This is topic retarding cam?? in forum Tech Talk at Northern California Ford Owners  .


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Posted by Daniel50 (Member # 5629) on :
 
i have gt-40p heads from tri state cylinder head.
-60cc Combustion Chamber
-5 Angle Valve Job
-1.940/1.540
and the usual full long tube exhuast, street heat intake, and the b303 cam.

i heard that retarding this cam 2 or even 4 degrees would add power througout the entire powerband. is it worth taking the time to retard the cam? and does it real make more power or better time?
 
Posted by 93PONY (Member # 60) on :
 
Yes.
I've seen gains of 2mph from retarding a camshaft on specific applications. Applications where the exhaust lobe is larger than the intake, the cam has advance ground in & the exhaust system is large & free-flowing.

The B303 has 5 degrees of advance built in.
Duration is rated at 224/224. Advancing the intake lobe makes the camshaft open/close sooner. Relative to the piston at TDC this effectively makes the intake 5 degrees smaller. On the exhaust side opening it sooner effectively makes it 5 degrees larger relative to the piston at TDC. (I say this because when the piston is at TDC there is very little airflow, so keeping the valve open longer around TDC does little for power compared to keeping the valve open while the piston is moving significantly through the stroke. Like when the intake valve closes, or the exhaust valve opens) (adding overlap is different....but I won't get into that since it does not apply here)
Effectively what 5 degrees of advance does to the camshaft is make it look like this (relative to the piston at TDC) 219/229 (remove 5 degrees from the intake, add 5 to the exhaust). Retarding the camshaft 4-6 degrees will make the intake lobe *look* larger (relative to the piston at TDC) & make more power up top. Additionally removing the extra exhaust duration will keep exhaust reversion at bay & add low/midrange power.

Again, this is on applications with plenty of exhaust system.

The 5.0 EFI intake manifolds are very restrictive compared to carborator setups. This is not something you would neccessarily do on a Carb setup.
 
Posted by Daniel50 (Member # 5629) on :
 
thanks shaun. your actually the guy who told sean that retarding the cam would make more power in my application. i think ill go ahead and do it. so retarding the cam 4 degreees looks like the next mod.
 




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