I am thinking about having a custom cam made, but am unsure of how much advance to have ground in. I have done some searching, but there did not seem to be a definative answer. Many of the 'tuner' cams have 4* advance. Some people say 2* is better or none at all.

Are there any guidelines to follow? The cam I am thinking of would be 218/218 or 220/220 with about 0.537/0.537 lift (XE lobes?). LSA would be 114. I am also thinking of reusing my stock timing chain which has 14,000 miles on it. Car is street driven and also used for track events on road courses.

Thanks

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Gary U:
<strong> I am thinking about having a custom cam made, but am unsure of how much advance to have ground in. I have done some searching, but there did not seem to be a definative answer. Many of the 'tuner' cams have 4* advance. Some people say 2* is better or none at all.

Are there any guidelines to follow? The cam I am thinking of would be 218/218 or 220/220 with about 0.537/0.537 lift (XE lobes?). LSA would be 114. I am also thinking of reusing my stock timing chain which has 14,000 miles on it. Car is street driven and also used for track events on road courses.

Thanks </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Since I got an X1 I had no choice with 4 degrees cut into it (I think, maybe its 2), but just get an adjustable timing set and 0 degrees in the cam, then you can do the adjustment with the crank sprocket yourself.

-Dave

 

I just installed a Comp 218/218, 114 LSA with zero advance. My 60' slowed down from 1.58 to 1.65. My mph went up slightly which netted me only a slight gain in et after weather correction. I have a 3600 stall and it is not loose enough for the rpm this cam likes with zero advance. I am going to put in an adjustable timing chain and go with 6 degrees of advance. My 60' and mph should then improve.

You got to get the torque to the ground at launch or your et will suffer even if your peak more hp/tq is higher with less advance. You want the most average power all the way through the rpm range your operating.

 

ttt for you.

I'd like to hear some more opinions on advancing a cam. How much is too much? What situations would you want more advance, when would you want less?

 

Me too! I am going to be running a Comp 216 220 .525 .532 114 lsa w/4 degrees advance ground in, Crane 1.8 rockers, TEA stage 2 FI o-ringed heads, and D1SC w/10 psi pulley.

Is 4 degrees too much for this setup? Comp ratio should be reduced from 10.25:1 to about 9.5:1 per TEA, so detonation risk should be reduced, but what about piston to valve clearance. My effective lift will be 555.9 563.3

 

Old school theory says that if you have to advance your cam, its too big...and if you have to retard it, its too small. Some have posted that the ideal intake valve closing time is about 44-46 degrees ABDC. One thing to remember is that the stock timing chain is so loose that your cam actually runs 1-2 degrees retarded from where the cam is ground. So, if you order your cam with 2 deg of advance, its probably actually running at 0. If you're using a stock timing chain, I'd stick with 2 deg advance with cams up to about 220. Over that I'd go with 4 deg. It also depends on what you are going to do w/ the cam...street, track, auto-x?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> Some have posted that the ideal intake valve closing time is about 44-46 degrees ABDC. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That was what Patrick G posted persumably based upon the research done by TR. I've followed that and looked closely at what cams seem to do the best and I've concluded that 42-44 degrees ABDC probably makes the best compromise for drivability and performance, at least in the higher duration cams of 220 degrees or more.

 

This is what I got from Patrick G
__________________________________________

(Example TR-220 Cam) 220/220 .553”/.553” 114 LSA 110 ICL

The cam’s Duration, LSA and ICL will be shown on the cam card.
The cam, such as the one above with a 114 LSA and a 110 ICL has 4 degrees “ground-in” advance.

This TR220 114 LSA + 4 cam has an intake closing point of 40 degrees After Bottom Dead Center (ABDC).
The ideal Intake Closing Point (ABDC) is thought to be 44 degrees.

This cam will need to be installed 4 degrees retarded from dot to dot in order to get the ideal 44 degree (ABDC).
This can be done using an adjustable timing set such as the Rollmaster.

_______________________________________________


Formula for calculating Intake Closing Point (ABDC):
(Duration / 2) + (ICL) - 180 = Intake Closing Point (ABDC)

Example:
(220 duration / 2) = 110 + (110 ICL) = 220 – 180 = 40 degrees Intake Closing Point (ABDC)

Complements: Patrick G

 

Anyone?