6.2 MORE POWER?

[Stokesva]

I have an 85 suburban with 6.2 C code. It is bone stock and has dual exhaust. The truck runs well - plenty of power with no load and has been maintained fairly well BUT I hooked an 7000LB Load to it and you would have thought I now had a chevette. What can I do to help this thing achieve more power without $3000 turbo kit/install? HELP?

[CleviteKid]

Click on this link: "THE RIGHT STUFF" (http://www.thedieselpage.com/reviews/avanteng.htm) for an article about ways to get much more power out of the naturally aspirated 6.2L and 6.5L engines. This particular example has a lot of modifications, but you can pick and choose.

Even the example is no longer state-of-the-art: The Diesel Depot has special camshafts for even more power out of both NA and turbo engines.

Dr. Lee :cool:

[Quack_Addict]

Towing a 7000 lb trailer is a task for pretty well any truck; Diesel or gas. Axle gear ratio plays a big part in towing... with a C-code engine in a 1/2 ton truck I would be surprised if you have gears taller than 3.42's (4.11 would be a more ideal ratio for your setup assuming you have a 700R4 transmission).

[Salemone]

Just put a turbo on--you can get a kit on e-bay
at a reasonable cost. Its actually easier than
mechanical solutions .

[Stokesva]

Thanks for the input guys. I know from towing many miles with my 6.5 Turbo suburban and other gasoline motored tow vehicles that I have had in the past that this 6.2 is really, really lacking in the towing power capacity. What turbo kits are out there other than Banks and looking at the installation location does the Air Conditioner unit on the firewall interfere with the installation? Any guidance is much appreciated.

[arveetek]

6.2L n/a and towing: while it may seem like they don't go together, it can be done.

I regularly tow a 29' fith-wheel RV that weighs in around 8500 lbs or so with my '81 (see specs below). The 6.2L started out in life as a bone stock '82 model C code engine. However, even this was a vast improvement in pulling power over the 305 it replaced. My original setup was a 305, TH350, and 3.42 gears. This yeilded me about 12 mpg on a good day with now towing power. It was quick and fun to drive, but if I hooked my fifth-wheel up to it, I could hardly ever get out of 2nd gear. I had to keep it wound up pretty high to get any power out of it.

So, I yanked out the 305/TH350, and installed the C code 6.2L diesel and 700R4. This was much better...now I could pull the same load in 3rd gear, and get moving easier due to the lower 1st gear. Still a little lacking in power. Next, I swapped the 3.42 rear axle for a 4.10. Much, much better.

Next, I turned up the fuel delivery in the injection pump about a 1/4 turn and bumped the timing up a bit. Again, significant improvement. I also removed the EGR valve in the intake and plugged the hole with a freeze plug. At this point, I made a trip with my RV all the way to Florida and back with no problems whatsoever, keeping up with the 70 mph traffic on the flats and pulling the mountains without too much trouble....still a bit slow...but acceptable.

Then, I ditched the somewhat factory exhuast, made up some Swanger exhaust adapters, and had 2.5" pipes bolted directly to the manifolds. The 2.5" pipes turned into 3" pipes. I also installed an EGT guage to see what was going on. At this point, I made a trip again with the RV to the 2001 Diesel Page Rendezvous in Dayton, Ohio. Most of the folks attending were quite surprised I had pulled that big trailer with my 6.2L N/A...it was fun showing what the 6.2L was capable of with just a few minor adjustments.

After that, I installed a J code intake, ditched the silencer, and ran a 4" hose from the air cleaner to the radiator support to help draw in fresh air.

That's pretty much where I am right now. My next project is almost ready to go: custom turbo system with 4" exhaust! I'm really excited to get started. I estimate I'll have around $500 or so invested in the turbo and exhaust system. I've gotten most of the parts piece by piece, from individuals, off of ebay, and from Banks Power.

So in conclusion, here's what I suggest for all 6.2L n/a owners who want more towing power:

1. Open up the intake by removing the EGR, or replacing intake manifold.

2. Remove intake silencer.

3. Run 4" hose for fresh air intake/ram air effect.

4. Bump up timing a few degrees.

5. Turn up fuel delivery in IP.

These first 5 steps really don't cost any money at all and will probably give you the most significant "seat of the pants" improvement, other than swapping rear axle ratios. After that, I recommend:

6. Install EGT guage.

7. Replace restrictive exhaust, preferrably using Dr. Lee's adapters.

8. Install 4.10 gearing....perhaps this should be higher on the list....really a "must have" for serious towing.

9. Finally, install turbo system if money permits.

Casey

[jcomp]

I agree that a new set of lower gears will be a big improvement. I noticed a huge improvement going from stock gears to 4.10s, while keeping the same size tires.

