Realistic Gains on a 2013 GT swapping from 2018 intake to Cobra Jet intake?

[palsmith]

I have a 2013 Brembo GT manual that I have driven and tracked since new. In 2021 I had a timing chain get loose and hurt motor while running at Barber (car had over 100,000 miles and several hundred road course laps). Installed a Frankenstein 3-2-1 long block that included L&M Gen 1 intake / exhaust cams and 2018 intake. I have stock exhaust manifolds and now have GT500 mufflers. Car made 426 rwhp @ 6900 rpm on a conservative tune at Palm Beach Dyno (and made 441 @7150 on E85) with stock GT mufflers. I recently bought a first generation Cobra Jet intake and was planning on getting a JLT intake and VMP twin 69mm throttle body. What is a realistic expectation for horsepower gains and potential torque loss?

 

[Mad Hatter]

To make it worth while you would probably need to have the Cobrajet ported. The castings are truly terrible with lots of rough edges and big gaps compared to the 2018 manifold. A 2018 will probably be slightly better the a unported stock Cobrajet, but check yours to see what it looks like.

Without getting headers, you would limit you power output somewhat as the engine has to breath.. Have to let those big 67mm TBs do their thing! With the 3-2-1 block, headers and the cobrajet setup and the rest of the bolt-ons you have, you could get to 500rwhp. At least that's what several of us have reached with 98 or E85 fuel.

In my case, I could not get gen2 heads for my Boss, so installed Livernois ported heads with the same valve's as the gen 2 etc. Non Boss Gen 1 heads suck.

Edit: Remember the Cobrajet makes great power to 8000rpm and beyond, if you dont plan on going that high maybe the 2018 manifold its a better option. High RPM wins races, but also kills all kinds of things (trannies, for example.)

 

[Wolf]

I know someone who just did this with their boss, 3-2-1 coyote with L&M intake and boss 302r exhaust cams, ported CJ intake and shorty headers (with cats)
Made 474 whp with a lund 91 tune
Definitely something I’d like to do down the road, I’m sure E85 would be right around 500 whp

 

[Mad Hatter]

Not to be too critical. But having the gen 3 block with its 12 to 1 compression is not going to be to happy with 91 octane fuel with a gen 2 head etc.. Am pretty sure a tuner like Shaun at AED would not tune the car for 91. A trip to the track on 91 could be very damaging!

 

[palsmith]

Not to be too critical. But having the gen 3 block with its 12 to 1 compression is not going to be to happy with 91 octane fuel with a gen 2 head etc.. Am pretty sure a tuner like Shaun at AED would not tune the car for 91. A trip to the track on 91 could be very damaging!

Run 93 and its does have conservative timing as a result. Also have an E85 tune as shown in dyno.

 

[2012Boss302]

Are you using Direct Injection or just port injection??

 

[Fabman]

 

[Fabman]

 

[Mad Hatter]

With both of these videos, the missing point is that the 2018+ manifolds are a production part while the Cobrajet is not. For me the Cobrajet HAS to be ported. It so full of badly matching joins and rough edges inside that it can't really flow well out of the box. Where as the 2018+ manifold looks much better inside. If a ported 2018 is as good as a stock Cobrajet, then I would bet that a ported Cobrajet is the winner overall.... And easier to setup on a gen1 or 2.

 

[Fabman]

With both of these videos, the missing point is that the 2018+ manifolds are a production part while the Cobrajet is not. For me the Cobrajet HAS to be ported. It so full of badly matching joins and rough edges inside that it can't really flow well out of the box. Where as the 2018+ manifold looks much better inside. If a ported 2018 is as good as a stock Cobrajet, then I would bet that a ported Cobrajet is the winner overall.... And easier to setup on a gen1 or 2.

Ported CJ all the way....

 

[noldevin]

Ported cj is going to be better all around than a 2018, especially on an s197 where it can't make use of the charge motion plates. They have similar peak power but that's where the equality ends. The CJ has a MUCH bigger power band and your improved engine should benefit from it. However, it lives for 7k+ rpm and that's going to present big challenges to take advantage of it fully and reliably on a road course. Also no aftermarket manifold really shines until you have headers to help the extra air get out.

 

[Fabman]

My CJ new vs. Ported.....Big difference.
I find with both my stock gen 2 w/intake only cams and then my gen 3-2 with intake only cams and CNC heads I get a nice wide powerband.
Makes 507 wheel and Grunts way down low and pulls past 8200. Pretty happy with the combination. I just wish they made a 7 liter Coyote....wouldn't that be something?

 

[Mad Hatter]

Headers are a must thats for sure. A cheap choice for headers is to buy a no name brand Long tube from ebay for US$250 and hack the end off and then add a decent racing collector. Costs a fraction of a Kooks and, at least for me, gave me better numbers.