Frankenplenum - ZR-1 Net Registry Forums

LGAFF · 01-05-2015

Several years ago I bought a plenum from phrogs that was missing the MAP sensor ears. I Siamesed that the Inj housings and the heads....with small intake cams(222 .415 primary/236.425 secondary) I made 441RWHP/7100RPM; that's untuned.

Since then I ported the inside of the plenum removing all of the water passages and guts(There are significant blockages to the #1 and # 2 intake ports, etc. Added a 63MM TB.....

I decided that now I am going to add volume to the plenum; I will be cutting off the roof unshrouding the runners adding an inch, and cutting the bottom off and doing the same.

I am also going to do some air intake testing.....I know people say there is nothing there, but I want to try a few ideas.

Here is where I started with the Siamese

Bearly Flying · 01-05-2015

Sounds like an interesting project, Lee.

Have fun and Good Luck.

LGAFF · 01-05-2015

The LT-5 Plenum is know to be too small.....on a manual trans car you really want at least 1X the CI of the motor, some say 1.5X. I also know that in testing larger plenums did better during engine development....approximately 55-80 additional cubic inches are needed.

A lot of people told me the plenum roof would not clear the hood, however I have 1.14inches in the front and 2" in the back. I think the issue is raising the entire plenum and not just the plenum body....the runners might hit the outside of the raised section of the hood; but the plenum box has room...I also have no AC.

I would like to have unshrouded the #7/#8 runners but the fuel rail is a challenge

Blue Flame Restorations · 01-05-2015

I like it when someone tries to do what others say they shouldn't.

efnfast · 01-06-2015

Lee, keep in mind the engine twists when you accelerate, it will lift one corner. Sounds like you'll be real tight. I like where you're headed with this. MORE POWER wuh-wuh-wuh.

Bearly Flying · 01-06-2015

A High Rise Hood would solve some of the height issues.

Be interesting to see what could be done.

Keep Us posted, and We like pictures.....

Paul Workman · 01-06-2015

Interesting project. I've been pondering something similar; thinking about using a split air box, vis a vis the Coyote's "Y" approach and straightening the runners; reducing that (90º) bend into the IH. (I believe it was Grahm (?) that said they were able to increase the 90 LT5 output to something well north of 430 chp by straightening out those runners some, IIRC. But, anyway, let's face it: GM isn't going to be coming up with anything for the LT5s. It's up to us ZR-1 loyalists to do it. And, so learning from what others are doing with the DOHC motors is a good place to take notes, I recon!

)

phrogs · 01-06-2015

Put some silly putty under the hood and see if it touches anywhere.

It might hang on long enough haha

I remember that plenum.
Pretty sure it came out of tommy morrisons stash

LGAFF · 01-07-2015

Way ahead of you phrogs, nabbed my daughters playdo and checked it...put the enture can shape on the plenum and dropped the hood. lots room

tccrab · 01-07-2015

Lee:

What about those people who put on the phenolic plenum spacers some years ago complaining about rubbing holes in the hood?
If I recall correctly, those spacers were only 1/2 inch or so, surely what you've got planned will need more room than that.

'Crabs

01-05-2015	#2
Bearly Flying Join Date: Dec 2012 Location: Ponoka, Alberta, Canada Posts: 158	Re: Frankenplenum Sounds like an interesting project, Lee. Have fun and Good Luck. __________________ 91 ZR-1 Arctic White/Gray 01 C-5 Magnetic Red/Black 85 FJ 1100 (Big Bore kit, Hooligan Bike) 05 FJR 1300 Yamaha (Long Distance, Sport Touring) And a whole whack of RC Planes

01-05-2015	#3
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,195	Re: Frankenplenum The LT-5 Plenum is know to be too small.....on a manual trans car you really want at least 1X the CI of the motor, some say 1.5X. I also know that in testing larger plenums did better during engine development....approximately 55-80 additional cubic inches are needed. A lot of people told me the plenum roof would not clear the hood, however I have 1.14inches in the front and 2" in the back. I think the issue is raising the entire plenum and not just the plenum body....the runners might hit the outside of the raised section of the hood; but the plenum box has room...I also have no AC. I would like to have unshrouded the #7/#8 runners but the fuel rail is a challenge __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 Last edited by LGAFF; 01-05-2015 at 11:43 PM.

