HELP - Need ISKY L480 cam card info for 240z

[swa240z]

Chickenman - Thanks for your feedback.  Isky sent out new .175" lash pads with the cam.  Rocker arms are the original arms that had about 64k miles on them.  They looked very clean and showed no noticeable signs of wear.

I still haven't heard back from Isky.  I called yesterday and was told that Ron was still working on the numbers.  If that's the case, then I assume there must be a mistake on the most recent cam card he sent me.  If I get some new numbers from Isky, madkaw and I will probably take one more run at dialing in the cam and I'll post the new cam card.  If I don't hear something in the next day or so, I'll probably just advance the cam about 2* to make up for the .035" I removed from the head and hope that is close enough to get the engine running good.  A dyno run is probably in my future so I can get things dialed in better.

[Chickenman]

Yes, you can measure at the valve retainer... it is just subject to more errors as the Isky article mentions. BTW, this is not unique to Isky. Most Cam manufactureres ( Crane, Sig Erickson , Lunati, Comp Cams )  all recommend measuring at Tappet lift. The only reason why some guys use the Valve retainer measurement on Datsuns is because of convenience. It's hard to get the Dial indicator positioned over the Camshaft correctly. And you often have to fabricate a special bracket. But reading directly off the Camshaft is definitely more accurate.

I'm heading out to Mission Raceway for some Historic races this weekend. I'll talk to Andy Pearson of Specialty Engineering on this. He is a top engine builder for L-Seriers on the West Coast of North America. His Datsun engines have won numerous SCCA National Runoffs and dozens of SCCA events. It will be interesting to see what he has to say, although I'm pretty sure he always degrees directly off the Cam lobe.

 

Edited August 16, 2016 by Chickenman
In reply to Madkaw

[Chickenman]

3 minutes ago, swa240z said:

Chickenman - Thanks for your feedback.  Isky sent out new .175" lash pads with the cam.  Rocker arms are the original arms that had about 64k miles on them.  They looked very clean and showed no noticeable signs of wear.

I still haven't heard back from Isky.  I called yesterday and was told that Ron was still working on the numbers.  If that's the case, then I assume there must be a mistake on the most recent cam card he sent me.  If I get some new numbers from Isky, madkaw and I will probably take one more run at dialing in the cam and I'll post the new cam card.  If I don't hear something in the next day or so, I'll probably just advance the cam about 2* to make up for the .035" I removed from the head and hope that is close enough to get the engine running good.  A dyno run is probably in my future so I can get things dialed in better.

I think the reason why Ron is having the delays, is determining the actual rocker arm ratio's on the L-Series finger followers. As mentioned, finger followers do not have a symmetrical rocker ratio as Domestic pushrod engines such as a SBC. Those are relatively easy to calculate as you are dealing with a round tappet, and although the ratio rises and falls as the cam lobe swipes across the tappet face, it is a symmetrical calculation. And the decades of Cheby, Ford and Chrysler development on Cam grinding have created reliable figures that they can use. But Tappet lift on all pushrod engines is the accepted standard and has been for a long time. No engine builder worth a dime degrees a pushrod engine at the valve. It's all .050" at the Tappet.

Our Datsun engines are a different matter as mentioned. The rocker arm ratio is asymmetrical, It starts off low then rises away as the cam lobe sweeps from the valve end of the wipe pad to the pivot end. Add to that the geometry change allowed by the L-seriers design which affect rocker ratio ( SBC etc designs are fixed ) and you can see the difficulty it entails.

BTW, it all may be a lot of worry about nothing. Isky has very high standards,  as do most Cam grinders these days. Computers, Cam Doctor and CNC machining makes human error less likely than in the 70's and 80's . Put it in at 2 degrees advanced as you plan for the head planned it will probably be just fine.

[madkaw]

I've been searching how to measure at the cam lobe. So you try and get the dial indicator on the rocket at the cam lobe ? I will see if there's enough room to get in there.


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[Chickenman]

Steve. Don't forget to check the Piston to Valve clearance with lightweight checking springs. You need at least .090" clearance. The Intake valve is usually the one that can cause interference, as it's opening BTDC as the piston is nearing TDC.The .035" off the head reduces the Piston to Valve clearance.

Edited August 16, 2016 by Chickenman
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[Chickenman]

39 minutes ago, madkaw said:

I've been searching how to measure at the cam lobe. So you try and get the dial indicator on the rocket at the cam lobe ? I will see if there's enough room to get in there.


Sent from my iPhone using Classic Zcar Club

No, you measure with the DIal Indicator aligned at the top of the Cam lobe. You don't even need the rockers installed. You just have to add 180 degree's to what the Timing card says. Timing card will should always be in Cam degrees... as that is how the Cam is ground and where you would check it on a Cam Doctor.

You may need to fabricate a steel fixture ( that is very stiff ) to swing the Dial Indicator over the Cam. Fixture bolts to Valve cover rail.  I seen some made out of a long piece of 1" x 3/16" wide flat steel, with a  piece of 3" to 4" flat steel welded to it vertically.  Vertical piece  needs to be super stiff... so I would think 1/4" thickness at least. . You just need something that bolts to the Valve cover rail, but will provide a solid flat mount that raises the mounting point for your Dial indicator well above the Cam lobe. Kinda like the letter " L "

Edit: Don't forget about the engine tilt when setting up Dial Indicator. A Magnetic protractor level  helps out a lot.

 

 

Edited August 16, 2016 by Chickenman