website:www.grannysspeedshop.com
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 will differ mostly with regards to
electrical connections and fuel system plumbing. The main mechanical components and
basic proceedures are generally the same.
NOTE: Since we are not performing your conversion, it's up to the installer to insure that all applicable emissions and legal considerations are met. This usually means
that the new engine must be of the same or newer year than the car, and has all the engine's systems complete and intact. The exception is usually the catalytic
converter, and that system usually has to be consistant with the requirements of the chassis. The engine will also likely be required to be from the same class of
vehicle (example: no engines from heavy duty trucks installed into passenger cars).
Before proceeding, be sure to consult the appropriate local authority on the legality and conditions necessary for a successful and legal engine conversion in your
area.
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.
Our 2nd gen RX-7/Ford Conversion Kits allow installing the 260/289/302/5.0/351W engines into the 2nd gen RX-7 with a simple bolt-in process.
Due to the location of the Ford engine's oil pump in the front of the engine, this engine must be mounted farther forward and slightly higher than the Chevy engine in order to clear the RX-7's steering rack.
The effect of this forward/higher engine position is that both hood clearance and radiator-to-accessory drive clearance are reduced. Here are a few ways to minimize issues in these areas...
Hood Clearance...A few methods are available to increase hood clearance. You can use one or all the methods listed below as needed...
......Intake Selection...Use one of the lower profile intake set-ups such as that used on the T-Bird.
......Subframe Shimming...1/2" thick spacers can be installed between the RX-7 chassis and the stock RX-7 front subframe. The net effect is that the entire engine and steering rack are lowered in relation to the body, which increases hood clearance. The steering rack is lowered along with the lower control arm's inner pivot points.
This is much preferred over simply lowering the steering rack and engine only, which would create a nasty bump-steer situation. Lowering the entire subframe minimizes any ill effects. This modification has no effect whatsoever on ride height due to the RX-7's strut style front suspension geometry.
......Plenum Milling...This method is often used when stuffing the 5.0 into the Miata as well. The idea is to mill the mating surface of the plenum where it attaches to the lower intake manifold. The amount milled depends on the clearance between the plenum and the valve cover, so use the shortest valve covers you can to maximize the gain.
Many mill to the point that the plenum actually contacts the valve cover, and then grind clearance into the bottom side of the plenum to eliminate the contact.
Radiator to Accessory Drive Clearance...Older carbureted engines have the option of using a short water pump, but the injected engines can use the shorter accessory drive set-up that was used on the T-Bird or the '94-'95 Mustang.
Effects On Maintenence & Reliability...
...If you already own a 2nd gen RX-7, then you already know about the rotary’s
maintenance requirements, have probably heard stories about dealer service
departments that lack proper training on rotary engines, and chances are, your beautiful
RX-7 is probably on it’s 2nd or 3rd engine by now. The RX-7 has not
been sold in the US since 1995, and replacement parts are getting scarce.
The Ford engine, on the other hand, is one of the most common engine on the
planet. Most any person with automotive experience has worked on one, and a large
factory trained network of technicians exist from coast to coast. The modern Ford
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 (or boost to build) to pass a car. No longer will you live
in constant fear of the dreaded carbon lock. With the V-8, your power is always available.
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 3rd gen 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 2nd gen RX-7 converted to Chevy
power (remember, the Chevy is a bit heavier than the Ford):
The example car is an ‘86, which was not lightened in any way. The car was
converted using a ZZ-4 crate engine & T-5 transmission. It has a full stock interior,
as well as the stock air
conditioning and power steering. The stock RX-7 cooling system was re-located but retained, as was
the
stock RX-7’s engine oil cooler. The battery was relocated to rear area just in front of the
tail lites. With a full tank of fuel, the balance is close to 50/50,
1535 lbs front / 1545 lbs rear, for a total of 3080 lbs (including the 200lb driver).
Subtract the weight of the 200lb driver, and the total weight is 2880, 235lbs heavier than
the RX-7's 2645 stock weight, and amazingly slightly less than the later Turbo II's stock weight
of 3003lbs.
Will the Ford Engine Clear My Hood?...
Some combinations of parts can clear your hood, but most common 5.0 engines with taller aftermarket intake manifolds will have a problem. Here's some pics of the clearance needed for a Trickflow intake and the scoop that looks good to cover it...
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....