SMALL BLOCK CHEVY
GEN I - '55 to present
The traditional small block Chevy (SBC) we've all come to know and love, as available in cars and trucks beginning in 1955.
The '55 to '58 SBC used "front" motor mounts, and had no "side" mount provisions, which are required for an RX-7/V-8 swap. Also required for the swap is the short water pump, used on all SBCs up until '68, the year the "long" water pump appeared. The Corvette continued to use the short water pump until '82, and the '75 to '80 V-8 Monza used the short pump as well. Short and long water pumps are interchangeable, as long as the correct pulleys and accessory brackets are used.
Pre-'68 SBCs also lack accessory mounting holes in the end of their cylinder heads, a requirement if you need to mount an RX-7 P/S pump or A/C compressor.
'55 to '75 SBCs used a points style distributor, which is much smaller in diameter than the HEI distributor used from '75 to '88. The stock HEI distributors used from '80 and up are all require a computer for proper operation (they lack a vacuum advance), therefore cannot be used with a performance carburetor.
As for oil pan styles, there are 3.
(#1) is the '55 to '80 models, which use an oil pan designed for their left side dipstick location.
(#2) is the '80 to '85 models which have the dipstick relocated to the right side.
(#3) was used from '86-up, when the move to a 1 piece rear main seal required yet another oil pan design, but it retained the right side dipstick location.
The move to the 1pc rear main seal was accompanied with the change to a smaller flywheel/crankshaft bolt circle, 3.00" vs. the earlier 3.58" dia. pattern that was used with 2pc rear main seal engines. Large and small pattern flywheels/flexplates are not interchangeable.
Beginning in '87, some blocks were machined at the factory for hydraulic roller cams, but all were changed to the "center bolt" valve cover design, a move to reduce potential oil leaks. Also in '87, the 4 center bolts in the intake manifold changed angles slightly, going to 72 degrees instead of the traditional 90 degrees, so slight modifications are required for mixing and matching heads and intakes from these two groups. The VORTEC 5000 and 5700 truck engines that became available in '96 use a new design 64cc head, a new tuned design intake manifild, and hydraulic roller lifters. While the intake manifold bolt pattern has changed, the exhaust bolt pattern on the head remains the same as the older engines.
GEN II - '92 to present LT-1 / LT-4
The second generation of Chevy smallblock was introduced in '92
and includes the '92-'96 350 LT-1, '96 350 LT-4, and '94 4300 SFI (4.3
liter, 265 cu.in V-8). The LT-1 350 was used in '92-'96 Corvettes,
Camaros, Firebirds and featured aluminum heads, while cast iron
heads were used on the Impala SS version. The LT-4 was an option
on the '96 Corvette. The 4300 4.3 liter version was used in the '94 and
'95 Caprice, in both sedans and station wagons.
Major design departures from the Gen I were a reverse flow cooling system, a water pump which is gear driven by the cam sprocket, and the front mounted Opti-Spark ignition distributor, also powered by the cam drive. A conventional rear distributor can be fitted, but only in conjunction with one of the special intake manifolds available for switching to a carburetor (a different oil pump drive must also be used). The intake manifold bolt pattern is different, and the angle is different as well, 73 degrees as opposed to the Gen I intake manifold bolt angle of 90 degrees. The exhaust bolt pattern remains the same as the Gen I. There is no provision for an engine driven fan. An engine driven fan was available on the Caprice LT-1 as part of a towing package, but it is way too long for the RX-7 engine bay.
Critical deminsions for the LT-1 are as follows :
24" from bottom of oil pan to top of intake manifold.
27-1/2" long from the block's rear surface to the tip of the water pump.
24-3/4" wide with stock exhaust manifolds.
525 lbs. total weight for the stock LT-1 (including ALL accessories and cast iron exhaust manifolds)
GEN III - '97 to present LS-1
Used in the '97 - up Corvette and Camaro/Firebird, this latest generation 346 cu/in design retains the same engine mount locations and bellhousing bolt pattern that is common to all 90 degree V-6 and V-8 small block Chevys. The aluminum Y-block design features 3mm thick iron liners and 6 bolt main caps, a crossbolt design. The aluminum heads used have a different bolt pattern, with each bore surrounded with 4 headbolts instead of the traditional 5. The oil pan is made of cast aluminum, and is availiable in many styles, from the shallow Corvette baffled and gated "wing" design, to the deep sump truck version. The oil pan is a stressed member, with some of the bellhousing bolts threading directly into the oil pan. The oil filter mount is cast into the oil pan, and the oil pump is a front mounted and driven gerotor design. (click here to go to a page showing the different LS1 pans as presented by TunedPort.com). There is no distributor as was traditional on earlier small blocks, as the LS-1 uses a direct fire ignition, with a seperate coil for each cylinder. The intake manifold is of a tuned length multi-port, sequential fuel injected, composite design, uses a single 75mm throttle body, and has no directly connected throttle linkage. A serpentine belt system drives the water pump and accessories. The cooling system is similar in flow to the GEN I, and uses a distribution system to direct the coolant first to the block, thru the heads, then to a new design mixing thermostat before being returned to the radiator. The results are 345 hp with 350 ft/lbs of torque, with a 6200 rpm fuel cutoff. 100lbs lighter than the LT-1, the long block weighs 397lbs.
Critical dimensions for the all aluminum LS-1 are:
25" from the bottom of the oil pan to the top of the intake manifold.
28" from the rear surface of the block to the tip of the water pump.
26" wide with stock exhaust manifolds.
460 lbs. total weight for the stock LS-1 (including ALL accessories and stock exhaust manifolds).
