Specifications

ENGINE INFORMATION
Being a manufacturer of engine and transmission conversion components, we receive numerous questions regarding engine specifications. We
are not experts with the internal workings of these engines; however, we are very familiar with the bolt patterns, motor mounts, flywheels, etc.
This section is intended to help identify engine use and interchangeability.
CHEVY V8: When it comes to bellhousing bolt patterns, the small & big block Chevys are the same. (This is known as the 90 degree bolt pattern).
These engines use a dowel pin alignment. The stock starter bolts to the bottom of the block except on some early blocks like the 265. (Note: These
early blocks, in which the starter bolts to the bellhousing, should not be used for conversions). The flywheel can either be
153 tooth measuring 12-3/4” in diameter, or 168 tooth measuring 14” in diameter. The 1985 & earlier flywheels are not interchangeable with the 1986
& later flywheels due to a change on the flywheel crank bolt pattern and balancing. If you are using a stock GM bellhousing, make sure you have
proper clearance for the flywheel. For the proper starter, GM used two different bolt patterns on the bottom of the block. The straight bolt pattern
is normally used with the 153T flywheel, and the offset or staggered starter bolt pattern is normally used with the 168T flywheel. Many Chevy blocks
today offer both starter bolt patterns on the block. Some of our conversion bellhousings require a special GM starter nose cone. If your stock starter
is interfering with our bellhousing, you may need to grind on the bellhousing a bit or purchase a hi-torque starter which does not have a nose cone.
Warning: Do not use one of our full conversion bellhousings with a diesel engine. The starter will not fit the bellhousing pocket on our bellhousings.
The oil pans on Chevy blocks have gone through a few changes. 1985 & earlier blocks are all the same except the dipstick access is either on the
driver’s side or passenger side. In 1986, GM changed their gasket design to a one piece rear main seal. The earlier style oil pans will not fit the newer
blocks. The computer controlled blocks in the ‘90s added oil level sensors. The pans that we manufacture do not have provisions for this sensor.
Most GM blocks used a triangular motor mount bolt pattern. Our conversion mounts all utilize this most common mounting configuration. Some late
‘90s blocks have varied from this bolt pattern. Please confirm that the block your converting has this triangular mounting pattern. LS1 blocks and
Vortec Gen. III V8 blocks use a square bolt pattern for the motor mount. We offer a full selection of conversion mounts for these blocks. GM also
changed the crank flange stickout location on the LS1 and Vortec Generation III V8 blocks. This crank is recessed .400” closer in than any other
stock Chevy block. When these blocks are used in a conversion, the torque converter or clutch components will need to be adjusted. LT1, LT4,
ZZ4, LS1, and Vortec blocks all use angle port heads which are not compatible with most of our header systems. We offer some specialized headers
for these blocks. These blocks also require a steam release port on the radiator. The radiator we offer can be ordered with this steam release provision.
CHEVY 90 degree V6: This block can either be the 3.8 (229) or 4.3 V6. These engines are identical to the Chevy V8 application with reference
to bellhousing, starter, and flywheel. The oil pan has year differences like the Chevy V8 except with the 1997 & newer aluminum oil pan. Vehicles
requiring oil pan modifications should not use this block. Motor mounts are also the same as the Chevy V8 with the exception of the location of the
triangular bolt pattern in reference to the back of the block. The mount is approximately 4-1/2” closer to the backside of the block.
CHEVY 60 degree V6: This is the 2.8L V6 used in S10s and Jeep Cherokees. This bellhousing bolt pattern is completely different than the 90
degree Chevy bolt pattern. GM automatics that have this bolt pattern will not bolt to the 90 degree blocks. In 1996, GM introduced a stock engine
replacement known as the 3.4L.
BUICK V6: Buick used two different bolt patterns like the engines listed above. The 225, 231, and 3.8L (rear wheel drive vehicle) all used the
standard Buick bolt pattern for which we offer motor mounts, bellhousings, and adapters. Engine blocks like the 3.8L transverse (front wheel drive
vehicle) have the same bolt pattern as the Chevy 2.8L V6. We do not offer adapters or motor mounts for the Buick aluminum 215 block.
FORD V8: Ford V8s use three different block bolt patterns. Most of the adapters and motor mounts we offer are for the Ford small block 302.
Ford used two flywheels, 157 tooth & 164 tooth. These starters index and bolt on to the bellhousing. It is imperative that you match the flywheel,
starter and bellhousing. If you mismatch any of these items, it will only cause you grief! The 351 Windsor is considered a small block but has a few
differences. One difference is that the heads of the block are wider. This may cause exhaust clearance problems on some conversions. Another
difference is the oil pan bolt pattern.
AMC/JEEP Iron Duke 151 4 cylinder: This 4 cyl. engine is manufactured by GM and used in Jeeps 1980-83. When converting to a Chevy
90 degree V6 or V8, no adapter is necessary. You are limited to a 10-1/2” clutch assembly and a GM Mini High Torque starter.
AMC/JEEP 150 4 cylinder: This 4 cyl. engine has the same bolt pattern as the GM 2.8L V6 and is used in Jeeps vehicles 1983 & newer.
AMC/JEEP V8s & In-line 6 cylinders: Jeep started using the 258 6 cyl., 304 & 360 V8 in 1972, the 401 V8 in 1974 and the 4.0L in 1991. These
blocks are listed together because their block bolt patterns are all the same. The same pattern makes engine swapping between these vehicles
simple; however, when using the 4.0L, it requires a special hole in the bellhousing for the flywheel sensor. We manufacture the conversion
bellhousings for these applications. When installing a V8 where the 6 cyl. was previously, we offer motor mounts for easy installation.
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engine information