Do these engines ever need to be "opened up" once in a while?

[argo]

I had noticed recently that my Suburban's exhaust was slightly hazy, even at idle. Not heavy with smoke, but just a bit of haze. I took it out for a drive today and opened it up on a stretch of cop free no traffic highway. I put the pedal about 80% down and held it there until I got to 80 MPH, then I coasted down to a stop, the did it again. I repeated this about 5 times. Each time I did so, the engine felt more responsive, smoother, and the level of haze coming from my tailpipes went down. Now I notice a smoother idle, faster starts, and smoother throttle response. Keep in mind that this engine rarely sees over 1/4 throttle application. I wonder if I am not working it hard enough? I can't remember the last time (before today) that I "floored it." Since this is used as a family car, it usually never breaks the speed limit, it never tows anything, could it be that I need to run it hard once in a while, like once every two or three tanks (2 months, on average)?

[rapidoxidationman]

I believe the proper term is "Italian Tuneup". Cleans out the pipes. I know that the VW Tdi's are susceptible to clogging up with carbon if you don't run 'em hard now and then to burn the crap out, can't see why any other engine wouldn't benefit from it. Just don't get caught;)

[dixiepc]

Argo,

Give us an update on how your Suburban is running, how the electric fans are doing, and what kind of fuel mileage you are getting now.

Thanks

[argo]

Everything is fantastic overall except for my goofball 700-R4. I just don't like the way it feels. But we are still getting 22 MPG around town, 27 highway, overall average is 23.8. The electric fan is working perfectly, and last summer the temperature never got over about 190. The only other issue was the alternator gave up (it was carried over from the gas engine and was of unknown age). Starts at 12* F with no fuss after 20 seconds of glow. I am very happy with it... except for the 700-R4. I want to put a 2.73 axle and TH-350C in instead.

[Robyn]

You can dump a quart of 2 stroke oil in the tank at the next fillemup and this will help clean out deposits and lube the IP and injectors.

The injectors to wear out, and if they have over 100K on them they are likely getting tired.

ATF added to a tank of fuel can help clean things out too. (quart to a tank full)

Missy

[dixiepc]

Thanks Argo,

I put a J-code engine (with a c-code IP) in a 92 4x4 Suburban. It has 7" lift, 4.10 gears, and 35" tires. I am getting about 15 mpg around town. I know that I can't expect the mileage that you get, but do you think that it would improve if I used c-code precups.

[argo]

dixiepc:

Part of the issue might be with gearing. I have 3.73:1 gears, and I run a 29" tire (LT-235-75-R15). You have 35 inch tires which means you should be running a 4.56:1 gear ratio. Your 4.10 gears are acting like 3.42:1 gears. Have you re-calibrated your speedometer? If not, you are probably getting better mileage than you are indicating as well because you are traveling further per revolution than the speedometer/odometer is calibrated for. You didn't state what highway MPG is like, but the height adds more aerodynamic drag. This might not significantly affect in town mileage, but will negatively impact highway MPG. Also consider that even if gearing is correct, you still have more mass to accelerate (bigger tires will act like heavier flywheels) and they have more rolling resistance. Needless to say, this all adds up as well.

As for using the smaller chambers, I do believe they would improve your mileage. The question I have is if it is worth it to go to the trouble and expense to install them unless you already need to open the engine up for something else. I do know that the 6.5L fuel miser engines use an updated version of the small throat chamber.

Robyn:

I intend to rebuild the injectors this summer. I don't know how many miles are on them. They bench tested good when I put them in, however, I didn't do anything to them other than that. I also plan to rebuild the pump as well. Given that it runs so well and that we rely on it so much I want to make sure that everything is in tip top shape as money and time will allow. That said, after my "sprints" it is not hazing at all, and it is running smoother and peppier than it has in a long time, so she probably needed a workout.

