Poor man's LS1 ITB fab-up
Thread Starter
Teching In
Joined: Apr 2010
Posts: 22
Likes: 28
Poor man's LS1 ITB fab-up I've got a project I'm working on that needed an ITB set-up to be even remotely similar to the car I'm trying to emulate, but in order to finish the car up correctly, the aftermarket LS1 ITB set-ups were either too expensive, or not the correct design visually. So I started looking around for parts that I could work using "normal" garage tools to create an effective ITB set-up (could use my 48 IDA Webers, but I wanted to stay away from the hassle).
After 6 months of looking around I chose an Edelbrock Pro-Flow LS1 intake, and a bunch of Chrysler LHS 48mm throttle bodies (made by Holley...nice surprise. Anyway, I thought I'd throw some photos your way to share the work thus far. Currently I've spent about $700 for everything mechanical (what you see in these first two posts), and now trying to decide how to control this using an OEM GM ecu (if possible).
The thumbnails below are in order of the work of cutting the new intake manifold up, straightening the runners, cutting the remainder of the plenum off the runners, fabricating mounting plate (which was then cut into individual plates after welding to relieve some warping issues), and then a couple of photos of the salvage 48mm ITBs from a Chrysler LHS 3.5L motor. The neat thing about these ITBs is that they are fairly simple (from an OEM perspective) lacking in the usual garbage attached to an OEM TB. The 3.5L uses two of these (one on each side of the intake), which made the purchase even cheaper ($40 / pair).
After 6 months of looking around I chose an Edelbrock Pro-Flow LS1 intake, and a bunch of Chrysler LHS 48mm throttle bodies (made by Holley...nice surprise. Anyway, I thought I'd throw some photos your way to share the work thus far. Currently I've spent about $700 for everything mechanical (what you see in these first two posts), and now trying to decide how to control this using an OEM GM ecu (if possible).
The thumbnails below are in order of the work of cutting the new intake manifold up, straightening the runners, cutting the remainder of the plenum off the runners, fabricating mounting plate (which was then cut into individual plates after welding to relieve some warping issues), and then a couple of photos of the salvage 48mm ITBs from a Chrysler LHS 3.5L motor. The neat thing about these ITBs is that they are fairly simple (from an OEM perspective) lacking in the usual garbage attached to an OEM TB. The 3.5L uses two of these (one on each side of the intake), which made the purchase even cheaper ($40 / pair).
Last edited by blueovalz; Apr 18, 2010 at 10:43 PM.
Thread Starter
Teching In
Joined: Apr 2010
Posts: 22
Likes: 28
Remaining photos show the fabrication of the adapter plate which will transition the round ITB into a semi-rectangular runner configuration. I'm using the Chrysler OEM mounting studs because of their shoulder which indexes the ITB over their holes. The adapter plate also allows me to change to different ITB mounting patterns later (or even go back to the Webers) without re-modifying the manifold itself.
Obviously I've got a lot of trimming and detailing to do, fabricate the throttle linkage assembly, install tuning stacks (or tubes), as well as connect all the vacuum ports for each TB into a single vacuum "box" for manifold pressure readings.
Obviously I've got a lot of trimming and detailing to do, fabricate the throttle linkage assembly, install tuning stacks (or tubes), as well as connect all the vacuum ports for each TB into a single vacuum "box" for manifold pressure readings.
Last edited by blueovalz; Apr 18, 2010 at 10:52 PM.
I commend your fabrication skills and taking on a project like this, but have you looked at it from a theoretical / functional standpoint? What are you runner lengths and why did you decide on those numbers? I hate to break this to you, but those throttle bodies are honestly too small.
This thread should help you out a lot:
https://ls1tech.com/forums/advanced-...tb-thread.html
This thread should help you out a lot:
https://ls1tech.com/forums/advanced-...tb-thread.html
Thread Starter
Teching In
Joined: Apr 2010
Posts: 22
Likes: 28
Thanks for the link! Functionally, these should work fine based on observed testing using similar configurations with the GT40, etc crowd. This setup will have longer runners than any aftermarket vertical set-up I've been able to find (outside of a purely custom built), and a bit shorter than the semi-horizontal angled ones (not what I'm wanting). But regardless of runner length, the tuning stacks will provide additional needed length for my application. Four vendors (in the US, Australia, and England) all say a 48mm throttle body will easily support my power goal (somewhere between 450 and 500 HP) and said the larger ones would provide very little gain over my planned use with stock LS2 heads. so the use of a 50mm, or even a 52mm will be of little gain. Heck, If I had money to spend on the Harrop intake system, I would be buying an original M8B rather than scratch-build a poor replica of one.
