4AD Connecting Rod Specifications?

The 4A, 4AB, 4AC, 4AD cars, including the SM 1500 Roadster and SMX
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ucantucan
Posts: 15
Joined: Fri Feb 10, 2006 1:44 am

4AD Connecting Rod Specifications?

Post by ucantucan »

Can anyone out there tell me what the diameter of the big end of a 4AD connecting rod should be. All my books are for the 4A and 4AB. My "new" roadster threw a rod bearing and so I'm in the process of an overhaul.

Greg Armstrong
Oshkosh, WI
BRG
Posts: 310
Joined: Sun Nov 27, 2005 4:33 am
First Name: Dave
Location: Tucson, Arizona

4AD Rod Specifications

Post by BRG »

Greg,

Spec. is 1.7500 +/- .0005. Running clearance .0005-.002. End float.006-.008.
BRG
NASOC Treasurer
NASOC 4AD Registrar
NASOC Parts Guy
Owner of a 1952 4AD, 1959 Singer Gazelle Estate, & 1959 Gazelle Convertible
ucantucan
Posts: 15
Joined: Fri Feb 10, 2006 1:44 am

Re: 4AD Rod Specifications

Post by ucantucan »

BRG wrote:Greg,

Spec. is 1.7500 +/- .0005. Running clearance .0005-.002. End float.006-.008.
BRG
Thanks, but I believe that is the crank pin dia., what I need is the dia. of the connecting rod before inserting the shell bearings. In other words the outside dia. of the shell bearings. The 4A and 4AB calls for shell bearing OD of 1.772 to 1.771, but that goes with a crankpin dia. of 1.6245 to 1.6250. Is there any chance that you have the specs. for the 4AD rod and shell bearings dia.

Thanks Greg
BRG
Posts: 310
Joined: Sun Nov 27, 2005 4:33 am
First Name: Dave
Location: Tucson, Arizona

4AD Rod Specifications

Post by BRG »

Greg,

Here is the specs from the bearing book I use for the interchange.
Brg O.D. or housing bore 1.8555/1.8560.
Max wall at crown .0523.

If the other rod bearings were in good shape then you could use the rod inner bearing surface measurement. If needed I should have a rod for your engine. :D
BRG
NASOC Treasurer
NASOC 4AD Registrar
NASOC Parts Guy
Owner of a 1952 4AD, 1959 Singer Gazelle Estate, & 1959 Gazelle Convertible
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