Cam Degreeing Question
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
Cam Degreeing Question
I am degreeing an XE-268 and the cam card call's for 28° BTDC @ .006 of lift on the #1 intake lobe. I am ***** dead on with that ... but my ICL is coming out lower than I would have expected (100). The LSA is 110 whilst the ICL is 106 for 4 degrees advanced .. built in. I verfied that I'm on true TDC with the degree wheel too.
Do I care about that ICL reading?
Do I care about that ICL reading?
Pro
Joined: Sep 2017
Posts: 516
Likes: 72
From: Modesto California
I am degreeing an XE-268 and the cam card call's for 28° BTDC @ .006 of lift on the #1 intake lobe. I am ***** dead on with that ... but my ICL is coming out lower than I would have expected (100). The LSA is 110 whilst the ICL is 106 for 4 degrees advanced .. built in. I verfied that I'm on true TDC with the degree wheel too.
Do I care about that ICL reading?
Do I care about that ICL reading?
Are you checking it with the heads off or on? Did you use a piston stop to verify your timing tab is dead on?
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
I used a piston stop and found true TDC. That's step 1. The heads are on. Dial indicator is on the push rod. BTW - this is on my Firebird 400.
I'm getting the ICL by bringing the engine around to max lobe lift per the specs on the cam card ... I think it's .343. Anyhow ... I zero out the dial indicator then bring the cam down one side at .050, it's at 53° then bring it back up and down the other side ..050 and it's at 146°. Add the two and dividing by 2.
And no ... I am not worried about the timing tab at this point.
I'm getting the ICL by bringing the engine around to max lobe lift per the specs on the cam card ... I think it's .343. Anyhow ... I zero out the dial indicator then bring the cam down one side at .050, it's at 53° then bring it back up and down the other side ..050 and it's at 146°. Add the two and dividing by 2.
And no ... I am not worried about the timing tab at this point.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Don't know how you nailed TDC #1 but I use something like 0.050" each side of TDC #1 and split the difference to zero the degree wheel (same method to set the timing pointer at zero also). Next if do want to verify ICL I use a solid lifter - has to be solid lifter - and use the same 0.050"/0.050" method for the intake lobe.
Yes it does get confusing when cam advance is built into the grind but you should be able to read it within 1/2 degree.
Hope this helps.
Also you don't need to zero out at max lift - just look for the same reading on both sides of the peak lift.
Yes it does get confusing when cam advance is built into the grind but you should be able to read it within 1/2 degree.
Hope this helps.
Also you don't need to zero out at max lift - just look for the same reading on both sides of the peak lift.
Last edited by cardo0; Oct 26, 2017 at 08:31 PM. Reason: Also.
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
I got TDC by splitting the difference of the dwell using a piston stop and degree wheel. Do I still need a solid lifter even though my dial indicator is right on the pushrod and the rocker arm is off? I can't imagine that with that setup that the plunger of the lifter is going to be depressed. I can see that I would need one if I were measuring off of the rocker arm with the spring being involved.
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
Drifting
Joined: Jun 2008
Posts: 1,565
Likes: 111
If your actual measurements are 6 degrees off the 106 ICL, you're not good. Keep measuring until you are within 1 degree. Don't even worry about the other valve events until you get the intake centerline right. I don't think you can use a hydraulic lifter for this. I recommend the tool that inserts into the lifter bore instead of trying to measure off the standard lifter or pushrod.
Last edited by Neil B; Oct 26, 2017 at 09:58 PM.
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Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
OK ... it appears that the XE cam intake lobes are asymmetric and leaning on the opening side. I think that would explain that. It's the only thing that makes sense since I'm dead on 28 degrees at .006".
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
Using the max lift then .050 on each side of max lift to check the lobe centerline will give incorrect results on a camshaft with Asymetrical lobes.... the only way to propely degree Asymetrical lobes is using then tappet timing events.
Will
Will
Drifting
Joined: Jun 2008
Posts: 1,565
Likes: 111
Makes sense. But if he's measuring on a hydraulic lifter with the dial indicator on the end of a pushrod, his measurement is likely the issue. I've found even when the cam is installed on the correct intake centerline, measured duration @.050 will still be off a few degrees.
