bastarddsm
20+ Year Contributor
- 5,761
- 1,690
- Aug 26, 2003
-
Mendota,
Illinois
Last fall I went through the trouble to modify an EvoIII intake to work on a 6 bolt head, as well as de-tabbed it and made provisions for dual fuel rails. I have been running staged injection on my car since mid 2011 on an intake I made from part of a stock 6 bolt intake. I've long suspected that it has been holding back performance of my car, although it did run 141mph at the shootout, so it can't be terrible.
Anyway, here is the beginning of this project. I've cut many tabs off, and began fitting up the secondary fuel rail. The second fuel rail mounts to the primary rail, via some bungs I welded on. These are the rails I used on my previous manifold. It's clear to see that this is not going to work as the fuel rail will interfere with the TPS.
Here is another view without the rails to see the de-tabbing work. Compare that to a pic of a stock EvoIII intake, yes lots of work. I have about 8hrs in this. I used a combination of a mill, sawzall, and cut off wheel to knock most of the tab off, then used a flap disc to get it closer, and finally hand filed it to match the adjacent contours. They came out really well. I even welded up some spots and re-filed just to make it nicer.
After lots of thinking and deliberation I decided I will move the secondary fuel rail in closer to the primary, and rotate the throttle body to get TPS clearance. I lost most of these pictures in a tragic phone death. I used the lathe and some 1" 6061 stock to machine a set of new secondary injector bungs.
I cut them to fit, drilled holes in the intake, and began tacking them on.
Once they were all tacked I began fully welding them.
A used intake is really dirty, and does not weld great. I use an ancient transformer based machine I built out of an old Forney are welder, and a Sears arc starter. It works good but it is not as nice as the modern square wave machines.
I then used a carbide burr and a tootsie roll to smooth them in.
Now that the Injector bosses are on I started addressing the throttle body rotation. You can see in the above picture I have cut off the throttle body flange. If you have had a EvoIII intake you know that the port for the brake booster comes out right by the throttle body and is at the wrong end of the intake for a dsm. I addressed this here but cutting it of, welding up the hole, and smoothing it like it was never there. I then tacked the flange back on at an angle to give me TPS clearance. I don't have the picture but this was mocked up on the car with the fuel lines (stock), throttle cable, and UICP.
Once the throttle body flange was welded on I needed to add ports for vacuum lines. I machined and welded on three bungs for boost gauge, MAP sensor, and Brake Booster. The FPR and BOV take their vaccum off the source that was used for PCV. I smoothed out the welds on these like I did with the injector bungs.
The EvoIII intake has several obstructions in the plenum, some of them deep down in there. I made a long shank burr with some plumbing fittings. Sketchy, but it works. The entire plenum was smoothed up.
Finally, we have the finished intake, all tabs and bumps removed, welds smoothed, and ready for paint.
And now with a coat of VHT wrinkle black on it, and then installed on the car.
I chose to go this route in an attempt to gain some low end, while improving flow over my previous manifold. Not shown is how I built up the flange with weld to allow it to seal on a 6 bolt head. Yes I know the 6 bolt port is much bigger, I did some research on this, and this type of port mismatch often occurs on big block chevys. It is generally believed that a mismatch on the port floor won't hurt much. I was hoping it would help encourage a tumble flow out of the ports, and promote efficient combustion. Not sure if it helped or not, it did help low rpm torque a bunch, and improved spool about 500rpm over my old manifold. As for the dual rail setup, I originally did that for $$ reasons, as a set of 750's and a set of 450's were all I thought I would ever need, and cheaper than buying a new set of 1200's. The ecu has no trouble running both sets without a driver box. Later on I was able to score a second set of 750's and that has gotten me to 140mph traps with $300 spent on injectors, and with way better idle quality than the bosch 1600's everyone was running when I did this. Now days we have the 2150's and the new 1600's, however they are not without flaws, and I think this is still a better solution. I just scored 2 sets of ball/disc 1200's for $300. They have great manners, and do not have the rusting issues that the 2150's have.
