WEAPON-X: LT4 Pulley Mod Guide
 

With modding responsibly, knowledge is power and we're only as good as the what we share. So, below is an LT4 pulley combo chart for you guys to peruse for some general info. We've done an insane amount of these across all platforms and our LSA chart helped a lot of people over the years, so I put this together a couple of weeks ago too:

https://weaponxmotorsports.com/blogs...ng-mods-needed

This will help you guys when you're planning/modding to help you figure out what you need at what levels. Granted all of this depends on a wide variety of things from plans of use for the car like street, strip, and/or track to where you are, ie temps, atmosphere, climate changes etc. Less air restriction such as free flowing intake, headers, exhaust, porting etc all drastically help reduce heat by increasing the ease of the blower and airflow in and out of the engine. Your cam profile will also affect the air movement!

Keep in mind, this is not an end all be all, as a lot of factors come into play and the recommendation in each cell is to be considered at a minimum, so if you upgraded something that might say OEM or No, it's OK as long as you're on the side of over modding and not under modding, as it can still help, but I'm just trying to make sure you guys are getting the most out of your upgrades and not running on the ragged edge of fueling, which will lead to detonation and potential piston ring failures, or worse. preventative heat mods such as heat exchangers, tanks, pumps etc can't be done too early really. Stock C7 Z06s, ZL1s, and CTS V's pull timing on pull 2 and pull 3 on the dyno due to increased heat. Even stock LT4 powered vehicles can benefit from some of these mods, but they really become a necessity as you push the blower. Even as you add more blower RPM, you have to add other parts to reduce restrictions and protect your motor. So, feel free to get a hold of us and we'll help point you in the right direction for your planned end game.

You can see the effective blower ratio in the 1st column, the % of increase over stock in the 2nd column, the RPM of the blower vs. the engine RPM in the 3rd column, the upper pulley choice in the 4th, lower pulley in the 5th, the car model as not all are available, whether the snout needs milled to clear the smaller upper pulley in column 6, whether the cats need omitted in column 7, and the estimated boost with proper mods in column 8.

Scrolling down to the next section, columns 1-3 are the blower ratio (lower divided by upper pulley) plus the percent increase, and blower RPM at 6,700 engine RPM, column 4 shows if the factory fuel system can support this on pump gas (not E85), if a higher octane is needed in column 5, if you need to do one of our heat exchanger upgrades in column 6, heat exchanger pump upgrade in column 7, and lastly a heat exchanger tank in column 8.

Questions or to put in a custom order, call 513-662-4000 or email sales@weapon-x.com

The upper pulley we can go all the way to a 15% increase aka 2.175", but the snout needs machined with anything less than a 9% aka 2.3" upper. We offer the snout machining, porting, and pressing a pulley on and can ship back. Our Griptec pulleys eliminate the static slip that occurs when the crank taxes the upper pulley, so "the lower is always better" thought process is gone.

https://weaponxmotorsports.com/produ...-zl1-gen-6-lt4

https://cdn.shopify.com/s/files/1/01...?1519666071591

Doing the lower, you can actually go up much further with over-driving the supercharger, but anything over a 15% really needs headers anyway to get rid of the restrictive cats which hold in heat. You can run up to a 25% lower with heads/cam/headers etc for that high 700whp range though.

IW lower kit goes up to 31% lower:
https://weaponxmotorsports.com/produ...-zl1-gen-6-lt4


ATI lower kit goes up to a 25% lower:
https://weaponxmotorsports.com/produ...ts-v-gen-3-lt4


Belt choices for various combos:
https://weaponxmotorsports.com/produ...ts-v-gen-3-lt4


http://i10.photobucket.com/albums/a1...pshmqcorc8.jpg

Links to the lower kits aren't working

This needs to be a sticky. Make it happen Mods/Admins!

This is the fixed link:

https://weaponxmotorsports.com/blogs...ng-mods-needed

Question for Weapon X: If the cats are the problem, then do you have to do headers or can you just remove/gut the cats?

