Install thread- Holley EFI Sniper on '72 402 big block
 

Part 1 Video https://youtu.be/ZOTmKqEPsHo

Moving the truck into the shop
https://i.imgur.com/kYFBqg2h.jpg

Old vs New
https://i.imgur.com/PWgIN4nh.jpg
https://i.imgur.com/UUTYdyuh.jpg

On the engine. Vacuum and throttle/trans cable connected.
https://i.imgur.com/gK33MXwh.jpg

3/4" hole drilled for O2 sensor. It's 10+ degrees above horizontal and near the collector.
https://i.imgur.com/wFpb0Aih.jpg

Derp. Included 2.5" exhaust clamps for O2 sensor mounting don't fit my 3" exhaust. I'll need to go buy some 3" clamps:
https://i.imgur.com/YLZqP9th.jpg

Draining some coolant to install the new temp sensor
https://i.imgur.com/KCowmx7h.jpg

Temp sensor install location. May need to relocate it as I've read the reading back there can be too low.
https://i.imgur.com/Y5ElynKh.jpg
https://i.imgur.com/BJeprTUh.jpg

To be continued!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Am subscribed -- your dog may want another basketball.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Watching with interest. Great truck by the way.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I'm in for the ride, been looking at this for my 84

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

You will really like the sniper.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Subscribed. Planning on the same thing for my 396. Looking forward to see if the stock cleaner fits. BTW....do you know what brand those headers are?

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

For the stock air cleaner, I may need a small riser. We'll see.

Headers, here you go: https://www.summitracing.com/int/par...1hkr/overview/
They fit well.A little low at the collector but liveable.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Got the fuel tank drained in to jerry cans.
Removed the mech fuel pump.
Assembled the elec fuel pump and filters.

Found a factory return line I intend to use. Need to get a fitting to step down from the 3/8" fuel hose to the 5/16" steel return line going into the fuel tank.

I intend to keep the 2 3/8" hoses (green and red below) next to each other, along the frame rail before running them up the firewall above the transmission, around the distributor into the EFI unit. I'd use the factory hard lines along the frame except they terminate way at the front by the radiator, not where I want to start running the 3/8" hose. The headers will be approx 3" away from the fuel line at the nearest point. I suspect this is OK for temps, but I'll look into something to wrap parts of the fuel hose with to protect it from heat as an extra step: https://www.amazon.ca/Heatshield-Pro...70_&dpSrc=srch

Here's the plan:
https://i.imgur.com/rtj8YUl.jpg

High flow mech fuel pump vs electric fuel pump.
https://i.imgur.com/A0etF0vh.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

subscribed

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Interesting subscribed

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Beautiful Truck!

Love my sniper in my '72 Blazer 350sbc, cold starts, warm starts, throttle response, reliability! You look like you are taking your time and going about it the right way. Not sure if the return line step down will cause a problem, seems like I read something on that once, you may want to research it a little. I ran new 3/8" lines for both of mine. You probably could remove your 5/16 dump on the fuel sending unit, drill and install a 3/8" if you had too.

Here's a little unsolicited, hopefully welcome advice, might save you some time and frustration:

1. Be patient, use the Holley tech support, they were very helpful getting it set up. Let them help you, if you have a question, they have answer. I called twice before I ever started installing mine, and a few times after.

2. There's an idle table that is not listed in the install instructions that they will walk you through if you cant get your idle where you want it.

3. I always let the fuel pump cycle before I start it, warm or cold and it will bump off in a 1/2 sec every time. Restarts can stumble if you don't. (I'm using an in-tank pump so that may be a difference)

4. There's a common whistle on these in acceleration, which they will say is normal characteristic, (it's annoying, unless you like the sound of City bus turbo's). You can totally get rid of it by using the Canton part# 85-154 ($30 on amazon) 1/4" 4 hole Phenolic Carb spacer. I tried a 1/2" open spacer first and caused a big vacuum leak which led to more issues. I'm a big believer in the 1/4" Canton, its proven to work with this set up, and shouldn't cause any clearance issues, I found a lot of guys were using it to eliminate the whistle.

