Black_Magic

Did a little experiment last week.

Weather was COLD here in St. Louis got down to 0º one night and the next day only may it up to 20º or so. They were predicting Freezing Rain/Sleet/Snow the next night. I decide to stack the Vettes so I could get my truck in the garage.

Garage has heat-A/C but when temp get below 15º the heat pump does do much so it was turned off. Temp in garage was 35-40 and outside ~15º.

So I decide to compare carb vs: EFI. Not scientific but just to have something to do.

1963 327/340HP – Solid Lifter - Holley Carb w/electric choke – Pertronic pointless ignition.

1966 383/445hp – Roller Cam - Holley Sniper EFI – Small cap HEI ignition.

In garage.

1963 – 2 pumps to set choke – started after a couple more pumps – idle ~1400 RPM. Touchy gas pedal – had to feather to rev up even slightly. Stinky gas smell. After couple minutes kick off choke – idle ~850 (normal) but still wanted to bog down if giving gas to fast. Few more minutes was OK.

1966 – No pumps – started right up – RPMs went up to ~1200 and immediately back down to 750 (normal) AFR a little rich – IAC normal. Gas pedal responsive. When temp reaches 160º everything is normal.

Parked both outside 17º and let set until both cold 1+ hours.

1963 – 2 pump to set choke – little more cranking the normal but same as above RPM/Choke. After couple of minutes kicked of choke and would not keep running. Restart. Needed 5-7 minute at fast idle before it would keep running but didn’t like me touching the gas pedal. After about 10 minutes was probably drivable.

1966 – No pumps – started right up – RPMs went up to ~1200 and immediately back down to 750 (normal) AFR a little rich – IAC normal. Gas pedal responsive. I drove with only 1 minute idling and engine had no bog. 200-4R was sluggish . Went around the block and you wouldn’t notice based on engine performance that is was COLD outside even though I was freezing. When temp reached 160º everything was normal.

Parked both and called it a day and wish spring would get here soon.

Again not scientific but I’m very happy with the Holley Sniper EFI.
AND
I don’t drive in this cold snowy weather so who cares But I could if I wanted to

No I’m not going to rebuild carb or change anything… Period

BTW…It was 60º today and snow tomorrow afternoon…Welcome to Missouri weather.

George

LouieM

Really useful comparison, George. Glad I live in a milder climate where subzero starting is an issue.

SI67

Takes me back. Grew up in University City. When I flew back in from my first quarter of college in the Bay Area, around December 22, the high was in the sixties. Two days later, there was an inch and a half of ice on everything. That's why I live in the Bay Area!

Beautiful cars! Are you using the stock intake manifold on your EFI car?

FLYNAVY30

Cool comparison. I had similar results, although not Corvette specific. My 1972 C20 Suburban has a 6.0L LS swap. For the first two years, I was running a Holley 650 double pumper. It was always a pain to get started in the morning, and usually stunk like gas. That being said, I don't claim to be an expert at setting up a carb. I finally swapped to the Holley Terminator with transmission controller (4L65E) and its absolutely perfect. Fires right up every time, doesn't stink like gas, and pulls down 16 MPG on the highway. In my opinion, these self tuning EFI kits are a 90 percent solution. After putting 1200 miles on the truck, I took it to Virginia speed for some additional tuning. They put it on the dyno to tune the WOT, and then drove it around to smooth out the part throttle regimes around town. They said the changes were minimal, mostly just smoothing the fuel and timing curves. Now the truck is an absolute pleasure to drive....power delivery/down shift/upshift is exactly like that of a new truck.

At some point, I will be converting my '64 to the Holley Sniper EFI as well. The kits just work.

Frankie the Fink

I don't think there are any surprises in that bit of ad hoc comparison. It depends on if you mind putting up with some nostalgia and saving some significant dollars over the convenience and ease of fuel injection. Most older drivers "know the deal" with the old carbs. Start the car, let it warm up, baby it for the first few miles in the cold, etc. Its become second nature to most... I'm OK with that in a hobby car - but not a daily driver... Not anymore.

Factoid

Thanks for the comparison, George, very helpful but not surprising. I just ordered a Blueprint engine with Holley Sniper for my ‘64 coupe. I’m hoping for the same outcome. Of course it will be 82 degrees here today.

Also, thanks for posting your tutorial on replacing C2 body mounts. It’s very helpful as I plan on doing just that this weekend.

jim lockwood

A few years ago I did some cold start experiments with Rochester FI.