Thanks for sharing, since I was under the false assumption that full exhaust and headers was a bad investment $/hp for less than 20 hp at $3000-4000.

Headers/cats are frequently spouted to be a poor choice of mods for the money. But people don't know the physics behind it I guess. Sure they don't gain 50+ RWHP like a pulley can. But put that pulley on and see how long before exhaust isn't coming out of one side because the cats are melted and plugged, if you don't catch it, you'll be ordering a new engine. Or have heat damage at the least.

An Intake + Pulley setup can be run but only with a mild pulley. If you're going above 9%, headers/no cats are a must. Don't go high flows either, they'll fail if you push your car frequently.

thanks, serves me right for rushing through and copy/pasting from the other thread where I started this lol

;)

You CAN gut the cats at lower power levels; however, you have the mains and rears and the ballooning will slow the air down and then increase the velocity after it's cooled slightly, so this does work to omit the restriction and prevent them from melting (do a couple pulls with a 9% on the dyno back to back and you'll smell 'em cookin'! ;)), but this will still not achieve what long tube headers can. I need to grab a pic of my stock ones, unlike the LT4 Z06 which has large oval manifolds after the merge, the LT4 wet sump gets a 2.5" outlet and it is really restrictive there, especially right after the merge! You guys get the idea:

http://i10.photobucket.com/albums/a1...psxmdhsxyb.jpg

http://i10.photobucket.com/albums/a1...pswhhcl9xj.jpg

I deleted my cats when we did my ported blower, stage 2 intake, and 103mm tb and I made 660whp on E85 running the stock pulley combo; however, headers still would've really picked up more. This was just testing before we started the rear mount turbo.



:clap2:

Header company's cats have always notoriously been bad for boost. We've had to cut them out over and over as they start to push out. It's not necessarily a fault of the header guys, but with the price of headers, not too many want to spend the money on the $900 GESI quality high flow cats. Kooks Green cats are the ONLY header cats I would run. We cut the GESI's in on the big power cars here that want cats. We've cut them into 750whp Escalades and CTS V3s thus far and did a back to back dyno and didn't skip a beat!

https://maxmax.com/Old_Web/images/Ca...rCollector.jpg

I wish there was a way to pass my state inspection with headers. Once they plug into the OBD port and the readiness systems aren't green you fail. No inspection for two years and they won't allow you to renew the vehicle registration :thumbdown:

I just Did Kooks LT 1 7/8” with HF cats and 3” back to NPP and gained 40Hp to real wheels...
555 bone stock, now with headers and rotofab 595.xx was almost 597 but tuner backed it down to get the torque up a little 633.xxTQ

Why do you think GM went with doing the upper vs lower for the Drag ZL1? Of course they don't mention any belt slip, or at least i haven't heard of any by GM.

Thanks for reinforcing my beliefs. I’d always heard great things about the GESI cats, which is why I went for them from Kooks this time around. Sure, they’re more money, but I don’t like fully catless street cars. Having something to take the edge off the exhaust note and odor is a good thing around here. Don’t want to attract the wrong kind of attention here on the west coast.

All my monitors are up, so you shouldn’t have a problem on the OBD portion. I even have the catalyst test turned off, and it still sets that monitor.

Ben, I called to speak with someone this week, but I imagine you guys a relly busy. Given that I am in cali, don't want to go e85, flex fuel, or meth, and want to run 91 octane, Looks like the safest thing would be for me to stay at 15% lower pulley + stock upper, with headers, and I should be good.

Sorry wrapping up that Forgeline giveaway tax return sales campaign, it's been nuts the last couple weeks and the guys have been on the phone non-stop.

Yes our intake
ATI 15% or IW/9.1" lower or a 2.175" upper
Kooks w green cats so they don't smell you comin' :bellyroll:

My gains were 40rwhp 33tq with 1 7/8” Kooks HF Cats and Stock NPP and RotoFab. Tuner got a little more but since E85 and lower pully change are coming we didn’t stress getting more at this stage. I’m hoping to get the pulley kit and get everything installed this month.