website:www.grannysspeedshop.com
...Ordering Information...
The purpose of this guide is to lay down the necessary tasks in an orderly fashion, to hopefully minimize the
time and effort required to pull off a successful COMPLETE conversion.
Many, if not most of the steps described here, are the same regardless of the engine
choice. Injected engines such as the TBI, TPI, Vortec and LT1 will differ mostly with regards to
electrical connections and fuel system plumbing. The main mechanical components and
basic proceedures are generally the same.
If you would like more info on completing a smog legal conversion in California, CLICK HERE
Additions and corrections to this guide are encouraged, and will hopefully result in an
evolutionary process that will eventually include EVERY detail required, right down to
the wrench type, sizes, torque specifications and parts required to carry out each
individual step.
Often times projects such as this are undertaken without a full understanding of
what is involved. Hopefully, this summary of the steps necessary will provide individuals
with the insight necessary to evaluate their own abilities, and help them come up with
accurate estimates for both time and cost. Most hot rodder types will not need these instructions,
but if they encounter a problem at some point, it's nice to know that helpful information is a close as their computer.
This is a very easy swap that can be executed successfully by the average shade tree mechanic. No special mechanical skills or tools are required.
We recommend using the Camaro/Firebird version of the LS1, as it has a workable accessory location and drive arrangement, as well as a transmission that has mounting points for both a rubber transmission mount and a "torque arm style" front diff mount. Beware of the Corvette versions, as they use a very wide accessory mounting scheme, do not use a throttle cable, and use a transmission that either does not have a mount provision or uses an incompatible transaxle/torque tube arrangement. LS2 engines have been used, but they need to be converted to the rear sump Camaro/Firebird oil pan & pick-up tube, as well as a cable style throttle body/PCM/harness.
Our FD/LS1 conversion is designed to keep your RX-7's excellent race car inspired steering geometry intact by maintaining it's stock steering rack location. Although lowering the RX-7's steering rack would have solved the single problem of hood clearance, it would have introduced multiple problems with bump steer, ground clearance, and radiator clearance. We feel our solution ultimately allows you a lower center of gravity without compromising the integrity of your OEM steering components, or your oil pan's ground clearance. Because of these features, hood modification will be required, but in exchange you will be able to safely enjoy a lower ride height, lower CG, and will be able to use the stock RX-7 or aftermarket upgrade radiator.
By taking advantage of our higher engine location, you are in effect lowering the rest of the car around your engine.
Effects On Maintenence & Reliability...
...If you already own a 3rd gen RX-7, then you already know about the rotary’s
high maintenance requirements, have probably heard many stories about dealer service
departments that lack proper training on rotary engines, and chances are, your beautiful
sub 100k mile RX-7 is probably on it’s 2nd or 3rd engine by now. These cars have not
been sold in the US for over 10 years now, and replacement parts are getting scarce.
The Chevy engine, on the other hand, is perhaps the most common engine on the
planet. Most any person with automotive experience has worked on one, and a well
factory trained network of technicians exist from coast to coast. The modern Chevy
engine routinely goes 100k between tune-ups, and replacement parts are among the
cheapest and most common.
Effects On Performance...
...As you might suspect, the switch to a V-8 powerplant has an effect on
performance too. The additional low-end torque makes the RX-7 very easy to drive, and
is available throughout the RPM range. No longer will you have to excessively slip the
clutch at a stop light to keep from killing the engine. No longer do you have to downshift,
wait for your RPMs to come up and boost to build to pass a car. No longer will you live
in constant fear of the dreaded boost spike. No longer will you have to worry about uncontrollable power and losing traction when the turbo hits. With the V-8, your power is always available and easy to apply smoothly.
If and when it comes time for an upgrade, things can really get interesting. Simple
$100. modifications can result in 15-20hp increases, while spending a mere $4-5000. can
get you up to around 500hp level. We are seeing low to mid 13 second 1/4mi times from
mild smog legal engines with around 300-325hp, which is better than the high 13 second
times that were possible with the RX-7’s stock twin turbo rotary engine.
Effects On Weight, Balance, and Handling...
...This is where you probably expected there to be a downside. People have
probably told you that your handling and perfect weight distribution will be ruined with
the addition of that big, heavy, american V-8. Just ask yourself if any of those so-called
experts you have been talking to have any actual experience with piston-powered RX-7s.
We’ve got the numbers to prove all those bystanders and spectators are just
that....bystanders and spectators.
Here are some real numbers from a typical 3rd gen RX-7 converted to Chevy
power:
The example car is a ‘94, which was not lightened in any way. The car was
converted using a Camaro engine & transmission, a stock ‘96 LT1 (factory equipped w/
aluminum heads), and a T56 6speed. It has a full stock interior, as well as the stock air
conditioning and power steering. The stock RX-7 cooling system was retained, as was the
stock RX-7’s engine oil cooler. The car has the Camaro’s stock cast iron exhaust
manifolds, and is completely OBD-II smog legal, right down to it’s cataylitic converter,
EGR, and dual O2 sensors. The battery was relocated to the passenger side storage bin
behind behind the seats. With a nearly full tank of fuel, the balance is a perfect 50/50,
1475 lbs front / 1475 lbs rear, for a total of 2950 lbs. About 90 lbs heavier than the stock
RX-7 with it’s TT rotary engine.
Keep in mind that the above example is of an iron blocked LT1 powered car. The LS1 with it's aluminum block is 60+ lbs lighter, complimented with a lightweight plastic composite intake manifold. Your LS1 equipped RX-7 will most likely weigh less than when it was equipped with the unreliable TT rotary.
Engine / Transmission Choices...
...The RX-7's engine compartment / steering rack location somewhat dictates which engines are best suited for this conversion. The reason we prefer to use Chevy's rear sump small block engines?...engines with an oil sump located to the rear, such as the small block Chevy, allow for a lower and more rearward engine location while still clearing the RX-7's steering rack. Front sump engines, even engine's with a small front sump such as the Ford 5.0 w/ the FOX body pan, would require either a far forward engine location or re-location of the RX-7's steering rack. Narrower engines such as pushrod V-8s will clear the RX-7's brake booster, while overhead cam engines such as the Ford 4.6 would require some creative re-working of the RX-7's brake system.
...If maximum smog-legal performance is your goal...we suggest using the liteweight Camaro/Firebird LS1 engine/transmission, as it is the best performing smog legal "certified" package that is both 50 state legal and easily adaptable to the RX-7 chassis. It has a very broad power band, with usable power at both ends of the power curve. This makes for a very user friendly power package that is well known and supported by repair and maintenance facilities across the US. Be warned however, that for street applications, the LS1 is a bit taller than the LT1, and will require hood modification to get the needed room. For a race application, lowering the steering rack is an optional compromise to maintain the stock RX-7 hoodline.
Skills Required...
...If you have a good grasp of things mechanical, do all your own automotive
maintenance, have a good selection of tools and know how to use them, you are probably
qualified to perform this swap.
Estimating Time For Completion...
...We have broken the conversion process down into smaller steps (links listed below). This allows the person actually doing the conversion to
estimate the time he should allow depending on his abilities and resources.
2....Considerations & Requirements....
4....Engine / Transmission Installation....
5....Exhaust / Throttle Cable / Accessory Drive / Pulleys....
6....Cooling / Fuel Systems....
7....RX-7 Wiring Harness Connector ID and Circuit Locations....
8....Electrical System Modifications By Circuit....
9....Start-up / Troubleshooting....