Converting a 402 to fuel injection

[Chris Bryant]

Just curious as to anyone's opinions on converting a 402 engine to fuel injection?

[70white402]

Converting any small block or big block to fuel injection will be a huge improvement over any carb setup. The injection setup has to be top notch, of course.

[70white402]

Gas tank with the pump inside makes a clean install.

[Jared Richey]

Not worth it, unless you are going with a modern LS engine and using FACTORY installed EFI that will go 300k+ miles with no issues.

These aftermarket EFI units have been shown to be nothing but problems. And not one person has been able to tell me about any increase in fuel mileage, Which is imo the ONLY reason I'd care for EFI of any sort. 

My 89 Caprice gets 20 mpg hwy with a throttle body. Tahoe gets 18. Both have proven they take the beating of years and miles.

 

 

[jft69z]

8 hours ago, Jared Richey said:

These aftermarket EFI units have been shown to be nothing but problems. And not one person has been able to tell me about any increase in fuel mileage, Which is imo the ONLY reason I'd care for EFI of any sort. 

I've had zero issues with the Holley Terminator Stealth EFI systems on both my Monte & Camaro. Granted, they are top level Holley units, not the 'Sniper' versions.

Started my Camaro yesterday after sitting all winter. One turn of the key it was running. That car was always cold blooded with a carb/choke until fully warmed up. With the EFI, start and run, done.

Throttle response is great, and fuel control is much better. With the Holley double pumpers I used to use, the idle fumes would damn near blind you, lol. (double pumpers tend to run rich at idle). Sure, with enough tuning, jet changes, idle circuit mods, etc, the carb could be improved, or fire up the laptop and tweak the EFi and be done.

[Scott S.]

Having had both systems, each has it's benefit/drawback. 

It depends on what you want to do with your Monte, type of driving, etc.

To me, although I like the fuel injection systems, the cost of switching on a classic doesn't balance the savings. 

The couple bucks a tank saved wouldn't pay for the system. 

Just my opinion.... Montelishi is a "summertime" driver, so she only goes a few thousand miles a year. 

[Leghome]

I really like my Sniper but would not do it again like as has been stated will never pay for itself

[Marks71]

        I think if a “will pay for itself over time” is what you’re after, then don’t get it. It will never pay for itself. I view it as an upgrade to a more current technology system that when set up properly increases performance and drivability. On par with a brake or suspension or even a sound system upgrade. 
        I installed an Edelbrock Pro Flow4 EFI system which included the distributor also, on a stock SBC in my brothers 57 Chevy pickup. I did it with the understanding that being pretty much computer illiterate, he’d have to get someone to do the tune. He loves it, doesn’t matter how long it’s been sitting, just turn the key and you’re good to go. It’s by far, not the cheapest system out there though. It’s been 3 years with no issues. As far as the longevity of the electronics, don’t know.

        As for me, I guess you could say I’m a simpleton, so the  original 2 bl. carb on my 71 isn’t going anywhere. Heck, I’m still running points in my distributor. If it was good enough for me in 74, it’s good enough in 25. 

 

[Robnhood]

I purchased a Holley Sniper 1 EFI with the hyperspark distributer for my 1942 International harvester pickup (Which has a chevrolet 350 another story). 

My rational for efi on the international was for driveability.    I basically wanted to be able to get in and turn the key and have it start.

I have a Holley Sniper 2 EFI with the Hyperspark distributer with the PDM for my Monte.  Again my thoughts were for driveability.

Keeping in mind that my Monte is not an SS, and certainly isn't orignal.  I have been going in the direction of what I think will work for me.

I don't anticipate any gas savings or huge power increases.  I just like how it works.

I say that now, and I haven't knocked on wood, but I haven't had any problems as of yet.

Murphy don't get me now!.

[Dtret]

IMHO. If we are  looking for something that “ will pay for itself over time “ then we are all in the wrong hobby. Everything has it’s positives and negatives you just have to weigh what is best for your situation. 

[Chris Bryant]

On 4/27/2025 at 9:03 PM, Jared Richey said:

Not worth it, unless you are going with a modern LS engine and using FACTORY installed EFI that will go 300k+ miles with no issues.

These aftermarket EFI units have been shown to be nothing but problems. And not one person has been able to tell me about any increase in fuel mileage, Which is imo the ONLY reason I'd care for EFI of any sort. 

My 89 Caprice gets 20 mpg hwy with a throttle body. Tahoe gets 18. Both have proven they take the beating of years and miles.

 

 

Yes I prefer to keep the car as original looking as possible.

[Jared Richey]

Another MAJOR thing to consider are you driving locally or on long trips? That aftermarket stuff goes out you are in a huge mess.

A carb can be sourced pretty much anywhere in the US at worst overnighted from summit and your on the road again. Factory efi parts same way all parts stores have the stuff.

Not so much with the aftermarket injection systems.

Cold start is nice but where is the fuel mileage? My 59 cadillac gets like 10 mpg, with an LS swap conversion planned in the future and factory efi it will literally double the gas mileage I'm weird I actually care about fuel mileage because I actually drive my cars a lot. The caddy is another huge problem where you gonna get 390 cadillac parts broken down somewhere. 

