2G Dialing BC 272 Cams

[miliman13]

Alot of unanswered threads.......

I'm asking for members who have previously degreed cams.
I used Jafro's video but i cant keep up and have questions, even pausing the video i'm left behind and cant seem to comprehend the constant zeroing of his digital gauge.


this is the cam card info
Advertised duration 268 272
@ .050" 208 212
Valve lift" 0.401 0.381

I get finding true TDC. I get Zero lash.

But what is my intent? To adjust until i see the degrees expected at .050" ?
And .050 how is it measured? ( on the closing event).
Do i zero at max lift then rotate until .050, or do i just leave the gauge alone and record the first and second .050
( opening and closing)?

And i'm assuming as long as i have sufficient ptv clearance its up to me to decide were i choose to retard and advance based on common recommendations.?

Thanks, i hope this doesn't turn to another dead thread.

 

[ThunderChild]

Your whole notion for degreeing cams is to get the in car specs to match the specs on the card.

So if you have X Duration @ .050" lift, start recording your duration when it hits .050" as the valve opens, and take final duration as soon as you get to .050" on valve closing.

Once you have the cams in car matching what the card specs say, make sure things run right, get on the dyno and start tuning. You'll make cam adjustments, see if you make/lose power and adjust from there to your liking.

 

[miliman13]

I was under the impression you needed to test advancing and retarding to make sure you maintain PTV Clarence in those expected adjustments.
So you know what your limit is while your on the dyno? other wise you would be doing it blind at that point correct?

So regardless of tight or wide in LSA you stay zeroed untill you hit the dyno?

Thanks for clarifying ..

 

[keltalon]

I was under the impression you needed to test advancing and retarding to make sure you maintain PTV Clarence in those expected adjustments.
So you know what your limit is while your on the dyno? other wise you would be doing it blind at that point correct?

So regardless of tight or wide in LSA you stay zeroed untill you hit the dyno?

Thanks for clarifying ..

I found that it is best for me to leave them at zero and tune from there. You are right degreeing is mostly done by many just to get your limits of adjustments because most who degree end up , after many hours of degreeing, move the cam gears all over the place anyway during the tuning process. I have found that if I set my piston to top dead center , I will then loosen the bolts on the cam gear and advance the gear until the valve hits the top of the piston I then record the degree limit, then I do the same by retarding the cam until valve touch the piston and record that number , this must be done for exhaust and intake cam gear. At this point I have my limits and I usually stay a couple of degrees away from the limits during the tuning process.

 

[miliman13]

I found that it is best for me to leave them at zero and tune from there. You are right degreeing is mostly done by many just to get your limits of adjustments because most who degree end up , after many hours of degreeing, move the cam gears all over the place anyway during the tuning process. I have found that if I set my piston to top dead center , I will then loosen the bolts on the cam gear and advance the gear until the valve hits the top of the piston I then record the degree limit, then I do the same by retarding the cam until valve touch the piston and record that number , this must be done for exhaust and intake cam gear. At this point I have my limits and I usually stay a couple of degrees away from the limits during the tuning process.

This makes sense. Thanks for the insight.

... I've read that adjusting the exhaust cam is common to change the torque curve.... this is done after a few dyno runs i presume to actually confirm results.. and not on a stand.

I originally liked the idea of adjusting to have more power on the lower end, instead of the top rpm range, I don't plan to drag race... but will want to do rally/circuit.. any recommendations or is this simply something addressed during tuning?

 

[ThunderChild]

Keltalon has it. I was under the impression you wanted a more basic explanation

His method for interference checking will work just fine. There's other ways that will help u account for thermal expansion, belt stretch etc. But as long as youre not doing crazy adjustment amounts you should be fine.

As far as what settings to use, that's highly subjective to a myriad of other input variables. Generally you'll do some base pulls and try what you've read works, and fine tune it down depending on results. If u want more power down low, advancing is going to be your freind, with wide LSA specs.