sensors before Holley told him it was a common problem. They just “suggest it” in the buying process due to cost.
 
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mashud46

Not-quite-so-new-guy
May 31, 2023
5
3
3
Thanks all for the comments. In response to all, I am replacing the stock tank (considering its almost 40 years old) and going with the Holley Sniper tank with the in-tank pump (internally regulated at 58 psi) and sending unit. My main concern was the TCC lockup kit but Holley has one for this application. Thanks all for the help
 
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