Project V8 RX-7: Part VI – Installing the E-Rod LS3


Howard drilling mount holes in the transmission tunnel for Samberg transmission mount
Howard drills holes in our RX-7’s transmission tunnel to position the Samberg mount. 

All that torque from our big V8 will be putting a lot of stress on the thin metal of the transmission tunnel; fortunately, Samberg has taken that into consideration by providing backing plates for the transmission mount that are placed on the inside of the car

Transmission mount attached, notice the small extra bolt above.  This attaches to the backing plate mounted inside the car and holds it in place if you ever need to take the mount off.  A very thoughtful design consideration so that you don’t have to pull up the carpeting and interior to put the bolts back in again.

Samberg transmission mount (Interior view)
View from the inside underneath the carpet.  Without that extra bolt up top this backing plate would fall down each time you removed the transmission mount. 

While the engine looks like it was made to fit in the RX-7 we still had to make clearance in a few spots.  Our biggest fitment issue we had was with the shifter.  While our Magnum transmission has several positions for mounting shifters in different configurations, none of them were quite far enough back to allow the shifter to pop up through the transmission tunnel where we needed it to be.

The shifter that came with our Tremec T-56 Magnum is unfortunately positioned too far forward to work well with our application even with the opening in the transmission tunnel enlarged in the forward direction to accomodate the old T-56 that used to call this RX-7 home.  Ideally, the shifter would be 4 inches further back than pictured above.

At the time of writing this article we just received a prototype shifter that should be a perfect solution but we have not yet had a chance to test fit it–stay tuned for an update very soon!

Moving along, the supporting metal on the underside of the RX-7’s hood makes a nice criss-cross right where the throttle body now lives so we had to cut some of that out—we’re not too worried about this compromising the hood’s integrity but if it does, then we have a good excuse for upgrading to a lightweight carbon fiber hood in the future!

RX-7 underhood clearance of LS3
The throttle body comes pretty close to the underside of the hood supports.  You can see where we chopped some of it out for clearance.

Also, while not absolutely necessary we chose to trim the metal pinch weld along the firewall to provide easier access when running our wiring harness.

firewall pinch weld trimmed for intake manifold and wiring clearance
We trimmed back the firewall pinch weld to facilitate running wires and to increase intake manifold clearance.  The thin plastic intake manifold cover is still touching the firewall a little bit.

On the engine side, we also clearanced the plastic intake manifold cover with a cutoff wheel.  The actual intake manifold itself underneath clears fine without any modification.

LS3 intake manifold cover trimmed
Trimmed back a couple inches, the plastic intake manifold cover clears the firewall fine now.  The intake manifold below requires no modifications.

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