In regards max HP, ITBs may not be an inefficient way to go about getting it. A small 4-barrel common plenum induction system will outflow 8 decent sized ITBs during the short single cylinder intake event at each port. But there were very few CanAm cars that ran Webers, and even with largest chokes available, they are still much more restrictive than the same "sized" TB.
In regards max HP, ITBs may not be an inefficient way to go about getting it. A small 4-barrel common plenum induction system will outflow 8 decent sized ITBs during the short single cylinder intake event at each port. But there were very few CanAm cars that ran Webers, and even with largest chokes available, they are still much more restrictive than the same "sized" TB.
Last edited by blueovalz; Apr 21, 2010 at 08:22 PM.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
TECH Enthusiast
Joined: Jul 2010
Posts: 571
Likes: 0
Rather than an OEM GM ECM, have you looked at the Mrgasquirt? It is available with sequential ignition and fuel.
http://www.msefi.com/index.php?sid=b...507b857a92b376
http://www.msefi.com/index.php?sid=b...507b857a92b376
Teching In
Joined: Sep 2006
Posts: 6
Likes: 0
Remaining photos show the fabrication of the adapter plate which will transition the round ITB into a semi-rectangular runner configuration. I'm using the Chrysler OEM mounting studs because of their shoulder which indexes the ITB over their holes. The adapter plate also allows me to change to different ITB mounting patterns later (or even go back to the Webers) without re-modifying the manifold itself.
Obviously I've got a lot of trimming and detailing to do, fabricate the throttle linkage assembly, install tuning stacks (or tubes), as well as connect all the vacuum ports for each TB into a single vacuum "box" for manifold pressure readings.
Obviously I've got a lot of trimming and detailing to do, fabricate the throttle linkage assembly, install tuning stacks (or tubes), as well as connect all the vacuum ports for each TB into a single vacuum "box" for manifold pressure readings.
blueovalz:
You are what Hot Rodding is all about!
Awesome work whether it runs great or not, you are doing it old school nd my hat is off to you.
I'm looking forward to your adventure.
Good Luck,
Ty O'Neal
I know this is an old thread but there are custom SD operating systems that work perfectly for these applications. Normal VE table that has a TPS vs RPM multiplier table that is active at all times so there is no weird transitions from SD to Alpha-N.
Thread Starter
Teching In
Joined: Apr 2010
Posts: 22
Likes: 28
Long awaited update, but still prepping. I've spent the last three years since I started this thread fabricating basically 75% of the fiberglass body and frame, suspension (using front C4 uprights), headers, rebuilding the 930 turbo transmission, and getting everything working EXCEPT for the ITBs, which went on the back burner for a while. Finally, last spring I installed a 4-v carb induction system just to work out the kinks in the oiling (dry sump with a lot of homemade parts, electrical, fuel, and cooling systems (lots of fabrication here as well). Now that that is all finished, and I've driven a few miles testing, I've re-installed the ITB set-up. I'm also installing the Holley HP EFI "self learning" ECU, and about to terminate the Un-terminated wiring harness for this system. Hopefully in a week or two, I should be getting close to bumping this off with the ITBs.
Using the 650 Holley carb (please forgive the female commentary). Click on the Youtube at lower right link if the picture is not right (or full screen mode)...not sure why this happens.
Terry
Terry
Last edited by blueovalz; Aug 19, 2013 at 09:53 PM.
Thread Starter
Teching In
Joined: Apr 2010
Posts: 22
Likes: 28
It's been a long time, but thought I'd post some final words on the project. The ITBs work great. The Holley HP EFI was tough for this "old school" boy to handle, but eventually I got everything worked out (the harness was the biggest problem). It's pretty versatile, and can handle just about any configuration you could throw at it. I'm using MAP, Coolant temp, WBO2, and TPS as inputs for control outside of the cam and crank sensors.
It's been a long time, but thought I'd post some final words on the project. The ITBs work great. The Holley HP EFI was tough for this "old school" boy to handle, but eventually I got everything worked out (the harness was the biggest problem). It's pretty versatile, and can handle just about any configuration you could throw at it. I'm using MAP, Coolant temp, WBO2, and TPS as inputs for control outside of the cam and crank sensors.
Tuning Holley HP EFI Manta Mirage M8E McLaren LS2 LS1 replica - YouTube
Tuning Holley HP EFI Manta Mirage M8E McLaren LS2 LS1 replica - YouTube