Ben@WeaponX

As some of you might recall, in early 2014 WEAPON-X set out to make a big cube 4.125 bore 427. We dropped the frame on my car with 1500 miles and got after it. The motor was sleeved with Darton sleeves, Wiseco made a custom piston to my spec, Callies Magnum crank and Ultra rods were tasked with the power, and we redid the cylinder heads with larger valves flowing a whopping 405cfm! Final compression ratio ended up at 13:1 for the healthy nitrous shot we were putting in.

The results on the OEM unported manifold were 540whp and you could really see in the logs, that the motor was choking. The 100mm carbon Halltech intake was breathing, but it choked through the 87mm ported throttlebody and the manifold. We swapped the drastically hogged out and epoxied stock ported manifold and without a single tuning change, the car laid down 570whp! We could still see the intake restriction, but short of making a sheet metal intake, there was nothing on the market, so that was that.

Fast forward a could years later when the aftermarket finally started catching up and the MSD manifold and 103mm throttlebody showed up. I was eager to get them on to see the difference.

We have two new parts to review after installation on our in-house 427ci C7 Corvette, more affectionately known as WEAPON7. With the exhaust side of the engine being pretty well sorted, we will be investigating other avenues for improvement on this engine combination. In the never ending search for more horsepower, we looked a little closer at the induction side of the engine.

Attachment 48360799

PARTS INSTALLED:

MSD Atomic Air Force LT1 Intake Manifold (IM)
Katech 103mm Gen V Throttle Body (TB)



TESTING AND RESULTS:

(MSD Atomic Air Force IM)
Testing of the MSD Atomic Air Force revealed a few things: the stock IM design flows very well up to around 5k even on a 427ci, but the the MSD Atomic walks away from the stock manifold when more airflow is required in the higher rpm range.

After retuning for the intake manifold, the 427 LT1 made an additional 35rwhp and 25ftlb of torque over 5k rpm. Horsepower and torque were very similar in the mid to low rpm range, but the IM really woke the engine up in the upper rev range. At 6800 rpm, the LT1 made 584rwhp and 482ftlb.



(Katech 103mm TB)
Next up was the 103mm TB, which took all of 15 minutes to install on the dyno. A few preliminary changes were made in the calibration to have a smooth start-up, and we were off to the races (err, dyno pulls). The larger TB did not have any driveability issues, as power delivery is still quite smooth.

Since the 103mm has a 40% larger maximum surface area, more tuning is required to really dial in the proper AFRs at WOT, but the changes were predictable and only took two pulls to hit our target. After all was said and done, the 103 netted us an additional 16rwhp and 12ftlb of torque. The increased TB area led to gains over the previous test (IM only) beginning at around 4600 rpm and climbed from there.



Attachment 48360803

CONCLUSIONS:

Our final numbers were an even 610rwhp and 510ftlb. The combined gains of the IM/TB pair were +59rwhp and +53ftlb with no decrease in torque down low. Power delivery is still silky smooth on the high revving 427 LT1, and we believe the ease of installation and tuning should make this combination an easy choice to make if searching for more streetable all-motor horsepower for your build. The next modification to be tested for this combo is to port-match the intake manifold runners to the heads. There could potentially be turbulence in the system at this point, and an increase in air velocity will probably lead to more power. We will keep you posted.

For custom builds, parts, short blocks, etc give us a call at 513-662-4000 today!

robert miller

Would a diff cam make a diff's on the RWTQ numbers. But as a N/A motor love the rwhp #. Robert

123sugey

I think we are on the same page... Torque is looking pretty low. I'm supercharged now and after the fact wish I went NA like my original plan... With a shot of nitrous more than likely. But, IMO a NA 427 should have a little more grunt on the torque side. Definitely a cam change could add gobs of torque. Just wondering why a lot more HP at expense of torque.

Katech_Zach

What did it make on the engine dyno?

We made 709.

marcouvo

The torque curve and peak torque is what I look for in a street car, not peak HP. A stroker should produce plenty.

Bucknut2006

So maybe not the most powerful?

pgviper

On track car... peak hp is what I would be looking for.

Really looking at this as on option for those looking to make a NA track car...

2017 GS + 427 = What many wish the z06 would have been

DP RS

Ben@WeaponX

Both of you are correct, this cam was designed for a big nitrous shot, the focus wasn't on the torque since the stall is a 3400 and I have plenty of power coming in on top of that.

Engine dyno doesn't mean much to me. I've got a Mustang Dyno Jason, even with a lowly 15% drivetrain loss it's 720. If you want to bring a car on down to dyno and/or line them up, let me know.

Let me know, we can do it. I have plenty of cams spec'ed from blower/nitrous cars to NA cars.

Katech_Zach

I believe world record claims should be reserved for controlled engine dyno tests.

robert miller

BEN, had to be a reason for it with the cam not doing no more on the tq #. But good rwhp # on a mustang dyno for sure.

Has to be one nice ride in it coming on like it does from the chart.. Plus being 13.1 on comp.

Ben@WeaponX

And I don't really care what your engine dyno says. We don't bench race cars on engine dynos. This is real world - my motor, my car, and my dyno results. If you'd like to challenge it, that's fine, door is open.

Thanks it was already the fastest on the C7 list for N/A and that pass wasn't even that great. I just went back on bottle Friday night and ran 9.7 at 142

Elite275

The pass was solid too. I was supposed to video it for him but my phone died! He only got two passes in before getting the boot, but the car was flying down the track.

Katech_Zach

We don't bench race either. We race at places like Le Mans, Sebring, and Daytona. We use the engine dyno to quantify power scientifically while controlling as many variables as possible. If you want to send me your engine I'll dyno test it for free for you.

Ben@WeaponX

You seem to have the issue here, what's easier bringing a car down or taking out a motor to prove you wrong? If you have a car, send it on down. Otherwise, the claim on a MUSTANG dyno stands.

Liter of cola

hey sooo... i kno you guys are like in the mine is bigger debate atm... but i wanted to ask, what do you guys do for wheel hop? is changeing out the control arm bushings for some delrin pieces good enough?

Ben@WeaponX

yea I hear ya

If you're having wheel hop, I'm guessing it's on the stiff sidewall OEM tires? There are some settings in the tune that you can use to help control this electronically, but I don't have wheel hop issues on my setup. The 355 Pirellis will break loose and the 345 Mickeys hook and roll out. I've cut 1.3s on the drag wheel setup. If you need a wheel setup, let me know!

Liter of cola

had no idea it could be the tires... wish they had non run flat Michelins in our size


could the bushings make the run flats stop hopping?

Ben@WeaponX

Not sure there, LG has rear bushings for like a grand that I was considering for drag racing but you'd have to ask them if it would help your issue as well.

Liter of cola

Yo ben... im lookin for a 376, LT1 or grand sport badge so i can put a z06 fender vent on my grand sport. I see you guys have a 427 badge. Who made that for you guys?