Comp Cams 7103 keyway adjustable billet cam gear

[Brooks James]

70 Dart, 360 magnum
Knock off air gap
750 double pumper
9 to 1 compression
Stock magnum heads
Cam adv duration Int 274 exh 286
Lift int 498 exh 512
LSA. 113.5
Adv power band 1800-5800
Cam was degreed, right on the adv specs
My question is: using the adjustable gear to advance/retard the cam, which way would cause the engine to have a lumpier IDLE ,
advance or retard ?
I know the LSA is wide by I wanted it to help maximize the nitrous, the higher lift/duration to increase the flow of hot spent gases out of the cyiinder. I have read that retarding the cam will push the the power peak to higher rpm, and vice versa. Im not worried about torque with the nitrous. The keyway adjustments are in 2 degree increments. In thinking that taking out 4 degrees , making it 109.5 would be a Good stating point? What do you think ?

 

[Garrett Ellison]

Changing the camshaft timing won’t have an effect on the LSA, only on the installed Intake and Exhaust centerline. The LSA is ground into the cam. With 9:1 compression, retarding the cam timing and making the intake close later is probably the last thing you’d want to do. I don’t know how much of an effect it would have on idle vacuum, but it will lose dynamic compression.

 

[rumblefish360]

Idle “Lumpiness” is more related to a narrow LSA by the way I’m reading your post. There are other factors involved. The cams ramp rate, compression factor in on this.

The Comp adjustable gear (or just manually moving it around) is a help in figuring out where a fine tuning of the cam will take place.

 

[Bewy]

Retarding the cam will reduce idle vacuum & give a lumpier idle.

 

[RustyRatRod]

You can advance or retard it to its maximums either way and you'll never hear the difference.

That said, you'll want to retard it if it will even have a snowball's chance in HELL of sounding more lumpy.

But that's the silliest reason in the WORLD to get to get a cam to sound different than it's designed installed intake center line.

 

[RustyRatRod]

Retarding the cam will reduce idle vacuum & give a lumpier idle.

It'll reduce vacuum and make it perform shitty, but IMO he'll be hard pressed to even hear the difference.

 

[RustyRatRod]

Oh and installing it at 109.5* is four degrees advanced. That's likely right where the cam card says to put it. If you want four degrees retarded, you need to go 117.5* intake center line. But I don't recommend it.

 

[rumblefish360]

Retarding the cam will reduce idle vacuum & give a lumpier idle.

Not arguing…. But….
I don’t think that sound by retarding the cam is the “Lumpy” sound he is thinking of or after.

 

[Bewy]

Only lumpy sound I know is the rough-ish idle you get from large-ish cams, which is what I thought the OP meant.