Hi, Could someone explain what happens when an engine builder retards the cam? I had a 347 stroker built from a long time engine builder locally and he is a fan of a 10:1-10.25:1 compression ratio. I used a brand new Ford Racing 347 short block, a pair of TFS Twisted Wedge,CNC Ported headswith 64cc chambers and TFS Stage 2 Cam (.542/.563 lift, 224 duration @.050). The builder wanted to lower the compression a bit to just over 10:1 and he didn't likethe valve opening and closing when the cam was setstright up. The cam has 4 degrees of advance built in, and from what I understand, he set it to 4 degrees retarded.

What effect does this have? does it rob significant power?

thanks!

 

Retarding the cam is done by slightly misaligning the timing gear set during the rebuild. What it does is mildly changes the time the valves are open and closing. The result is less fuel and air in the cyl. Depending on the motor such things like that can be good depending on overlap and duration. You should not notice any significant performance loss at the higher RPMs with only a few degree change especially on a cam that was already advanced, and the motor should start easier, idle better, and perform a little smoother at low RPMS. Retarding the cam is only something an experienced, and highly knowledgeable motor rebuilder should do. I understand the basics of how it works but would never consider doing it myself.

 

Thank you for the answer. This rebuilder is very experienced and trusted, for better or worse, has a hang up on keeping compression under 10.5:1 even with aluminum heads...he didn;t like the valve opening and closing with the cam I had straight up....