Mopar Muscle – October 2019

big-block, there are time-honored tips, tricks, and advice for

building a strong, durable, and leak-free engine.

We turned to veteran Mopar engine builder Dan Cook to share

some of the basics. He’s a walking encyclopedia of knowledge

when it comes to RBs and has built more of them than most

of us will ever see in a lifetime. He’s learned what works, what

doesn’t, and where an engine-building budget can be stretched

by focusing on the most important elements.

“Unless you’re building an engine strictly for drag racing and

plan to launch against an 8,000-stall converter, you don’t have

to go crazy or spend a million dollars on exotic parts,” Cook says.

“The right mix of strong rotating parts and proven yet inexpensive

support components will deliver great power and great durability,

as long as you take the time to build it correctly.”

And by that, he means checking every bearing clearance and

other tolerances against the factory specs. He’s also a big advocate

of cleanliness.

“The two biggest things that kill an engine are a dirty

assembly and failure to check all the clearances,” he says.

“Get both of those right and the engine will run darn-near forever.”

We also mentioned building a leak-free engine, and that’s

a very important part of every RB build, because, frankly, Mopar’s

big-block is renowned for all the places oil tends to seep out

of it, namely the rear main seal and the joining lines between

components, such as the timing cover and block. Many of the

tips outlined here deal with keeping it all contained.

Whether it’s your first big-block build or your tenth, there

is advice here to make it your best. Good luck!

BEST BLOCK

There were 16 different RB block castings between 1959

and 1978. When searching for a foundation for an engine

build, the 1966–1972 440 block casting #2536430 is the one

to get. It’s stronger than earlier RB blocks, which don’t

have as much nickel in the mix, as well as the later 1973–1978

440 blocks with casting #3698830 and the 1978-only casting

#4006630, which simply have less meat in their castings.

Please note there is a consensus that Chrysler did produce

some 440s shortly after 1978, such as for motorhomes or

parts-department replacements.

“55” TO KEEP IT ALIVE

Overboring the block up to 0.060 inch is a pretty common

practice for an RB rebuild, but builder Dan Cook says that

for higher-performance engines, it can lead to heating issues.

He recommends stretching the cylinder bores no more than

0.055 inch to ensure the engine keeps its cool.

FEELIN’ HALF-GROOVY

The factory used half-groove main bearings (an oil groove

only on the top half of the bearing), and there’s no need to

go full-groove bearings unless the engine’s primary duty will

be racing. Also: The stock mains are a weak link in the RB

block for higher-performance builds. They’ll stand up to about

650 hp, but beyond that, they’re living on borrowed time.

FREEZE-PLUG PLAN

RB freeze plugs are notorious for poor sealing. Rather than

driving them home dry, use some Permatex Form-A-Gasket

on them to help prevent leaks. Don’t use common silicone

sealant, because it will dry up and push out the freeze plugs

MOPAR MUSCLE OCTOBER 2019 35