Advancing cam 2 degrees

[DART66GT]

Ive read a couple of old posts that said to advance cam 2 degrees in stock 318. Technically how does this increase performance. I am looking for MPG,bottom end and midrange from my 75 stock 318 . It is a 4spd o/d 66 Dart with a 3.55 sure grip. I wiil be converting from 2 barrel to T-quad and performer manifold.

 

[moper]

I think if you were to swap to a 4bbl intake, I'd say stick a stock 340 cam in it, int he "straight up" position, and it will be fine. I wouldnt advance a 2bblcam.

 

[dusterdon]

advancing a cam is a way to pick up some bottom end when you've slightly overcammed the motor.

 

[Tarr]

moves the power band lower. I had a 340 with a 284/484 duration/lift that sounded like a stock 318 because I had advanced the cam 6 degrees. Ran great on the street with a 2300 stall in a Volare. I added an 8 3/4 and ran either a 2.83/3.23 or 430 gear depending on what I wanted. The 4.30 was for the local 3/8 mile track. It was a low comp. 340 with 650 holley and hookers. Ran 13.08 on street tires on a very tired motor.

 

[MomsR/T]

the full, layman's response to the question is this:

You have 2 "timings" that are discussed in automotives - ignition timing and cam timing...................both are in regards to their timing in relation to the piston (usually at TDC)


While ign timing is relative to WHEN the spark plug fires, valve timing is relative to WHEN the valves start to open.

When you advance the cam, you open the intake valve sooner and close the exhaust valve sooner.

If you were to take a cold cranking compression measurement now, advanced the cam 2*, and took another compression test, you'll see pressure INCREASED.

This will be true for your dynamic compression as well.............

Its true that advancing the cam brings power in sooner while retarding it bring power in later.................

If you dyno the car, you'll make a torque "curve".......................advancing the cam or retarding the cam will not change the curve, rather it will move the curve forward or back on the scale; but NOT change the curve the cam creates.

When playing with valve timing, please ensure p/v (piston to valve) clearance.............

Valve timing is not infanite.............and you can measure this with cranking compression................ie. 0* may make 135 psi, +2* may make 148 psi, +4* may make 155 psi..............................but then when you goto +6* you may see a decrease to 142 psi......................this is the point of deminishing return.

Now you know that this cam will not benefit you @ anymore than +4* and we would assume the same going the other way (retarding). But, this gives us an 8* sweet spot to "play with".

When you advance, please note you'll most likely need to change spark advance for best benefit..............