Chevrolet 8.1 Vortec advice

Tom Meyer · 01-03-2021, 06:11 PM

We tow with a 02 Suburban 3/4 ton 4l85E trans, 4.1 gears 265/65 /16 tires. We got about 7mpg. This last year got rid of the cats put in a balance tube up front and a flowmaster cat back system on. From there we went on a wheel dyno for the tuneup, picked up 50 lb of toque and 40 hp at 2300 rpm. It has great power towing but now gets 7mpg. We will be doing a intake mod [google 8.1 mod] have the intake done just need to install it. I just do not think these almost 500 ci motors are made to get mileage, but they pull great and are cheaper to maintain than a diesel. Tom

Bob Don · 01-04-2021, 08:32 PM

I had a 2002 2500HD 2wd with Allison tranny and 8.1 vortec. I got right around 10mpg towing about 8K #s. The tranny temp would go up a little going up hills but nothing too bad. When conditions allowed, I ran around 75 mph with the trailer with no issues.

C29404 · 01-05-2021, 09:22 AM

Tom, thanks for the reply; the one thing I can say for this thing is it does not lack for any power! If it was weak and got poor mileage then that would lead me to believe something was wrong and point me in some direction for action. I believe you are correct in the fact that its just big and its going to get what it gets. A lot of gas can be bought for the cost of another truck. Might just add an auxiliary tank to avoid so many fuel stops! Bob, was your pick-up stock and did it hunt between gears when towing at highway speed?

Bob Don · 01-07-2021, 09:01 AM

Quote:

Originally Posted by C29404

Bob, was your pick-up stock and did it hunt between gears when towing at highway speed?

Pick up was stock. No gear hunting on highway except for going up hill.

C29404 · 01-07-2021, 06:32 PM

55 to 60 miles per hour its around 17 to 1800 then at 70+ 2200 and up.
I currently have a 285/70-17 wheel and tire combo on it, when I bought it it had the 245/70-16 wheels and tires, changed them for towing stability not so much for looks. I've also got a camper shell/cap on the bed. I have looked at the profile of the truck versus the trailer and there is a lot of flat trailer showing around the edges, one of those bubbles may be in the cards. I also stumbled across the manifold modification a while back, if I can find another manifold to modify i'll give it a try. I appreciate all of the input I have received on this matter and I am going to give some of this a try. Thanks

01-03-2021, 06:11 PM	#1
Tom Meyer Senior Member Join Date: Aug 2003 Location: Pierce NE Posts: 936 Likes: 78 Liked 354 Times in 120 Posts	Re: Chevrolet 8.1 Vortec advice We tow with a 02 Suburban 3/4 ton 4l85E trans, 4.1 gears 265/65 /16 tires. We got about 7mpg. This last year got rid of the cats put in a balance tube up front and a flowmaster cat back system on. From there we went on a wheel dyno for the tuneup, picked up 50 lb of toque and 40 hp at 2300 rpm. It has great power towing but now gets 7mpg. We will be doing a intake mod [google 8.1 mod] have the intake done just need to install it. I just do not think these almost 500 ci motors are made to get mileage, but they pull great and are cheaper to maintain than a diesel. Tom __________________ Tom Meyer 5240 SS Stock ??? Last edited by Tom Meyer; 01-03-2021 at 06:16 PM.

01-04-2021, 08:32 PM	#2
Bob Don VIP Member Join Date: Oct 2002 Location: Greater Boston Posts: 1,495 Likes: 1,114 Liked 900 Times in 191 Posts	Re: Chevrolet 8.1 Vortec advice I had a 2002 2500HD 2wd with Allison tranny and 8.1 vortec. I got right around 10mpg towing about 8K #s. The tranny temp would go up a little going up hills but nothing too bad. When conditions allowed, I ran around 75 mph with the trailer with no issues. __________________ Bob Don 128 SS

01-05-2021, 09:22 AM	#3
C29404 Junior Member Join Date: Dec 2016 Posts: 20 Likes: 0 Liked 0 Times in 0 Posts	Re: Chevrolet 8.1 Vortec advice Tom, thanks for the reply; the one thing I can say for this thing is it does not lack for any power! If it was weak and got poor mileage then that would lead me to believe something was wrong and point me in some direction for action. I believe you are correct in the fact that its just big and its going to get what it gets. A lot of gas can be bought for the cost of another truck. Might just add an auxiliary tank to avoid so many fuel stops! Bob, was your pick-up stock and did it hunt between gears when towing at highway speed?

01-07-2021, 06:32 PM	#5
C29404 Junior Member Join Date: Dec 2016 Posts: 20 Likes: 0 Liked 0 Times in 0 Posts	Re: Chevrolet 8.1 Vortec advice 55 to 60 miles per hour its around 17 to 1800 then at 70+ 2200 and up. I currently have a 285/70-17 wheel and tire combo on it, when I bought it it had the 245/70-16 wheels and tires, changed them for towing stability not so much for looks. I've also got a camper shell/cap on the bed. I have looked at the profile of the truck versus the trailer and there is a lot of flat trailer showing around the edges, one of those bubbles may be in the cards. I also stumbled across the manifold modification a while back, if I can find another manifold to modify i'll give it a try. I appreciate all of the input I have received on this matter and I am going to give some of this a try. Thanks