[Robnhood]

45 minutes ago, Jared Richey said:

Another MAJOR thing to consider are you driving locally or on long trips? That aftermarket stuff goes out you are in a huge mess.

A carb can be sourced pretty much anywhere in the US at worst overnighted from summit and your on the road again. Factory efi parts same way all parts stores have the stuff.

Not so much with the aftermarket injection systems.

Cold start is nice but where is the fuel mileage? My 59 cadillac gets like 10 mpg, with an LS swap conversion planned in the future and factory efi it will literally double the gas mileage I'm weird I actually care about fuel mileage because I actually drive my cars a lot. The caddy is another huge problem where you gonna get 390 cadillac parts broken down somewhere. 

One thing that I did run into with the aftermarket injection system was that I couldn't buy the sniper efi 2 kit is that one of the major parts distributors couldn't ship it to NY.  Another one could.  I suppose not really a big deal, but I can see this becoming more of a problem in the future.

[Chris Bryant]

On 4/29/2025 at 6:24 PM, Jared Richey said:

Another MAJOR thing to consider are you driving locally or on long trips? That aftermarket stuff goes out you are in a huge mess.

A carb can be sourced pretty much anywhere in the US at worst overnighted from summit and your on the road again. Factory efi parts same way all parts stores have the stuff.

Not so much with the aftermarket injection systems.

Cold start is nice but where is the fuel mileage? My 59 cadillac gets like 10 mpg, with an LS swap conversion planned in the future and factory efi it will literally double the gas mileage I'm weird I actually care about fuel mileage because I actually drive my cars a lot. The caddy is another huge problem where you gonna get 390 cadillac parts broken down somewhere. 

Locally for right now. Want to make sure car is in tip top shape before taking a long trip and having a break down. You seem to know a lot about these first gens.

[Robnhood]

3 hours ago, Chris Bryant said:

Locally for right now. Want to make sure car is in tip top shape before taking a long trip and having a break down. You seem to know a lot about these first gens.

Same here.  

[RON T]

Hey Chris. There will be some of these members that you are conversing with at the Eastern meet. Ask away   👍 

BTY, I don’t drive a 71 SS for gas mileage, . My Turbo jet 4 barrel runs just fine. So what if it take 45 seconds to warm up :).. just sayin. 

[SPLATT71MC]

EFI won't necessarily get you better gas mileage or at least not a significant improvement. Want gas mileage, add an overdrive and gear the rear axle appropriately.

[Chris Bryant]

It looks like i will be able to come to Somerset KY next week for the car show as i am currently unemployed. 

[1Bad_Monte]

Chris,

I am running the Sniper 2 on my original 350 that’s now a monster 383.  It ran horrible when I first installed it but there’s always a guy.  Found Dr. EFI on most every Holley and EFI forum and scheduled an apt.  Night and day difference after he logged on and tuned it.  If you haven’t used the Sniper EFI software to dial in your tune, or are not planning on it, IMHO this is money well spent. 
 

-Jr.

[SPLATT71MC]

4 hours ago, 1Bad_Monte said:

Chris,

I am running the Sniper 2 on my original 350 that’s now a monster 383.  It ran horrible when I first installed it but there’s always a guy.  Found Dr. EFI on most every Holley and EFI forum and scheduled an apt.  Night and day difference after he logged on and tuned it.  If you haven’t used the Sniper EFI software to dial in your tune, or are not planning on it, IMHO this is money well spent. 
 

-Jr.

I've been following a couple of his builds on another forum. He's doing a GTO and a LS powered 1st gen Cougar.

 

[Robnhood]

On 5/7/2025 at 1:27 PM, RON T said:

Hey Chris. There will be some of these members that you are conversing with at the Eastern meet. Ask away   👍 

BTY, I don’t drive a 71 SS for gas mileage, . My Turbo jet 4 barrel runs just fine. So what if it take 45 seconds to warm up :).. just sayin. 

It probably goes without saying, but if it isn't running good before EFI, then it probably isn't going to after.  

The problems caused by vacuum leaks especially are magnified with EFI.

[abigfoot]

Why would anyone with a 50 plus year old car worry about an option paying for itself as far as gas mileage?   I wouldn't think anyone is using their classic as a daily driver back and forth to work etc  but I may be wrong.  

[Chris Bryant]

I agree. I didn't buy a big block Chevy for fuel economy. lol

[Robnhood]

On 8/9/2025 at 9:45 AM, abigfoot said:

Why would anyone with a 50 plus year old car worry about an option paying for itself as far as gas mileage?   I wouldn't think anyone is using their classic as a daily driver back and forth to work etc  but I may be wrong.  

Probably for the same reason we spend countless dollars restoring our cars, "We just don't know any different."  

I just look at it from the perspective that everyone has to do what works for them.

[Scott S.]

Not that I drive either Monte that much, but come summer, Montelishi is my go to drive.