Over the years much information has been published in books, magazines, newsletters
and on the internet concerning many topics of interest to Mopar restorers. One area that
has not been very well documented, however, is brake system components. The purpose of
this article is to clear up some misinformation, help owners to have their cars correct,
and in some cases even save owners some time and money.
| The power brake booster is p/n 3461118. Original boosters
can be rebuilt. They are painted semi-gloss black and usually are seen with a daub of hemi
orange paint above the installed master cylinder. One often seen item that is functional
but is not concours correct is the booster check valve. Later replacement check valves
have a raised right angle nipple, where on the original check valves did not have this
nipple. |
 |
|
Original style power booster check valve
installed on a booster. Probably was installed on booster when painted, in which case it
would be painted black. |
|
Later style replacement power booster
check valve is installed on this car's booster. |
|
| Master cylinders owners have installed on their cars are
often not correct. There are two basic master cylinder designs depending if the car has
drum brakes or front disc. Drum brake master cylinders have equal size front and rear
fluid reservoir chambers. Disc brake master cylinders have one fluid chamber that is much
larger than the other. The reason for this is because the displacement of the disc brake
caliper piston requires a much larger volume of brake fluid than the displacement of wheel
cylinder pistons. T/A’s and AAR’s came standard with front disc brakes. However
it is very common these days to spot drum brake master cylinders installed on these cars.
This is a potentially dangerous mistake because it is possible to have too little brake
fluid available for the calipers when using a drum brake master cylinder. The original
master cylinder installed on disc brake 1970 E- bodies (except hemi) was the p/n 2944453.
It can be identified by a casting number 2229171 on the bottom. These assemblies are date
coded with information stamped in the outlet side of the casting ( 0 100 would be the 100th
day of 1970). Although there is not a kit available through the aftermarket specifically
for this OE part, a Raybestos MK551 kit has the correct diameter internal seals and these
seals can be used to replace worn out ones on the original pistons.
Master cylinders can also be professionally rebuilt at places like Brake and Equipment
Warehouse in Minneapolis and White Post Restorations in Virginia. There are several
aftermarket master cylinders that install and function correctly if an original part
cannot be found. Raybestos and Napa part numbers 36283 and 36307 work fine but do not look
exactly like the original. If your car has a drum brake master cylinder it should be
replaced with a disc brake one! Disc brake master cylinders from that era were painted
gloss black, even the filler cap. The gold anodized filler caps we see on so many restored
Mopars look nice but are no more correct than chrome valve covers or headers. |
|
|
Chrysler part number 2944453 is the
master cylinder used on all 1970 E bodies with disc brakes except for 426 hemi. The
distinctive shape on the front of the casting is sometimes referred to as the
"thermometer" front. |
|
The Chrysler part number 2944453 can be
identified by the casting number 2229171. |
|
The datecode is stamped in the outlet
side of the master cylinder casting in the second line. This example was made on the 173rd
day of 1973. |
|
| Rotors are also available from the aftermarket. These can be
purchased through local aftermarket auto parts stores like NAPA at a lower price without
the shipping charges that the restoration parts businesses charge. (Raybestos p/n 7008,
NAPA p/n 85530) Aftermarket rotors differ slightly from OE in that they are one piece
instead of the original two piece design. On original rotors the flange where the wheel
studs are installed was held in place by the installion of the mounting studs. Aftermarket
rotors are machined out of a single casting but function correctly. The studs are included
on the rotors but on the aftermarket versions they are all standard thread. The studs can
be replaced with reverse thread ones on the driver’s side to be correct if desired. Calipers
are still readily available through the aftermarket. These are a single piston design for
E bodies. Currently available calipers are rebuilt assemblies, not new, and therefore they
are original OEM castings with new internals. |
|
|
Original (left) and aftermarket (right)
rotors show the difference in mounting flange on original rotors. |
|
| Front brake hoses are also available from the local auto
parts store. They are nearly identical to original with the exception of some information
stenciled on the hose. Original front hoses also have a date code stamped in to one of
their brass fittings. Though not available at local parts stores, excellent reproduction
brake lines and parking brake cables are available through the restoration parts industry.
|
|
|
Date codes stamped in end fittings on
NOS front brake hoses. |
|
| There were two styles of parking brake cables used in 1970.
One style had a flat steel outer cover. The other style had a spring coil winding. I
believe the flat steel was used on all Trans am cars. For the rear drum brakes, the
original wheel cylinders have a casting number 3461776. Kits to rebuild original wheel
cylinders or complete new aftermarket wheel cylinders are readily available through auto
parts stores. Hardware kits are available through the aftermarket. New drums available at
auto parts stores work well. When placed next to original drums minor differences can be
seen in the castings. For cars with rallye wheels the outer surface of the drum behind the
installed wheel was painted red. On cars that had the 15x7 steel wheels this area was not
painted.
It should go without saying that the brake pads and shoes are still readily available.
The only items that are not easy to find are the proportioning valve that is installed in
the area below the master cylinder and I am not aware of anyone selling the rear brake
hose. |
|
|
Portion of NOS parking brake cable
showing flat steel covering. |
|
I hope this information helps to keep your car stopping as
quickly as it accelerates!
White Post Restorations
One Old Car Dr.
P.O. Drawer D
White Post, Virginia 22663 540-837-1140
www.whitepost.com
Brake & Equipment Warehouse, Inc.
455 Harrison St. N.E.
Minneapolis, MN 55413 612-378-3141 |