My NA 6.2 never seemed to have the low end grunt of some other diesels; it needed to rev up a bit to keep things moving along. Of course, you've got a few PSI of "atmospheric supercharging" compared to mine.

[Stokesva]

Thanks for the great feedback. I have pulled the EGR and the intake - already got some 4 inch flex line to replace with for my new RAM AIR INTAKE smile.gif . What size freeze plug should I use to plug the hole? Does anybody know this off the top of their head? I am also thinking about removing the inner ring/flange that sits up about 2 inches in the air cleaner housing - if I remove this will it cause any problems? I assume it will improve flow.

[C.K. Piquup]

Hey Arveetek,What upper intake are you using with the turbo?Is it a Banks bought individually?

[kconnair]

Hey Casey,

What kind of mileage are you getting now with your upgraded combo? I am working on a couple of variations on my 2 6.2 Suburbans - I have changed the intake on the 1/2 ton, but I have yet to turn up the IP, or advance the timing.

Thanks,

Kevin.

[CleviteKid]

Hey Stokesva:

Once your EGR is gone, by all means remove that ring. It's only purpose in life was to guide the exhaust from the EGR to the cylinders. Mine disappeared years ago when I first hammered a freeze plug into the manifold. Don't remember the size - maybe someone else does, or has a manifold hanging around and they can measure it.

Dr. Lee :cool:

[arveetek]

Stokesva,

I don't remember what size of freeze plug I used...I just removed the whole intake manifold, and took it with me to the auto store...that way I could make sure I found one that fit. I also installed new J code intake manifolds at the same time...this also blocked off the exhaust passages in the manifold.

C.K. Piquup,

The pressure chamber is one of the last items I'm working on. Banks wants $185 for that piece of aluminum...too rich for my blood for all it is. I'm going to make one out of of some spare diamond tread aluminum plate that I have. Should be fairly simple...and look pretty cool and be different. Really all it will be is just a square box with a hole in the bottom and a hose fitting welded into one side. I'm going to install the hose fitting straight in on the side instead of at an angle so that I can point the fitting to either the passenger side or driver's side. That way, if I ever want to install an intercooler, I can just turn the thing 90 degrees and install some new pipes! :D

Kevin,

When I started with the stock 6.2L C code and 3.42 gears, I was getting around 20 mpg. After all the changes and power enhancements, it's dropped to 18.5 mpg. Still pretty good in my book!

Casey

[Stokesva]

Thanks guys for all your great input. I have already implemented the EGR removal - added freeze plug - will likely go to the J-Code intake ASAP - I can see that would make a big difference for unrestricted flow of CFM. Are those available from autoparts stores as a replacement item for certain years 6.2s or am I going to have to hunt one down? I guess I will go to 4.10s next. Anybody got a rough cost estimate on ring/pinion + install - ~$750 an axle? Once again - thanks for rallying with some great information.

[britannic]

Scan eBay daily, check the DP classifieds and place a want ad until you find a J code intake or visit your local pick and pulls for a while.

[ 05-30-2004, 06:15 PM: Message edited by: britannic ]

[Ratau]

Casey

What size wheels are on your truck?

Danie

[arveetek]

Originally posted by Ratau:
Casey

What size wheels are on your truck?

Danie 16" 8 lug aluminum wheels with 265/75/R16 tires, approx. 31" in diameter. I just switched to these tires a couple of months ago. I had been using 245/75/R16 tires before that, which is what gave me the above fuel mileage figures. I haven't really checked the mileage that closely since installing the new tires....haven't driven it that much. I can definitely tell there is a lower cruising rpm on the highway...should yield me slightly better mileage. It's amazing what a simple tire change to the next size will do.

Casey

[Topmech]

Freeze plug for egr plug is 1 53/64

[Keith Richards]

Also if your suburban is 1/2 ton you might as well, instead of switching gears, try to find a used 12 bolt axle ,or even better 14 bolt to swap in that already has the 4.10 ratio or maybe even 4.56 (really low) for serious towing.These axles will last alot longer towing heavy loads with.I wouldnt even bother switching gears if you have a 10 bolt under it,just my thoughts.Good luck.

