AJ126 Rebuild Thread – From Overheat Failure to 500–600HP Build (Looking for Guidance

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Today | 01:08 PM

#41

cpthetech

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Junior Member

Joined: Mar 2026

Posts: 25

Likes: 1

From: Las Vegas, NV

Quote:

Originally Posted by clubairth1

Wow a massive project!
One small comment? The lower pulley gets bigger in diameter and the upper pulley gets smaller in diameter to get you more boost. I use VAP but there are other tuners out there.

Have you considered a bigger IC?
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Thanks man, and good correction on the pulley wording. You’re right — lower pulley gets larger, upper pulley gets smaller. I should’ve worded that clearer.

I’ve looked into VAP a little bit and they seem to be one of the main names for this platform. I’m still trying to keep the build somewhat balanced and reliable, but since the engine is out and apart, this is definitely the time to make decisions on pulleys, cooling, and supporting mods.

As far as a bigger IC/heat exchanger, yes, that’s high on my list. Being in Vegas, I’m more concerned with IAT control and heat soak than chasing a dyno number. Cooling has been one of my biggest focuses on this build because these cars already seem borderline in hot climates when driven hard.

Today | 01:10 PM

#42

cpthetech

Thread Starter

Junior Member

Joined: Mar 2026

Posts: 25

Likes: 1

From: Las Vegas, NV

Quote:

Originally Posted by OldGuy1

Adding to the pulley bit and stating the obvious, if you are planning some performance upgrades, now is the time for pulleys! LOL.

As an FYI, I also had my SC ported by VAP (Jokerz is their partner for the porting) and am VERY happy with the power. From a VAP perspective, you are looking at about 450 BHP for the bottom pulley, 475 BHP for both pulleys and 550 BP if you also have it ported. The improvement from my original 340 BHP to the bottom pulley 450 was dramatic and a good midpoint. Unless you want to hunt BMWs, LOL

I am sure other folks have similar packages...

Last comment, I believe you are building the definitive AJ126 rebuild thread! Well done!

Appreciate that, and that’s exactly the kind of real-world info I was looking for.

I’ve been debating the pulley setup because I want the car to wake up, but I don’t want to build something that becomes heat-soaked or unreliable right away. The numbers you listed make sense: bottom pulley alone being around that 450 BHP range sounds like a really good midpoint, especially for a street car in Vegas heat.

The ported supercharger is what really caught my attention. Since mine is already off the car, I’ve been considering having the machine shop or a specialist handle the porting while everything is apart. I didn’t know VAP used Jokerz for that, so that’s good info. 550 BHP with both pulleys and a ported blower sounds strong, but I’d want to make sure cooling, fuel, and tuning are all matched correctly before pushing it that far.

For now, I’m leaning toward a pulley/tune setup with upgraded cooling, no E85, and keeping the build as reliable as I can. But I agree — now is the time to do the pulleys if I’m going to do them.

And I really appreciate the comment about the thread. That’s honestly what I’m trying to do: document the AJ126 rebuild as thoroughly as possible because this platform has very little clear information compared to other engines. Even JLR answers seem to vary depending on who you ask.