L24 Rebuild -Again!

[madkaw]

And no specific Datsun instructions, but I do have a cam card.

[siteunseen]

Jump a train to Memphis.

You gotta go!

[madkaw]

Waiting to call Isky

Edited July 6, 2015 by madkaw

[Chickenman]

Waiting to call Isky

Hmm... how stiff is that mounting plate bolted to the front of the head? Some sort of Tin Plate? Looks a bit flimsy.... Edit: Looks like a backing plate for an electrical junction box.

 

Any slightest movement there is going to be multiplied by the lever action of your Dial Indicator mounting arm.

 

I prefer to make a metal rail out of flat 24" x 2" x .125" mild steel and bolt it down the side of the Valve cover rail.  Drill holes in it to match Valve cover holes and bolt her down with 3 short 6mm bolts. That way you can attach the Dial Indicator Arm with the shortest length possible and a have a very stiff mounting plate. Stiff is always good !!! Just my .02c..

Edited July 6, 2015 by Chickenman

[240260280z]

For stock 240z Cam sprockets:

 

0° (position 1)

 
Cam Advance

  4° (position 2)
  8° (position 3)
  9° (position 1 + 1 chain link)

13° (position 2 + 1 chain link)

17° (position 3 + 1 chain link)

18° (position 1 + 2 chain links)

22° (position 2 + 2 chain links)

26° (position 3 + 2 chain links)

27° (position 1 + 3 chain links)

 
Cam Retard
-1° (position 3 - 1 chain link)
-5° (position 2 - 1 chain link)
-9° (- 1 chain link)
 
Note: Crank Advance is Cam Advance/2

 

Edited July 6, 2015 by Blue

[Patcon]

Chickenman

I believe that is a cover plate for a 4x4 metal electrical box. They are pretty stiff. You could bend it if you tried but they aren't overly flimsy. Not as stiff a 1/8" plate though.

[madkaw]

waiting on Ron to call me back, but he said the cam card is WRONG! 

[madkaw]

Richard,

good call on the box cover. It actually fits the bolt spacing perfectly-no drilling. Yes it's not very thick, but there isn't much pressure being exerted pushing a dial indicator rod in. Hell, the engine stand bounces around more-. 

I looked at my Schneider card from my 480 lift cam and I realize now how far off the isky numbers are and how close mine probably are to being right. At least I can put this puppy together if Ron ever calls back 

[Chickenman]

Curious as to what the Isky cam specs will actually be. One of the Cam profiles that a lot of guys run up in the PNW is a Shadbolt M445 grind. This was developed way back in the 70's. Still a good cam to this day.

 

280 advertised duration. Timing was Intake opens 30 degrees BTDC, closes 70 degrees ABDC. Exhaust opens 70 degrees BBDC, closes  30 degrees ATDC. Pretty sure Lobe Centerline was 106 degrees. Lift was .480".

 

Was a pretty darned good Slalom and Race cam. Good power to 7,500 RPM on an, L18 or L24. L16 ( 8,000 rpm ). Worked well on the street. Needed at least 3.90 gears though. L16's liked 4.11 or 4.36 gears. Bottom RPM range depended on displacement. L16 was pretty peaky. Worked really well on a  L18 or an L20B with a 4 banger. Awesome cam on an L24 or bigger as well.

Edited July 7, 2015 by Chickenman

[Diseazd]

Richard....Stage III Isky Cam is .490 lift; Intake 36-74; Exhaust is 74-36 duration is 290 degrees..... at .050 duration is 242 degrees.

[madkaw]

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

Steve,

[Chickenman]

Richard....Stage III Isky Cam is .490 lift; Intake 36-74; Exhaust is 74-36 duration is 290 degrees..... at .050 duration is 242 degrees.

That's a pretty stout cam ( Isky L-490 ) . Might be a bit much for the street, but should be good for track days. The M445 Shadbolt is more of a Stage II... FWIW.

 

Isky L480 specs are very close to Shadbolt M445. Lobe Center Angle isn't shown though which is important. But if I recall correctly, Isky likes to use around 106 -108 on the Stage II and III  grinds and 103 - 105 on the Race grinds ( Z-196 and Z-273 ) for the L series.

Edited July 7, 2015 by Chickenman