[CleviteKid]

I agree with Keith, that the 10-bolt is not a good choice for heavy towing. However, the 12-bolt is actually not that much stronger than the 10-bolt. The 9-1/2" 14 bolt semi-floater was used in LOTS of trucks recently, and TheDieselPage original 300 HP Project Truck used this axle. It would be a good choice for a retrofit.

Dr. Lee :cool:

[Stokesva]

Okay,
I am officially in the Market for a 14 bolt - with 4.10 gear and very excited about it - looks like strong stuff. What axle should I look for for the front end - 4X4 to match up with the 14 bolt?

I think I will look for a new front axle too with 4.10 already rather than pay to upgrade light duty stuff.

Also where do I get exhaust adapter flanges to upgrade my exhause to 3 inch? What would be the optimum setup - duals or single? I have to replace my exhaust. The update of the intake to J code style has already blown out the rusty weak spots in BOTH my mufflers SO I would say there is certainly more exhaust pressure now. :D

[NH2112]

You have 3 choices for a front axle to match your 14-bolt rear. One is to regear your current 10-bolt and get 8-lug 3/4 ton hubs for it. You could also find a Dana 44 out of an older 3/4 ton (mid 70s), they're very similar to the 10-bolt in strength, but can be built with stronger axleshafts, U-joints, etc. However, they use externally-mounted locking hubs (like a Jeep's) which some people say aren't as strong as the internally-mounted ones used on the 10-bolt. Lastly, and most expensive, you can find a Dana 60 from a 1-ton. Personally, unless I was going to be doing some serious 4-wheelin' I'd go with the 10-bolt or Dana 44.

[arveetek]

Originally posted by Stokesva:


Also where do I get exhaust adapter flanges to upgrade my exhause to 3 inch? What would be the optimum setup - duals or single? I have to replace my exhaust. The update of the intake to J code style has already blown out the rusty weak spots in BOTH my mufflers SO I would say there is certainly more exhaust pressure now. :D In order to hook any pipe larger than 2" up to your stock manifolds, you'll have to use Dr. Lee's manifold adapter design. They bolt onto the manifold outlets, allowing 2.5" pipes to be bolted directly to the manifolds. Then you can step up to 3" or larger pipe from there. I have a set on my '81. I took Dr. Lee's drawings to the machine shop, and they made them for me.

I won't be needing mine in the next week or so...I'm going to start installing my turbo next weekend and will do away with the adapters. I'm hoping to sell them to another DP member. I'll even throw in the 2.5" mandrel-bent elbows coming off the manifolds. The driver's side has a pyro bung welded onto it. This will simplify installation. Then you can step up to 3" duals or singles.

Casey

[Stokesva]

Casey,
What is your price? I am pretty sure I want to get them from you. Let me know and we can hammer out the details on payment, shipping etc. Looking forward to the 'hand me downs' - what do you recommend doing with the exhaust once I get to 3.5 - duals or into a single 3.5 I assume?

Jim

[CleviteKid]

If you are going to stay naturally aspirated, 3" duals with a balance (or crossover or "H") pipe are the recommended setup.

Dr. Lee :cool:

[arveetek]

Jim,

I'd follow Dr. Lee's advice and go to 3" duals with crossover pipe.

Email me at arveetek AT j s c o m m.net (replace the AT with @ and leave out the spaces in the rest of the address) and we'll hammer out the details.

Casey

[Stokesva]

Sounds good. 3 inch duals it is. Any thoughts on mufflers Doc? I dont want the
truck to be too loud - It is an everyday driver.

[CleviteKid]

I have Dynomax SuperTurbos - 3" inlet and 3" outlet, and 3" internal tubes. I like the sound, but it is NOT Rolls-Royce quiet, unless it is a Rolls-Royce engine in a British WWII fighter plane.

The model number from Dynomax is 17770. Check them out at DYNOMAX SUPERTURBO (http://www.dynomax.com/documents/super_turbo_specs.pdf) .

This muffler (just one) will flow 563 CFM, and a pair of them are adequate for 512 "free-flow" horsepower, according to Dynomax. That is enuf for all conceivable mods I will be making to the SAA engine :D .

Dr. Lee :cool: