Working on a 2003 engine with a S&S 106 kit . Owner said if he would get on it hard it would blow the dip stick out . Too much crank case pressure .Engine has stock rocker boxes and S&S heads . Removed the rocker boxes and found it has the correct gasket on the front head but a cometic gasket on the rear . This will block off the breather . Looking at the rear head the breather hole is a 1/4 hole with thread and has a orifice in it .Thats is the question , why is there a orifice in the breather hole ?
https://assetcloud02.roccommerce.net/files/_sscycle/2/7/10/51-1108_cylinderheadstc88_20080428.pdf
Here's their info.
I'd say the question is why are there two different head gaskets?
The SnS lower rocker gasket has a breather passage cut out that carries pressure to the breather head bolt area. Someone must have worked on the rear cylinder and used a standard Hd/Cometic type that's obviously meant to cover an Hd head casting. Far as I know only SnS lower gaskets can be used w their heads.
Quote from: FLDavetrain on January 20, 2019, 10:57:12 AM
The SnS lower rocker gasket has a breather passage cut out that carries pressure to the breather head bolt area. Someone must have worked on the rear cylinder and used a standard Hd/Cometic type that's obviously meant to cover an Hd head casting. Far as I know only SnS lower gaskets can be used w their heads.
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You can drill the missing hole in a stock Harley Twin Cam lower rocker box gasket. Easy, and works perfectly on S&S heads. :up:
John
I have S&S heads on my 03. If using stock rocker boxes you must use the special S&S lower rocker box gaskets made specifically for this application. Both heads. Otherwise you have blocked off breathing through any head using a stock gasket. The S&S gaskets are also thicker to give enough cross section space to let the motor breathe. S&S rocker boxes use a bit different breathing strategy.
When using stock style rocker boxes I set it up to breathe stock style, including umbrella valves. (Except to atmosphere ). Never blown a dipstick.