Frankenplenum

[-=Jeff=-]

Is this for the black car? if so.. wanna sell your hood?

[LGAFF]

My hood has chipping paint in the center, someone dropped the hood on something at some point, but I am keeping the stock hood

[Bob Eyres]

Originally Posted by LGAFF

What part of the plenum is rubbing?

The parts that scrape are, the ribs on the plastic intake duct, and I'm not sure what you call it but it's the sheet metal shroud around the throttle mechanism. The actual plenum does not hit.
The intake duct ribs could be swelled up a bit from stock because I have one of Mark Colplon's stainless liners inside it.

Both of these areas aren't real bad. Just enough to take the paint off, not enough to scratch the fiberglass.

[LGAFF]

Good feedback, thanks Bob!

[tpepmeie]

Originally Posted by XfireZ51

Pete used a Hogan sheetmetal plenum on Kevin's 441 several years ago. I believe it really didn't offer much improvement.

I can offer an opinion on that sheetmetal intake. I did have it flow tested, and it was 2 to 6 cfm better than my (highly) modified plenum and housings. That was with the TB and Airhorn attached, and the other ports taped.

From what I remember, Pete and Kevin said it lost a ton of torque almost all the way through the rev range, only crossing over >7000 rpm. I could be wrong on that--its been awhile.

Why? My belief is two factors. 1) the runner cross section area was pretty big. I didn't measure it, but visually, most of the runner was oval with no divider. Only like maybe an inch at the head was two separate holes. 2) the runners were exceptionally short, as they have to be for hood clearance in that style of manifold. We need runner length to catch the stronger harmonic waves for best cylinder filling. That's why I didn't go to a sheetmetal manifold on the 427. The stock runner length is pretty good for the rev range we need. Downside is that the runners have to contort to get that length without too much height, if that makes sense.

Anybody got $10k to develop a cross-over style IR manifold?



Seriously, Lee is on the right path by enlarging the plenum. We need more volume for the big motors. Especially because the TB is undersize when you get to that level. I saw over 1" of manifold vacuum @ 7000 rpm. A large plenum box would crutch that a little. Of course, a big billet oval throttle body will help too

[LGAFF]

[QUOTE=tpepmeie; a big billet oval throttle body will help too [/QUOTE]


Cobrajet is running a single blade 1640cfm TB

Also remember the LT-5 Dogbone TB; not only was it bigger, but it pushed air down the center of the plenum to better balance airflow to the rear runners.

[LGAFF]

Raised/Dropped plenum should compliment my straight through air horn

[Pete]

With the Hogan's we did loose some low end torque about 20 when you make 450 @ 3500 and you loose 15-20 you barely feel it,anyway the more low end you make the harder it is to stick it to the ground.
The low end has nothing to do with high speed runs (1/2 or 1 mile) or even 1/4 after your 60ft.

This was in an automatic and drove just fine could not notice a difference.

It did raise the power to 7k rpm from 6800 it gained 12-14RWHP.

Lingenfelter has sown that we need more plenum volume.
The work that goes into it,is not cost effective,among other issues.

It's like we went from Tune Port Intake to LT1 intake.

Pete

[SAM/CH ZR-1]

I don't think to increase the plenum volume will bring a significant benefit. The intake has to many corners and angels. That restrict the airflow. The size limited trottle body and airhorn are additional air restrictors.

With our racing team we removed on a 350 cui LT5 the plenum and installed single runners and put our eye on the correct runner volume, lenght and shape. With stock compression ratio and stock cams but fully ported heads we got around 580 crank HP at 7'500 rpms. It was our first build LT5 for the 2014 racing season. We did first steps and are satisfied with the results.

For the coming season we design new runners and cam profiles and continue our researches.

I hope to see some of you guys this May in BG.

[LGAFF]

I anticipate 15hp or so...its actually already been proven when they were developing the LT-5