5. Tom Kise with Holley tech has an 11 part post that goes through the most commons issues and how to avoid them on the Holley Sniper EFI owners and tech Facebook group listed under files. Great info!

I had a few issues to work through, some due to installation mistakes, but once I got it straightened out she's been great ever since. I even turned the learning off after a few weeks (Holley Tech recommendation) and unplugged my monitor and threw it in the console. I found myself obsessing over the monitor and wasn't crazy about the look of it, just like an original looking dash.

This is just my experience, I learned a lot from guys that had already gone down this road, reading ton's of threads and facebook post, like I'm sure you are. You'll read a lot of bad stuff on the Sniper and Fitech efi's, but installed correctly they will do exactly what they are meant to do, improve reliability, throttle response, and gas mileage. But, if your engine was having problems and not running right to begin with, it might not run right with efi. If I can be of any help PM me anytime.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Nice pictures and detail...It gets me thinking!

I thought I would be the only one to spot that!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

It will be interesting to compare differences in how it runs, carb vs sniper. I'm sure you made baseline mileage and acceleration notes.
I had a dog once that loved to chew on my football. He finally unlaced it and popped the inner tube.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Thanks! I ordered the spacer on amazon. I'll be using these other inputs you provided too.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Subscribed

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I would be careful using the factory 5/16 return. Don't the directions specifically say to run the return entirely in 3/8?

I installed the sniper on a 79 c-30, and i was going to do the same thing- use a sending unit with a return. its been awhile but swear I got the advice not to do that. I ended up using the bulkhead fitting holley supplies and drilled into my gas tank.

if you were deadset on using the factory return line, I would take the factory metal line off completely and connect the rubber hose right to the sending unit.

edit- PS what headers are you running? looking for some for my lowered big block

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I’m in for info on it. Good video and sweet truck. I think I’m gonna do my seats like you have in the houndstooth.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I'm running a FiTech on my 468 BBC. The 468 really woke up with the FiTech. I totally agree with you the majority of issues are user caused and EFI will not be the cure to all existing problems.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

One question, are you using a single or dual plane intake with the Sniper system?

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Regarding 5/16 return line, Holley's recommendation is a 3psi max pressure loss along the return line to the tank. In my case, the return line will be about 7' of 3/8" rubber hose into about 4' 5/16" factory steel hose to the tank. The pressure loss will be all friction (not hyrostatic), so I can do a calculation of the flow rate the return line would require to create a 3psi pressure loss. I do related stuff for the oil and gas industry within pipeline for my job. I've read online of other ppl using the factory 5/16" return line with this kit with no issues, and in my case only a fraction of it will be 5/16" with most of it being 3/8". I'm trying to avoid drilling into the tank.

Headers are these. They fit will, had to grind a little off the flanges to mount to the heads. https://www.summitracing.com/int/par...1hkr/overview/

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I have the Performer RPM intake which is a dual plane (According to what I looked up).

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I can’t wait to install mine.. also the reason I haven’t ordered it yet..

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I've used a FiTech TBI on my ZZ4 69 Camaro and really like it. The trick is to follow directions precisely and ground it well.

I went a different direction on my 72 :gmc2: and installed a F.I.R.S.T TPI system which now has 12k miles on it with out a hitch. This is not your fathers 89 Corvette motor. lol

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Part 2: https://youtu.be/hIClWrLBrBA

Got the fuel system installed.

Removed the mechanical pump and used the included plate to cover the hole. The original bolts were too long for the plate, so I had to find some shorter bolts.

The electric fuel pump is mounted along the frame using some existing holes (lucky).
https://i.imgur.com/5VXUn1Nh.jpg

https://i.imgur.com/vJWJmjqh.jpg

I ordered some of these off amazon.
https://i.imgur.com/YdnR4l2h.jpg

And after a bunch of looking found this 3/8" to 1/4" step down to connect to the factory return steel line into the stock tank. From the EFI unit in the engine bay, the 3/8" rubber return hose goes down the firewall, along the frame, through 2 of the rubber retainer clamps, into the 3/8" to 1/4" step down fitting, into a new 1/4" rubber hose, into the factory 1/4" steel return hose which goes into the cab and tank.
https://i.imgur.com/6BLLowjh.jpg

