Page 12 - 2018 Racecar Engineering Engine Parts and Accessories Catalog

REAR MAIN SEAL ADAPTERS

Rear Main Seal Adapters
Chevrolet Small Block Rear Main Seal Adapters
Convert one-piece rear main seal on 1986 and newer small block Chevrolet to old style, two-
piece rear seal to accept earlier (pre-1986) crankshaft. Billet aluminum adapters include hardware.
Alignment tool allows quick, easy installation.
Part No. Description
ALL26125 For Early (Pre-1986) Oil Pan
ALL26126 For Late (1987-Up) Oil Pan
ALL26127 Alignment Tool

Chevrolet Small Block Rear Main Seal Adapters
Part No. Description
CAN21-850 Rear Main Seal Adapter, for Old Style (1986-Up) Oil Pan w/1-Pc. Seal
Chevrolet Big Block Rear Main Seal Adapters
Use an early style, Mark IV crank with two-piece rear main seal in the Mark V and VI blocks
with one-piece rear seals. Late style oil pan must be used.
Part No. Description
EAG500 Rear Main Seal Adapter
Chevrolet Small Block Rear Main Seal Adapters
Billet aluminum adapters convert 1986-up engines with one-piece rear main seal to use old style,
two-piece seal and early crankshaft.
Part No. Description
MOR38315 Rear Main Seal Adapter, for New Style (1986-Up) Oil Pan w/1-Pc. Seal
MOR38415 Rear Main Seal Adapter, for Old Style (Pre-1980) Oil Pan w/Driver's Side Dipstick
MOR38315
TECH TIP

Pushrods: Still Doing The Job After All These Years
Pushrod engines are often ridiculed by the "elite" automotive media, however, the fact remains that in high performance circles where conventional V-8's are
the norm, the pushrod style engine is still king. The pushrod engine is physically smaller compared to its OHC counterpart because the camshaft and relatively
simple cam drive are inside the block, making the engine narrower. The OHC Ford 4.6/5.0/5.4L modular engine, for example, is significantly wider and has a far
more complex timing system compared to its predecessor, the Windsor small block.
Taking the brunt of the media's abuse is the pushrod itself, a length of metal tubing that transfers motion from the camshaft and lifter to activate the rocker
arm. Pushrods have come under scrutiny since the introduction of the SpinTron, a machine that uses a powerful AC motor and a substitute crankshaft to spin the
components of a test engine. The SpinTron's Laser Valve Tracking System (LVTS) camera records component motion. Data is imaged, graphed and examined so
that engineers can identify problem areas and develop solutions. According to Chris Padgitt of Comp Cams, the SpinTron can also measure valve float, valve spring
harmonics, pushrod deflection and "lofting", a condition where valves stay open at high RPM due to a loss of contact between the cam lobes and the lifters.
Prior to the SpinTron, engineers found that valvetrain vibration was caused by component flexing, much from the pushrods. Vibration increased with engine
speed, creating damaging harmonics. Aggressive cam profiles, extreme valve spring pressures and large, heavy valves further aggravated matters and lofting
caused the valves to remain open longer than they should.
Engineers quickly learned that these problems could be reduced or even eliminated by just using a more rigid pushrod. At one time, a 5/16" diameter x .080"
wall pushrod was acceptable for many high performance applications, but that is no longer the case. Increasing pushrod rigidity merely involves larger diameter,
thicker wall tubing. Of course, larger diameter pushrods increase mass and convincing engine builders to use a heavier pushrod hasn't been easy, particularly
when lightweight valve train components are the vital to high RPM. However, builders have learned that the mass of the "pushrod side" components is not quite
as critical compared to that of the "valve side" components.
In the past, valve train manufacturer's traditionally stocked only 5/16" and 3/8" diameter pushrods and larger, 7/16" diameter pushrods were only available by
special order. Now Comp Cams, Crane Cams, Manley Performance and Trend Performance have begun stocking 7/16" diameter pushrods in both straight tube and
dual taper designs. In pursuit of maximum performance at high RPM, NHRA Pro Stock competitors have begun using 1/2" or 9/16" diameter pushrods. When in
question, it's always best to consult the manufacturer of the camshaft for the proper pushrods to use.
With diameter and wall thickness addressed, length is the next consideration. Naturally, the longer the pushrod is, the more susceptible it may be to flexing and
vibration. "FE" Fords, B/RB Chryslers, 400-455 Olds and tall deck, big block Chevrolets all use pushrods well in excess of 9." All may be candidates for a pushrod
upgrade if 5/16" pushrods are currently used in a high performance application. "The pushrod is still viewed as the weak link in the valve train", according to
Padgitt. The ultimate pushrod would not only be very rigid, but lightweight as well. Some valve train manufacturer's are currently using Metal Matrix Composite
(MMC). Similar to the material used in the manufacture of composite driveshafts, MMC has the strength equivalent of 4130 steel, yet is up to 60% lighter. Initial
SpinTron testing of MMC pushrods has shown reduced flexing, valve float and valve bounce, but there is work still to be done.
The introduction of the GM Gen. III LS engine in 1997 and the subsequent release of the modern Chrysler Hemi in 2003 has demonstrated that the pushrod
engine is here to stay. All of these signs ultimately point to the continued development and improvement of the pushrod engine.

2018 ENGINE BUILDER CATALOG 11