I hope everyone enjoys seeing this unusual mod that I have done, and what it takes to get this done.
Anyway, here is the beginning of this project. I've cut many tabs off, and began fitting up the secondary fuel rail. The second fuel rail mounts to the primary rail, via some bungs I welded on. These are the rails I used on my previous manifold. It's clear to see that this is not going to work as the fuel rail will interfere with the TPS.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Here is another view without the rails to see the de-tabbing work. Compare that to a pic of a stock EvoIII intake, yes lots of work. I have about 8hrs in this. I used a combination of a mill, sawzall, and cut off wheel to knock most of the tab off, then used a flap disc to get it closer, and finally hand filed it to match the adjacent contours. They came out really well. I even welded up some spots and re-filed just to make it nicer.
You must be logged in to view this image or video.
After lots of thinking and deliberation I decided I will move the secondary fuel rail in closer to the primary, and rotate the throttle body to get TPS clearance. I lost most of these pictures in a tragic phone death. I used the lathe and some 1" 6061 stock to machine a set of new secondary injector bungs.
You must be logged in to view this image or video.
I cut them to fit, drilled holes in the intake, and began tacking them on.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Once they were all tacked I began fully welding them.
You must be logged in to view this image or video.
A used intake is really dirty, and does not weld great. I use an ancient transformer based machine I built out of an old Forney are welder, and a Sears arc starter. It works good but it is not as nice as the modern square wave machines.
You must be logged in to view this image or video.
I then used a carbide burr and a tootsie roll to smooth them in.
You must be logged in to view this image or video.
Now that the Injector bosses are on I started addressing the throttle body rotation. You can see in the above picture I have cut off the throttle body flange. If you have had a EvoIII intake you know that the port for the brake booster comes out right by the throttle body and is at the wrong end of the intake for a dsm. I addressed this here but cutting it of, welding up the hole, and smoothing it like it was never there. I then tacked the flange back on at an angle to give me TPS clearance. I don't have the picture but this was mocked up on the car with the fuel lines (stock), throttle cable, and UICP.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Once the throttle body flange was welded on I needed to add ports for vacuum lines. I machined and welded on three bungs for boost gauge, MAP sensor, and Brake Booster. The FPR and BOV take their vaccum off the source that was used for PCV. I smoothed out the welds on these like I did with the injector bungs.
You must be logged in to view this image or video.
The EvoIII intake has several obstructions in the plenum, some of them deep down in there. I made a long shank burr with some plumbing fittings. Sketchy, but it works. The entire plenum was smoothed up.
You must be logged in to view this image or video.
Finally, we have the finished intake, all tabs and bumps removed, welds smoothed, and ready for paint.
You must be logged in to view this image or video.
And now with a coat of VHT wrinkle black on it, and then installed on the car.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
I chose to go this route in an attempt to gain some low end, while improving flow over my previous manifold. Not shown is how I built up the flange with weld to allow it to seal on a 6 bolt head. Yes I know the 6 bolt port is much bigger, I did some research on this, and this type of port mismatch often occurs on big block chevys. It is generally believed that a mismatch on the port floor won't hurt much. I was hoping it would help encourage a tumble flow out of the ports, and promote efficient combustion. Not sure if it helped or not, it did help low rpm torque a bunch, and improved spool about 500rpm over my old manifold. As for the dual rail setup, I originally did that for $$ reasons, as a set of 750's and a set of 450's were all I thought I would ever need, and cheaper than buying a new set of 1200's. The ecu has no trouble running both sets without a driver box. Later on I was able to score a second set of 750's and that has gotten me to 140mph traps with $300 spent on injectors, and with way better idle quality than the bosch 1600's everyone was running when I did this. Now days we have the 2150's and the new 1600's, however they are not without flaws, and I think this is still a better solution. I just scored 2 sets of ball/disc 1200's for $300. They have great manners, and do not have the rusting issues that the 2150's have.
I hope everyone enjoys seeing this unusual mod that I have done, and what it takes to get this done.
