HELP - Need ISKY L480 cam card info for 240z

[swa240z]

All - I just recently had my stock cam reground by Isky to an L480 grind for my '72 240.  I received a cam card with the cam but the information on the card was not correct  I talked to Ron at Isky and he sent me a different cam card and it appears to be wrong too.  Using a degree wheel and a piston stop, I have dialed in my engine for TDC but none of the open and close numbers on the cam card are very close to what we have actually measured.  All measurements were taken at .050" valve lift with zero lash.

I talked to Ron once again this past Friday and he said he would run some numbers and get right back with me, but I haven't heard back.  Normally, this would not be a big deal, but I had .035" shaved off the head (for compression ratio purposes) so I bought a Kameari adjustable cam gear so I could dial the cam back in, but without good numbers, I can't move forward with the engine install.  If you have an Isky L480 grind cam in your L24, please share your cam card information and note whether it is a regrind or a new cam.  Thanks for your help!

Steve

[Chickenman]

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Edited August 14, 2016 by Chickenman

[Zed Head]

3 hours ago, swa240z said:

stock cam reground by Isky to an L480 grind for my '72 240.

 I received a cam card with the cam but the information on the card was not correct

Using a degree wheel and a piston stop, I have dialed in my engine for TDC 

 I talked to Ron at Isky and he sent me a different cam card and it appears to be wrong too.  

none of the open and close numbers on the cam card are very close to what we have actually measured.  

 If you have an Isky L480 grind cam in your L24, please share your cam card information and note whether it is a regrind or a new cam.

One problem here is that you don't know if the card is wrong or the cam.  If Isky sent you their L480 card, then it will be the same card you get from anyone out here.  They probably just a file that says "L480 grind" on a computer and print copies out.  Or just copy an old card from the 70's on their copy machine.  Might not tell you much.  Are you saying that you have two cam cards now from Isky that say "L480" but have different numbers?  How about taking some pictures and posting them?

How far off are the numbers and in what way?  What kind of degree wheel are you using?  Is it an actual wheel or tape on the damper?

[siteunseen]

Schneider fills in the blanks, there is an ink pen marking through HOT for valve lash.

[Chickenman]

^ Note the wording in the Shneider card at right upper corner. Checking clearance at .050" ( at Tappet ). Not at valve.

Also note duration is checked at .050" Camlift ....  not Valve lift.

 

Isky has a warning about checking at Valve lift because of measurement errors introduced by clearance ramps and rocker arm ratio variances. A sliding finger follower is particularly, bad because the ratio varies as the cam lobe wipes across the rocker pad. All pushrod engines are checked at Tappet lift and you must use a solid tappet. The Tappet is really just a solid spacer to get the Dial Indicator located on. OHC engines are usually measured ( these days ) directly off of the cam lobe. Back in the 70's they used to measure off the Valve retainer... but that introduced too many errors.

I'd call Isky and ask if the specs are checked at the Cam Lobe  or Valve stem. Cam Lobe is much more accurate and is the standard these day.

Scroll down about halfway.

 

http://www.iskycams.com/cam-degreeing.html

 

CHECKING VALVE SEAT TIMING - CLEARANCE RAMP ERROR

Checking the cam at the lifter is much more accurate but can still cause confusion if you try to check the actual valve seat timing, which involves checking on the clearance ramps of the cam lobe. The clearance ramps are the slow lifting portions of the lobe which provide a smooth, transition between the base circle and the cam flank on both the opening and closing sides of the lobe. On the clearance ramps, the first .010" or .015" of lifter movement is usually at the slow rate of .0005' per cam degree. In addition to gradually taking up the valve lash (necessary because of valve expansion and small deflections of the valve gear components), the clearance ramp provides the initial, gentle acceleration of the valve off its seat.

An example of these clearance ramps is described in the cam lift curve of Figure 9. As indicated in Figure 9, only the end of the clearance ramp directly adjacent to the cam flank is actually used to open and seat the valve, while the remainder is used to take up the clearance and compensate for small deflections or runout in the valve gear.

Since the clearance ramp rate of lift (velocity) is .0005" per cam degree, a slight error on your part of say .001" in checking the valve seat timing at a certain point on these clearance ramps, could account for 2 cam degrees (4 crank degrees) of error in determining the timing point as exemplified in Figure 10. And it is very easy to accumulate .001" error if the dial indicator's stem is not running parallel to the lifter (cosine error) or if you view the dial indicator's calibrations from an angle (parallax error) or if the cam bearings or tappet bosses are worn slightly. Obviously then to properly determine the position of your camshaft in the engine, the cam timing must be checked at a lifter height off the base circle where the velocity (rate of cam rise) is high enough so that small checking height errors of .001" or so will not result in gross degree wheel reading error.

ISKENDERIAN .050 LIFTER RISE METHOD

Many years ago a standard height was sought after by ISKENDERIAN engineers where all racing camshafts could be timed to give accurate results and in 1958 it was decided and later published in our top tuner's manual, "Valve Timing for Maximum Output" that .050" lifter rise off the base circle would be the accepted standard for our camshafts. This figure was ideal because it was not far enough off the base circle to confuse the engine builder when timing the camshaft, and it was high enough to show effective valve timing (a point where the valve is far enough open to pass an effective air flow). Also, the velocity (rate of cam lift) of most camshafts is approximately .004" per cam degree at .050' lifter rise. Therefore, a .002" error in checking height would only affect the degree wheel reading about 1 crank degree as shown in Figure 11. The ISKENDERIAN .050" lifter rise check has now become a standard in the racing cam industry.