I heat tape wrapped some of the fuel line and post pump filter just as a precaution, and it looks cool.
https://i.imgur.com/mjndZLyh.jpg

Also got the 3" exhaust clamps from amazon so O2 sensor is installed.
https://i.imgur.com/7sszeDIh.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Nice work.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Thanks for posting this info.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Great write up and videos! this is definitely making me rethink my plan for my truck. I was planning to drop a TBI 350 with a 700r4 in my 72, but now think the extra headaches may not be worth it.
How do you guys think the sniper or FiTech systems compare to the late 80s tbi for power, drivability, etc?

Thanks,
Jim

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I went and looked at prices. Am I mistaken that these systems are $3500, plus or minus? Not picking on anyone, just trying to be sure about costs.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

They run about $1000.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Old gold.
I think the big advantage these new units have over the older tbi units is much more computing power. Which allows an ability to self learn and more accurately compensate for different conditions.
That is my understanding

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I was looking at FI tech for a while. I read their support went downhill with the large volume of sales then ended up getting. With Holley, it's a big company and I feel I can get better support.


$1000 plus $300 for the optional fuel system.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I just finished the Install of the sniper EFI on my 72 K10 yesterday, You're going to love it!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I'm about to call Holley for a support question. Maybe you can chime in. The Yellow wire from the Holley harness is supposed to measure RPM. Do I hook it up to the same wire that goes from my distributor to my tach (brown wire)? The instructions are not 100% clear to me.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I have an MSD box, so the yellow wire was not used, so i wont be of any help sorry!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Holley told me I have to use the brown wire on the optional 10 pin connector to now go to my tach. The yellow wire on the 7 pin connector will go to where my original tach signal came from on the distributor.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Aus79c20 and Ekliptix, thanks guys, I think I'm headed down this path!
Jim

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Made some wiring progress tonight.
https://i.imgur.com/3q2ZNhyh.jpg

This is an optional 10 pin connector. Most of the wires are for nitrous, etc, so I cut and heat shrinked most of them. I only need the brown wire remaining to send a signal to my tach.
https://i.imgur.com/aVkjyksh.jpg

Started getting some things tucked away. I need to buy some black wire loom to cover those 3 wires at the top. I attached the fuse and relay to a screw by that AC box thing.
https://i.imgur.com/L3neJOqh.jpg

Tried to hide the wires as much as possible. This is the power from the battery, ran through the fender.
https://i.imgur.com/L2I07i2h.jpg

What's left is connecting a blue wire (power) to the fuel pump, grounding the fuel pump, ensuring the O2 sensor cable is secure, terminating the yellow wire to the distributor tach signal, connecting the brown wire to the tach, connecting the pink wire to 12v when the ignition is on.

Then put some gas in the tank, follow the start up instructions including priming the pump and dumping gas into a can to fill the source hose with fuel.

The end is in sight!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Lookin good. I’m anxious to see how it does with that big cam and low vacuum.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Yea, I have not 100% identified what the low vacuum is from. This EFI unit won't fix a vacuum leak but i'm not sure if that's what I have.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Good news and bad news.

The good: The truck is running!!! It idles super smooth and there's no unspent fuel coming out the exhaust.

The bad: There's coolant leaking from the intake manifold where a crack has appeared, likely from me over tightened the heat temp sensor.

Need to do:
1) replace/fix intake manifold where it cracked.
2) adjust throttle cable to provide 100% open throttle. Reads 85% position at peddle WOT.
3) wait 3 months for snow to melt

Part 3 Video: https://youtu.be/JSnHy1DTm8E

Finished engine bay
https://i.imgur.com/qaTdR0bh.jpg

Running and warming up
https://i.imgur.com/1eLElLsh.jpg

Me "What's that sound?"
https://i.imgur.com/fnm3wZph.jpg

Green juice is good, right?
https://i.imgur.com/iVzCDe2h.jpg

Random pic of chains used to get 1 car and 2 trucks unstuck from my driveway this weekend. 305 studded winter tires, love 'em.
https://i.imgur.com/6fV4j3Xh.jpg