CLICK HERE for dimensional information on manual and automatic transmissions.
- The T-350 is by far the most common automatic transmission available for the Chevy V-8 engine, and is available with a lock-up converter, called a T-350C. There were 3 different lengths of tailhousings available, the 6", 9", and 12" long versions. The 3 different length tailhousings all require a different length driveshafts, but they all share a common rear mount location, allowing the same transmission crossmember to be used with all T-350's. While a reliable transmission and well supported by the aftermarket, the lack of an overdrive gear means increased engine rpm, over that of the stock rotary, when used for this conversion. If you want to use the T-350, you can, and many people do. Fortunately, if you want to change to an overdrive transmission at a later date, the 200-4R has the same overall length and output spline as the T-350 (providing your T-350 has the most common 6" long tailhousing), so when you step up to overdrive, a new driveshaft is not necessary.
NOTE : If you decide at a later date that you would like to use a different transmission in your V-8 powered RX-7, we will exchange your existing trans crossmember (provided that it's in good condition) for the one you need, at no extra charge, except for shipping !!!
- The 200-4R is the recommended choice if an automatic transmission is desired. It was used from '81 to '87 in everything from RWD Cadillacs to GNX Buicks. Weighing in at a lite 157 lbs, it features a "universal" bellhousing bolt pattern that fits Chevrolets as well as BOP (Buick, Olds, Pontiac, Cadillac). The main case is a one-piece design, with no detachable tailhousing. Rated for a maximum vehicle gross weight of 6000lbs, overall torque capacity is only 20 ft/lbs less than that of the 700R4. Closer and more desireable gear spacing is another advantage over the 700R4. First gear has a ratio of 2.741 (vs. 3.059 for the 700R4), while the overdrive ratio, at .674, is nearly identical to that of the stock RX-7. This means that cruise rpm will be the same with the V-8 as it was with the rotary engine. A kickdown cable from a T-350 will fit and can be used to make the adaption to a carbureted engine easier, but proper adjustment is important. The 200-4R uses 3 control wires. (2) are for the internal converter lockup solenoid, while the 3rd is a feedback wire that indicates when the transmission is in overdrive. The transmission can be used without hooking up the converter lockup, but a built-in over temp switch will automatically lock it up if the trans fluid temp exceeds 260F. A simple relay and vacuum switch can be used to restore automatic converter lockup when used with an un-computerized, carbureted engine. The modified 200-4R has about the same capacity as a modified 700-R4, 600 ft/lbs and 700 hp. The output spline and overall length are the same as the short shaft T-350, so the same output yoke and driveshaft will fit either transmission.
- The 700-R4 is now called the 4L60, and computer controlled 700-R4s are now called 4L60-E (the "E" stands for electronic). The 700R-4 can and has been used for RX-7 conversions, but expect to do some minor modifications to the trans. tunnel. The 700R-4 is quite a bit heavier than the 2004-R and has more parasitic losses. An engine computer is not required for proper operation of the pre-'92 transmissions, but minor re-wiring is required for operation of the lock-up converter. The 4L60-E REQUIRES the proper ECM/engine combination to function correctly. Output shaft spline is the same as the T-350 and 200-4R, but the overall length is longer. The 700-R4 from a 60 degree V-6 will NOT fit a 90 degree V-6 or any V-8, as the bellhousing bolt pattern is different. The Corvette 700-R4 does not have provision for a conventional transmission mount.
- The Borg Warner T-5 5 spd manual transmission, at only 87lbs including the bellhousing, is the preferred choice for a light-weight RX-7 conversion. It was used in the '83 to '92 Camaro/Firebird. '88 and up boxes feature organic synchros, and are called "World Class". The V-6 unit has a 1"-14 spline input shaft (requires a special clutch disc if used with a V-8), while the more desirable V-8 gearbox uses an input shaft with 1-1/8"x26 spline. Overdrive is close to the same as the stock RX-7 at either .63, which came behind throttle body injected engines, or the .73 ratio that was used with Tuned Port engines. The shifter is in the correct spot for the 1st gen cars, and very close for the 2nd generation. Use an older bellhousing with a "straight-up" transmission bolt pattern, rather than the 17 degree angled pattern bellhousing used on the '83 & up Camaro's. Any Nova, Chevelle, or pre- '83 Camaro or Corvette bellhousing will work. This puts the shifter in the middle of the console, rather than off to the left. Our T-5 cross-member has a special angle that permits this application. Aftermarket hydraulic throwout bearings are available for use in these non-hydraulic bellhousings, or a hydraulic clutch slave cylinder can be fitted. Driveline length is the same as the T-350 and uses the same driveline yoke.
- Weighing in at 125 lbs dry, the T-56 is the 6 spd transmission used behind '93 to '97 LT-1 powered Camaro/Firebirds. The '93 box used a 2.97 or 3.36 1st gear, combined with a .62 ratio for 6th. For use with a V-8 powered RX-7, the '94-'97 box is better suited with a 2.66 1st gear and .50 ratio for 6th gear. The T-56 uses the same driveline yoke as the T-400, and is the same length overall as the T-5. Shifter location is a little over 1" farther back than the Camaro T-5, and to the left of center. The special T-56 clutch and bellhousing are required, as is a special flywheel when used with a pre-1986 crankshaft. There is no provision for a mechanical speedo cable output. The T-56 slave cyl. comes with a 1" bore, and should be used with a 7/8" clutch master cyl to get the proper feel (use a 1" clutch master cyl. for a quicker, but stiffer, clutch pedal).
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