[Interceptor]

So I installed a Holley Sniper EFI unit over the weekend, thought I would share a few thoughts.

Hardest part of the install was grinding out the factory QJ manifold to fit the Holley configuration, just used the 4150 gasket as a template and hogged it out as needed with zip wheel and die grinder. Cut a window into the plenum divider as per advice on the internet . Factory throttle linkage took a bit of thought and tweaking but worked out fine, it's all hidden under the air cleaner anyways. I used an inline fuel pump and would definitely go with a new tank and internal pump next time -- there's not nearly as much room back by the tank as you might think. Factory repop air cleaner fit perfectly. Wiring was pretty straightforward, car has an HEI. I had an O2 bung in the exhaust already but their clamp-on setup looked OK.

First startup was ugly but instantaneous, and smoothed right out within 2 or 3 minutes. Self-learning seems to be taking care of itself, as advertised. Everything works perfectly, cold starts are instant and it runs smooth right away same as if it was hot. As a side benefit, I don't smell like gas and exhaust after every drive.

I will update whether there is any change in mileage, or any issues that come up.

[bendutro]

Thanks, update after a few tanks for sure.

[ZeGermanHam]

Very cool! Thanks for posting. It's a costly upgrade, but all things considered, it seems totally worth it. I'm planning to use the Holley Stealth EFI in my '66.

[azbirds]

Definitely keep us posted. My driver is getting 9mpg and needs some help. Putting in a 200-4R in today, hopefully that helps some.

[yahooskidoo]

Pictures of the window in the divider please. Did my sr 72 455ho intake but no window.

[64speed]

I am interested to hear your progress as well

[Interceptor]

Originally Posted by yahooskidoo

Pictures of the window in the divider please. Did my sr 72 455ho intake but no window.

Sorry, didn't take pics of that. Basically I cut down 3/4" at the two thinnest points shown in your photo with a zip wheel and then straight across for a 3/4" deep window.

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[455'73inElCamino]

Any updates here?

[64speed]

Originally Posted by 455'73inElCamino

Any updates here?

Yeah enquiring minds want to know

[Interceptor]

No highway trips yet to check mileage, and I never cared about mileage around town so have no baseline. I do know that there is no longer a yellow film around the tailpipes from running rich.

[STEELCITYFIREBIRD]

On which car?

Engine deets?
(Cam, cr and heads)

[Interceptor]

Originally Posted by STEELCITYFIREBIRD

On which car?

Engine deets?
(Cam, cr and heads)

70 GTO, 400 w/TH200-4r and 3.55's. Last road trip w/carb averaged 16mpg US at 70-80mph. Lunati 0702 Voodoo 9.3:1 CR #13 heads.

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[455'73inElCamino]

Wow. I am only getting 13 mpg on highway

3.73 gears, 2004r no lockup with 2000 rpm stall, quadrajet, edelbrock heads, 10.7:1, stump puller cam.

[STEELCITYFIREBIRD]

Over the road Driveability vs carb? Cruise, under load and WOT?
.......would you install another again/recommend?

[64speed]

Get out there and drive this thing some. Enquiring minds want to know LOL

[HWYSTR455]

Originally Posted by 455'73inElCamino

Wow. I am only getting 13 mpg on highway

3.73 gears, 2004r no lockup with 2000 rpm stall, quadrajet, edelbrock heads, 10.7:1, stump puller cam.

13mpg on the highway? I've seen better on the highway without an OD trans. You sure you're not running really rich?

Any particular reason you're not running lockup?

.

[455'73inElCamino]

Originally Posted by HWYSTR455

13mpg on the highway? I've seen better on the highway without an OD trans. You sure you're not running really rich?

Any particular reason you're not running lockup?.

My prior lower performance setup I was able to run AFR at or above 14.7:1 at cruise with around 50 degrees advance and still only got 13 miles to the gallon.

I am running a non lockup converter because I bought a Art Carr transmission and this company didn't sell them with a lockup. In retrospect, I wish I had the lockup.

I have considered converting to a lockup converter and adding in the electronics to do it, but it has been too low on my priority list.

Adding a sniper/fitech EFI is higher on my priority list.

[HWYSTR455]

Something is seriously not right there, and would have to guess the trans with those kinds of AFRs.

I ran a 400 iron head engine with a th400 behind it, 373 gears, and at 60mph got better than those numbers.

The previous 461 e-head combo with a 4L80E and 373 would get in the 21-23mpg range at 60mph.

E-transmissions are more efficient than 2004r/700s, for one, they have the ability to 'coast' (unlock) when you go <3% TPS, or at whatever value you set. They also have the ability to reduce psi at TPS values, requiring less power, there was less drag.

Lockup is a godsend. There's very little wasted energy. That should help you improve your MPG, but still think there's something else going on there.

The 442 has no OD, and 342 gears behind a th400. Once I would get over X rpm, at a steady state cruise, in order to maintain that rpm/mph, with a carb, I had to keep the throttle open where the vacuum advance would drop out, a point where it needed it most. It would also creep temps in that condition. Timing control via the EFI ecu overcame that situation, and would pick up 4-6mpg. (and run cooler)

Anyway, hate to say it, but think a number of your problems stem from your trans. You don't live in the mountains or something do you? High elevation? Maybe that's a factor in your mpgs.

.

[455'73inElCamino]

Maybe all of this should move to another thread. Do I just start one or does a moderator move this?

It has always been my thinking that my mpg should be higher. I live in the Syracuse NY area so no mountains or high altitude. I don't think that it is a tune/faulty O2 sensor giving me bogus AFR values as my spark plugs look like they should.

Vacuum runs at about 18-21" Hg at cruise (old engine would run at 23-25 Hg). Could it be pumping losses in that my setup should have the throttle open more? I have only read about pumping losses but don't understand if it is a real issue to address on engines like ours.

Could it be that the torque converter is inefficient? I don't think so but I am no expert. I have a LED indicator and it never shows my 2004r temp being up to operating temperature. It implies to me that I should remove the trans cooler. But could this be a factor in MPG?

EDIT: Aerodynamics - I can't believe this is a major factor either.

[JLMounce]

Sure you don't have any exhaust leaks before, or near your oxygen sensor? The sensor can only read what it sees and if it's seeing fresh air, it's going to show leaner, even though the engine may not actually be running in that state. Have you read plug at all?

I agree with hwystr455 on this one, even without a lockup converter in your 200r4, you should be doing significantly better than 13mpg.

FWIW I run a KRE headed 462 with a TH400, 3.73's and 26" tires. at 65 mph (2400rpm) I get in the 16-17mpg range with my FiTech. If your current setup is in fact running at or near stoich, going to an EFI won't significantly improve your mpg. Things like decel fuel cut help slightly, but not by the 5-7 mpg that you should probably be seeing.