What's the biggest cam I can use with factory heads on an LG4??? I'm gonna put an Edelbrock Performer Intake on and some Headers.


Thanks

 

Yup, I'm wondering the same thing.....

 

The Performer isn't much better than stock, get the RPM. And a Comp 262XE 462/469 lift and power 1300-5600 rpms.

Then again, maybe the Performer would be better to suit that cam, if so, just stick with the stock intake, I believe someone on here, I think five7kid says they're decent intakes..

 

Depends on how much top end you want to gain and how much low end torque your willing to give up to get it.
If you have stock rear gearing and a low stall converter, there are definiate limits on how far you should go before low end torque goes away.
The stock LG4 cam is about 185 deg@.050"
The Stock 305HO cam is about 203@.050"
The stock HO cam likes higher compression and higher rear gearing. 3.73"s

If I was stuck with say 2.73's I'd keep the camshaft duration
at or less than this. Your low cr 305 will benefit from raised compression
if you go for a larger cam.

 

So what are you saying?? I don't understand.

 

With a hydraulic or flat tappet cam, the more duration, in degrees, your cam has, the less low rpm torque the engine can develop. This is because it is holding the valves open for a longer period of time, thus not allowing as much cylinder pressure to be developed, as opposed to a shorter duration cam that holds the valves open for a shorter period of time.

If you have a 305 and 2.73 rear gears, this will definitely be felt as a loss of low rpm, or off the line, power. This is because you are basically working a trade off: as you increase cam duration and lift you are taking power from the low rpm part of the hp and torque curve and moving it to the higher rpm part of the curve, say 3500 rpm and higher.

That's the reason a "peanut cam" (.350 intake lift and .385 exhaust lift) makes good low rpm power but runs out at 4000 rpm. To gain power up to say 5500 rpm, you must increase the lift and duration.

A 2.73/1 rear gear ratio DEMANDS an engine with lots of torque, just to get moving because it will keep the engine from getting into the higher rpm regions as fast as a set of 3.42/1 gears.

So you would need to do a balancing act in that situation. You can do better than the peanut cam but can't go too far or the bottom end power will be worse than a six cylinder Camaro. And that makes for a less than fun to drive car, doesn't it?

Here's a handful of good hydraulic flatt tappet choices for the 305 and 2.73 combo.

Comp XE 250 or 256.

Crane PowerMax 260 or 266.

Move up to 3.23 or 3.42 gears, too. That's like adding 40 more hp and really gets you off the line faster--and still lets you go on the highway

 

Thanks for the info.