youout

I am going to dump my stock LS3 intake for a Fast LSXr 102mm manifold and maybe the Big Mouth Throttle body.

The engine ( LS2) has a fairly aggressive street cam ( in 2008) from Comp, LG 1 ¾ ceramic coated street headers feeding 2.5 exhaust system, reworked L92 heads – Manley SS race flow valves, hand polished ( not ported), dual springs. The heads will flow 310 CFM at .650 lift on the intake. Exhaust is at 68% of intake.

The car runs great but seems to fall off in HP above 5,800. The car makes 410 HP max at 5,800 to the wheels ( auto) so it is a ways from maxing out the duty cycle on the injectors.

I feel that I am running out of air above 5,800. To get the top end where it needs to be so I can get better quarter mile times I am considering the following

Fast LSXr 102mm only using my stock 90mm GM throttle body

Fast LSXr 102mm and a Big Mouth 102mm throttle body.

Has anyone used the intake only and then added the Big Mouth and if so what difference was there?

By using the combination will I realy see 15HP on the top end?

I am not interested in spending $500+ for the Big Mouth unless it will make a difference. In either case I have to retune and only want to do that once.

After this install I think I am done tweaking the motor. My goal was 435 HP to the wheels. This is a 6.0 NA and does not have any forged components.

C7&7

You will probably meet your horsepower goal with either but I would go with the 102. I have the 90 on mine with the fast 102 and I had velocity issues because of the inlet size difference that caused an idle stumble when I would cruise up to a stop and go to neutral.

taken19

Your numbers do seem a bit off. I am made 476 rwgp on a dynojet with CAI, stock ported TB, ported LS2 intake manifold, 1-3/4" LG street series headers, Spin's 230/234 cam, UD pulley and 11.4 CR.

The L92 heads and LS3 intake breathe much better than the LS2 setup (probably why you went there in the first place), and a FAST 102 will most likely give about 10-15 rwhp. From my research Iit appears that the stock LS3 top end will perform as well or better than ported LS2 heads and a ported LS2 intake. The bigmouth TB probably isn't necessary with your goals, but you could port your stocker for about $150.

Do you have a CAI yet? If not, that cold be part of the reason for the air shortage >5800. What is your CR with the L92 heads? I think those heads it will lower your ratio if thinner gaskets aren't used or heads milled down. If you listed the cam specs, some of the cam experts may be able to help out with potential issues. If the total combination of parts isn't matched well, it could very well give you these results.

Hope this helps.

ls3gotcha

look up v max motorsports velocity ring $50 bux .

That will fix your issue.

C7&7

I actually did buy one of these....after I got it right with tuning.

youout

i have always felt I was about 25 hP or more short from what I have seen with others mods. here is what is installed. i think my cam may be a little light but i did not put the stall in right away and looking back i should have done that to give DTE more room on the cam spec's.

RECOMMEND INSTALLING A 3200 OR 3600 STALL WHEN DOING A CAM. IT MAKES A HUGE DIFFERENCE IN HOW THE CAR DRIVES AND PERFORMES.

yes installed L92 heads for more air with hopes of getting more out of this motor / cam

VaraRam, 160 stat, LG long tubes (ceramic coated), 3.15 DTE gear set - stage 3, LS3 heads with Manley Race flo valves & Patriot gold dual springs, L76 intake, UD pulley, ported TB, catch can, Yank 3200 stall, additional transmission cooler, tuned by Speed, Inc. and RSD line lock

vara ram was the first mod and that is a great way to get air to the engine. it has had its issues as you guys know. they always took care of me and it is still not perfect but i like the idea of direct induction.

Dynojet graph is latest after installl of Yank 3200. no other mods were made at that time.

for those with the BIG mouth TB have you installed with a VR and was the fit / connection easy to get the VR in and out of the installed position?
also anyone with a 6.0 did the Fast install without any issues on the firewall?

taken19

The gears are definitely hiding about 10 rwhp and I have heard that the stall can hide 10-25 rwhp on the dyno. That may be the 25 hp you were looking for. Sorry, I missed that in your original post.

youout

i have the same and agree with you about the power train eating up the HP. what i am thinking is that i am loosing HP because i am running out of air above 5,800 rpm based on my dyno results.

looking for anyones experience with the fast 102 on a 6.0 motor with the 102 big mouth

youout

anyone have experience installing a Fast 102 intake with a Big Mouth 102mm TB on a 6.0 in a 2007.

any installation issues?

did you for sure get a return on your investment $$ for HP

FloydSummerOf68

Even with that the power seems light.

My 3200 stalled A6 LS2 makes right at 400rwhp on a dynojet SAE corrected.

That 224/230 cam should definitely be making more than 410rwhp in an LS3. Do you have any "before" numbers? The dyno could just read low.

Edit - Ok, I re-read and see that you have an LS2 car....but with an LS3 intake? How did that happen? Going to a Ported FAST is going to HUGELY help your numbers (in the neighborhood of 25rwhp) on an LS2 assuming the LS3 intake was a typo and you meant LS2 intake.

youout

it is an LS2 but has L92 ( just like LS3) heads on it so I was able to install a LS3 intake. I still have the stock TB on it. when looking at the dyno sheet it shows how HP drops off. not sure if i need to go the fast 102 or what.

i am looking for someones real experiences using a Fast 102 on a 6.0 block.

FloydSummerOf68

Something has got to be terribly wrong if you're only making 410 rwhp through that cam with LS3 heads and intake.

The LS3 intake is FAR superior to the LS2 intake.

youout

i do have the LS2 90 mm TB. could that be what is limiting HP development

FloydSummerOf68

No, the 90mm TB is not a big restriction.

youout

i think i lost a little compression when doing the head install. my guess I am about 10.90 or less. close to stock. iwas looking to get 11.25 but because of piston to valve clearence we played it safe.

Corvette6.0

does anybody know what kind of air intake you can use with the BIG mouth 102 throttle body?

timd38

I think you will find that unless your get over 1,000 HP, the stock trottle body is fine. Ha but what do I know.......