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
Makes sense. But if he's measuring on a hydraulic lifter with the dial indicator on the end of a pushrod, his measurement is likely the issue. I've found even when the cam is installed on the correct intake centerline, measured duration @.050 will still be off a few degrees.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I'm just not believing the nose of the cam lobe is all that asymmetric for 0.050". But if you are using a dial indicator on an accurate follower device and the degree wheel set up tight you should be able to easily see how many degrees 0.050" are on each side of max indicated lift.
They sell lifter follower tools now but thier not all that cheap. Myself I use 2 hydraulic lifters mated together with one inverted but this is too tall to use with the heads on. I read a lot of owners do the measurement at the p-rod but that looks way to error prone to me. In your case I would try to find a solid lifter to use.
Good luck.
They sell lifter follower tools now but thier not all that cheap. Myself I use 2 hydraulic lifters mated together with one inverted but this is too tall to use with the heads on. I read a lot of owners do the measurement at the p-rod but that looks way to error prone to me. In your case I would try to find a solid lifter to use.
Good luck.
Drifting
Joined: Jun 2008
Posts: 1,565
Likes: 111
I guess you could always move the centerline a few degrees and re-check the .050 valve events to see if they move with the centerline. At the end of the day, if the asymmetric lobe makes the centerline method invalid, then verify the IVC @.050 event. If that is where you want it (per cam card), then run it that way.
Last edited by Neil B; Oct 28, 2017 at 10:12 AM.
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
I guess you could always move the centerline a few degrees and re-check the .050 valve events to see if they move with the centerline. At the end of the day, if the asymmetric lobe makes the centerline method invalid, then verify the IVC @.050 event. If that is where you want it (per cam card), then run it that way.
Here's what I have:
@ .050 9° BTDC
@ .050 31° ABDC
@ .006 29° BTDC
@ .006 54° ABDC
Last edited by corvette_maniac; Oct 28, 2017 at 03:29 PM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
The cam card doesn't have the .050 valve events; only the .006. The #1 opening is right on at 29° and the closing is at 54 ABDC but calls for 60 on the cam card. That's probably the only thing that concerns me. But then you can also see that the duration is 263 (@ .006) which is why the valve closing is 6 degrees early... and 220 (@ .050). Should I call it good .. or am I still off?
Here's what I have:
@ .050 9° BTDC
@ .050 31° ABDC
@ .006 29° BTDC
@ .006 54° ABDC
Here's what I have:
@ .050 9° BTDC
@ .050 31° ABDC
@ .006 29° BTDC
@ .006 54° ABDC
I can see we have a misunderstanding here. I'm trying to describe 0.050" down from max lift but I see you are measuring 0.050" up from the base circle.
Totally different measurements.Also using that 0.050" lift point on an asymmetric lobe would then have a much larger discrepancy than a point that is 0.050" down from max lift on the nose of the lobe.
I see you are getting only 263* duration on a advertised 268* cam. I see only 2 explenations for this. Either the cam is incorrectly ground or your measurement is incorrect. To late now to do a run-out of the cam lobes while in a pair of V-blocks. Unless you want to remove the cam again. I really think if you are this concerned you should slow down and pick up a solid lifter some where. But the other hand says your not going to race NASCAR with this motor and since you nailed #1 TDC you could just use the mfr ICL on your degree wheel and call it done - as countless other have done.. BTW you should see somewhat an indication of max lift on your dial indicator when the degree wheel passes ICL. Check it out.
Good luck and don't pull your hair out over this issue.
Last edited by cardo0; Oct 28, 2017 at 11:43 PM. Reason: Stupid autocorrect!
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
I can see we have a misunderstanding here. I'm trying to describe 0.050" down from max lift but I see you are measuring 0.050" up from the base circle. Totally different measurements.
Also using that 0.050" lift point on an asymmetric lobe would then have a much larger discrepancy than a point that is 0.050" down from max lift on the nose of the lobe.