[dixiepc]

Argo,

My speedometer is controlled by a DRAC and I have calibrated it and checked it with many times with mile markers (different ones) and it is very accurate. I did not list any highway miles as I have not made any longer trips. I live in a small town in the north Georgia mountains and have put on about 3000 miles since the conversion. I have kept a good record of mileage. I have a dual fan setup from a 2005 Chevy 1500 that I will install shortly, I know that will help. My j-code is a military engine so the precups are at least two sizes bigger than the c cups. Your post about your conversion helped me out alot with my conversiom.

Thanks

P.S. At 65 mph I am running right 1800 rpm.

[argo]

Argo,

My speedometer is controlled by a DRAC and I have calibrated it and checked it with many times with mile markers (different ones) and it is very accurate. I did not list any highway miles as I have not made any longer trips. I live in a small town in the north Georgia mountains and have put on about 3000 miles since the conversion. I have kept a good record of mileage. I have a dual fan setup from a 2005 Chevy 1500 that I will install shortly, I know that will help. My j-code is a military engine so the precups are at least two sizes bigger than the c cups. Your post about your conversion helped me out alot with my conversiom.

Thanks

P.S. At 65 mph I am running right 1800 rpm.

If you are in the mountains and pulling those big tires then I think you are doing really good! Keep in mind that I live in Delaware. It is very flat here. What we call "hills" you probably would call a big speed bump. Also, you are doing good RPM wise. I turn 1,800 at 60 MPH. Considering I have 3.73 gears, and you have the equivalent of 3.42 gears with your tires, that sounds about right. My brother lives in Pennsylvania, on the south side of the Poconos, and I doubt that I would get the mileage I do if I lived there; it has to labor on some of the steeper hills. I think that small ports might help you a bit, but I don't think that you'd recoup the cost, unless of course you were already opening up your engine for other things. Now on the other hand, your engine probably works better under load than mine; I think you are more likely to see a highway fuel economy improvement with smaller chambers. Around town and climbing hills, I think you might not see a significant improvement. What is the opinion of others here?

By the way, I am glad that my posts were helpful to you!

[dixiepc]

Argo,

I have had some people tell me that I would get better mileage if I put on a turbo. I am way past the hotrod stage of my life and this just might work. What do you think?

Monty

P.S. I like Mater too.

[Edahall]

Argo,

I have had some people tell me that I would get better mileage if I put on a turbo. I am way past the hotrod stage of my life and this just might work. What do you think?

Monty

P.S. I like Mater too.

I doubt a turbo will give you better mileage unloaded. My experience is they do help a little if you're pulling heavy loads but not solo. If you haven't already freed up the exhaust, that might be something to look into.

[dixiepc]

Edahall,

I do have 2 1/2" duals with Flowmaster 50 SUV's. I am using the factory exhaust manifols. I have been thinking about using headers and putting in a crossover pipe. I see you have some of Stan's headers. Do you like them and did they help with your mileage?

Thanks

[More Power]

Do these engines ever need to be "opened up" once in a while?

Yes, but think about exhaust/combustion temperature moreso than just "opening it up once in a while". The 6.2 I owned ran better (crisper/smoother) after a few hundred miles of towing. The average exhaust temperature was higher, and I suspect it helped to burn off the carbon deposits that developed on the injectors nozzles and combustion chambers.

A few hundred miles of light-duty commuting erased the benefit. Still ran well, but I could tell the difference. A diesel fuel treatment with the right ingredients might help.

[argo]

dixiepc:

A turbo is a mixed bag. If you are able to keep your foot out of the extra power, it might help in stop and go traffic. I can't see it helping much with steady state cruising though. However, with hilly terrain and 35s, it might help 1-2 MPG.

More Power:

I figured that loading the engine and running it hotter would burn off the carbon deposits. Thankfully we live in a rural area, not a big city. I think that stop and crawl traffic would soot these up more. Even still, this engine gets very light duty for the most part, carting the kids around and doing the grocery run. The most strenuous work it has ever done was pull my F-150 up the driveway to the garage when the harmonic balancer on the truck went bad. pulling a 5,000 lb truck 200 feet at 5 MPH is something my camry could do.

[JohnC]

The crossover pipe will likely help, too.

[dixiepc]

Thanks everyone for all the help.

[sholsten]

We called it "blowing the soot " out.