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madkaw

Need help with degree timing Isky Cam

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L24 with a Isky L490 grind cam.

Previous experience degreeing Schneider cam, so I have done this before.

Double and triple checked TDC. Checked with head off and with piston stop.

 

Timing marks(stock) line up correctly on cam and crank.

Checked and triple checked links on timing chain which is pretty new.

 

Timing on intake valve is retarded like 30+ degrees. I've tried with and without lash clearance to arrive at Isky numbers-no go.

I've tried a different or newer dial gauge.

 

I have an adjustable cam sprocket, but I wouldn't be able to gain these kind of numbers by just an adjustment. It seems to me I would have to skip teeth on crank or cam to gain 30+ degrees. Waiting for CA time to call Isky.

 

Intake opens at about 5 degrees ATDC and should be about 30 BTDC

 

Any suggestions-PLEASE!

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L24 with a Isky L490 grind cam.

Previous experience degreeing Schneider cam, so I have done this before.

Double and triple checked TDC. Checked with head off and with piston stop.

 

Timing marks(stock) line up correctly on cam and crank.

Checked and triple checked links on timing chain which is pretty new.

 

Timing on intake valve is retarded like 30+ degrees. I've tried with and without lash clearance to arrive at Isky numbers-no go.

I've tried a different or newer dial gauge.

 

I have an adjustable cam sprocket, but I wouldn't be able to gain these kind of numbers by just an adjustment. It seems to me I would have to skip teeth on crank or cam to gain 30+ degrees. Waiting for CA time to call Isky.

 

Intake opens at about 5 degrees ATDC and should be about 30 BTDC

 

Any suggestions-PLEASE!

What does the timing for the valve closing look like?  Is it also ~30deg late, or is it something different?  

 

Are your timing numbers for .050" or something else?

 

I don't think Isky does this, but I have seen one cam card that gave .050" timing, but the .050" was to be measured at the cam and not the valve.  Their cam card didn't mention this, and it took me a while to figure that one out.

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At .050 with no lash I am 0 TDC open and 50 atdc close

So they are not both the same - intake opening is later than spec by 31 deg, and closing is earlier by 19 deg.  I'm ASSuming that you meant 50 ABDC...

 

Just out of curiosity, what are the measured valve lifts at the spec (i.e., 31 BTDC and 69 ABDC)?

Edited by TimZ

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With .008 lash EXHAUST SIDE

 

38 BBDC

15 BTDC

 

Dial indicator is set up on exhaust side presently, so at 74 degrees BBDC there is no lift, and 38 degrees at .050

No lift indicated at closing point (36 ATDC)

 

 So I guess you were right about not being the same. I apologize but I haven't done this a lot and it's easy for me to get dyslexic 

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With .008 lash EXHAUST SIDE

 

38 BBDC

15 BTDC

 

Dial indicator is set up on exhaust side presently, so at 74 degrees BBDC there is no lift, and 38 degrees at .050

No lift indicated at closing point (36 ATDC)

 

 So I guess you were right about not being the same. I apologize but I haven't done this a lot and it's easy for me to get dyslexic 

No problem - it can be pretty confusing given that the meaning of the numbers flips depending on which quadrant you are in.

 

Also I should have been more specific - I was looking for the actual valve lift at 69 and 31.  However this just made something click in my brain - the 69 and 31 numbers don't make any sense.  Those numbers would yield a 0.050" duration of 280 and that's way too close to the "advertised" 290 duration.  So I went and checked Isky's website and the L-490 cam should have 242 deg of duration at 0.050".

 

Your numbers are coming out at more like 230/233 intake/exhaust (again I'm assuming you meant 15 ATDC above), so it's still not quite right, but that's more easily attributable to lash pad/wipe pattern/valve lash/etc.

 

Sounds like a call to Isky is in order.

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If I did my math right your 0.050" numbers should be

 

Intake

open 12 btdc

close 50 abdc

 

Exhaust

open 50 bbdc

close 12 atdc

 

That's closer to what you are measuring, but I'm still curious about the ~10 deg discrepancy in duration.  The website is also showing 0.010"/0.012" cold lash setting.  Maybe try setting the valve lash to those numbers and see what you get.  If that doesn't work try setting them both to zero lash.  

Also, where is your wipe pattern coming out on the rocker pad?

Edited by TimZ

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and........the numbers are in. Cam card says

 

 

       Intake                                                                               exhaust

 

open 2.5BTDC                                                      open   40.5 BBDC

Closed  40.5 BDC                                               closed    2.5 ATDC

 

 

My numbers on #3 hole sprocket

 

Intake                                                                                  exhaust

                         

3 BTDC                                                                   43 BBDC

39  BBDC                                                             2 ATDC

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and........the numbers are in. Cam card says

 

 

       Intake                                                                               exhaust

 

open 2.5BTDC                                                      open   40.5 BBDC

Closed  40.5 BDC                                               closed    2.5 ATDC

 

 

My numbers on #3 hole sprocket

 

Intake                                                                                  exhaust

                         

3 BTDC                                                                   43 BBDC

39  BBDC                                                             2 ATDC

Those numbers look like they must be correct, especially given that they match really well with your measurements.  However they look like your cam must be something other than the L-490 grind.  Is that your understanding?

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Did you recently buy this from ISKY or is it an "isky regrind" that you got from someone else?
 

Also, did you set you valve stem heights exactly equal? Without equalized stems, or even with them and slightly not-right lash pads, each valve runs on a different cam profile...

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Hmmm.   Weird - the spec looks more like the L475, but 1 degree more duration.  

Just to be clear, I ran the L475 grind for a long time and was really happy with it.  It's just weird that the specs don't jibe with what's published for the l490.  

 

Xnke - I'm pretty sure that the "Ron" that gave him the updated spec was Ron Iskendarian, so it likely came from Isky.   That said, Isky does do a lot of regrinds, so perhaps it's possible that this used to be a 490 and got reground.  Still, weird that Ron would give him that spec if it's supposed to be a 490...

 

Madkaw - sorry, I feel like you've already got your solution and now I'm just prattling on over pedantry, but that is confusing to me.  Did the rest of the info on the updated cam card match the l490?

Edited by TimZ

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Sorry Tim,

Ron sent it as a PDF file and don't know how to attach that. I'm going to print it out and take a pic of the card.

Yes the intake and exhaust run different shims if that does effect things.

 

I appreciate the help . Wish I hadn't lost a whole day on bad numbers, but that's hot rodding I guess.

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