I see you are getting only 263* duration on a advertised 268* cam. I see only 2 explenations for this. Either the cam is incorrectly ground or your measurement is incorrect. To late now to do a run-out of the cam lobes while in a pair of V-blocks. Unless you want to remove the cam again. I really think if you are this concerned you should slow down and pick up a solid lifter some where. But the other hand says your not going to race NASCAR with this motor and since you nailed #1 TDC you could just use the mfr ICL on your degree wheel and call it done - as countless other have done.. BTW you should see somewhat an indication of max lift on your dial indicator when the degree wheel passes ICL. Check it out.
Good luck and don't pull your hair out over this issue.
Totally different measurements.Also using that 0.050" lift point on an asymmetric lobe would then have a much larger discrepancy than a point that is 0.050" down from max lift on the nose of the lobe.
I see you are getting only 263* duration on a advertised 268* cam. I see only 2 explenations for this. Either the cam is incorrectly ground or your measurement is incorrect. To late now to do a run-out of the cam lobes while in a pair of V-blocks. Unless you want to remove the cam again. I really think if you are this concerned you should slow down and pick up a solid lifter some where. But the other hand says your not going to race NASCAR with this motor and since you nailed #1 TDC you could just use the mfr ICL on your degree wheel and call it done - as countless other have done.. BTW you should see somewhat an indication of max lift on your dial indicator when the degree wheel passes ICL. Check it out.
Good luck and don't pull your hair out over this issue.
Drifting
Joined: Jun 2008
Posts: 1,565
Likes: 111
Using the XE268 specs (224/230@.050 110 LS 106 ICL), I came up with the following valve events @.050 using the Wallace Racing calculator:
IVO is 6.0 ° BTDC ( - indicates ATDC)
IVC is 38.0 ° ABDC
EVO is 49.0 ° BBDC
EVC is 1.0 ° ATDC ( - indicates BTDC)
Overlap is 7 °
If it were me, I would start by using the intake centerline method and then once the cam is on 106 ICL, I would then check the valve events @.050. I would shoot to get the centerline and the intake valve closing as close as possible to spec. For an asymmetric cam, getting the IVC event correct is probably more important than the intake centerline.
IVO is 6.0 ° BTDC ( - indicates ATDC)
IVC is 38.0 ° ABDC
EVO is 49.0 ° BBDC
EVC is 1.0 ° ATDC ( - indicates BTDC)
Overlap is 7 °
If it were me, I would start by using the intake centerline method and then once the cam is on 106 ICL, I would then check the valve events @.050. I would shoot to get the centerline and the intake valve closing as close as possible to spec. For an asymmetric cam, getting the IVC event correct is probably more important than the intake centerline.
Thread Starter
Racer
Joined: Jul 2006
Posts: 478
Likes: 56
From: Woodstock Georgia
Using the XE268 specs (224/230@.050 110 LS 106 ICL), I came up with the following valve events @.050 using the Wallace Racing calculator:
IVO is 6.0 ° BTDC ( - indicates ATDC)
IVC is 38.0 ° ABDC
EVO is 49.0 ° BBDC
EVC is 1.0 ° ATDC ( - indicates BTDC)
Overlap is 7 °
If it were me, I would start by using the intake centerline method and then once the cam is on 106 ICL, I would then check the valve events @.050. I would shoot to get the centerline and the intake valve closing as close as possible to spec. For an asymmetric cam, getting the IVC event correct is probably more important than the intake centerline.
IVO is 6.0 ° BTDC ( - indicates ATDC)
IVC is 38.0 ° ABDC
EVO is 49.0 ° BBDC
EVC is 1.0 ° ATDC ( - indicates BTDC)
Overlap is 7 °
If it were me, I would start by using the intake centerline method and then once the cam is on 106 ICL, I would then check the valve events @.050. I would shoot to get the centerline and the intake valve closing as close as possible to spec. For an asymmetric cam, getting the IVC event correct is probably more important than the intake centerline.
I actually had thought that the cam was a tad small for my 9:1 400 4 speed/3.08 only to find that it's even smaller. I am tempted to change it at this point ... after all ... I'm already there ... only have to pull the radiator.