01-05-2015	#4
Blue Flame Restorations Join Date: Feb 2010 Location: Pendleton, IN Posts: 3,909	Re: Frankenplenum I like it when someone tries to do what others say they shouldn't. __________________ 1988 KOH Prototype EX5023 sold 1990 ZR-1 #444 Convertible 1990 ZR-1 Black #966 1991 ZR-1 Quazar Blue #296 1957 Duntov SS Project

01-06-2015	#5
efnfast Join Date: Nov 2011 Location: Dunbarton NH Posts: 7,538	Re: Frankenplenum Lee, keep in mind the engine twists when you accelerate, it will lift one corner. Sounds like you'll be real tight. I like where you're headed with this. MORE POWER wuh-wuh-wuh.

01-06-2015	#6
Bearly Flying Join Date: Dec 2012 Location: Ponoka, Alberta, Canada Posts: 158	Re: Frankenplenum A High Rise Hood would solve some of the height issues. Be interesting to see what could be done. Keep Us posted, and We like pictures..... __________________ 91 ZR-1 Arctic White/Gray 01 C-5 Magnetic Red/Black 85 FJ 1100 (Big Bore kit, Hooligan Bike) 05 FJR 1300 Yamaha (Long Distance, Sport Touring) And a whole whack of RC Planes

01-05-2015	#1
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,195	Frankenplenum Several years ago I bought a plenum from phrogs that was missing the MAP sensor ears. I Siamesed that the Inj housings and the heads....with small intake cams(222 .415 primary/236.425 secondary) I made 441RWHP/7100RPM; that's untuned. Since then I ported the inside of the plenum removing all of the water passages and guts(There are significant blockages to the #1 and # 2 intake ports, etc. Added a 63MM TB..... I decided that now I am going to add volume to the plenum; I will be cutting off the roof unshrouding the runners adding an inch, and cutting the bottom off and doing the same. I am also going to do some air intake testing.....I know people say there is nothing there, but I want to try a few ideas. Here is where I started with the Siamese __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 Last edited by LGAFF; 01-05-2015 at 09:29 PM.

01-06-2015	#7
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Frankenplenum Interesting project. I've been pondering something similar; thinking about using a split air box, vis a vis the Coyote's "Y" approach and straightening the runners; reducing that (90º) bend into the IH. (I believe it was Grahm (?) that said they were able to increase the 90 LT5 output to something well north of 430 chp by straightening out those runners some, IIRC. But, anyway, let's face it: GM isn't going to be coming up with anything for the LT5s. It's up to us ZR-1 loyalists to do it. And, so learning from what others are doing with the DOHC motors is a good place to take notes, I recon!) __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry

01-06-2015	#8
phrogs Join Date: Jul 2004 Location: Kalamazoo MI Posts: 1,756	Re: Frankenplenum Put some silly putty under the hood and see if it touches anywhere. It might hang on long enough haha I remember that plenum. Pretty sure it came out of tommy morrisons stash __________________ JOHNNY P Currently own 90 ZR-1 #845 DRM 500 engine package 90 #226 Parts car Hit me up if you need anything.

01-07-2015	#9
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,195	Re: Frankenplenum Way ahead of you phrogs, nabbed my daughters playdo and checked it...put the enture can shape on the plenum and dropped the hood. lots room __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

01-07-2015	#10
tccrab Join Date: Oct 2004 Location: Folsom CA Posts: 1,657	Re: Frankenplenum Lee: What about those people who put on the phenolic plenum spacers some years ago complaining about rubbing holes in the hood? If I recall correctly, those spacers were only 1/2 inch or so, surely what you've got planned will need more room than that. 'Crabs __________________ TomC '90ZR1 #792 Honorary Pirate [B]If it ain't FUN, you're doing something terribly WRONG. [/B]

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