318 Poly Performance Cam

[Belle66]

First off, boy this is a great forum, I've learned so much browsing old posts. Got a question I'm hoping someone out there can answer. I've got a 318 poly and the previous owner told me it has a non stock cam. He said that there weren't many out there. It also has a Weiand intake manifold. The sound of the exhaust leads me to believe it's got some overlap. The previous owner also had some stronger valve springs that he was going to install because of suspected valve float due to the cam. I can't remember anymore details than that. At high engine rpms the engine does break up but haven't gone through the ignition.

Any of y'all got an idea about what cam is in there? And if stronger springs are needed?

 

[RustyRatRod]

No idea on the cam, but every cam needs correct valve springs to run the way it is designed. Try removing a valve cover and measuring lift with a dial indicator directly off the valve spring retainer. That should give you some idea to choose a good spring. Here is a good resource for polysphere information.

http://www.1962to1965mopar.ornocar.com/poly318.html

 

[Belle66]

Thanks, was hoping there'd be an easy answer. Yup next step is to measure at opening, closing, lift, overlap. But you made a good point that spring deflection's a good way to judge.

 

[RustyRatRod]

Not just the deflection, but on the sprAng end, you're including the whole ball of wax. Good luck.