 

Edited August 15, 2016 by Chickenman

[Zed Head]

9 hours ago, swa240z said:

without good numbers, I can't move forward with the engine install.

Not clear how this halts engine install.  Anyway, interesting problem.

Here's the Isky page just to round things out - http://iskycams.com/cart/index.php?main_page=product_info&products_id=959

[swa240z]

Hey all - thanks for the replies.  I'll see if I can get some of your questions answered.  I have received two very different L-480 cam cards from Isky - both for a Datsun 6 cylinder L series engine.  I have attached both for reference.   The card with the writing on it is the most recent one they sent me.  I have been working with madkaw on this since he has far more experience dialing in cams than I do, but he is stumped as well.

Zed Head is correct in that I don't know if the cam card is wrong or if the cam is wrong.  This was supposed to be a regrind of my original cam, but I can't tell if I got back the one I sent them.  The markings on the end of the cam indicates that it is a customer supplied cam and the grind date matches the time frame that Isky had my cam according to Ron at Isky.

Since my cam gear is adjustable, I have been able to adjust so that the intake was closing at about 36* ATDC (35* ATDC per cam card), but the open was at about 12.5* BTDC (3* ATDC per cam card)- so I'm almost 15* off on the open.  Since we were so far off on the open, we didn't try to dial in the close # at this point.  Measurements were done with zero lash and .050 valve rise per Ron, but he didn't get specific as to where to take the measurement.  The dial indicator is sitting on top of the Isky valve spring retainer since that is about the only "flat" spot to take a measurement from.

Zed Head - I guess I could put the engine in before I get this issue figured out, but it sure is a lot easier to do this with the engine on the stand.  

Chickenman - that is good info from Isky.  I did not see that when I was surfing their site.  I'll clarify with Ron as to what the proper procedure is for our setup.

I'm going to call Ron again today to see if he has figured anything out, but I'd still like to see if there are other versions of the Isky L-480 cam card floating around out there.  Thanks again for your help!

Steve

Isky L-480 Cam Card - Original.pdf

DATSUN 6CYL, L-480 109LC - Updated.pdf

Edited August 15, 2016 by swa240z

[madkaw]

I'll make note that we think error is with Isky because he did the same to me as far as supplying the incorrect cam card with the cam.
I have dialed in my cams using the retainer as the measuring point. Schneider had no issue with this method but warned of faulty numbers because of the inconsistent rocker arm ratios .
I try to be careful to get the dial indicator in line with the angle of the valve . Reading are only done at .050 valve lift which in my understanding is the standard to method so help deter the ramp effect .
The other problem we are seeing is that cam lobe center numbers don't add up to the card based on my math, but I am truly a novice at this .


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[Zed Head]

Kind of looks like Mr. Isky doesn't really give a squat about the old Datsuns.  His money is probably in all of those thousands of Chevys out there.

[Chickenman]

Personally, I would check the Cam lobe lift as per the first card. At the Cam lobe. Make sure that the dial indicator is lined up EXACTLY 90 degrees to the crank center-line. Don't forget that the engine is tilted about 6 degrees from vertical and so the Dial indicator must be aligned the same.  I'm thinking the numbers will come out correct then.

You will likely have to add 180 degrees to the timings on the card. Reason being is that they are a generic card printed for Domestic pushrod engines. The Cam on those is beneath the tappet and pushes upwards. The L-series OHC engine has the Cam located above the follower and pushes down... so that changes the Cheby/Ford/Chrysler cam card readings 180 degrees.

If Ron made even a minute miscalculation in the rocker ratio, his numbers will be off. And the Rocker ratio of an L-series engine is not symmetrical like that of a SBC or other engine with round tappets. One other thing. Back in the 70's and 80's all you could buy was OEM Datsun rockers. These days you can get aftermarket rocker arms. But it's already been proven that the ratio can vary from factory. So that throws even more errors into the equation.

Edit: In the original Racer Brown article ( Page 99 on How to Modify Datsun Engines . by Bill Fisher and Bob Waar ) he mentions that Datsun produced two different rocker arms. An Early and a Late style. The early ones could be " fudged " to produce a 1.5165 to 1 ratio. The later arms could be " set up " as high as 1.5438 to 1. Some aftermarket rockers these days are as low as 1.48 to 1. And where the lobe is positioned on the wiping pad also alters rocker ratio ( see " fudging " ).  All in all there are just too many variable in the Datsun finger follower design to measure at the Valve Retainer. 

Bottom line. Measure at the Cam lobe for the most accurate job. It's funny that Isky doesn't even follow there own advice... Ed would have never allowed that.

 

[Chickenman]

Steve. Don't forget Lash Caps if you don't already have them. Stock ones won't work. Link that ZH supplied shows you need .175" Lash Pads with that regrind. . Stock is around .120"

[madkaw]

I don't know- most everywhere I have read and seen it is using the retainer to measure off of. I've also read it is important to have the dial indicator in line with valve angle - nothing else. BRAAP on hybridz has a nice thread on degree ing a cam which he shows the dial indicator on the retainer .
I believe the numbers supplied are not correct , but open to any ideas


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