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Gwatney/Rick Crawford radius rod intakes or Fast 102
Trying to decide which way to go as I've heard mixed reviews about the gains of the LS3 version of the Fast 102. I have the Tick stage 2 cam 229/244 with stock heads and intake at the moment. Looking to upgrade both heads and intake. Any real world data or tests about either of these intakes would be greatly appreciated. Maybe Tony Mamo can chime in with some info about the Fast
Notice the Rick Crawford is within 5-8 cfm of the Ported Fast LSXR LS3. An unported Fast might flow the same or less than the Rick Crawford intake. I don't know, I haven't tested an unported LSXR LS3.
In theory, all times equal 5-8 cfm would be 10 to 15hp. However, it's not equal. The Fast uses a bigger runner to get the extra few cfm so velocity is less and that's important as Rick said in another thread. It's very possible the two intakes are within a few hp of each other. However, the higher velocity Rick Crawford will drive better. The Crawford with the 92mm throttle body will also be less hassle to tune for good driveability on an older cable throttle body car than a 102 TB.
Many people will ignore the velocity issue and go big. I did that on the cathedral set up on my 383 LS1 91RS. The RS had a Fast LSXRT intake and 102 mm TB. For my moderate rpm LS1 383, it turned out based on dyno testing a ported LS6 intake with a 90mm snout made better hp & tq than the LSXRT. The Fast LSXRT intake has been collecting dust on the shelf for almost two years
Dyno and or track testing for the specific combo of parts is probably needed to determine for sure which is better.
If your motor is under 400 cubes, I would try the Crawford before the Fast.
Hell, I may still put a Crawford on my new 416 if the Fast LS3 LSXR is as disappointing as the LSXRT proved on my RS.
I know dollar for dollar the radius modded intake will be cheaper but I'm not gonna let the price difference of the Fast make my decision. When I do heads I just don't want the intake to be my restriction even if that means paying big money for a fast. I've seen nothing but good results for the radius rodded intakes but reviews of the Fast are all over the place that's why I was hoping someone that has used the LS3 Fast could share their results if possible
I agree with you in that if you need something more than a stock LS3 manifold, you need enough to satisfy the particular engine setup you have.
MY thinking is for the guy with a bit more cam and maybe a mild port job on the heads, the rod mod would be the icing on the cake for a well-rounded(AND STEALTHY!) setup that could be worth around 500+ FWHP. A case where the "little mods" add up.
I agree with you in that if you need something more than a stock LS3 manifold, you need enough to satisfy the particular engine setup you have.
MY thinking is for the guy with a bit more cam and maybe a mild port job on the heads, the rod mod would be the icing on the cake for a well-rounded(AND STEALTHY!) setup that could be worth around 500+ FWHP. A case where the "little mods" add up.
that is true. I'm just indecisive on what heads to go with. Car is just a cammed LS3 with full bolt ons right now. I just don't want to give up low end torque. The fasts seem to shine up top on peak power but on the street your really not there that much which is why I'm leaning to a Crawford intake
Agreed. Bigger engines &/or those winding up pretty high still need the FAST. The rod mod just extends the capabilities of the LS3 enough for those who might be sitting on the fence about needing a FAST, or whatever.
I prefer the FAST for NA setups because I don't like having epoxy and metal pieces inside my intake manifold. As years go by heat cycles cause things to come loose. We've seen a few of the modified stock intakes that don't look that great after a few years. We've seen good results with the FAST both in mid range torque and top end power. Over 6500RPM the larger plenum and runners of the FAST seem to really shine, at 7000 on even a basic head/cam can be +40 over a stock manifold.
The downside to the FAST is on boosted cars, for them I prefer a cast or stock intake as we've seen the FAST flex a lot. Even on a NA 416 the FAST flexes a little but we haven't seen any damage at that power level.
09-18-2017, 02:37 PM
Gwatney/Rick Crawford radius rod intakes or Fast 102 
