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8.1 / 4L85 highway setup
- Thread starter Jon81K5
- Start date
This x100. I looked at the Allison option when I first started by build and though it's a really nice tranny, especially the later 6-speed versions, they're a big tranny. And like mentioned here, adapting older tcases to them is lots of money, that's why I decided on the NV4500.
Since the OP here already has an OD tranny, I personally don't feel like the cost/benefit of swapping tranny's or even gear sets is really going to net him anything significant enough to justify the costs. That's why just use what he has (which is already a bitchin drivetrain) and try to make it just a tad bit better with some other things like tune, etc.
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beags86
Eastbound and Down
400hp? What else did you do to it? Headers, cam, injectors, port work?
Even on a fat block I have a hard time believing just a tune is worth 80+ hp.
Just headers/exhaust, and air intake. Other than that, stock. This is not confirmed obviously, just speculation, so don't take it as hard numbers. But it was a significant increase in power between pre/post tune. 8.1's are chocked back a lot more from the factory tune than regular 5.3/6.0's (The big things in the tune are removing EGR and Torque Management). I even asked Josh @ Team 208 Motorsports when he was doing the tune to give me an honest estimate, and he said those numbers (as he has done lots of 8.1 tunes). I was a bit skeptical when he spit out those numbers, but as soon as I drove the truck, I couldn't help but to agree with his assessment. Even when I told my brother this info, he was calling bull crap at me. But just a few months ago he drove the truck for the first time after the tune, and even he had to agree that it has to be about 400hp. A truck as big as my CCLB V3500 should not haul as fast as it does now. I would love to one day actually dyno the thing.
yes I needed 1" body lift and tho I could have cut the tunnel up to use the ORD shifters the cables are much cleaner. I wanted an automatic that would last during towing that's why I chose the Allison. It's a 5 speed but it came with an 8.1L
It's not the cheap option but it's got the cool factor nailed down 
It's a 5 speed but it came with an 8.1L
Agreed
beags86
Eastbound and Down
I guess I'm saying that it's not possible, just I did a lot of research on the 8.1s before I decide to build my 496 the old fashioned way.
And I just didn't find the numbers that I wanted out of the factory 8.1.
A lot of reading I had done, 400hp just seemed so far away. The guys that had Dyno tunes had spent a lot of money and time to get to 375, with ALot of parts.
So it just didn't make sense to me.
To each their own really
beags86
Eastbound and Down
Yep, if I was building your truck I would have done the same. Makes more sense. But for a little hot rod Stepside that really won't get driven much, I wanted to keep the ol school big block look (no coils, goofy intake, etc,) and more power for the money, no rayler heads/ cam...
I 100% agree. In fact, I plan to in the future build a street/strip truck almost exactly like your stepside (I would take either a stepside or fleetside 2wd short bed...I love them both) and I plan to use an old school BBC and build it up too. I've always loved your stepside.
beags86
Eastbound and Down
Thanks man.
I picked up an 05 Allison for my 8.1 swap, glad to see that it is working for guys. I only got a 5 speed too but it was only $500 so its hard to beat. I'm hoping my longbed std cab will be long enough.
chulisohombre
1/2 ton status
It’s a cool setup You have and sounds like it works well. I’d just leave it alone personally as everyone else has said. That’s a big engine no matter what you do to it. Most people are lucky to get 12 mpg out of them but have that power on demand. You’re still within good cruising rpm at 70 as well. I have a 465 and and 4.10 on 35s. I need another gear on the highway. You have that and a lot more power. Have fun and enjoy it. I know I would.
454Sub
5/8 ton status
That 8.1 with a cam swap will respond just like a 7.4 did to one. It's an identical setup, minus being metric and having cathedral port style heads.
Rylar is super expensive and I personally am doing a CNP Gen 6 454 to avoid that and still get LS tunability, but that 8.1 we did made 600 or so hp if memory serves but on a chassis dyno assuming 45% loss through the Allison and t case. Yes it was expensive, but that engine with milled and ported heads, larger ratio rockers, a ported intake and Comps largest cam that would fit plain rips the tires off on the truck it's in.
But it does cost an ungodly amount of money, as roller cams are expensive, and all of it. But now with elbows being sold and carb intakes, you can avoid raylars extrmeely overpriced 8.1 intake.
Rylar is super expensive and I personally am doing a CNP Gen 6 454 to avoid that and still get LS tunability, but that 8.1 we did made 600 or so hp if memory serves but on a chassis dyno assuming 45% loss through the Allison and t case. Yes it was expensive, but that engine with milled and ported heads, larger ratio rockers, a ported intake and Comps largest cam that would fit plain rips the tires off on the truck it's in.
But it does cost an ungodly amount of money, as roller cams are expensive, and all of it. But now with elbows being sold and carb intakes, you can avoid raylars extrmeely overpriced 8.1 intake.
I honestly think Raylar has such a strong hold on the 8.1 market, that he is mis-leading in a lot of things he claims (cause he knows he can at this point). I do think his products are top notch, don't get me wrong there, but I think a lot of the info he puts on his website about the 8.1 is stretching the truth just to try and convince everyone that you can't touch an 8.1 without his parts. But whatever, like I said before, to each their own.
My brother and I are building an 8.1 to put into our buggy we are starting to build (mainly cause we had an extra 8.1 around, and it's different for a buggy, so why not). We are porting the intake ourselves, we will end up getting Raylar's either 202 or 203 cam, will get some head work done...and this one will most likely get a turbo (doing a rebuild now and throwing a different set of rings on the pistons to better match a turbo). We are pretty confident we can get it close to 600 hp by the time it's all said and done.
454Sub
5/8 ton status
An 8.1 will get 600 with a cam on a stock ported intake and stock milled and ported heads.
I would be 100% on the 8.1 boat if someone else offered heads for them.
I would be 100% on the 8.1 boat if someone else offered heads for them.
The big thing for us is we want it to be a dependable 600hp that we can still trail wheel if we want. We want to keep boost low, around 5psi. It obviously won't take too much to get a 496 block to 600hp, that's what's nice about starting with an 8.1...just gotta deal with some of the aftermarket limitation.
Dart makes a set of heads for them, but they are still cast and just as heavy as factory, and expensive enough that IMO the best options are to either mill/port the stock heads and deal with how heavy they are, or pay the big bucks for the aftermarket Raylar heads...I guess it just depends on what you want out of it.
454Sub
5/8 ton status
I never understood why nobody did anything with them. The cathedral port is proven with the LS design. The head size is the same as a standard 454, why nobody ever made an aluminum head for them that's reasonable is kind of shocking.
beags86
Eastbound and Down
It's not to late, you have to figure they are now really getting used for alot of swaps. Some company could recognize that and step up to the plate
