If you are ready for some awesome power out of your NA or NB Miata, then look no further. Boss Frog has developed some new V8 swap kits that will turn your car from mild to wild! Boss Frog has been building top quality rollbars and accessories for Miatas for over 5 years, and is far from being a garage startup or a one-man operation. You can be assured that these kits will have the outstanding quality and customer support of the other Boss Frog products.
Please call toll free 604-970-3454 for current Chevrolet V8 Kit Pricing.
Boss Frog Chevrolet V8 Swap Kit FAQ >>
Boss Frog uses the following key drivetrain components;
Engine - the Miata Venom V8 kits use the LS series GM engines typically used in Corvettes, Camaros, Firebirds and GTOs, because they are lighter and more powerful than the Ford 5.0 liter V8’s. Read More
Engine Subframe (LSx) – this kit includes a
professionally designed engine subframe, precision built in a welding
fixture for the best possible fit. Our plasma profiled mounting brackets
and heavy wall rectangular tubing are much stronger than round tubing
subframes, and we reinforce the front cross member and uprights to gain
additional strength where it is needed. Our kit does not require cutting
into the transmission tunnel, dashboard removal, oil pan modifications, or
additional steering joints.
The only changes from stock are some trimming of the engine bay gussets,
swapping the lower steering knuckle for a slightly longer version, and
relocating the sway bar slightly forward.
The kit includes;
- engine subframe
- urethane motor mounts and block adapters
- extended steering joint
- front sway bar relocation parts
- grade 8 hardware and installation instructions
Headers - Needless to say, the space between the LSx engine and
the chassis is rather tight, and a stock set of headers will not fit
without modification. You can make the modifications yourself, or buy this
kit pre-made. Even though mid-tube or long-tube headers are nice, they
make fitting into the tight space a nightmare, so we use the shortys.
The kit includes;
- custom short-tube headers
- gaskets and hardware
Transmission - the transmission selected is a Borg Warner T56 syncromesh 6-speed manual transmission that was used in Vipers, Corvettes, Cobras, and F-body cars. These transmissions use a hydraulic clutch and have an excellent performance record.
Transmission Mount (T56) – this kit includes heavy 14ga frame
rail channels to increase the torsional strength of your chassis. The
channels include mounting plates where the transmission cross member is
bolted. The transmission cross member has wide gussets at the ends, to
decrease flexing between the frame rails. The transmission is attached to
a urethane mount, to allow some movement while holding it firmly in place.
The kit includes;
- frame rail channels (2)
- transmission crossmember
- urethane transmission mount
- grade 8 hardware and installation instructions
Clutch Hydraulics – the Miata clutch
hydraulics are too small for the LSx clutches, so a new hydraulic system
is required. A stock LSx or universal clutch master cylinder will not fit,
so a special adapter is needed. In addition, the GM slave cylinder
includes a special quick disconnect fitting that needs to be replaced.
The kit includes;
- new clutch master cylinder, modified to fit the Miata clutch pedal
- master cylinder adapter plate
- slave cylinder adapter fitting
- master cylinder adapter fitting
- 36” stainless braided hose
- mounting hardware and instructions
Differential - Boss Frog looked seriously at the Getrag differential used in Cadillac CTS. The bottom line is that these transmissions were developed for 260HP V6 engines, and they have had serious problems with seals, loss of pre-load, whining, and wheel hop which has resulted in recalls and thousands of angry customers (see the Cadillac forums). Of course these vehicles were heavier than a Miata, but even the similar size Pontiac Solstice was recalled for these same differential problems. The differential that Boss Frog uses is the track proven Ford 8.8 with a custom independent rear suspension. This bulletproof differential has hundreds of gear ratio and limited slip options combinations available, all of which are readily available anywhere.
Differential Subframe (Ford 8.8) – this kit
fits the Ford 8.8 IRS differential center section from ’89-’97
Thunderbirds, which has two vertical mounting holes on the front, and two
horizontal mounting holes on the rear. The kit utilizes four existing
mounting brackets that are stock on the NB rear subframe, and are easily
added to the NA rear subframe. The unique design of the Boss Frog
Differential Mount features a two-piece formed mounting system that is
much stronger than tubular mounts. The lower differential mount attaches
solidly to the rear subframe in four places, and the rear differential
mount attaches to the vertical member of the rear subframe, using existing
holes for alignment. Because of this unique mounting system, the
differential can be mounted very high in the rear subframe to maximize
ground clearance.
Boss Frog also uses a pair of differential braces that bolt between the
lower differential plate and the floor/frame, to stiffen the rear subframe
and help eliminate wheel hop. The kit also uses urethane bushings both the
front and rear of the differential, to dampen the shock load. Stock rear
sway bars, shocks and springs can be retained. This kit can also be used
to replace the stock differential for high horsepower turbo or blown
Miatas.
The kit includes;
- lower differential mount assembly
- rear differential mount assembly
- urethane bushings (front and rear)
- differential braces
- grade 8 hardware and installation instructions
Driveshaft – Boss Frog’s driveshaft has the biggest joints and tube
size available in these kits – over 15% stronger than a stock or
competitive kit driveshaft.
Boss Frog uses a 1310 series driveshaft assembly which includes the rear flange yoke and a front slip yoke for the T56.
The kit includes;
- custom length 1310 series driveshaft
- front and rear yokes
- grade 8 mounting hardware
Axles - the Miata CV joints were never intended to handle the 350+
horsepower that these LSX engines are capable of, so Boss Frog uses the
larger Ford outer CVs. The axles have large 1-1/8” diameter custom
half-shafts made from high strength 4340
shafting, and new Mazda rear hubs are broached for the Ford outer CVs.
Read More
New axles are based on the Ford IRS setup for 7.5 differentials, which is
the same arrangement used in other popular kit cars such as the AC Cobras.
The CV’s are remanufactured to factory specs before being mated to the new
half shafts.
The kit includes:
- custom made 4340 half axles, with Ford inner and outer CV’s
- new rear wheel bearings
- new OE rear wheel hubs, broached for the larger Ford outer CV
- hub spacer washers
- installation instructions
Boss Frog kits will give you the strongest overall drivetrain available, so that you can put down the most reliable horsepower at the track or the strip. The kits are divided up into various components and systems, so that you can purchase exactly what you want, when you are ready for it
Any questions about kits, parts or installations are welcome. Contact Bishop by phone at 604-970-3454 or e-mail and we will respond promptly. If you're in the neighborhood, then drop by the shop in North Vancouver BC and we will gladly give you a tour of our facilities, but beware – there may be a Monster in our shop when you visit! We really love to share the fun with other Miata and MX-5 owners who want to take their cars to the next level of performance, appearance and handling!
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