A lil lumpy

[original72]

I have a 440 that has 9.5 compression.... the cam is a comp cams XE274H.... specs out at 488 intake and 491 exhaust..... with a 106 centerline.... duration is 230 intake and 236 exhaust...... just wondering if this would cause the car to have a slight lumpy idle without the car in gear...... tach reads 950 RPMs...

Thanks
Bill

[BLAM]

That 106 Centerline will sure make it lumpy!  Usually street cars are 108 to 112, 110 being the most common.

[Rolling_Thunder]

my new cam is on a 115 centerline     

[Runner]

That 106 Centerline will sure make it lumpy!   Usually street cars are 108 to 112, 110 being the most common.

  being a comp cam,  im sure its a 110 lsa and is installed at 106 intake ceterline.

   should have a little lope to it

[original72]

correct... it is a 110 degree lobe separation and 106 degree installed centerline.... now next question... IF i move the centerline to say 110 degrees will this put the power band higher or lower from the 1800 to 5500 RPMs and would it be recommended to do so to smooth out the idle if i decide i want it smoother since it will just be a weekend driver when done........ and thanks for all the responses so far guys....

Bill

[Runner]

  it will sound nice, but not ratical at all.   should be a nice driver.  i would install it at the recomended 106 if it was me.   also when you start moving a cam around, piston to valve clearance can become more of an issue.

[Chryco Psycho]

by installing it at 110 you are retarding the cam which will raise the powerband a few hundred RPM so that would be the wrong way , or just install a better cam while you are in there

[Just 6T9 CHGR]

or just install a better cam while you are in there

Ouch!!

[firefighter3931]

correct... it is a 110 degree lobe separation and 106 degree installed centerline.... now next question... IF i move the centerline to say 110 degrees will this put the power band higher or lower from the 1800 to 5500 RPMs and would it be recommended to do so to smooth out the idle if i decide i want it smoother since it will just be a weekend driver when done........ and thanks for all the responses so far guys....

Bill

Bill, advancing/retarding the cam timing won't affect idle quality appreciably....it just moves the powerband around. Advancing it will move it down...retarding moves it back. 4* will move it 200-300 rpm either way. I would leave it as is and tune it. Set the base timing at 16-18* at idle and look to see how much total advance it has. If the engine speeds up (at idle) as you advance the distributor, it's telling you that it wants more spark lead.   Once the timing is dialed in, readjust the idle speed and mixture as needed. A 230*@.050 cam will have some lope....that is normal. If the base timing is too retarded it will idle rougher. More often than not, advancing the timing shows big improvements in idle quality and bottom end power.

Ron