Test conditions: The temperatures were around 40F for all tests. All cold enrichment designed into the Rochester FI was deliberately disabled. Innovate Motosports equipment monitored air/fuel ratio. Winter fuel was in the tank.

Test results: Consistently, air fuel ratio would be at or below stoich, 14.7:1, in approximately 1 minute after the engine fired. Consistently. At that ratio, the car is driveable without any stumbling or hesitation.

Conclusions: You can draw your own. My purpose in doing this test was to determine how long the FI cold enrichment mechanism of Rochester FI should remain on after a cold start. I got my answer: Not very.

Jim

Black_Magic

'65 Vette "461" intake with plenum milled

Here is some info ====>> Click Here intake.
Here is some info ====>> Click Here on EFI install.

George

Muttley

Are the manifold exhaust heat passages open on either or both of the cars?

warrenmj

I’d like to see you repeat your test when you have temps of 50-60 degrees and post your results.

4 Speed Dave

I have had a Sniper EFI on my 70 K20 truck for over 1.5 years now and have gone through 2 winters with it. I keep the truck outside all the time. It starts just as you described in the cold weather. Maybe you know or not but there is a AFR enrichment factor based upon the outside engine coolant temp and also IAT (intake air temp). Below 160 degrees the computer will be adding fuel to your base AFR. In really cold temps it is not uncommon to see it add 20% on top of your base target AFR. I have found on my 406 mild cam 10.5 CR engine in the truck I had to adjust many of these fuel tables toward the leaner side to reduce the amount of fuel it adds at lower temps. You can adjust most tables on the hand held but to access others you need to use the Holley software on your computer. This 70 truck drives just like a new car. Even in cold temps on the first startup of the day. Start it up let it idle for 5 seconds. Put it in drive and take off down the road no burping farting or stumbles. As far as driveablilty in not so perfect conditions the EFI blows a carb away hands down.

Black_Magic

1963 normal heat riser

1966 NO heat riser

Black_Magic

Follow up

1963 with temps above 45 or so is normal like it was new. But in the very cold weather it stumbled a little..

However I don't drive it in the winter time.

I don't remember how my '64 back in 64 acted but it was my everyday driver and did not have a garage but I don't recall it having any problems.

65silververt

The Holley Sniper EFI makes a huge difference in hot humid climates/times of year as well! That was the main reason I decided to try it and I couldn’t be happier with the results.

CorvetteMikeB

Me too!

dplotkin

Fuel injection, especially port EFI but even the TBI systems might be the single most important improvement to the internal combustion reciprocating engine ever made, No single technology beyond perhaps Sorenson's original Delco coil and distributer ignition has had more to do with improving efficiency, performance, drivability and emissions.

Those of you who know the history of fuel injection - especially Bendix and its efforts to perfect its Electro-Jector (forerunner to D-Jetronic) know that engineers then were aware of how wonderful electronic injection would be if they could just figure out the electronics! Up to that point gasoline injection was mechanical (direct in Mercedes just like today). They knew then that a carburetor was an imperfect device chock full of compromise and that injection would solve a lot of problems.

You and your old Corvette are living proof!

I enjoy my recalcitrant carburetors and the individual starting regimens I must endure (and remember). I have no problem feathering my old cars to life, waiting for them to hold an idle, smelling of unburned hydrocarbons and causing all kinds of cold start trauma. I love it!

But last week, when it was -11 I crawled into my '17 Tundra with seats as hard as granite, twisted the key and to life she came without complaint of any kind. I would miss that were it gone. I have no desire to return to the days of jumper cables and starting fluid.

Dan

JLMICCA

Great comparison. I grew up in Rochester, NY and remember the cold start ritual well. I think you have pointed out one of the greatest advantages to EFI being that you don't have pig rich episodes before warm up which contributes to cylinder washing and engine wear. For me, EFI is a way of preserving an original engine. Keep the car on the shelf to go back to judging.

JLMICCA

I mean, keep the carb on the shelf to go back for judging.

CorvetteMikeB

Nice thing about the Holley Sniper is that their EFI fuel injection system can also control 4L60E, 4L65E etc automatic transmissions with overdrives.

4 Speed Dave

The Sniper EFI system does not have the capability of controlling a transmission. However the Holley Terminator series does have that capability however it does come with a cost. The Sniper is quite a bit different in that the Terminator has a traditional stand alone computer where as the Sniper does not.