A customer of mine sent his dyno results from his 406 buildup with good results. 472HP @ 6000rpm and 449FtLbs TQ at 4460rpm. I am just passing on information.

http://www.lt1intake.com/dyno_Bill.htm

 

John, what precisely (other than porting) did he have to do to the LT1 intake to make it match the 1206?

I love the TQ graph. It looks like he was a touch rich on the lower rpm, which would account for that slight dip. Had he worked a little more on the lower RPM side, that TQ curve would be even flatter. But still a fairly flat torque curve. Pity he didn't get the dyno to run at a lower RPM to show that the TQ curve is still fairly flat all the way down to 2000 rpm.

 

I am always amazed at the low end torque of these fine little short runner intakes. Had similar results with a MiniRam on a 408 with a much smaller cam (210/210 @ .050 flat tappet hydraulic). Pegged peak torque at 2700 which was as low as the dyno could hold it. Around 470 ft/lbs, if memory serves. Maxed out around 415 HP at 5500 but that was "as installed" in the car with full exhaust, all accessories, street air cleaner setup, etc.

That was my first build up using a short-runner intake similar to the LT-1 and I really was just "guessing" mostly at the combo. I figured since it was a daily driver (stock stall, highway gears) and I wanted plenty of low-end grunt I would shove in a that little cam. In order to help prop up the bottom end torque which I THOUGHT would be kinda lacking.

I shouldn't have worried so much. WAY too much low end torque to use on street tires. I don't know how or why short runners don't seem to hurt the low end torque much, but they really aren't anything to worry about, in my limited experience.

With some traction the torque was usable (sorta). If you could get it to hook it would hit from a 20 MPH roll with the brutality of a rear-end collision. We later put in a bigger cam and traded off a little bottom end for some top end pull. Plenty, in fact, to suck the headlights out of a ZR-1 Corvette from a 70 MPH highway roll to whenever you felt like letting off. That was a FUN engine.

If I had it to do over again I would definitely get one of your converted LT-1 intakes over the MiniRam. The MiniRam is a VERY nice intake but it's wicked expensive for what it is.

 

I asked Bill that exact question. Here's his reply.

"No welding, lots of grinding, and very thin runner dividers. Actually, they're NOT QUITE to a 1206, but larger than a 1205."


He in turn sent a picture of the mated intake and heads. You can see it is matched pretty well looking through his mirror.

 

You ever look at the cylinder PW adjustments in tunercat for the LT1 stuff?

I've been saying forever (along with other folks) that the LT1 has uneven air distribution problems, yet select folks dissagree. Recently, I got a chance to checkout tunercat on an LT1 and the stock settings. It was interesting to see that both GM agrees, and how much GM changed some of the cyls.

If you havn't seen it, I'll try to post a screenshot.

I say this because, before I built my singleplane I had considered the LT1 conversion. But then I started talking to people who did it, including folks with forced induction, and the problems they encountered.

I always found it odd that people with LT1 cars don't complain about this, until I got a chance to see the stock tune. Now it all makes perfect sense.

-- Joe

 

Joe, haven't played with the LT1 stuff much, but I am aware of the "uneven" air distribution feedback ESPECIALLY on a blower application. I believe that is why there is the ability to "trim" individual injectors to compensate for this. I agree, if I was going forced induction, I too would lean to a single plane manifold and convert it to EFI.

Of course, a person could also look at using a VIC if they are using an older 3rd Gen ECM.

 

Damon, this is something I have been trying to say to people for a LONG TIME. A person's choice of cam (and cubic inches) is also an important part of the equation. With a Miniram, you can run a smaller cam to compensate for TQ and still have your top end power.

I personally would rather have a "broad range" short runner intake that makes a flat torque line and use a smaller cam than use a bigger cam to compensate for an intake's inability to flow at the top end (i.e. a big cam with a TPI intake). The latter starts getting into compromises that affects a lot of other things such as fuel economy and driveability.

 

The cylinder trim is a nice feature though, regardless of intake. Sorta wish we could do that with a '730/'749 to make up for a lazy injector/whatever.

--- Joe

 

That is why I mentioned using a VIC (Variable Injector Controller). No intake is perfect and there will always be a slight imbalance. It is something I am seriously looking at for a buddy who also has a Miniram making big HP.

 

That is a nice match. At first that mirror threw me. I was thinking "Round? Since when do SBCs have round ports?" Then I realized it was mirror looking inside.

John, have you experimented with porting inside the LT1 intakes to smoothen out the ports? This is something I am thinking about doing with my Miniram, as well as possibly having it coated.

 

I did the exact same thing when I first viewed the pic.

 

Glad it wasn't only me.

 

<--- same.
I too like a flat torque curve and in with a v8 why would anybody be "lacking" any low end torque, lol. You'd have to seriously try to get rid of a v8's "low end".
As for the cam being the low end and the intake being the high end, that's exactly how you SHOULD build a street motor. I've seen some guys try and do this with race engines and it doesn't work. In a race motor everything is tuned for a specific RPM range usually dependant on the gearing, this is where you balance the cam and intake together to get the most in your range.
One question I have about the distribution problems.... why the small plenum . Just make it bigger so the average velocity in the plenum is lower. This will result in much better distribution and more power, trust me and a few others that have done it. It works on paper and in real life .

 

I probably would have done the same "WTF? Duh!" at first glance, but I cheated. I've done the mirror trick before, so it didn't appear unusual to me.

 

I have a MiniRam intake on my 406 and have the same issues with uneven air distribution. I've thought about placing a divider in the plenum to direct air to the #5,6,7 and 8 cylinders. Just recently I began to wonder if a monoblade throttle body would help this situation by allowing more air to enter the plenum at the center?

Just a thought.

www.geocities.com/dzperf